text: /*-------------------------------------------------------------------------
   *
   * tablecmds.c
   *	  Commands for creating and altering table structures and settings
   *
   * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   *
   * IDENTIFICATION
   *	  src/backend/commands/tablecmds.c
   *
   * The following only applies to changes made to this file as part of
   * YugaByte development.
   *
   * Portions Copyright (c) YugaByte, Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you
   * may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
   * implied.  See the License for the specific language governing
   * permissions and limitations under the License.
   *-------------------------------------------------------------------------
   */
  #include "postgres.h"
  
  #include "access/genam.h"
  #include "access/heapam.h"
  #include "access/heapam_xlog.h"
  #include "access/multixact.h"
  #include "access/reloptions.h"
  #include "access/relscan.h"
  #include "access/sysattr.h"
  #include "access/tupconvert.h"
  #include "access/xact.h"
  #include "access/xlog.h"
  #include "catalog/catalog.h"
  #include "catalog/dependency.h"
  #include "catalog/heap.h"
  #include "catalog/index.h"
  #include "catalog/indexing.h"
  #include "catalog/namespace.h"
  #include "catalog/objectaccess.h"
  #include "catalog/partition.h"
  #include "catalog/pg_am.h"
  #include "catalog/pg_collation.h"
  #include "catalog/pg_constraint.h"
  #include "catalog/pg_depend.h"
  #include "catalog/pg_foreign_table.h"
  #include "catalog/pg_inherits.h"
  #include "catalog/pg_namespace.h"
  #include "catalog/pg_opclass.h"
  #include "catalog/pg_tablespace.h"
  #include "catalog/pg_trigger.h"
  #include "catalog/pg_type.h"
  #include "catalog/binary_upgrade.h"
  #include "catalog/storage.h"
  #include "catalog/storage_xlog.h"
  #include "catalog/toasting.h"
  #include "commands/cluster.h"
  #include "commands/comment.h"
  #include "commands/defrem.h"
  #include "commands/event_trigger.h"
  #include "commands/policy.h"
  #include "commands/sequence.h"
  #include "commands/tablecmds.h"
  #include "commands/tablespace.h"
  #include "commands/tablegroup.h"
  #include "commands/trigger.h"
  #include "commands/typecmds.h"
  #include "commands/user.h"
  #include "executor/executor.h"
  #include "foreign/foreign.h"
  #include "miscadmin.h"
  #include "nodes/makefuncs.h"
  #include "nodes/nodeFuncs.h"
  #include "nodes/parsenodes.h"
  #include "optimizer/clauses.h"
  #include "optimizer/planner.h"
  #include "optimizer/predtest.h"
  #include "optimizer/prep.h"
  #include "optimizer/var.h"
  #include "parser/parse_clause.h"
  #include "parser/parse_coerce.h"
  #include "parser/parse_collate.h"
  #include "parser/parse_expr.h"
  #include "parser/parse_oper.h"
  #include "parser/parse_relation.h"
  #include "parser/parse_type.h"
  #include "parser/parse_utilcmd.h"
  #include "parser/parser.h"
  #include "partitioning/partbounds.h"
  #include "pgstat.h"
  #include "rewrite/rewriteDefine.h"
  #include "rewrite/rewriteHandler.h"
  #include "rewrite/rewriteManip.h"
  #include "storage/bufmgr.h"
  #include "storage/lmgr.h"
  #include "storage/lock.h"
  #include "storage/predicate.h"
  #include "storage/smgr.h"
  #include "utils/acl.h"
  #include "utils/builtins.h"
  #include "utils/fmgroids.h"
  #include "utils/inval.h"
  #include "utils/lsyscache.h"
  #include "utils/memutils.h"
  #include "utils/partcache.h"
  #include "utils/relcache.h"
  #include "utils/ruleutils.h"
  #include "utils/snapmgr.h"
  #include "utils/syscache.h"
  #include "utils/timestamp.h"
  #include "utils/tqual.h"
  #include "utils/typcache.h"
  
  /* YB includes. */
  #include "catalog/pg_authid.h"
  #include "catalog/pg_database.h"
  #include "commands/dbcommands.h"
  #include "commands/ybccmds.h"
  #include "executor/ybcModifyTable.h"
  #include "pg_yb_utils.h"
  
  /*
   * ON COMMIT action list
   */
  typedef struct OnCommitItem
  {
  	Oid			relid;			/* relid of relation */
  	OnCommitAction oncommit;	/* what to do at end of xact */
  
  	/*
  	 * If this entry was created during the current transaction,
  	 * creating_subid is the ID of the creating subxact; if created in a prior
  	 * transaction, creating_subid is zero.  If deleted during the current
  	 * transaction, deleting_subid is the ID of the deleting subxact; if no
  	 * deletion request is pending, deleting_subid is zero.
  	 */
  	SubTransactionId creating_subid;
  	SubTransactionId deleting_subid;
  } OnCommitItem;
  
  static List *on_commits = NIL;
  
  
  /*
   * State information for ALTER TABLE
   *
   * The pending-work queue for an ALTER TABLE is a List of AlteredTableInfo
   * structs, one for each table modified by the operation (the named table
   * plus any child tables that are affected).  We save lists of subcommands
   * to apply to this table (possibly modified by parse transformation steps);
   * these lists will be executed in Phase 2.  If a Phase 3 step is needed,
   * necessary information is stored in the constraints and newvals lists.
   *
   * Phase 2 is divided into multiple passes; subcommands are executed in
   * a pass determined by subcommand type.
   */
  
  #define AT_PASS_UNSET			-1	/* UNSET will cause ERROR */
  #define AT_PASS_DROP			0	/* DROP (all flavors) */
  #define AT_PASS_ALTER_TYPE		1	/* ALTER COLUMN TYPE */
  #define AT_PASS_OLD_INDEX		2	/* re-add existing indexes */
  #define AT_PASS_OLD_CONSTR		3	/* re-add existing constraints */
  #define AT_PASS_COL_ATTRS		4	/* set other column attributes */
  /* We could support a RENAME COLUMN pass here, but not currently used */
  #define AT_PASS_ADD_COL			5	/* ADD COLUMN */
  #define AT_PASS_ADD_INDEX		6	/* ADD indexes */
  #define AT_PASS_ADD_CONSTR		7	/* ADD constraints, defaults */
  #define AT_PASS_MISC			8	/* other stuff */
  #define AT_NUM_PASSES			9
  
  typedef struct AlteredTableInfo
  {
  	/* Information saved before any work commences: */
  	Oid			relid;			/* Relation to work on */
  	char		relkind;		/* Its relkind */
  	TupleDesc	oldDesc;		/* Pre-modification tuple descriptor */
  	/* Information saved by Phase 1 for Phase 2: */
  	List	   *subcmds[AT_NUM_PASSES]; /* Lists of AlterTableCmd */
  	/* Information saved by Phases 1/2 for Phase 3: */
  	List	   *constraints;	/* List of NewConstraint */
  	List	   *newvals;		/* List of NewColumnValue */
  	bool		new_notnull;	/* T if we added new NOT NULL constraints */
  	int			rewrite;		/* Reason for forced rewrite, if any */
  	Oid			newTableSpace;	/* new tablespace; 0 means no change */
  	bool		chgPersistence; /* T if SET LOGGED/UNLOGGED is used */
  	char		newrelpersistence;	/* if above is true */
  	Expr	   *partition_constraint;	/* for attach partition validation */
  	/* true, if validating default due to some other attach/detach */
  	bool		validate_default;
  	/* Objects to rebuild after completing ALTER TYPE operations */
  	List	   *changedConstraintOids;	/* OIDs of constraints to rebuild */
  	List	   *changedConstraintDefs;	/* string definitions of same */
  	List	   *changedIndexOids;	/* OIDs of indexes to rebuild */
  	List	   *changedIndexDefs;	/* string definitions of same */
  } AlteredTableInfo;
  
  /* Struct describing one new constraint to check in Phase 3 scan */
  /* Note: new NOT NULL constraints are handled elsewhere */
  typedef struct NewConstraint
  {
  	char	   *name;			/* Constraint name, or NULL if none */
  	ConstrType	contype;		/* CHECK or FOREIGN */
  	Oid			refrelid;		/* PK rel, if FOREIGN */
  	Oid			refindid;		/* OID of PK's index, if FOREIGN */
  	Oid			conid;			/* OID of pg_constraint entry, if FOREIGN */
  	Node	   *qual;			/* Check expr or CONSTR_FOREIGN Constraint */
  	ExprState  *qualstate;		/* Execution state for CHECK expr */
  } NewConstraint;
  
  /*
   * Struct describing one new column value that needs to be computed during
   * Phase 3 copy (this could be either a new column with a non-null default, or
   * a column that we're changing the type of).  Columns without such an entry
   * are just copied from the old table during ATRewriteTable.  Note that the
   * expr is an expression over *old* table values.
   */
  typedef struct NewColumnValue
  {
  	AttrNumber	attnum;			/* which column */
  	Expr	   *expr;			/* expression to compute */
  	ExprState  *exprstate;		/* execution state */
  } NewColumnValue;
  
  /*
   * Error-reporting support for RemoveRelations
   */
  struct dropmsgstrings
  {
  	char		kind;
  	int			nonexistent_code;
  	const char *nonexistent_msg;
  	const char *skipping_msg;
  	const char *nota_msg;
  	const char *drophint_msg;
  };
  
  static const struct dropmsgstrings dropmsgstringarray[] = {
  	{RELKIND_RELATION,
  		ERRCODE_UNDEFINED_TABLE,
  		gettext_noop("table \"%s\" does not exist"),
  		gettext_noop("table \"%s\" does not exist, skipping"),
  		gettext_noop("\"%s\" is not a table"),
  	gettext_noop("Use DROP TABLE to remove a table.")},
  	{RELKIND_SEQUENCE,
  		ERRCODE_UNDEFINED_TABLE,
  		gettext_noop("sequence \"%s\" does not exist"),
  		gettext_noop("sequence \"%s\" does not exist, skipping"),
  		gettext_noop("\"%s\" is not a sequence"),
  	gettext_noop("Use DROP SEQUENCE to remove a sequence.")},
  	{RELKIND_VIEW,
  		ERRCODE_UNDEFINED_TABLE,
  		gettext_noop("view \"%s\" does not exist"),
  		gettext_noop("view \"%s\" does not exist, skipping"),
  		gettext_noop("\"%s\" is not a view"),
  	gettext_noop("Use DROP VIEW to remove a view.")},
  	{RELKIND_MATVIEW,
  		ERRCODE_UNDEFINED_TABLE,
  		gettext_noop("materialized view \"%s\" does not exist"),
  		gettext_noop("materialized view \"%s\" does not exist, skipping"),
  		gettext_noop("\"%s\" is not a materialized view"),
  	gettext_noop("Use DROP MATERIALIZED VIEW to remove a materialized view.")},
  	{RELKIND_INDEX,
  		ERRCODE_UNDEFINED_OBJECT,
  		gettext_noop("index \"%s\" does not exist"),
  		gettext_noop("index \"%s\" does not exist, skipping"),
  		gettext_noop("\"%s\" is not an index"),
  	gettext_noop("Use DROP INDEX to remove an index.")},
  	{RELKIND_COMPOSITE_TYPE,
  		ERRCODE_UNDEFINED_OBJECT,
  		gettext_noop("type \"%s\" does not exist"),
  		gettext_noop("type \"%s\" does not exist, skipping"),
  		gettext_noop("\"%s\" is not a type"),
  	gettext_noop("Use DROP TYPE to remove a type.")},
  	{RELKIND_FOREIGN_TABLE,
  		ERRCODE_UNDEFINED_OBJECT,
  		gettext_noop("foreign table \"%s\" does not exist"),
  		gettext_noop("foreign table \"%s\" does not exist, skipping"),
  		gettext_noop("\"%s\" is not a foreign table"),
  	gettext_noop("Use DROP FOREIGN TABLE to remove a foreign table.")},
  	{RELKIND_PARTITIONED_TABLE,
  		ERRCODE_UNDEFINED_TABLE,
  		gettext_noop("table \"%s\" does not exist"),
  		gettext_noop("table \"%s\" does not exist, skipping"),
  		gettext_noop("\"%s\" is not a table"),
  	gettext_noop("Use DROP TABLE to remove a table.")},
  	{RELKIND_PARTITIONED_INDEX,
  		ERRCODE_UNDEFINED_OBJECT,
  		gettext_noop("index \"%s\" does not exist"),
  		gettext_noop("index \"%s\" does not exist, skipping"),
  		gettext_noop("\"%s\" is not an index"),
  	gettext_noop("Use DROP INDEX to remove an index.")},
  	{'\0', 0, NULL, NULL, NULL, NULL}
  };
  
  struct DropRelationCallbackState
  {
  	char		relkind;
  	Oid			heapOid;
  	Oid			partParentOid;
  	bool		concurrent;
  };
  
  /* Alter table target-type flags for ATSimplePermissions */
  #define		ATT_TABLE				0x0001
  #define		ATT_VIEW				0x0002
  #define		ATT_MATVIEW				0x0004
  #define		ATT_INDEX				0x0008
  #define		ATT_COMPOSITE_TYPE		0x0010
  #define		ATT_FOREIGN_TABLE		0x0020
  #define		ATT_PARTITIONED_INDEX	0x0040
  
  /*
   * Partition tables are expected to be dropped when the parent partitioned
   * table gets dropped. Hence for partitioning we use AUTO dependency.
   * Otherwise, for regular inheritance use NORMAL dependency.
   */
  #define child_dependency_type(child_is_partition)	\
  	((child_is_partition) ? DEPENDENCY_AUTO : DEPENDENCY_NORMAL)
  
  static void truncate_check_rel(Relation rel);
  static List *MergeAttributes(List *schema, List *supers, char relpersistence,
  				bool is_partition, List **supOids, List **supconstr,
  				int *supOidCount);
  static bool MergeCheckConstraint(List *constraints, char *name, Node *expr);
  static void MergeAttributesIntoExisting(Relation child_rel, Relation parent_rel);
  static void MergeConstraintsIntoExisting(Relation child_rel, Relation parent_rel);
  static void StoreCatalogInheritance(Oid relationId, List *supers,
  						bool child_is_partition);
  static void StoreCatalogInheritance1(Oid relationId, Oid parentOid,
  						 int32 seqNumber, Relation inhRelation,
  						 bool child_is_partition);
  static int	findAttrByName(const char *attributeName, List *schema);
  static void AlterIndexNamespaces(Relation classRel, Relation rel,
  					 Oid oldNspOid, Oid newNspOid, ObjectAddresses *objsMoved);
  static void AlterSeqNamespaces(Relation classRel, Relation rel,
  				   Oid oldNspOid, Oid newNspOid, ObjectAddresses *objsMoved,
  				   LOCKMODE lockmode);
  static ObjectAddress ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
  					  bool recurse, bool recursing, LOCKMODE lockmode);
  static ObjectAddress ATExecValidateConstraint(Relation rel, char *constrName,
  						 bool recurse, bool recursing, LOCKMODE lockmode);
  static int transformColumnNameList(Oid relId, List *colList,
  						int16 *attnums, Oid *atttypids);
  static int transformFkeyGetPrimaryKey(Relation pkrel, Oid *indexOid,
  						   List **attnamelist,
  						   int16 *attnums, Oid *atttypids,
  						   Oid *opclasses);
  static Oid transformFkeyCheckAttrs(Relation pkrel,
  						int numattrs, int16 *attnums,
  						Oid *opclasses);
  static void checkFkeyPermissions(Relation rel, int16 *attnums, int natts);
  static CoercionPathType findFkeyCast(Oid targetTypeId, Oid sourceTypeId,
  			 Oid *funcid);
  static void validateCheckConstraint(Relation rel, HeapTuple constrtup);
  static void validateForeignKeyConstraint(char *conname,
  							 Relation rel, Relation pkrel,
  							 Oid pkindOid, Oid constraintOid);
  static void ATController(AlterTableStmt *parsetree,
  			 Relation rel, List *cmds, bool recurse, LOCKMODE lockmode);
  static void ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
  		  bool recurse, bool recursing, LOCKMODE lockmode);
  static void ATRewriteCatalogs(List **wqueue,
  							  LOCKMODE lockmode,
  							  YBCPgStatement *rollbackHandle);
  static void ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation *mutable_rel,
  		  AlterTableCmd *cmd, LOCKMODE lockmode);
  static void ATRewriteTables(AlterTableStmt *parsetree,
  				List **wqueue, LOCKMODE lockmode);
  static void ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap, LOCKMODE lockmode);
  static AlteredTableInfo *ATGetQueueEntry(List **wqueue, Relation rel);
  static void ATSimplePermissions(Relation rel, int allowed_targets);
  static void ATWrongRelkindError(Relation rel, int allowed_targets);
  static void ATSimpleRecursion(List **wqueue, Relation rel,
  				  AlterTableCmd *cmd, bool recurse, LOCKMODE lockmode);
  static void ATTypedTableRecursion(List **wqueue, Relation rel, AlterTableCmd *cmd,
  					  LOCKMODE lockmode);
  static List *find_typed_table_dependencies(Oid typeOid, const char *typeName,
  							  DropBehavior behavior);
  static void ATPrepAddColumn(List **wqueue, Relation rel, bool recurse, bool recursing,
  				bool is_view, AlterTableCmd *cmd, LOCKMODE lockmode);
  static ObjectAddress ATExecAddColumn(List **wqueue, AlteredTableInfo *tab,
  				Relation rel, ColumnDef *colDef, bool isOid,
  				bool recurse, bool recursing,
  				bool if_not_exists, LOCKMODE lockmode);
  static bool check_for_column_name_collision(Relation rel, const char *colname,
  								bool if_not_exists);
  static void add_column_datatype_dependency(Oid relid, int32 attnum, Oid typid);
  static void add_column_collation_dependency(Oid relid, int32 attnum, Oid collid);
  static void ATPrepAddOids(List **wqueue, Relation rel, bool recurse,
  			  AlterTableCmd *cmd, LOCKMODE lockmode);
  static void ATPrepDropNotNull(Relation rel, bool recurse, bool recursing);
  static ObjectAddress ATExecDropNotNull(Relation rel, const char *colName, LOCKMODE lockmode);
  static void ATPrepSetNotNull(Relation rel, bool recurse, bool recursing);
  static ObjectAddress ATExecSetNotNull(AlteredTableInfo *tab, Relation rel,
  				 const char *colName, LOCKMODE lockmode);
  static ObjectAddress ATExecColumnDefault(Relation rel, const char *colName,
  					Node *newDefault, LOCKMODE lockmode);
  static ObjectAddress ATExecAddIdentity(Relation rel, const char *colName,
  				  Node *def, LOCKMODE lockmode);
  static ObjectAddress ATExecSetIdentity(Relation rel, const char *colName,
  				  Node *def, LOCKMODE lockmode);
  static ObjectAddress ATExecDropIdentity(Relation rel, const char *colName, bool missing_ok, LOCKMODE lockmode);
  static void ATPrepSetStatistics(Relation rel, const char *colName, int16 colNum,
  					Node *newValue, LOCKMODE lockmode);
  static ObjectAddress ATExecSetStatistics(Relation rel, const char *colName, int16 colNum,
  					Node *newValue, LOCKMODE lockmode);
  static ObjectAddress ATExecSetOptions(Relation rel, const char *colName,
  				 Node *options, bool isReset, LOCKMODE lockmode);
  static ObjectAddress ATExecSetStorage(Relation rel, const char *colName,
  				 Node *newValue, LOCKMODE lockmode);
  static void ATPrepDropColumn(List **wqueue, Relation rel, bool recurse, bool recursing,
  				 AlterTableCmd *cmd, LOCKMODE lockmode);
  static ObjectAddress ATExecDropColumn(List **wqueue, Relation rel, const char *colName,
  				 DropBehavior behavior,
  				 bool recurse, bool recursing,
  				 bool missing_ok, LOCKMODE lockmode);
  static ObjectAddress ATExecAddIndex(AlteredTableInfo *tab, Relation *mutable_rel,
  			   IndexStmt *stmt, bool is_rebuild, LOCKMODE lockmode);
  static ObjectAddress ATExecAddConstraint(List **wqueue,
  					AlteredTableInfo *tab, Relation rel,
  					Constraint *newConstraint, bool recurse, bool is_readd,
  					LOCKMODE lockmode);
  static ObjectAddress ATExecAddIndexConstraint(AlteredTableInfo *tab, Relation rel,
  						 IndexStmt *stmt, LOCKMODE lockmode);
  static ObjectAddress ATAddCheckConstraint(List **wqueue,
  					 AlteredTableInfo *tab, Relation rel,
  					 Constraint *constr,
  					 bool recurse, bool recursing, bool is_readd,
  					 LOCKMODE lockmode);
  static ObjectAddress ATAddForeignKeyConstraint(List **wqueue, AlteredTableInfo *tab,
  						  Relation rel, Constraint *fkconstraint, Oid parentConstr,
  						  bool recurse, bool recursing,
  						  LOCKMODE lockmode);
  static void CloneFkReferencing(Relation pg_constraint, Relation parentRel,
  				   Relation partRel, List *clone, List **cloned);
  static void ATExecDropConstraint(Relation rel, const char *constrName,
  					 DropBehavior behavior,
  					 bool recurse, bool recursing,
  					 bool missing_ok, LOCKMODE lockmode);
  static void ATPrepAlterColumnType(List **wqueue,
  					  AlteredTableInfo *tab, Relation rel,
  					  bool recurse, bool recursing,
  					  AlterTableCmd *cmd, LOCKMODE lockmode);
  static bool ATColumnChangeRequiresRewrite(Node *expr, AttrNumber varattno);
  static ObjectAddress ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
  					  AlterTableCmd *cmd, LOCKMODE lockmode);
  static ObjectAddress ATExecAlterColumnGenericOptions(Relation rel, const char *colName,
  								List *options, LOCKMODE lockmode);
  static void ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab,
  					   LOCKMODE lockmode);
  static void ATPostAlterTypeParse(Oid oldId, Oid oldRelId, Oid refRelId,
  					 char *cmd, List **wqueue, LOCKMODE lockmode,
  					 bool rewrite);
  static void RebuildConstraintComment(AlteredTableInfo *tab, int pass,
  						 Oid objid, Relation rel, List *domname,
  						 const char *conname);
  static void TryReuseIndex(Oid oldId, IndexStmt *stmt);
  static void TryReuseForeignKey(Oid oldId, Constraint *con);
  static void change_owner_fix_column_acls(Oid relationOid,
  							 Oid oldOwnerId, Oid newOwnerId);
  static void change_owner_recurse_to_sequences(Oid relationOid,
  								  Oid newOwnerId, LOCKMODE lockmode);
  static ObjectAddress ATExecClusterOn(Relation rel, const char *indexName,
  				LOCKMODE lockmode);
  static void ATExecDropCluster(Relation rel, LOCKMODE lockmode);
  static bool ATPrepChangePersistence(Relation rel, bool toLogged);
  static void ATPrepSetTableSpace(AlteredTableInfo *tab, Relation rel,
  					const char *tablespacename, LOCKMODE lockmode);
  static void ATExecSetTableSpace(Oid tableOid, Oid newTableSpace, LOCKMODE lockmode);
  static void ATExecPartedIdxSetTableSpace(Relation rel, Oid newTableSpace);
  static void ATExecSetRelOptions(Relation rel, List *defList,
  					AlterTableType operation,
  					LOCKMODE lockmode);
  static void ATExecEnableDisableTrigger(Relation rel, const char *trigname,
  						   char fires_when, bool skip_system, LOCKMODE lockmode);
  static void ATExecEnableDisableRule(Relation rel, const char *rulename,
  						char fires_when, LOCKMODE lockmode);
  static void ATPrepAddInherit(Relation child_rel);
  static ObjectAddress ATExecAddInherit(Relation child_rel, RangeVar *parent, LOCKMODE lockmode);
  static ObjectAddress ATExecDropInherit(Relation rel, RangeVar *parent, LOCKMODE lockmode);
  static void drop_parent_dependency(Oid relid, Oid refclassid, Oid refobjid,
  					   DependencyType deptype);
  static ObjectAddress ATExecAddOf(Relation rel, const TypeName *ofTypename, LOCKMODE lockmode);
  static void ATExecDropOf(Relation rel, LOCKMODE lockmode);
  static void ATExecReplicaIdentity(Relation rel, ReplicaIdentityStmt *stmt, LOCKMODE lockmode);
  static void ATExecGenericOptions(Relation rel, List *options);
  static void ATExecEnableRowSecurity(Relation rel);
  static void ATExecDisableRowSecurity(Relation rel);
  static void ATExecForceNoForceRowSecurity(Relation rel, bool force_rls);
  
  static void copy_relation_data(SMgrRelation rel, SMgrRelation dst,
  				   ForkNumber forkNum, char relpersistence);
  static const char *storage_name(char c);
  
  static void RangeVarCallbackForDropRelation(const RangeVar *rel, Oid relOid,
  								Oid oldRelOid, void *arg);
  static void RangeVarCallbackForAlterRelation(const RangeVar *rv, Oid relid,
  								 Oid oldrelid, void *arg);
  static PartitionSpec *transformPartitionSpec(Relation rel, PartitionSpec *partspec, char *strategy);
  static void ComputePartitionAttrs(Relation rel, List *partParams, AttrNumber *partattrs,
  					  List **partexprs, Oid *partopclass, Oid *partcollation, char strategy);
  static void CreateInheritance(Relation child_rel, Relation parent_rel);
  static void RemoveInheritance(Relation child_rel, Relation parent_rel);
  static ObjectAddress ATExecAttachPartition(List **wqueue, Relation rel,
  					  PartitionCmd *cmd);
  static void AttachPartitionEnsureIndexes(Relation rel, Relation attachrel);
  static void QueuePartitionConstraintValidation(List **wqueue, Relation scanrel,
  								   List *partConstraint,
  								   bool validate_default);
  static void CloneRowTriggersToPartition(Relation parent, Relation partition);
  static ObjectAddress ATExecDetachPartition(Relation rel, RangeVar *name);
  static ObjectAddress ATExecAttachPartitionIdx(List **wqueue, Relation rel,
  						 RangeVar *name);
  static void validatePartitionedIndex(Relation partedIdx, Relation partedTbl);
  static void refuseDupeIndexAttach(Relation parentIdx, Relation partIdx,
  					  Relation partitionTbl);
  static void update_relispartition(Relation classRel, Oid relationId,
  					  bool newval);
  
  
  /* ----------------------------------------------------------------
   *		DefineRelation
   *				Creates a new relation.
   *
   * stmt carries parsetree information from an ordinary CREATE TABLE statement.
   * The other arguments are used to extend the behavior for other cases:
   * relkind: relkind to assign to the new relation
   * ownerId: if not InvalidOid, use this as the new relation's owner.
   * typaddress: if not null, it's set to the pg_type entry's address.
   * queryString: for error reporting
   *
   * Note that permissions checks are done against current user regardless of
   * ownerId.  A nonzero ownerId is used when someone is creating a relation
   * "on behalf of" someone else, so we still want to see that the current user
   * has permissions to do it.
   *
   * If successful, returns the address of the new relation.
   * ----------------------------------------------------------------
   */
  ObjectAddress
  DefineRelation(CreateStmt *stmt, char relkind, Oid ownerId,
  			   ObjectAddress *typaddress, const char *queryString)
  {
  	char		relname[NAMEDATALEN];
  	Oid			namespaceId;
  	Oid			relationId = InvalidOid;
  	Oid			tablespaceId;
  	Relation	rel;
  	TupleDesc	descriptor;
  	List	   *inheritOids;
  	List	   *old_constraints;
  	bool		localHasOids;
  	int			parentOidCount;
  	List	   *rawDefaults;
  	List	   *cookedDefaults;
  	Datum		reloptions;
  	ListCell   *listptr;
  	AttrNumber	attnum;
  	static char *validnsps[] = HEAP_RELOPT_NAMESPACES;
  	Oid			ofTypeId;
  	ObjectAddress address;
  
  	/* YB variables. */
  	Oid			rowTypeId = InvalidOid;
  	bool		relisshared = false;
  
  	/*
  	 * Truncate relname to appropriate length (probably a waste of time, as
  	 * parser should have done this already).
  	 */
  	StrNCpy(relname, stmt->relation->relname, NAMEDATALEN);
  
  	/*
  	 * Check consistency of arguments
  	 */
  	if (stmt->oncommit != ONCOMMIT_NOOP
  		&& stmt->relation->relpersistence != RELPERSISTENCE_TEMP)
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  				 errmsg("ON COMMIT can only be used on temporary tables")));
  
  	if (stmt->partspec != NULL)
  	{
  		if (relkind != RELKIND_RELATION)
  			elog(ERROR, "unexpected relkind: %d", (int) relkind);
  
  		relkind = RELKIND_PARTITIONED_TABLE;
  	}
  
  	/*
  	 * Look up the namespace in which we are supposed to create the relation,
  	 * check we have permission to create there, lock it against concurrent
  	 * drop, and mark stmt->relation as RELPERSISTENCE_TEMP if a temporary
  	 * namespace is selected.
  	 */
  	namespaceId =
  		RangeVarGetAndCheckCreationNamespace(stmt->relation, NoLock, NULL);
  
  	/*
  	 * Security check: disallow creating temp tables from security-restricted
  	 * code.  This is needed because calling code might not expect untrusted
  	 * tables to appear in pg_temp at the front of its search path.
  	 */
  	if (stmt->relation->relpersistence == RELPERSISTENCE_TEMP
  		&& InSecurityRestrictedOperation())
  		ereport(ERROR,
  				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  				 errmsg("cannot create temporary table within security-restricted operation")));
  
  	/*
  	 * Select tablespace to use.  If not specified, use default tablespace
  	 * (which may in turn default to database's default).
  	 */
  	if (stmt->tablespacename)
  	{
  		tablespaceId = get_tablespace_oid(stmt->tablespacename, false);
  	}
  	else
  	{
  		tablespaceId = GetDefaultTablespace(stmt->relation->relpersistence);
  		/* note InvalidOid is OK in this case */
  	}
  
  	/* Check permissions except when using database's default */
  	if (OidIsValid(tablespaceId) && tablespaceId != MyDatabaseTableSpace)
  	{
  		AclResult	aclresult;
  
  		aclresult = pg_tablespace_aclcheck(tablespaceId, GetUserId(),
  										   ACL_CREATE);
  		if (aclresult != ACLCHECK_OK)
  			aclcheck_error(aclresult, OBJECT_TABLESPACE,
  						   get_tablespace_name(tablespaceId));
  	}
  
  	if (tablespaceId == GLOBALTABLESPACE_OID)
  	{
  		if (IsYugaByteEnabled())
  		{
  			if (!IsYsqlUpgrade)
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("shared relations cannot be created outside of YSQL upgrade")));
  			else if (!IsSystemNamespace(namespaceId))
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("shared relations can only be created in pg_catalog")));
  			else if (stmt->partbound)
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("shared relations can not be partitioned")));
  
  			relisshared = true;
  
  			/*
  			 * If not superuser, ensure having CREATE privileges over template1 -
  			 * this is where DocDB would actually store the shared relation.
  			 */
  			if (!superuser())
  			{
  				AclResult	aclresult;
  
  				aclresult = pg_database_aclcheck(TemplateDbOid, GetUserId(), ACL_CREATE);
  
  				if (aclresult != ACLCHECK_OK)
  					aclcheck_error(aclresult, OBJECT_DATABASE,
  								   get_database_name(TemplateDbOid));
  			}
  
  			/*
  			 * We actually need a lot more checks - e.g. that shared relation
  			 * is not temporary, does not have tablegroup, etc.
  			 * But since this is needed for YSQL upgrade only, we more or less
  			 * assume "user" knows what he's doing.
  			 */
  		}
  		else
  		{
  			/* In all cases disallow placing user relations in pg_global */
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  					 errmsg("only shared relations can be placed in pg_global tablespace")));
  		}
  	}
  
  	if (IsYsqlUpgrade && relkind == RELKIND_VIEW && IsSystemNamespace(namespaceId))
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("creating system views during YSQL upgrade is not yet supported")));
  
  	/*
  	 * Select tablegroup to use. If not specified, InvalidOid.
  	 * Disallow mixing of COLOCATED=true/false syntax and TABLEGROUP. Cannot use tablegroups
  	 * in colocated databases.
  	 * If the pg_tablegroup system table has not been created, get_tablegroup_oid will produce
  	 * an error.
  	 */
  	Oid tablegroupId = InvalidOid;
  	if (stmt->tablegroup)
  	{
  		OptTableGroup *grp = stmt->tablegroup;
  		if (MyDatabaseColocated)
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("cannot use tablegroups in a colocated database")));
  		else if (!grp->has_tablegroup)
  		{
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  					 errmsg("Cannot use NO TABLEGROUP in CREATE TABLE statement.")));
  		}
  		else
  			tablegroupId = get_tablegroup_oid(grp->tablegroup_name, false);
  	}
  
  	/*
  	 * Check permissions for tablegroup. To create a table within a tablegroup, a user must
  	 * either be a superuser, the owner of the tablegroup, or have create perms on it.
  	 */
  	if (OidIsValid(tablegroupId) && !pg_tablegroup_ownercheck(tablegroupId, GetUserId()))
  	{
  		AclResult  aclresult;
  
  		aclresult = pg_tablegroup_aclcheck(tablegroupId, GetUserId(), ACL_CREATE);
  		if (aclresult != ACLCHECK_OK)
  			aclcheck_error(aclresult, OBJECT_TABLEGROUP,
  						   get_tablegroup_name(tablegroupId));
  	}
  
  	/*
  	 * Prepend to stmt->options to be parsed for reloptions if tablegroupId is valid.
  	 * We set this here instead of in parse_utilcmd since we need to do the above
  	 * preprocessing and RBAC checks first. This still happens before transformReloptions
  	 * so this option is included in the reloptions text array.
  	 */
  	if (OidIsValid(tablegroupId))
  	{
  		stmt->options = lcons(makeDefElem("tablegroup",
  										  (Node *) makeInteger(tablegroupId), -1),
  										  stmt->options);
  	}
  
  	/* Identify user ID that will own the table */
  	if (!OidIsValid(ownerId))
  		ownerId = (IsYugaByteEnabled() && IsYsqlUpgrade && IsSystemNamespace(namespaceId))
  					? BOOTSTRAP_SUPERUSERID
  					: GetUserId();
  
  	/*
  	 * Parse and validate reloptions, if any.
  	 */
  	reloptions = transformRelOptions((Datum) 0, stmt->options, NULL, validnsps,
  									 true, false);
  
  	if (relkind == RELKIND_VIEW)
  		(void) view_reloptions(reloptions, true);
  	else
  		(void) heap_reloptions(relkind, reloptions, true);
  
  	if (stmt->ofTypename)
  	{
  		AclResult	aclresult;
  
  		ofTypeId = typenameTypeId(NULL, stmt->ofTypename);
  
  		aclresult = pg_type_aclcheck(ofTypeId, GetUserId(), ACL_USAGE);
  		if (aclresult != ACLCHECK_OK)
  			aclcheck_error_type(aclresult, ofTypeId);
  	}
  	else
  		ofTypeId = InvalidOid;
  
  	/*
  	 * Look up inheritance ancestors and generate relation schema, including
  	 * inherited attributes.  (Note that stmt->tableElts is destructively
  	 * modified by MergeAttributes.)
  	 */
  	stmt->tableElts =
  		MergeAttributes(stmt->tableElts, stmt->inhRelations,
  						stmt->relation->relpersistence,
  						stmt->partbound != NULL,
  						&inheritOids, &old_constraints, &parentOidCount);
  
  	/*
  	 * Create a tuple descriptor from the relation schema.  Note that this
  	 * deals with column names, types, and NOT NULL constraints, but not
  	 * default values or CHECK constraints; we handle those below.
  	 */
  	descriptor = BuildDescForRelation(stmt->tableElts);
  
  	/*
  	 * Notice that we allow OIDs here only for plain tables and partitioned
  	 * tables, even though some other relkinds can support them.  This is
  	 * necessary because the default_with_oids GUC must apply only to plain
  	 * tables and not any other relkind; doing otherwise would break existing
  	 * pg_dump files.  We could allow explicit "WITH OIDS" while not allowing
  	 * default_with_oids to affect other relkinds, but it would complicate
  	 * interpretOidsOption().
  	 */
  	localHasOids = interpretOidsOption(stmt->options,
  									   (relkind == RELKIND_RELATION ||
  										relkind == RELKIND_PARTITIONED_TABLE));
  	descriptor->tdhasoid = (localHasOids || parentOidCount > 0);
  
  	/*
  	 * If a partitioned table doesn't have the system OID column, then none of
  	 * its partitions should have it.
  	 */
  	if (stmt->partbound && parentOidCount == 0 && localHasOids)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot create table with OIDs as partition of table without OIDs")));
  
  	/*
  	 * Find columns with default values and prepare for insertion of the
  	 * defaults.  Pre-cooked (that is, inherited) defaults go into a list of
  	 * CookedConstraint structs that we'll pass to heap_create_with_catalog,
  	 * while raw defaults go into a list of RawColumnDefault structs that will
  	 * be processed by AddRelationNewConstraints.  (We can't deal with raw
  	 * expressions until we can do transformExpr.)
  	 *
  	 * We can set the atthasdef flags now in the tuple descriptor; this just
  	 * saves StoreAttrDefault from having to do an immediate update of the
  	 * pg_attribute rows.
  	 */
  	rawDefaults = NIL;
  	cookedDefaults = NIL;
  	attnum = 0;
  
  	foreach(listptr, stmt->tableElts)
  	{
  		ColumnDef  *colDef = lfirst(listptr);
  		Form_pg_attribute attr;
  
  		attnum++;
  		attr = TupleDescAttr(descriptor, attnum - 1);
  
  		if (colDef->raw_default != NULL)
  		{
  			RawColumnDefault *rawEnt;
  
  			Assert(colDef->cooked_default == NULL);
  
  			rawEnt = (RawColumnDefault *) palloc(sizeof(RawColumnDefault));
  			rawEnt->attnum = attnum;
  			rawEnt->raw_default = colDef->raw_default;
  			rawEnt->missingMode = false;
  			rawDefaults = lappend(rawDefaults, rawEnt);
  			attr->atthasdef = true;
  		}
  		else if (colDef->cooked_default != NULL)
  		{
  			CookedConstraint *cooked;
  
  			cooked = (CookedConstraint *) palloc(sizeof(CookedConstraint));
  			cooked->contype = CONSTR_DEFAULT;
  			cooked->conoid = InvalidOid;	/* until created */
  			cooked->name = NULL;
  			cooked->attnum = attnum;
  			cooked->expr = colDef->cooked_default;
  			cooked->skip_validation = false;
  			cooked->is_local = true;	/* not used for defaults */
  			cooked->inhcount = 0;	/* ditto */
  			cooked->is_no_inherit = false;
  			cookedDefaults = lappend(cookedDefaults, cooked);
  			attr->atthasdef = true;
  		}
  
  		if (colDef->identity)
  			attr->attidentity = colDef->identity;
  	}
  
  	/* Handles WITH (table_oid = x). */
  	relationId = GetTableOidFromRelOptions(
  		stmt->options, tablespaceId, stmt->relation->relpersistence);
  
  	/* Handles WITH (row_type_oid = x). */
  	rowTypeId = GetRowTypeOidFromRelOptions(stmt->options);
  
  	/*
  	 * Create the relation.  Inherited defaults and constraints are passed in
  	 * for immediate handling --- since they don't need parsing, they can be
  	 * stored immediately.
  	 */
  	relationId = heap_create_with_catalog(relname,
  										  namespaceId,
  										  tablespaceId,
  										  relationId,
  										  rowTypeId,
  										  ofTypeId,
  										  ownerId,
  										  descriptor,
  										  list_concat(cookedDefaults,
  													  old_constraints),
  										  relkind,
  										  stmt->relation->relpersistence,
  										  relisshared,
  										  false,
  										  localHasOids,
  										  parentOidCount,
  										  stmt->oncommit,
  										  reloptions,
  										  true,
  										  allowSystemTableMods,
  										  false,
  										  InvalidOid,
  										  typaddress);
  
  	/*
  	 * We must bump the command counter to make the newly-created relation
  	 * tuple visible for opening.
  	 */
  	CommandCounterIncrement();
  
  	if (IsYugaByteEnabled())
  	{
  		CheckIsYBSupportedRelationByKind(relkind);
  		YBCCreateTable(stmt, relkind, descriptor, relationId, namespaceId, tablegroupId, tablespaceId);
  	}
  
  	/* For testing purposes, user might ask us to fail a DLL. */
  	YBTestFailDdlIfRequested();
  
  	/*
  	 * Open the new relation and acquire exclusive lock on it.  This isn't
  	 * really necessary for locking out other backends (since they can't see
  	 * the new rel anyway until we commit), but it keeps the lock manager from
  	 * complaining about deadlock risks.
  	 */
  	rel = relation_open(relationId, AccessExclusiveLock);
  
  	/* Process and store partition bound, if any. */
  	if (stmt->partbound)
  	{
  		PartitionBoundSpec *bound;
  		ParseState *pstate;
  		Oid			parentId = linitial_oid(inheritOids),
  					defaultPartOid;
  		Relation	parent,
  					defaultRel = NULL;
  
  		/* Already have strong enough lock on the parent */
  		parent = heap_open(parentId, NoLock);
  
  		/*
  		 * We are going to try to validate the partition bound specification
  		 * against the partition key of parentRel, so it better have one.
  		 */
  		if (parent->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  					 errmsg("\"%s\" is not partitioned",
  							RelationGetRelationName(parent))));
  
  		/*
  		 * The partition constraint of the default partition depends on the
  		 * partition bounds of every other partition. It is possible that
  		 * another backend might be about to execute a query on the default
  		 * partition table, and that the query relies on previously cached
  		 * default partition constraints. We must therefore take a table lock
  		 * strong enough to prevent all queries on the default partition from
  		 * proceeding until we commit and send out a shared-cache-inval notice
  		 * that will make them update their index lists.
  		 *
  		 * Order of locking: The relation being added won't be visible to
  		 * other backends until it is committed, hence here in
  		 * DefineRelation() the order of locking the default partition and the
  		 * relation being added does not matter. But at all other places we
  		 * need to lock the default relation before we lock the relation being
  		 * added or removed i.e. we should take the lock in same order at all
  		 * the places such that lock parent, lock default partition and then
  		 * lock the partition so as to avoid a deadlock.
  		 */
  		defaultPartOid =
  			get_default_oid_from_partdesc(RelationGetPartitionDesc(parent));
  		if (OidIsValid(defaultPartOid))
  			defaultRel = heap_open(defaultPartOid, AccessExclusiveLock);
  
  		/* Tranform the bound values */
  		pstate = make_parsestate(NULL);
  		pstate->p_sourcetext = queryString;
  
  		bound = transformPartitionBound(pstate, parent, stmt->partbound);
  
  		/*
  		 * Check first that the new partition's bound is valid and does not
  		 * overlap with any of existing partitions of the parent.
  		 */
  		check_new_partition_bound(relname, parent, bound);
  
  		/*
  		 * If the default partition exists, its partition constraints will
  		 * change after the addition of this new partition such that it won't
  		 * allow any row that qualifies for this new partition. So, check that
  		 * the existing data in the default partition satisfies the constraint
  		 * as it will exist after adding this partition.
  		 */
  		if (OidIsValid(defaultPartOid))
  		{
  			check_default_partition_contents(parent, defaultRel, bound);
  			/* Keep the lock until commit. */
  			heap_close(defaultRel, NoLock);
  		}
  
  		/* Update the pg_class entry. */
  		StorePartitionBound(rel, parent, bound);
  
  		heap_close(parent, NoLock);
  	}
  
  	/* Store inheritance information for new rel. */
  	StoreCatalogInheritance(relationId, inheritOids, stmt->partbound != NULL);
  
  	/*
  	 * Process the partitioning specification (if any) and store the partition
  	 * key information into the catalog.
  	 */
  	if (stmt->partspec)
  	{
  		char		strategy;
  		int			partnatts;
  		AttrNumber	partattrs[PARTITION_MAX_KEYS];
  		Oid			partopclass[PARTITION_MAX_KEYS];
  		Oid			partcollation[PARTITION_MAX_KEYS];
  		List	   *partexprs = NIL;
  
  		partnatts = list_length(stmt->partspec->partParams);
  
  		/* Protect fixed-size arrays here and in executor */
  		if (partnatts > PARTITION_MAX_KEYS)
  			ereport(ERROR,
  					(errcode(ERRCODE_TOO_MANY_COLUMNS),
  					 errmsg("cannot partition using more than %d columns",
  							PARTITION_MAX_KEYS)));
  
  		/*
  		 * We need to transform the raw parsetrees corresponding to partition
  		 * expressions into executable expression trees.  Like column defaults
  		 * and CHECK constraints, we could not have done the transformation
  		 * earlier.
  		 */
  		stmt->partspec = transformPartitionSpec(rel, stmt->partspec,
  												&strategy);
  
  		ComputePartitionAttrs(rel, stmt->partspec->partParams,
  							  partattrs, &partexprs, partopclass,
  							  partcollation, strategy);
  
  		StorePartitionKey(rel, strategy, partnatts, partattrs, partexprs,
  						  partopclass, partcollation);
  
  		/* make it all visible */
  		CommandCounterIncrement();
  	}
  
  	/*
  	 * If we're creating a partition, create now all the indexes, triggers,
  	 * FKs defined in the parent.
  	 *
  	 * We can't do it earlier, because DefineIndex wants to know the partition
  	 * key which we just stored.
  	 */
  	if (stmt->partbound)
  	{
  		Oid			parentId = linitial_oid(inheritOids);
  		Relation	parent;
  		List	   *idxlist;
  		ListCell   *cell;
  
  		/* Already have strong enough lock on the parent */
  		parent = heap_open(parentId, NoLock);
  		idxlist = RelationGetIndexList(parent);
  
  		/*
  		 * For each index in the parent table, create one in the partition
  		 */
  		foreach(cell, idxlist)
  		{
  			Relation	idxRel = index_open(lfirst_oid(cell), AccessShareLock);
  			AttrNumber *attmap;
  			IndexStmt  *idxstmt;
  			Oid			constraintOid;
  
  			attmap = convert_tuples_by_name_map(RelationGetDescr(rel),
  												RelationGetDescr(parent),
  												gettext_noop("could not convert row type"));
  			idxstmt =
  				generateClonedIndexStmt(NULL, RelationGetRelid(rel), idxRel,
  										attmap, RelationGetDescr(rel)->natts,
  										&constraintOid);
  			DefineIndex(RelationGetRelid(rel),
  						idxstmt,
  						InvalidOid,
  						RelationGetRelid(idxRel),
  						constraintOid,
  						false, false, false, false, false);
  
  			index_close(idxRel, AccessShareLock);
  		}
  
  		list_free(idxlist);
  
  		/*
  		 * If there are any row-level triggers, clone them to the new
  		 * partition.
  		 */
  		if (parent->trigdesc != NULL)
  			CloneRowTriggersToPartition(parent, rel);
  
  		/*
  		 * And foreign keys too.  Note that because we're freshly creating the
  		 * table, there is no need to verify these new constraints.
  		 */
  		CloneForeignKeyConstraints(parentId, relationId, NULL);
  
  		heap_close(parent, NoLock);
  	}
  
  	/*
  	 * Now add any newly specified column default values and CHECK constraints
  	 * to the new relation.  These are passed to us in the form of raw
  	 * parsetrees; we need to transform them to executable expression trees
  	 * before they can be added. The most convenient way to do that is to
  	 * apply the parser's transformExpr routine, but transformExpr doesn't
  	 * work unless we have a pre-existing relation. So, the transformation has
  	 * to be postponed to this final step of CREATE TABLE.
  	 */
  	if (rawDefaults || stmt->constraints)
  		AddRelationNewConstraints(rel, rawDefaults, stmt->constraints,
  								true, true, false, queryString);
  
  	ObjectAddressSet(address, RelationRelationId, relationId);
  
  	/*
  	 * Clean up.  We keep lock on new relation (although it shouldn't be
  	 * visible to anyone else anyway, until commit).
  	 */
  	relation_close(rel, NoLock);
  
  	return address;
  }
  
  /*
   * Emit the right error or warning message for a "DROP" command issued on a
   * non-existent relation
   */
  static void
  DropErrorMsgNonExistent(RangeVar *rel, char rightkind, bool missing_ok)
  {
  	const struct dropmsgstrings *rentry;
  
  	if (rel->schemaname != NULL &&
  		!OidIsValid(LookupNamespaceNoError(rel->schemaname)))
  	{
  		if (!missing_ok)
  		{
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_SCHEMA),
  					 errmsg("schema \"%s\" does not exist", rel->schemaname)));
  		}
  		else
  		{
  			ereport(NOTICE,
  					(errmsg("schema \"%s\" does not exist, skipping",
  							rel->schemaname)));
  		}
  		return;
  	}
  
  	for (rentry = dropmsgstringarray; rentry->kind != '\0'; rentry++)
  	{
  		if (rentry->kind == rightkind)
  		{
  			if (!missing_ok)
  			{
  				ereport(ERROR,
  						(errcode(rentry->nonexistent_code),
  						 errmsg(rentry->nonexistent_msg, rel->relname)));
  			}
  			else
  			{
  				ereport(NOTICE, (errmsg(rentry->skipping_msg, rel->relname)));
  				break;
  			}
  		}
  	}
  
  	Assert(rentry->kind != '\0');	/* Should be impossible */
  }
  
  /*
   * Emit the right error message for a "DROP" command issued on a
   * relation of the wrong type
   */
  static void
  DropErrorMsgWrongType(const char *relname, char wrongkind, char rightkind)
  {
  	const struct dropmsgstrings *rentry;
  	const struct dropmsgstrings *wentry;
  
  	for (rentry = dropmsgstringarray; rentry->kind != '\0'; rentry++)
  		if (rentry->kind == rightkind)
  			break;
  	Assert(rentry->kind != '\0');
  
  	for (wentry = dropmsgstringarray; wentry->kind != '\0'; wentry++)
  		if (wentry->kind == wrongkind)
  			break;
  	/* wrongkind could be something we don't have in our table... */
  
  	ereport(ERROR,
  			(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  			 errmsg(rentry->nota_msg, relname),
  			 (wentry->kind != '\0') ? errhint("%s", _(wentry->drophint_msg)) : 0));
  }
  
  /*
   * RemoveRelations
   *		Implements DROP TABLE, DROP INDEX, DROP SEQUENCE, DROP VIEW,
   *		DROP MATERIALIZED VIEW, DROP FOREIGN TABLE
   */
  void
  RemoveRelations(DropStmt *drop)
  {
  	ObjectAddresses *objects;
  	char		relkind;
  	ListCell   *cell;
  	int			flags = 0;
  	LOCKMODE	lockmode = AccessExclusiveLock;
  
  	/* DROP CONCURRENTLY uses a weaker lock, and has some restrictions */
  	if (drop->concurrent)
  	{
  		flags |= PERFORM_DELETION_CONCURRENTLY;
  		lockmode = ShareUpdateExclusiveLock;
  		Assert(drop->removeType == OBJECT_INDEX);
  		if (list_length(drop->objects) != 1)
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("DROP INDEX CONCURRENTLY does not support dropping multiple objects")));
  		if (drop->behavior == DROP_CASCADE)
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("DROP INDEX CONCURRENTLY does not support CASCADE")));
  	}
  
  	/*
  	 * First we identify all the relations, then we delete them in a single
  	 * performMultipleDeletions() call.  This is to avoid unwanted DROP
  	 * RESTRICT errors if one of the relations depends on another.
  	 */
  
  	/* Determine required relkind */
  	switch (drop->removeType)
  	{
  		case OBJECT_TABLE:
  			relkind = RELKIND_RELATION;
  			break;
  
  		case OBJECT_INDEX:
  			relkind = RELKIND_INDEX;
  			break;
  
  		case OBJECT_SEQUENCE:
  			relkind = RELKIND_SEQUENCE;
  			break;
  
  		case OBJECT_VIEW:
  			relkind = RELKIND_VIEW;
  			break;
  
  		case OBJECT_MATVIEW:
  			relkind = RELKIND_MATVIEW;
  			break;
  
  		case OBJECT_FOREIGN_TABLE:
  			relkind = RELKIND_FOREIGN_TABLE;
  			break;
  
  		default:
  			elog(ERROR, "unrecognized drop object type: %d",
  				 (int) drop->removeType);
  			relkind = 0;		/* keep compiler quiet */
  			break;
  	}
  
  	/* Lock and validate each relation; build a list of object addresses */
  	objects = new_object_addresses();
  
  	foreach(cell, drop->objects)
  	{
  		RangeVar   *rel = makeRangeVarFromNameList((List *) lfirst(cell));
  		Oid			relOid;
  		ObjectAddress obj;
  		struct DropRelationCallbackState state;
  
  		/*
  		 * These next few steps are a great deal like relation_openrv, but we
  		 * don't bother building a relcache entry since we don't need it.
  		 *
  		 * Check for shared-cache-inval messages before trying to access the
  		 * relation.  This is needed to cover the case where the name
  		 * identifies a rel that has been dropped and recreated since the
  		 * start of our transaction: if we don't flush the old syscache entry,
  		 * then we'll latch onto that entry and suffer an error later.
  		 */
  		AcceptInvalidationMessages();
  
  		/* Look up the appropriate relation using namespace search. */
  		state.relkind = relkind;
  		state.heapOid = InvalidOid;
  		state.partParentOid = InvalidOid;
  		state.concurrent = drop->concurrent;
  		relOid = RangeVarGetRelidExtended(rel, lockmode, RVR_MISSING_OK,
  										  RangeVarCallbackForDropRelation,
  										  (void *) &state);
  
  		/* Not there? */
  		if (!OidIsValid(relOid))
  		{
  			DropErrorMsgNonExistent(rel, relkind, drop->missing_ok);
  			continue;
  		}
  
  		/* OK, we're ready to delete this one */
  		obj.classId = RelationRelationId;
  		obj.objectId = relOid;
  		obj.objectSubId = 0;
  
  		add_exact_object_address(&obj, objects);
  	}
  
  	performMultipleDeletions(objects, drop->behavior, flags);
  
  	free_object_addresses(objects);
  }
  
  /*
   * Before acquiring a table lock, check whether we have sufficient rights.
   * In the case of DROP INDEX, also try to lock the table before the index.
   * Also, if the table to be dropped is a partition, we try to lock the parent
   * first.
   */
  static void
  RangeVarCallbackForDropRelation(const RangeVar *rel, Oid relOid, Oid oldRelOid,
  								void *arg)
  {
  	HeapTuple	tuple;
  	struct DropRelationCallbackState *state;
  	char		relkind;
  	char		expected_relkind;
  	bool		is_partition;
  	Form_pg_class classform;
  	LOCKMODE	heap_lockmode;
  
  	state = (struct DropRelationCallbackState *) arg;
  	relkind = state->relkind;
  	heap_lockmode = state->concurrent ?
  		ShareUpdateExclusiveLock : AccessExclusiveLock;
  
  	/*
  	 * If we previously locked some other index's heap, and the name we're
  	 * looking up no longer refers to that relation, release the now-useless
  	 * lock.
  	 */
  	if (relOid != oldRelOid && OidIsValid(state->heapOid))
  	{
  		UnlockRelationOid(state->heapOid, heap_lockmode);
  		state->heapOid = InvalidOid;
  	}
  
  	/*
  	 * Similarly, if we previously locked some other partition's heap, and the
  	 * name we're looking up no longer refers to that relation, release the
  	 * now-useless lock.
  	 */
  	if (relOid != oldRelOid && OidIsValid(state->partParentOid))
  	{
  		UnlockRelationOid(state->partParentOid, AccessExclusiveLock);
  		state->partParentOid = InvalidOid;
  	}
  
  	/* Didn't find a relation, so no need for locking or permission checks. */
  	if (!OidIsValid(relOid))
  		return;
  
  	tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relOid));
  	if (!HeapTupleIsValid(tuple))
  		return;					/* concurrently dropped, so nothing to do */
  	classform = (Form_pg_class) GETSTRUCT(tuple);
  	is_partition = classform->relispartition;
  
  	/*
  	 * Both RELKIND_RELATION and RELKIND_PARTITIONED_TABLE are OBJECT_TABLE,
  	 * but RemoveRelations() can only pass one relkind for a given relation.
  	 * It chooses RELKIND_RELATION for both regular and partitioned tables.
  	 * That means we must be careful before giving the wrong type error when
  	 * the relation is RELKIND_PARTITIONED_TABLE.  An equivalent problem
  	 * exists with indexes.
  	 */
  	if (classform->relkind == RELKIND_PARTITIONED_TABLE)
  		expected_relkind = RELKIND_RELATION;
  	else if (classform->relkind == RELKIND_PARTITIONED_INDEX)
  		expected_relkind = RELKIND_INDEX;
  	else
  		expected_relkind = classform->relkind;
  
  	if (relkind != expected_relkind)
  		DropErrorMsgWrongType(rel->relname, classform->relkind, relkind);
  
  	/* Allow DROP to either table owner or schema owner */
  	if (!pg_class_ownercheck(relOid, GetUserId()) &&
  		!pg_namespace_ownercheck(classform->relnamespace, GetUserId()))
  		aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(get_rel_relkind(relOid)),
  					   rel->relname);
  
  	if (!allowSystemTableMods && IsSystemClass(relOid, classform))
  		ereport(ERROR,
  				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  				 errmsg("permission denied: \"%s\" is a system catalog",
  						rel->relname)));
  
  	ReleaseSysCache(tuple);
  
  	/*
  	 * In DROP INDEX, attempt to acquire lock on the parent table before
  	 * locking the index.  index_drop() will need this anyway, and since
  	 * regular queries lock tables before their indexes, we risk deadlock if
  	 * we do it the other way around.  No error if we don't find a pg_index
  	 * entry, though --- the relation may have been dropped.
  	 */
  	if ((relkind == RELKIND_INDEX || relkind == RELKIND_PARTITIONED_INDEX) &&
  		relOid != oldRelOid)
  	{
  		state->heapOid = IndexGetRelation(relOid, true);
  		if (OidIsValid(state->heapOid))
  			LockRelationOid(state->heapOid, heap_lockmode);
  	}
  
  	/*
  	 * Similarly, if the relation is a partition, we must acquire lock on its
  	 * parent before locking the partition.  That's because queries lock the
  	 * parent before its partitions, so we risk deadlock it we do it the other
  	 * way around.
  	 */
  	if (is_partition && relOid != oldRelOid)
  	{
  		state->partParentOid = get_partition_parent(relOid);
  		if (OidIsValid(state->partParentOid))
  			LockRelationOid(state->partParentOid, AccessExclusiveLock);
  	}
  }
  
  /*
   * ExecuteTruncate
   *		Executes a TRUNCATE command.
   *
   * This is a multi-relation truncate.  We first open and grab exclusive
   * lock on all relations involved, checking permissions and otherwise
   * verifying that the relation is OK for truncation.  In CASCADE mode,
   * relations having FK references to the targeted relations are automatically
   * added to the group; in RESTRICT mode, we check that all FK references are
   * internal to the group that's being truncated.  Finally all the relations
   * are truncated and reindexed.
   */
  void
  ExecuteTruncate(TruncateStmt *stmt)
  {
  	List	   *rels = NIL;
  	List	   *relids = NIL;
  	List	   *relids_logged = NIL;
  	ListCell   *cell;
  
  	/*
  	 * Open, exclusive-lock, and check all the explicitly-specified relations
  	 */
  	foreach(cell, stmt->relations)
  	{
  		RangeVar   *rv = lfirst(cell);
  		Relation	rel;
  		bool		recurse = rv->inh;
  		Oid			myrelid;
  		LOCKMODE	lockmode = AccessExclusiveLock;
  
  		rel = heap_openrv(rv, lockmode);
  		myrelid = RelationGetRelid(rel);
  		/* don't throw error for "TRUNCATE foo, foo" */
  		if (list_member_oid(relids, myrelid))
  		{
  			heap_close(rel, lockmode);
  			continue;
  		}
  		truncate_check_rel(rel);
  		rels = lappend(rels, rel);
  		relids = lappend_oid(relids, myrelid);
  		/* Log this relation only if needed for logical decoding */
  		if (RelationIsLogicallyLogged(rel))
  			relids_logged = lappend_oid(relids_logged, myrelid);
  
  		if (recurse)
  		{
  			ListCell   *child;
  			List	   *children;
  
  			children = find_all_inheritors(myrelid, lockmode, NULL);
  
  			foreach(child, children)
  			{
  				Oid			childrelid = lfirst_oid(child);
  
  				if (list_member_oid(relids, childrelid))
  					continue;
  
  				/* find_all_inheritors already got lock */
  				rel = heap_open(childrelid, NoLock);
  
  				/*
  				 * It is possible that the parent table has children that are
  				 * temp tables of other backends.  We cannot safely access
  				 * such tables (because of buffering issues), and the best
  				 * thing to do is to silently ignore them.  Note that this
  				 * check is the same as one of the checks done in
  				 * truncate_check_rel() called below, still it is kept
  				 * here for simplicity.
  				 */
  				if (RELATION_IS_OTHER_TEMP(rel))
  				{
  					heap_close(rel, lockmode);
  					continue;
  				}
  
  				truncate_check_rel(rel);
  				rels = lappend(rels, rel);
  				relids = lappend_oid(relids, childrelid);
  				/* Log this relation only if needed for logical decoding */
  				if (RelationIsLogicallyLogged(rel))
  					relids_logged = lappend_oid(relids_logged, childrelid);
  			}
  		}
  		else if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("cannot truncate only a partitioned table"),
  					 errhint("Do not specify the ONLY keyword, or use TRUNCATE ONLY on the partitions directly.")));
  	}
  
  	ExecuteTruncateGuts(rels, relids, relids_logged,
  						stmt->behavior, stmt->restart_seqs);
  
  	/* And close the rels */
  	foreach(cell, rels)
  	{
  		Relation	rel = (Relation) lfirst(cell);
  
  		heap_close(rel, NoLock);
  	}
  }
  
  /*
   * ExecuteTruncateGuts
   *
   * Internal implementation of TRUNCATE.  This is called by the actual TRUNCATE
   * command (see above) as well as replication subscribers that execute a
   * replicated TRUNCATE action.
   *
   * explicit_rels is the list of Relations to truncate that the command
   * specified.  relids is the list of Oids corresponding to explicit_rels.
   * relids_logged is the list of Oids (a subset of relids) that require
   * WAL-logging.  This is all a bit redundant, but the existing callers have
   * this information handy in this form.
   */
  void
  ExecuteTruncateGuts(List *explicit_rels, List *relids, List *relids_logged,
  					DropBehavior behavior, bool restart_seqs)
  {
  	List	   *rels;
  	List	   *seq_relids = NIL;
  	EState	   *estate;
  	ResultRelInfo *resultRelInfos;
  	ResultRelInfo *resultRelInfo;
  	SubTransactionId mySubid;
  	ListCell   *cell;
  	Oid		   *logrelids;
  
  	/*
  	 * Check the explicitly-specified relations.
  	 *
  	 * In CASCADE mode, suck in all referencing relations as well.  This
  	 * requires multiple iterations to find indirectly-dependent relations. At
  	 * each phase, we need to exclusive-lock new rels before looking for their
  	 * dependencies, else we might miss something.  Also, we check each rel as
  	 * soon as we open it, to avoid a faux pas such as holding lock for a long
  	 * time on a rel we have no permissions for.
  	 */
  	rels = list_copy(explicit_rels);
  	if (behavior == DROP_CASCADE)
  	{
  		for (;;)
  		{
  			List	   *newrelids;
  
  			newrelids = heap_truncate_find_FKs(relids);
  			if (newrelids == NIL)
  				break;			/* nothing else to add */
  
  			foreach(cell, newrelids)
  			{
  				Oid			relid = lfirst_oid(cell);
  				Relation	rel;
  
  				rel = heap_open(relid, AccessExclusiveLock);
  				ereport(NOTICE,
  						(errmsg("truncate cascades to table \"%s\"",
  								RelationGetRelationName(rel))));
  				truncate_check_rel(rel);
  				rels = lappend(rels, rel);
  				relids = lappend_oid(relids, relid);
  				/* Log this relation only if needed for logical decoding */
  				if (RelationIsLogicallyLogged(rel))
  					relids_logged = lappend_oid(relids_logged, relid);
  			}
  		}
  	}
  
  	/*
  	 * Check foreign key references.  In CASCADE mode, this should be
  	 * unnecessary since we just pulled in all the references; but as a
  	 * cross-check, do it anyway if in an Assert-enabled build.
  	 */
  #ifdef USE_ASSERT_CHECKING
  	heap_truncate_check_FKs(rels, false);
  #else
  	if (behavior == DROP_RESTRICT)
  		heap_truncate_check_FKs(rels, false);
  #endif
  
  	/*
  	 * If we are asked to restart sequences, find all the sequences, lock them
  	 * (we need AccessExclusiveLock for ResetSequence), and check permissions.
  	 * We want to do this early since it's pointless to do all the truncation
  	 * work only to fail on sequence permissions.
  	 */
  	if (restart_seqs)
  	{
  		foreach(cell, rels)
  		{
  			Relation	rel = (Relation) lfirst(cell);
  			List	   *seqlist = getOwnedSequences(RelationGetRelid(rel), 0);
  			ListCell   *seqcell;
  
  			foreach(seqcell, seqlist)
  			{
  				Oid			seq_relid = lfirst_oid(seqcell);
  				Relation	seq_rel;
  
  				seq_rel = relation_open(seq_relid, AccessExclusiveLock);
  
  				/* This check must match AlterSequence! */
  				if (!pg_class_ownercheck(seq_relid, GetUserId()))
  					aclcheck_error(ACLCHECK_NOT_OWNER, OBJECT_SEQUENCE,
  								   RelationGetRelationName(seq_rel));
  
  				seq_relids = lappend_oid(seq_relids, seq_relid);
  
  				relation_close(seq_rel, NoLock);
  			}
  		}
  	}
  
  	/* Prepare to catch AFTER triggers. */
  	AfterTriggerBeginQuery();
  
  	/*
  	 * To fire triggers, we'll need an EState as well as a ResultRelInfo for
  	 * each relation.  We don't need to call ExecOpenIndices, though.
  	 */
  	estate = CreateExecutorState();
  	resultRelInfos = (ResultRelInfo *)
  		palloc(list_length(rels) * sizeof(ResultRelInfo));
  	resultRelInfo = resultRelInfos;
  	foreach(cell, rels)
  	{
  		Relation	rel = (Relation) lfirst(cell);
  
  		InitResultRelInfo(resultRelInfo,
  						  rel,
  						  0,	/* dummy rangetable index */
  						  NULL,
  						  0);
  		resultRelInfo++;
  	}
  	estate->es_result_relations = resultRelInfos;
  	estate->es_num_result_relations = list_length(rels);
  
  	/*
  	 * Process all BEFORE STATEMENT TRUNCATE triggers before we begin
  	 * truncating (this is because one of them might throw an error). Also, if
  	 * we were to allow them to prevent statement execution, that would need
  	 * to be handled here.
  	 */
  	resultRelInfo = resultRelInfos;
  	foreach(cell, rels)
  	{
  		estate->es_result_relation_info = resultRelInfo;
  		ExecBSTruncateTriggers(estate, resultRelInfo);
  		resultRelInfo++;
  	}
  
  	/*
  	 * OK, truncate each table.
  	 */
  	mySubid = GetCurrentSubTransactionId();
  
  	foreach(cell, rels)
  	{
  		Relation	rel = (Relation) lfirst(cell);
  
  		/* Skip partitioned tables as there is nothing to do */
  		if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  			continue;
  
  		/*
  		 * Normally, we need a transaction-safe truncation here.  However, if
  		 * the table was either created in the current (sub)transaction or has
  		 * a new relfilenode in the current (sub)transaction, then we can just
  		 * truncate it in-place, because a rollback would cause the whole
  		 * table or the current physical file to be thrown away anyway.
  		 */
  		if (IsYBRelation(rel))
  		{
  			// Call YugaByte API to truncate tables.
  			YBCTruncateTable(rel);
  		}
  		else if (rel->rd_createSubid == mySubid ||
  				 rel->rd_newRelfilenodeSubid == mySubid)
  		{
  			/* Immediate, non-rollbackable truncation is OK */
  			heap_truncate_one_rel(rel);
  		}
  		else
  		{
  			Oid			heap_relid;
  			Oid			toast_relid;
  			MultiXactId minmulti;
  
  			/*
  			 * This effectively deletes all rows in the table, and may be done
  			 * in a serializable transaction.  In that case we must record a
  			 * rw-conflict in to this transaction from each transaction
  			 * holding a predicate lock on the table.
  			 */
  			CheckTableForSerializableConflictIn(rel);
  
  			minmulti = GetOldestMultiXactId();
  
  			/*
  			 * Need the full transaction-safe pushups.
  			 *
  			 * Create a new empty storage file for the relation, and assign it
  			 * as the relfilenode value. The old storage file is scheduled for
  			 * deletion at commit.
  			 */
  			RelationSetNewRelfilenode(rel, rel->rd_rel->relpersistence,
  									  RecentXmin, minmulti);
  			if (rel->rd_rel->relpersistence == RELPERSISTENCE_UNLOGGED)
  				heap_create_init_fork(rel);
  
  			heap_relid = RelationGetRelid(rel);
  
  			/*
  			 * The same for the toast table, if any.
  			 */
  			toast_relid = rel->rd_rel->reltoastrelid;
  			if (OidIsValid(toast_relid))
  			{
  				Relation	toastrel = relation_open(toast_relid,
  													 AccessExclusiveLock);
  
  				RelationSetNewRelfilenode(toastrel,
  										  toastrel->rd_rel->relpersistence,
  										  RecentXmin, minmulti);
  				if (toastrel->rd_rel->relpersistence == RELPERSISTENCE_UNLOGGED)
  					heap_create_init_fork(toastrel);
  				heap_close(toastrel, NoLock);
  			}
  
  			/*
  			 * Reconstruct the indexes to match, and we're done.
  			 */
  			reindex_relation(heap_relid, REINDEX_REL_PROCESS_TOAST, 0);
  		}
  
  		pgstat_count_truncate(rel);
  	}
  
  	/*
  	 * Restart owned sequences if we were asked to.
  	 */
  	foreach(cell, seq_relids)
  	{
  		Oid			seq_relid = lfirst_oid(cell);
  
  		ResetSequence(seq_relid);
  	}
  
  	/*
  	 * Write a WAL record to allow this set of actions to be logically
  	 * decoded.
  	 *
  	 * Assemble an array of relids so we can write a single WAL record for the
  	 * whole action.
  	 */
  	if (list_length(relids_logged) > 0)
  	{
  		xl_heap_truncate xlrec;
  		int			i = 0;
  
  		/* should only get here if wal_level >= logical */
  		Assert(XLogLogicalInfoActive());
  
  		logrelids = palloc(list_length(relids_logged) * sizeof(Oid));
  		foreach(cell, relids_logged)
  			logrelids[i++] = lfirst_oid(cell);
  
  		xlrec.dbId = MyDatabaseId;
  		xlrec.nrelids = list_length(relids_logged);
  		xlrec.flags = 0;
  		if (behavior == DROP_CASCADE)
  			xlrec.flags |= XLH_TRUNCATE_CASCADE;
  		if (restart_seqs)
  			xlrec.flags |= XLH_TRUNCATE_RESTART_SEQS;
  
  		XLogBeginInsert();
  		XLogRegisterData((char *) &xlrec, SizeOfHeapTruncate);
  		XLogRegisterData((char *) logrelids, list_length(relids_logged) * sizeof(Oid));
  
  		XLogSetRecordFlags(XLOG_INCLUDE_ORIGIN);
  
  		(void) XLogInsert(RM_HEAP_ID, XLOG_HEAP_TRUNCATE);
  	}
  
  	/*
  	 * Process all AFTER STATEMENT TRUNCATE triggers.
  	 */
  	resultRelInfo = resultRelInfos;
  	foreach(cell, rels)
  	{
  		estate->es_result_relation_info = resultRelInfo;
  		ExecASTruncateTriggers(estate, resultRelInfo);
  		resultRelInfo++;
  	}
  
  	/* Handle queued AFTER triggers */
  	AfterTriggerEndQuery(estate);
  
  	/* We can clean up the EState now */
  	FreeExecutorState(estate);
  
  	/*
  	 * Close any rels opened by CASCADE (can't do this while EState still
  	 * holds refs)
  	 */
  	rels = list_difference_ptr(rels, explicit_rels);
  	foreach(cell, rels)
  	{
  		Relation	rel = (Relation) lfirst(cell);
  
  		heap_close(rel, NoLock);
  	}
  }
  
  /*
   * Check that a given rel is safe to truncate.  Subroutine for ExecuteTruncate
   */
  static void
  truncate_check_rel(Relation rel)
  {
  	AclResult	aclresult;
  
  	/*
  	 * Only allow truncate on regular tables and partitioned tables (although,
  	 * the latter are only being included here for the following checks; no
  	 * physical truncation will occur in their case.)
  	 */
  	if (rel->rd_rel->relkind != RELKIND_RELATION &&
  		rel->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is not a table",
  						RelationGetRelationName(rel))));
  
  	/* Permissions checks */
  	aclresult = pg_class_aclcheck(RelationGetRelid(rel), GetUserId(),
  								  ACL_TRUNCATE);
  	if (aclresult != ACLCHECK_OK)
  		aclcheck_error(aclresult, get_relkind_objtype(rel->rd_rel->relkind),
  					   RelationGetRelationName(rel));
  
  	if (!allowSystemTableMods && IsSystemRelation(rel))
  		ereport(ERROR,
  				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  				 errmsg("permission denied: \"%s\" is a system catalog",
  						RelationGetRelationName(rel))));
  
  	/*
  	 * Don't allow truncate on temp tables of other backends ... their local
  	 * buffer manager is not going to cope.
  	 */
  	if (RELATION_IS_OTHER_TEMP(rel))
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot truncate temporary tables of other sessions")));
  
  	/*
  	 * Also check for active uses of the relation in the current transaction,
  	 * including open scans and pending AFTER trigger events.
  	 */
  	CheckTableNotInUse(rel, "TRUNCATE");
  }
  
  /*
   * storage_name
   *	  returns the name corresponding to a typstorage/attstorage enum value
   */
  static const char *
  storage_name(char c)
  {
  	switch (c)
  	{
  		case 'p':
  			return "PLAIN";
  		case 'm':
  			return "MAIN";
  		case 'x':
  			return "EXTENDED";
  		case 'e':
  			return "EXTERNAL";
  		default:
  			return "???";
  	}
  }
  
  /*----------
   * MergeAttributes
   *		Returns new schema given initial schema and superclasses.
   *
   * Input arguments:
   * 'schema' is the column/attribute definition for the table. (It's a list
   *		of ColumnDef's.) It is destructively changed.
   * 'supers' is a list of names (as RangeVar nodes) of parent relations.
   * 'relpersistence' is a persistence type of the table.
   * 'is_partition' tells if the table is a partition
   *
   * Output arguments:
   * 'supOids' receives a list of the OIDs of the parent relations.
   * 'supconstr' receives a list of constraints belonging to the parents,
   *		updated as necessary to be valid for the child.
   * 'supOidCount' is set to the number of parents that have OID columns.
   *
   * Return value:
   * Completed schema list.
   *
   * Notes:
   *	  The order in which the attributes are inherited is very important.
   *	  Intuitively, the inherited attributes should come first. If a table
   *	  inherits from multiple parents, the order of those attributes are
   *	  according to the order of the parents specified in CREATE TABLE.
   *
   *	  Here's an example:
   *
   *		create table person (name text, age int4, location point);
   *		create table emp (salary int4, manager text) inherits(person);
   *		create table student (gpa float8) inherits (person);
   *		create table stud_emp (percent int4) inherits (emp, student);
   *
   *	  The order of the attributes of stud_emp is:
   *
   *							person {1:name, 2:age, 3:location}
   *							/	 \
   *			   {6:gpa}	student   emp {4:salary, 5:manager}
   *							\	 /
   *						   stud_emp {7:percent}
   *
   *	   If the same attribute name appears multiple times, then it appears
   *	   in the result table in the proper location for its first appearance.
   *
   *	   Constraints (including NOT NULL constraints) for the child table
   *	   are the union of all relevant constraints, from both the child schema
   *	   and parent tables.
   *
   *	   The default value for a child column is defined as:
   *		(1) If the child schema specifies a default, that value is used.
   *		(2) If neither the child nor any parent specifies a default, then
   *			the column will not have a default.
   *		(3) If conflicting defaults are inherited from different parents
   *			(and not overridden by the child), an error is raised.
   *		(4) Otherwise the inherited default is used.
   *		Rule (3) is new in Postgres 7.1; in earlier releases you got a
   *		rather arbitrary choice of which parent default to use.
   *----------
   */
  static List *
  MergeAttributes(List *schema, List *supers, char relpersistence,
  				bool is_partition, List **supOids, List **supconstr,
  				int *supOidCount)
  {
  	ListCell   *entry;
  	List	   *inhSchema = NIL;
  	List	   *parentOids = NIL;
  	List	   *constraints = NIL;
  	int			parentsWithOids = 0;
  	bool		have_bogus_defaults = false;
  	int			child_attno;
  	static Node bogus_marker = {0}; /* marks conflicting defaults */
  	List	   *saved_schema = NIL;
  
  	/*
  	 * Check for and reject tables with too many columns. We perform this
  	 * check relatively early for two reasons: (a) we don't run the risk of
  	 * overflowing an AttrNumber in subsequent code (b) an O(n^2) algorithm is
  	 * okay if we're processing <= 1600 columns, but could take minutes to
  	 * execute if the user attempts to create a table with hundreds of
  	 * thousands of columns.
  	 *
  	 * Note that we also need to check that we do not exceed this figure after
  	 * including columns from inherited relations.
  	 */
  	if (list_length(schema) > MaxHeapAttributeNumber)
  		ereport(ERROR,
  				(errcode(ERRCODE_TOO_MANY_COLUMNS),
  				 errmsg("tables can have at most %d columns",
  						MaxHeapAttributeNumber)));
  
  	/*
  	 * Check for duplicate names in the explicit list of attributes.
  	 *
  	 * Although we might consider merging such entries in the same way that we
  	 * handle name conflicts for inherited attributes, it seems to make more
  	 * sense to assume such conflicts are errors.
  	 */
  	foreach(entry, schema)
  	{
  		ColumnDef  *coldef = lfirst(entry);
  		ListCell   *rest = lnext(entry);
  		ListCell   *prev = entry;
  
  		if (!is_partition && coldef->typeName == NULL)
  		{
  			/*
  			 * Typed table column option that does not belong to a column from
  			 * the type.  This works because the columns from the type come
  			 * first in the list.  (We omit this check for partition column
  			 * lists; those are processed separately below.)
  			 */
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_COLUMN),
  					 errmsg("column \"%s\" does not exist",
  							coldef->colname)));
  		}
  
  		while (rest != NULL)
  		{
  			ColumnDef  *restdef = lfirst(rest);
  			ListCell   *next = lnext(rest); /* need to save it in case we
  											 * delete it */
  
  			if (strcmp(coldef->colname, restdef->colname) == 0)
  			{
  				if (coldef->is_from_type)
  				{
  					/*
  					 * merge the column options into the column from the type
  					 */
  					coldef->is_not_null = restdef->is_not_null;
  					coldef->raw_default = restdef->raw_default;
  					coldef->cooked_default = restdef->cooked_default;
  					coldef->constraints = restdef->constraints;
  					coldef->is_from_type = false;
  					list_delete_cell(schema, rest, prev);
  				}
  				else
  					ereport(ERROR,
  							(errcode(ERRCODE_DUPLICATE_COLUMN),
  							 errmsg("column \"%s\" specified more than once",
  									coldef->colname)));
  			}
  			prev = rest;
  			rest = next;
  		}
  	}
  
  	/*
  	 * In case of a partition, there are no new column definitions, only dummy
  	 * ColumnDefs created for column constraints.  Set them aside for now and
  	 * process them at the end.
  	 */
  	if (is_partition)
  	{
  		saved_schema = schema;
  		schema = NIL;
  	}
  
  	/*
  	 * Scan the parents left-to-right, and merge their attributes to form a
  	 * list of inherited attributes (inhSchema).  Also check to see if we need
  	 * to inherit an OID column.
  	 */
  	child_attno = 0;
  	foreach(entry, supers)
  	{
  		RangeVar   *parent = (RangeVar *) lfirst(entry);
  		Relation	relation;
  		TupleDesc	tupleDesc;
  		TupleConstr *constr;
  		AttrNumber *newattno;
  		AttrNumber	parent_attno;
  
  		/*
  		 * A self-exclusive lock is needed here.  If two backends attempt to
  		 * add children to the same parent simultaneously, and that parent has
  		 * no pre-existing children, then both will attempt to update the
  		 * parent's relhassubclass field, leading to a "tuple concurrently
  		 * updated" error.  Also, this interlocks against a concurrent ANALYZE
  		 * on the parent table, which might otherwise be attempting to clear
  		 * the parent's relhassubclass field, if its previous children were
  		 * recently dropped.
  		 *
  		 * If the child table is a partition, then we instead grab an
  		 * exclusive lock on the parent because its partition descriptor will
  		 * be changed by addition of the new partition.
  		 */
  		if (!is_partition)
  			relation = heap_openrv(parent, ShareUpdateExclusiveLock);
  		else
  			relation = heap_openrv(parent, AccessExclusiveLock);
  
  		/*
  		 * Check for active uses of the parent partitioned table in the
  		 * current transaction, such as being used in some manner by an
  		 * enclosing command.
  		 */
  		if (is_partition)
  			CheckTableNotInUse(relation, "CREATE TABLE .. PARTITION OF");
  
  		/*
  		 * We do not allow partitioned tables and partitions to participate in
  		 * regular inheritance.
  		 */
  		if (relation->rd_rel->relkind == RELKIND_PARTITIONED_TABLE &&
  			!is_partition)
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("cannot inherit from partitioned table \"%s\"",
  							parent->relname)));
  		if (relation->rd_rel->relispartition && !is_partition)
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("cannot inherit from partition \"%s\"",
  							parent->relname)));
  
  		if (relation->rd_rel->relkind != RELKIND_RELATION &&
  			relation->rd_rel->relkind != RELKIND_FOREIGN_TABLE &&
  			relation->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("inherited relation \"%s\" is not a table or foreign table",
  							parent->relname)));
  
  		/*
  		 * If the parent is permanent, so must be all of its partitions.  Note
  		 * that inheritance allows that case.
  		 */
  		if (is_partition &&
  			relation->rd_rel->relpersistence != RELPERSISTENCE_TEMP &&
  			relpersistence == RELPERSISTENCE_TEMP)
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("cannot create a temporary relation as partition of permanent relation \"%s\"",
  							RelationGetRelationName(relation))));
  
  		/* Permanent rels cannot inherit from temporary ones */
  		if (relpersistence != RELPERSISTENCE_TEMP &&
  			relation->rd_rel->relpersistence == RELPERSISTENCE_TEMP)
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg(!is_partition
  							? "cannot inherit from temporary relation \"%s\""
  							: "cannot create a permanent relation as partition of temporary relation \"%s\"",
  							parent->relname)));
  
  		/* If existing rel is temp, it must belong to this session */
  		if (relation->rd_rel->relpersistence == RELPERSISTENCE_TEMP &&
  			!relation->rd_islocaltemp)
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg(!is_partition
  							? "cannot inherit from temporary relation of another session"
  							: "cannot create as partition of temporary relation of another session")));
  
  		/*
  		 * We should have an UNDER permission flag for this, but for now,
  		 * demand that creator of a child table own the parent.
  		 */
  		if (!pg_class_ownercheck(RelationGetRelid(relation), GetUserId()))
  			aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(relation->rd_rel->relkind),
  						   RelationGetRelationName(relation));
  
  		/*
  		 * Reject duplications in the list of parents.
  		 */
  		if (list_member_oid(parentOids, RelationGetRelid(relation)))
  			ereport(ERROR,
  					(errcode(ERRCODE_DUPLICATE_TABLE),
  					 errmsg("relation \"%s\" would be inherited from more than once",
  							parent->relname)));
  
  		parentOids = lappend_oid(parentOids, RelationGetRelid(relation));
  
  		if (relation->rd_rel->relhasoids)
  			parentsWithOids++;
  
  		tupleDesc = RelationGetDescr(relation);
  		constr = tupleDesc->constr;
  
  		/*
  		 * newattno[] will contain the child-table attribute numbers for the
  		 * attributes of this parent table.  (They are not the same for
  		 * parents after the first one, nor if we have dropped columns.)
  		 */
  		newattno = (AttrNumber *)
  			palloc0(tupleDesc->natts * sizeof(AttrNumber));
  
  		for (parent_attno = 1; parent_attno <= tupleDesc->natts;
  			 parent_attno++)
  		{
  			Form_pg_attribute attribute = TupleDescAttr(tupleDesc,
  														parent_attno - 1);
  			char	   *attributeName = NameStr(attribute->attname);
  			int			exist_attno;
  			ColumnDef  *def;
  
  			/*
  			 * Ignore dropped columns in the parent.
  			 */
  			if (attribute->attisdropped)
  				continue;		/* leave newattno entry as zero */
  
  			/*
  			 * Does it conflict with some previously inherited column?
  			 */
  			exist_attno = findAttrByName(attributeName, inhSchema);
  			if (exist_attno > 0)
  			{
  				Oid			defTypeId;
  				int32		deftypmod;
  				Oid			defCollId;
  
  				/*
  				 * Yes, try to merge the two column definitions. They must
  				 * have the same type, typmod, and collation.
  				 */
  				ereport(NOTICE,
  						(errmsg("merging multiple inherited definitions of column \"%s\"",
  								attributeName)));
  				def = (ColumnDef *) list_nth(inhSchema, exist_attno - 1);
  				typenameTypeIdAndMod(NULL, def->typeName, &defTypeId, &deftypmod);
  				if (defTypeId != attribute->atttypid ||
  					deftypmod != attribute->atttypmod)
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("inherited column \"%s\" has a type conflict",
  									attributeName),
  							 errdetail("%s versus %s",
  									   format_type_with_typemod(defTypeId,
  																deftypmod),
  									   format_type_with_typemod(attribute->atttypid,
  																attribute->atttypmod))));
  				defCollId = GetColumnDefCollation(NULL, def, defTypeId);
  				if (defCollId != attribute->attcollation)
  					ereport(ERROR,
  							(errcode(ERRCODE_COLLATION_MISMATCH),
  							 errmsg("inherited column \"%s\" has a collation conflict",
  									attributeName),
  							 errdetail("\"%s\" versus \"%s\"",
  									   get_collation_name(defCollId),
  									   get_collation_name(attribute->attcollation))));
  
  				/* Copy storage parameter */
  				if (def->storage == 0)
  					def->storage = attribute->attstorage;
  				else if (def->storage != attribute->attstorage)
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("inherited column \"%s\" has a storage parameter conflict",
  									attributeName),
  							 errdetail("%s versus %s",
  									   storage_name(def->storage),
  									   storage_name(attribute->attstorage))));
  
  				def->inhcount++;
  				/* Merge of NOT NULL constraints = OR 'em together */
  				def->is_not_null |= attribute->attnotnull;
  				/* Default and other constraints are handled below */
  				newattno[parent_attno - 1] = exist_attno;
  			}
  			else
  			{
  				/*
  				 * No, create a new inherited column
  				 */
  				def = makeNode(ColumnDef);
  				def->colname = pstrdup(attributeName);
  				def->typeName = makeTypeNameFromOid(attribute->atttypid,
  													attribute->atttypmod);
  				def->inhcount = 1;
  				def->is_local = false;
  				def->is_not_null = attribute->attnotnull;
  				def->is_from_type = false;
  				def->storage = attribute->attstorage;
  				def->raw_default = NULL;
  				def->cooked_default = NULL;
  				def->collClause = NULL;
  				def->collOid = attribute->attcollation;
  				def->constraints = NIL;
  				def->location = -1;
  				inhSchema = lappend(inhSchema, def);
  				newattno[parent_attno - 1] = ++child_attno;
  			}
  
  			/*
  			 * Copy default if any
  			 */
  			if (attribute->atthasdef)
  			{
  				Node	   *this_default = NULL;
  				AttrDefault *attrdef;
  				int			i;
  
  				/* Find default in constraint structure */
  				Assert(constr != NULL);
  				attrdef = constr->defval;
  				for (i = 0; i < constr->num_defval; i++)
  				{
  					if (attrdef[i].adnum == parent_attno)
  					{
  						this_default = stringToNode(attrdef[i].adbin);
  						break;
  					}
  				}
  				Assert(this_default != NULL);
  
  				/*
  				 * If default expr could contain any vars, we'd need to fix
  				 * 'em, but it can't; so default is ready to apply to child.
  				 *
  				 * If we already had a default from some prior parent, check
  				 * to see if they are the same.  If so, no problem; if not,
  				 * mark the column as having a bogus default. Below, we will
  				 * complain if the bogus default isn't overridden by the child
  				 * schema.
  				 */
  				Assert(def->raw_default == NULL);
  				if (def->cooked_default == NULL)
  					def->cooked_default = this_default;
  				else if (!equal(def->cooked_default, this_default))
  				{
  					def->cooked_default = &bogus_marker;
  					have_bogus_defaults = true;
  				}
  			}
  		}
  
  		/*
  		 * Now copy the CHECK constraints of this parent, adjusting attnos
  		 * using the completed newattno[] map.  Identically named constraints
  		 * are merged if possible, else we throw error.
  		 */
  		if (constr && constr->num_check > 0)
  		{
  			ConstrCheck *check = constr->check;
  			int			i;
  
  			for (i = 0; i < constr->num_check; i++)
  			{
  				char	   *name = check[i].ccname;
  				Node	   *expr;
  				bool		found_whole_row;
  
  				/* ignore if the constraint is non-inheritable */
  				if (check[i].ccnoinherit)
  					continue;
  
  				/* Adjust Vars to match new table's column numbering */
  				expr = map_variable_attnos(stringToNode(check[i].ccbin),
  										   1, 0,
  										   newattno, tupleDesc->natts,
  										   InvalidOid, &found_whole_row);
  
  				/*
  				 * For the moment we have to reject whole-row variables. We
  				 * could convert them, if we knew the new table's rowtype OID,
  				 * but that hasn't been assigned yet.
  				 */
  				if (found_whole_row)
  					ereport(ERROR,
  							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  							 errmsg("cannot convert whole-row table reference"),
  							 errdetail("Constraint \"%s\" contains a whole-row reference to table \"%s\".",
  									   name,
  									   RelationGetRelationName(relation))));
  
  				/* check for duplicate */
  				if (!MergeCheckConstraint(constraints, name, expr))
  				{
  					/* nope, this is a new one */
  					CookedConstraint *cooked;
  
  					cooked = (CookedConstraint *) palloc(sizeof(CookedConstraint));
  					cooked->contype = CONSTR_CHECK;
  					cooked->conoid = InvalidOid;	/* until created */
  					cooked->name = pstrdup(name);
  					cooked->attnum = 0; /* not used for constraints */
  					cooked->expr = expr;
  					cooked->skip_validation = false;
  					cooked->is_local = false;
  					cooked->inhcount = 1;
  					cooked->is_no_inherit = false;
  					constraints = lappend(constraints, cooked);
  				}
  			}
  		}
  
  		pfree(newattno);
  
  		/*
  		 * Close the parent rel, but keep our lock on it until xact commit.
  		 * That will prevent someone else from deleting or ALTERing the parent
  		 * before the child is committed.
  		 */
  		heap_close(relation, NoLock);
  	}
  
  	/*
  	 * If we had no inherited attributes, the result schema is just the
  	 * explicitly declared columns.  Otherwise, we need to merge the declared
  	 * columns into the inherited schema list.  Although, we never have any
  	 * explicitly declared columns if the table is a partition.
  	 */
  	if (inhSchema != NIL)
  	{
  		int			schema_attno = 0;
  
  		foreach(entry, schema)
  		{
  			ColumnDef  *newdef = lfirst(entry);
  			char	   *attributeName = newdef->colname;
  			int			exist_attno;
  
  			schema_attno++;
  
  			/*
  			 * Does it conflict with some previously inherited column?
  			 */
  			exist_attno = findAttrByName(attributeName, inhSchema);
  			if (exist_attno > 0)
  			{
  				ColumnDef  *def;
  				Oid			defTypeId,
  							newTypeId;
  				int32		deftypmod,
  							newtypmod;
  				Oid			defcollid,
  							newcollid;
  
  				/*
  				 * Partitions have only one parent and have no column
  				 * definitions of their own, so conflict should never occur.
  				 */
  				Assert(!is_partition);
  
  				/*
  				 * Yes, try to merge the two column definitions. They must
  				 * have the same type, typmod, and collation.
  				 */
  				if (exist_attno == schema_attno)
  					ereport(NOTICE,
  							(errmsg("merging column \"%s\" with inherited definition",
  									attributeName)));
  				else
  					ereport(NOTICE,
  							(errmsg("moving and merging column \"%s\" with inherited definition", attributeName),
  							 errdetail("User-specified column moved to the position of the inherited column.")));
  				def = (ColumnDef *) list_nth(inhSchema, exist_attno - 1);
  				typenameTypeIdAndMod(NULL, def->typeName, &defTypeId, &deftypmod);
  				typenameTypeIdAndMod(NULL, newdef->typeName, &newTypeId, &newtypmod);
  				if (defTypeId != newTypeId || deftypmod != newtypmod)
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("column \"%s\" has a type conflict",
  									attributeName),
  							 errdetail("%s versus %s",
  									   format_type_with_typemod(defTypeId,
  																deftypmod),
  									   format_type_with_typemod(newTypeId,
  																newtypmod))));
  				defcollid = GetColumnDefCollation(NULL, def, defTypeId);
  				newcollid = GetColumnDefCollation(NULL, newdef, newTypeId);
  				if (defcollid != newcollid)
  					ereport(ERROR,
  							(errcode(ERRCODE_COLLATION_MISMATCH),
  							 errmsg("column \"%s\" has a collation conflict",
  									attributeName),
  							 errdetail("\"%s\" versus \"%s\"",
  									   get_collation_name(defcollid),
  									   get_collation_name(newcollid))));
  
  				/*
  				 * Identity is never inherited.  The new column can have an
  				 * identity definition, so we always just take that one.
  				 */
  				def->identity = newdef->identity;
  
  				/* Copy storage parameter */
  				if (def->storage == 0)
  					def->storage = newdef->storage;
  				else if (newdef->storage != 0 && def->storage != newdef->storage)
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("column \"%s\" has a storage parameter conflict",
  									attributeName),
  							 errdetail("%s versus %s",
  									   storage_name(def->storage),
  									   storage_name(newdef->storage))));
  
  				/* Mark the column as locally defined */
  				def->is_local = true;
  				/* Merge of NOT NULL constraints = OR 'em together */
  				def->is_not_null |= newdef->is_not_null;
  				/* If new def has a default, override previous default */
  				if (newdef->raw_default != NULL)
  				{
  					def->raw_default = newdef->raw_default;
  					def->cooked_default = newdef->cooked_default;
  				}
  			}
  			else
  			{
  				/*
  				 * No, attach new column to result schema
  				 */
  				inhSchema = lappend(inhSchema, newdef);
  			}
  		}
  
  		schema = inhSchema;
  
  		/*
  		 * Check that we haven't exceeded the legal # of columns after merging
  		 * in inherited columns.
  		 */
  		if (list_length(schema) > MaxHeapAttributeNumber)
  			ereport(ERROR,
  					(errcode(ERRCODE_TOO_MANY_COLUMNS),
  					 errmsg("tables can have at most %d columns",
  							MaxHeapAttributeNumber)));
  	}
  
  	/*
  	 * Now that we have the column definition list for a partition, we can
  	 * check whether the columns referenced in the column constraint specs
  	 * actually exist.  Also, we merge NOT NULL and defaults into each
  	 * corresponding column definition.
  	 */
  	if (is_partition)
  	{
  		foreach(entry, saved_schema)
  		{
  			ColumnDef  *restdef = lfirst(entry);
  			bool		found = false;
  			ListCell   *l;
  
  			foreach(l, schema)
  			{
  				ColumnDef  *coldef = lfirst(l);
  
  				if (strcmp(coldef->colname, restdef->colname) == 0)
  				{
  					found = true;
  					coldef->is_not_null |= restdef->is_not_null;
  
  					/*
  					 * Override the parent's default value for this column
  					 * (coldef->cooked_default) with the partition's local
  					 * definition (restdef->raw_default), if there's one. It
  					 * should be physically impossible to get a cooked default
  					 * in the local definition or a raw default in the
  					 * inherited definition, but make sure they're nulls, for
  					 * future-proofing.
  					 */
  					Assert(restdef->cooked_default == NULL);
  					Assert(coldef->raw_default == NULL);
  					if (restdef->raw_default)
  					{
  						coldef->raw_default = restdef->raw_default;
  						coldef->cooked_default = NULL;
  					}
  				}
  			}
  
  			/* complain for constraints on columns not in parent */
  			if (!found)
  				ereport(ERROR,
  						(errcode(ERRCODE_UNDEFINED_COLUMN),
  						 errmsg("column \"%s\" does not exist",
  								restdef->colname)));
  		}
  	}
  
  	/*
  	 * If we found any conflicting parent default values, check to make sure
  	 * they were overridden by the child.
  	 */
  	if (have_bogus_defaults)
  	{
  		foreach(entry, schema)
  		{
  			ColumnDef  *def = lfirst(entry);
  
  			if (def->cooked_default == &bogus_marker)
  				ereport(ERROR,
  						(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
  						 errmsg("column \"%s\" inherits conflicting default values",
  								def->colname),
  						 errhint("To resolve the conflict, specify a default explicitly.")));
  		}
  	}
  
  	*supOids = parentOids;
  	*supconstr = constraints;
  	*supOidCount = parentsWithOids;
  	return schema;
  }
  
  
  /*
   * MergeCheckConstraint
   *		Try to merge an inherited CHECK constraint with previous ones
   *
   * If we inherit identically-named constraints from multiple parents, we must
   * merge them, or throw an error if they don't have identical definitions.
   *
   * constraints is a list of CookedConstraint structs for previous constraints.
   *
   * Returns true if merged (constraint is a duplicate), or false if it's
   * got a so-far-unique name, or throws error if conflict.
   */
  static bool
  MergeCheckConstraint(List *constraints, char *name, Node *expr)
  {
  	ListCell   *lc;
  
  	foreach(lc, constraints)
  	{
  		CookedConstraint *ccon = (CookedConstraint *) lfirst(lc);
  
  		Assert(ccon->contype == CONSTR_CHECK);
  
  		/* Non-matching names never conflict */
  		if (strcmp(ccon->name, name) != 0)
  			continue;
  
  		if (equal(expr, ccon->expr))
  		{
  			/* OK to merge */
  			ccon->inhcount++;
  			return true;
  		}
  
  		ereport(ERROR,
  				(errcode(ERRCODE_DUPLICATE_OBJECT),
  				 errmsg("check constraint name \"%s\" appears multiple times but with different expressions",
  						name)));
  	}
  
  	return false;
  }
  
  
  /*
   * StoreCatalogInheritance
   *		Updates the system catalogs with proper inheritance information.
   *
   * supers is a list of the OIDs of the new relation's direct ancestors.
   */
  static void
  StoreCatalogInheritance(Oid relationId, List *supers,
  						bool child_is_partition)
  {
  	Relation	relation;
  	int32		seqNumber;
  	ListCell   *entry;
  
  	/*
  	 * sanity checks
  	 */
  	AssertArg(OidIsValid(relationId));
  
  	if (supers == NIL)
  		return;
  
  	/*
  	 * Store INHERITS information in pg_inherits using direct ancestors only.
  	 * Also enter dependencies on the direct ancestors, and make sure they are
  	 * marked with relhassubclass = true.
  	 *
  	 * (Once upon a time, both direct and indirect ancestors were found here
  	 * and then entered into pg_ipl.  Since that catalog doesn't exist
  	 * anymore, there's no need to look for indirect ancestors.)
  	 */
  	relation = heap_open(InheritsRelationId, RowExclusiveLock);
  
  	seqNumber = 1;
  	foreach(entry, supers)
  	{
  		Oid			parentOid = lfirst_oid(entry);
  
  		StoreCatalogInheritance1(relationId, parentOid, seqNumber, relation,
  								 child_is_partition);
  		seqNumber++;
  	}
  
  	heap_close(relation, RowExclusiveLock);
  }
  
  /*
   * Make catalog entries showing relationId as being an inheritance child
   * of parentOid.  inhRelation is the already-opened pg_inherits catalog.
   */
  static void
  StoreCatalogInheritance1(Oid relationId, Oid parentOid,
  						 int32 seqNumber, Relation inhRelation,
  						 bool child_is_partition)
  {
  	ObjectAddress childobject,
  				parentobject;
  
  	/* store the pg_inherits row */
  	StoreSingleInheritance(relationId, parentOid, seqNumber);
  
  	/*
  	 * Store a dependency too
  	 */
  	parentobject.classId = RelationRelationId;
  	parentobject.objectId = parentOid;
  	parentobject.objectSubId = 0;
  	childobject.classId = RelationRelationId;
  	childobject.objectId = relationId;
  	childobject.objectSubId = 0;
  
  	recordDependencyOn(&childobject, &parentobject,
  					   child_dependency_type(child_is_partition));
  
  	/*
  	 * Post creation hook of this inheritance. Since object_access_hook
  	 * doesn't take multiple object identifiers, we relay oid of parent
  	 * relation using auxiliary_id argument.
  	 */
  	InvokeObjectPostAlterHookArg(InheritsRelationId,
  								 relationId, 0,
  								 parentOid, false);
  
  	/*
  	 * Mark the parent as having subclasses.
  	 */
  	SetRelationHasSubclass(parentOid, true);
  }
  
  /*
   * Look for an existing schema entry with the given name.
   *
   * Returns the index (starting with 1) if attribute already exists in schema,
   * 0 if it doesn't.
   */
  static int
  findAttrByName(const char *attributeName, List *schema)
  {
  	ListCell   *s;
  	int			i = 1;
  
  	foreach(s, schema)
  	{
  		ColumnDef  *def = lfirst(s);
  
  		if (strcmp(attributeName, def->colname) == 0)
  			return i;
  
  		i++;
  	}
  	return 0;
  }
  
  
  /*
   * SetRelationHasSubclass
   *		Set the value of the relation's relhassubclass field in pg_class.
   *
   * NOTE: caller must be holding an appropriate lock on the relation.
   * ShareUpdateExclusiveLock is sufficient.
   *
   * NOTE: an important side-effect of this operation is that an SI invalidation
   * message is sent out to all backends --- including me --- causing plans
   * referencing the relation to be rebuilt with the new list of children.
   * This must happen even if we find that no change is needed in the pg_class
   * row.
   */
  void
  SetRelationHasSubclass(Oid relationId, bool relhassubclass)
  {
  	Relation	relationRelation;
  	HeapTuple	tuple;
  	Form_pg_class classtuple;
  
  	/*
  	 * Fetch a modifiable copy of the tuple, modify it, update pg_class.
  	 */
  	relationRelation = heap_open(RelationRelationId, RowExclusiveLock);
  	tuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relationId));
  	if (!HeapTupleIsValid(tuple))
  		elog(ERROR, "cache lookup failed for relation %u", relationId);
  	classtuple = (Form_pg_class) GETSTRUCT(tuple);
  
  	if (classtuple->relhassubclass != relhassubclass)
  	{
  		classtuple->relhassubclass = relhassubclass;
  		CatalogTupleUpdate(relationRelation, &tuple->t_self, tuple);
  	}
  	else
  	{
  		/* no need to change tuple, but force relcache rebuild anyway */
  		CacheInvalidateRelcacheByTuple(tuple);
  	}
  
  	heap_freetuple(tuple);
  	heap_close(relationRelation, RowExclusiveLock);
  }
  
  /*
   *		renameatt_check			- basic sanity checks before attribute rename
   */
  static void
  renameatt_check(Oid myrelid, Form_pg_class classform, bool recursing)
  {
  	char		relkind = classform->relkind;
  
  	if (classform->reloftype && !recursing)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot rename column of typed table")));
  
  	/*
  	 * Renaming the columns of sequences or toast tables doesn't actually
  	 * break anything from the system's point of view, since internal
  	 * references are by attnum.  But it doesn't seem right to allow users to
  	 * change names that are hardcoded into the system, hence the following
  	 * restriction.
  	 */
  	if (relkind != RELKIND_RELATION &&
  		relkind != RELKIND_VIEW &&
  		relkind != RELKIND_MATVIEW &&
  		relkind != RELKIND_COMPOSITE_TYPE &&
  		relkind != RELKIND_INDEX &&
  		relkind != RELKIND_PARTITIONED_INDEX &&
  		relkind != RELKIND_FOREIGN_TABLE &&
  		relkind != RELKIND_PARTITIONED_TABLE)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is not a table, view, materialized view, composite type, index, or foreign table",
  						NameStr(classform->relname))));
  
  	/*
  	 * permissions checking.  only the owner of a class can change its schema.
  	 */
  	if (!pg_class_ownercheck(myrelid, GetUserId()))
  		aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(get_rel_relkind(myrelid)),
  					   NameStr(classform->relname));
  	if (!allowSystemTableMods && IsSystemClass(myrelid, classform))
  		ereport(ERROR,
  				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  				 errmsg("permission denied: \"%s\" is a system catalog",
  						NameStr(classform->relname))));
  }
  
  /*
   *		renameatt_internal		- workhorse for renameatt
   *
   * Return value is the attribute number in the 'myrelid' relation.
   */
  static AttrNumber
  renameatt_internal(Oid myrelid,
  				   const char *oldattname,
  				   const char *newattname,
  				   bool recurse,
  				   bool recursing,
  				   int expected_parents,
  				   DropBehavior behavior)
  {
  	Relation	targetrelation;
  	Relation	attrelation;
  	HeapTuple	atttup;
  	Form_pg_attribute attform;
  	AttrNumber	attnum;
  
  	/*
  	 * Grab an exclusive lock on the target table, which we will NOT release
  	 * until end of transaction.
  	 */
  	targetrelation = relation_open(myrelid, AccessExclusiveLock);
  	renameatt_check(myrelid, RelationGetForm(targetrelation), recursing);
  
  	/*
  	 * if the 'recurse' flag is set then we are supposed to rename this
  	 * attribute in all classes that inherit from 'relname' (as well as in
  	 * 'relname').
  	 *
  	 * any permissions or problems with duplicate attributes will cause the
  	 * whole transaction to abort, which is what we want -- all or nothing.
  	 */
  	if (recurse)
  	{
  		List	   *child_oids,
  				   *child_numparents;
  		ListCell   *lo,
  				   *li;
  
  		/*
  		 * we need the number of parents for each child so that the recursive
  		 * calls to renameatt() can determine whether there are any parents
  		 * outside the inheritance hierarchy being processed.
  		 */
  		child_oids = find_all_inheritors(myrelid, AccessExclusiveLock,
  										 &child_numparents);
  
  		/*
  		 * find_all_inheritors does the recursive search of the inheritance
  		 * hierarchy, so all we have to do is process all of the relids in the
  		 * list that it returns.
  		 */
  		forboth(lo, child_oids, li, child_numparents)
  		{
  			Oid			childrelid = lfirst_oid(lo);
  			int			numparents = lfirst_int(li);
  
  			if (childrelid == myrelid)
  				continue;
  			/* note we need not recurse again */
  			renameatt_internal(childrelid, oldattname, newattname, false, true, numparents, behavior);
  		}
  	}
  	else
  	{
  		/*
  		 * If we are told not to recurse, there had better not be any child
  		 * tables; else the rename would put them out of step.
  		 *
  		 * expected_parents will only be 0 if we are not already recursing.
  		 */
  		if (expected_parents == 0 &&
  			find_inheritance_children(myrelid, NoLock) != NIL)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  					 errmsg("inherited column \"%s\" must be renamed in child tables too",
  							oldattname)));
  	}
  
  	/* rename attributes in typed tables of composite type */
  	if (targetrelation->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
  	{
  		List	   *child_oids;
  		ListCell   *lo;
  
  		child_oids = find_typed_table_dependencies(targetrelation->rd_rel->reltype,
  												   RelationGetRelationName(targetrelation),
  												   behavior);
  
  		foreach(lo, child_oids)
  			renameatt_internal(lfirst_oid(lo), oldattname, newattname, true, true, 0, behavior);
  	}
  
  	attrelation = heap_open(AttributeRelationId, RowExclusiveLock);
  
  	atttup = SearchSysCacheCopyAttName(myrelid, oldattname);
  	if (!HeapTupleIsValid(atttup))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_COLUMN),
  				 errmsg("column \"%s\" does not exist",
  						oldattname)));
  	attform = (Form_pg_attribute) GETSTRUCT(atttup);
  
  	attnum = attform->attnum;
  	if (attnum <= 0)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot rename system column \"%s\"",
  						oldattname)));
  
  	/*
  	 * if the attribute is inherited, forbid the renaming.  if this is a
  	 * top-level call to renameatt(), then expected_parents will be 0, so the
  	 * effect of this code will be to prohibit the renaming if the attribute
  	 * is inherited at all.  if this is a recursive call to renameatt(),
  	 * expected_parents will be the number of parents the current relation has
  	 * within the inheritance hierarchy being processed, so we'll prohibit the
  	 * renaming only if there are additional parents from elsewhere.
  	 */
  	if (attform->attinhcount > expected_parents)
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  				 errmsg("cannot rename inherited column \"%s\"",
  						oldattname)));
  
  	/* new name should not already exist */
  	(void) check_for_column_name_collision(targetrelation, newattname, false);
  
  	/* apply the update */
  	namestrcpy(&(attform->attname), newattname);
  
  	CatalogTupleUpdate(attrelation, &atttup->t_self, atttup);
  
  	InvokeObjectPostAlterHook(RelationRelationId, myrelid, attnum);
  
  	heap_freetuple(atttup);
  
  	heap_close(attrelation, RowExclusiveLock);
  
  	relation_close(targetrelation, NoLock); /* close rel but keep lock */
  
  	return attnum;
  }
  
  /*
   * Perform permissions and integrity checks before acquiring a relation lock.
   */
  static void
  RangeVarCallbackForRenameAttribute(const RangeVar *rv, Oid relid, Oid oldrelid,
  								   void *arg)
  {
  	HeapTuple	tuple;
  	Form_pg_class form;
  
  	tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
  	if (!HeapTupleIsValid(tuple))
  		return;					/* concurrently dropped */
  	form = (Form_pg_class) GETSTRUCT(tuple);
  	renameatt_check(relid, form, false);
  	ReleaseSysCache(tuple);
  }
  
  /*
   *		renameatt		- changes the name of an attribute in a relation
   *
   * The returned ObjectAddress is that of the renamed column.
   */
  ObjectAddress
  renameatt(RenameStmt *stmt)
  {
  	Oid			relid;
  	AttrNumber	attnum;
  	ObjectAddress address;
  
  	/* lock level taken here should match renameatt_internal */
  	relid = RangeVarGetRelidExtended(stmt->relation, AccessExclusiveLock,
  									 stmt->missing_ok ? RVR_MISSING_OK : 0,
  									 RangeVarCallbackForRenameAttribute,
  									 NULL);
  
  	if (!OidIsValid(relid))
  	{
  		ereport(NOTICE,
  				(errmsg("relation \"%s\" does not exist, skipping",
  						stmt->relation->relname)));
  		return InvalidObjectAddress;
  	}
  
  	attnum =
  		renameatt_internal(relid,
  						   stmt->subname,	/* old att name */
  						   stmt->newname,	/* new att name */
  						   stmt->relation->inh, /* recursive? */
  						   false,	/* recursing? */
  						   0,	/* expected inhcount */
  						   stmt->behavior);
  
  	if (IsYugaByteEnabled())
  	{
  		YBCRename(stmt, relid);
  	}
  
  	ObjectAddressSubSet(address, RelationRelationId, relid, attnum);
  
  	return address;
  }
  
  /*
   * same logic as renameatt_internal
   */
  static ObjectAddress
  rename_constraint_internal(Oid myrelid,
  						   Oid mytypid,
  						   const char *oldconname,
  						   const char *newconname,
  						   bool recurse,
  						   bool recursing,
  						   int expected_parents)
  {
  	Relation	targetrelation = NULL;
  	Oid			constraintOid;
  	HeapTuple	tuple;
  	Form_pg_constraint con;
  	ObjectAddress address;
  
  	AssertArg(!myrelid || !mytypid);
  
  	if (mytypid)
  	{
  		constraintOid = get_domain_constraint_oid(mytypid, oldconname, false);
  	}
  	else
  	{
  		targetrelation = relation_open(myrelid, AccessExclusiveLock);
  
  		/*
  		 * don't tell it whether we're recursing; we allow changing typed
  		 * tables here
  		 */
  		renameatt_check(myrelid, RelationGetForm(targetrelation), false);
  
  		constraintOid = get_relation_constraint_oid(myrelid, oldconname, false);
  	}
  
  	tuple = SearchSysCache1(CONSTROID, ObjectIdGetDatum(constraintOid));
  	if (!HeapTupleIsValid(tuple))
  		elog(ERROR, "cache lookup failed for constraint %u",
  			 constraintOid);
  	con = (Form_pg_constraint) GETSTRUCT(tuple);
  
  	if (myrelid && con->contype == CONSTRAINT_CHECK && !con->connoinherit)
  	{
  		if (recurse)
  		{
  			List	   *child_oids,
  					   *child_numparents;
  			ListCell   *lo,
  					   *li;
  
  			child_oids = find_all_inheritors(myrelid, AccessExclusiveLock,
  											 &child_numparents);
  
  			forboth(lo, child_oids, li, child_numparents)
  			{
  				Oid			childrelid = lfirst_oid(lo);
  				int			numparents = lfirst_int(li);
  
  				if (childrelid == myrelid)
  					continue;
  
  				rename_constraint_internal(childrelid, InvalidOid, oldconname, newconname, false, true, numparents);
  			}
  		}
  		else
  		{
  			if (expected_parents == 0 &&
  				find_inheritance_children(myrelid, NoLock) != NIL)
  				ereport(ERROR,
  						(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  						 errmsg("inherited constraint \"%s\" must be renamed in child tables too",
  								oldconname)));
  		}
  
  		if (con->coninhcount > expected_parents)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  					 errmsg("cannot rename inherited constraint \"%s\"",
  							oldconname)));
  	}
  
  	if (con->conindid
  		&& (con->contype == CONSTRAINT_PRIMARY
  			|| con->contype == CONSTRAINT_UNIQUE
  			|| con->contype == CONSTRAINT_EXCLUSION))
  		/* rename the index; this renames the constraint as well */
  		RenameRelationInternal(con->conindid, newconname, false);
  	else
  		RenameConstraintById(constraintOid, newconname);
  
  	ObjectAddressSet(address, ConstraintRelationId, constraintOid);
  
  	ReleaseSysCache(tuple);
  
  	if (targetrelation)
  	{
  		/*
  		 * Invalidate relcache so as others can see the new constraint name.
  		 */
  		CacheInvalidateRelcache(targetrelation);
  
  		relation_close(targetrelation, NoLock); /* close rel but keep lock */
  	}
  
  	return address;
  }
  
  ObjectAddress
  RenameConstraint(RenameStmt *stmt)
  {
  	Oid			relid = InvalidOid;
  	Oid			typid = InvalidOid;
  
  	if (stmt->renameType == OBJECT_DOMCONSTRAINT)
  	{
  		Relation	rel;
  		HeapTuple	tup;
  
  		typid = typenameTypeId(NULL, makeTypeNameFromNameList(castNode(List, stmt->object)));
  		rel = heap_open(TypeRelationId, RowExclusiveLock);
  		tup = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
  		if (!HeapTupleIsValid(tup))
  			elog(ERROR, "cache lookup failed for type %u", typid);
  		checkDomainOwner(tup);
  		ReleaseSysCache(tup);
  		heap_close(rel, NoLock);
  	}
  	else
  	{
  		/* lock level taken here should match rename_constraint_internal */
  		relid = RangeVarGetRelidExtended(stmt->relation, AccessExclusiveLock,
  										 stmt->missing_ok ? RVR_MISSING_OK : 0,
  										 RangeVarCallbackForRenameAttribute,
  										 NULL);
  		if (!OidIsValid(relid))
  		{
  			ereport(NOTICE,
  					(errmsg("relation \"%s\" does not exist, skipping",
  							stmt->relation->relname)));
  			return InvalidObjectAddress;
  		}
  	}
  
  	return
  		rename_constraint_internal(relid, typid,
  								   stmt->subname,
  								   stmt->newname,
  								   (stmt->relation &&
  									stmt->relation->inh),	/* recursive? */
  								   false,	/* recursing? */
  								   0 /* expected inhcount */ );
  
  }
  
  /*
   * Execute ALTER TABLE/INDEX/SEQUENCE/VIEW/MATERIALIZED VIEW/FOREIGN TABLE
   * RENAME
   */
  ObjectAddress
  RenameRelation(RenameStmt *stmt)
  {
  	Oid           relid;
  	ObjectAddress address;
  	Relation      rel;
  	bool          needs_yb_rename;
  
  	/*
  	 * Grab an exclusive lock on the target table, index, sequence, view,
  	 * materialized view, or foreign table, which we will NOT release until
  	 * end of transaction.
  	 *
  	 * Lock level used here should match RenameRelationInternal, to avoid lock
  	 * escalation.
  	 */
  	relid = RangeVarGetRelidExtended(stmt->relation, AccessExclusiveLock,
  									 stmt->missing_ok ? RVR_MISSING_OK : 0,
  									 RangeVarCallbackForAlterRelation,
  									 (void *) stmt);
  
  	if (!OidIsValid(relid))
  	{
  		ereport(NOTICE,
  				(errmsg("relation \"%s\" does not exist, skipping",
  						stmt->relation->relname)));
  		return InvalidObjectAddress;
  	}
  
  	RenameRelationInternal(relid, stmt->newname, false);
  
  	/* YB rename is not needed for a primary key dummy index. */
  	rel             = RelationIdGetRelation(relid);
  	needs_yb_rename = IsYBRelation(rel) &&
  	                  !(rel->rd_rel->relkind == RELKIND_INDEX && rel->rd_index->indisprimary);
  	RelationClose(rel);
  
  	/* Do the work */
  	if (needs_yb_rename)
  	{
  		YBCRename(stmt, relid);
  	}
  
  	ObjectAddressSet(address, RelationRelationId, relid);
  
  	return address;
  }
  
  /*
   *		RenameRelationInternal - change the name of a relation
   */
  void
  RenameRelationInternal(Oid myrelid, const char *newrelname, bool is_internal)
  {
  	Relation	targetrelation;
  	Relation	relrelation;	/* for RELATION relation */
  	HeapTuple	reltup;
  	Form_pg_class relform;
  	Oid			namespaceId;
  
  	/*
  	 * Grab an exclusive lock on the target table, index, sequence, view,
  	 * materialized view, or foreign table, which we will NOT release until
  	 * end of transaction.
  	 */
  	targetrelation = relation_open(myrelid, AccessExclusiveLock);
  	namespaceId = RelationGetNamespace(targetrelation);
  
  	/*
  	 * Find relation's pg_class tuple, and make sure newrelname isn't in use.
  	 */
  	relrelation = heap_open(RelationRelationId, RowExclusiveLock);
  
  	reltup = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(myrelid));
  	if (!HeapTupleIsValid(reltup))	/* shouldn't happen */
  		elog(ERROR, "cache lookup failed for relation %u", myrelid);
  	relform = (Form_pg_class) GETSTRUCT(reltup);
  
  	if (get_relname_relid(newrelname, namespaceId) != InvalidOid)
  		ereport(ERROR,
  				(errcode(ERRCODE_DUPLICATE_TABLE),
  				 errmsg("relation \"%s\" already exists",
  						newrelname)));
  
  	/*
  	 * Update pg_class tuple with new relname.  (Scribbling on reltup is OK
  	 * because it's a copy...)
  	 */
  	namestrcpy(&(relform->relname), newrelname);
  
  	CatalogTupleUpdate(relrelation, &reltup->t_self, reltup);
  
  	InvokeObjectPostAlterHookArg(RelationRelationId, myrelid, 0,
  								 InvalidOid, is_internal);
  
  	heap_freetuple(reltup);
  	heap_close(relrelation, RowExclusiveLock);
  
  	/*
  	 * Also rename the associated type, if any.
  	 */
  	if (OidIsValid(targetrelation->rd_rel->reltype))
  		RenameTypeInternal(targetrelation->rd_rel->reltype,
  						   newrelname, namespaceId);
  
  	/*
  	 * Also rename the associated constraint, if any.
  	 */
  	if (targetrelation->rd_rel->relkind == RELKIND_INDEX ||
  		targetrelation->rd_rel->relkind == RELKIND_PARTITIONED_INDEX)
  	{
  		Oid			constraintId = get_index_constraint(myrelid);
  
  		if (OidIsValid(constraintId))
  			RenameConstraintById(constraintId, newrelname);
  	}
  
  	/*
  	 * Close rel, but keep exclusive lock!
  	 */
  	relation_close(targetrelation, NoLock);
  }
  
  /*
   * Disallow ALTER TABLE (and similar commands) when the current backend has
   * any open reference to the target table besides the one just acquired by
   * the calling command; this implies there's an open cursor or active plan.
   * We need this check because our lock doesn't protect us against stomping
   * on our own foot, only other people's feet!
   *
   * For ALTER TABLE, the only case known to cause serious trouble is ALTER
   * COLUMN TYPE, and some changes are obviously pretty benign, so this could
   * possibly be relaxed to only error out for certain types of alterations.
   * But the use-case for allowing any of these things is not obvious, so we
   * won't work hard at it for now.
   *
   * We also reject these commands if there are any pending AFTER trigger events
   * for the rel.  This is certainly necessary for the rewriting variants of
   * ALTER TABLE, because they don't preserve tuple TIDs and so the pending
   * events would try to fetch the wrong tuples.  It might be overly cautious
   * in other cases, but again it seems better to err on the side of paranoia.
   *
   * REINDEX calls this with "rel" referencing the index to be rebuilt; here
   * we are worried about active indexscans on the index.  The trigger-event
   * check can be skipped, since we are doing no damage to the parent table.
   *
   * The statement name (eg, "ALTER TABLE") is passed for use in error messages.
   */
  void
  CheckTableNotInUse(Relation rel, const char *stmt)
  {
  	int			expected_refcnt;
  
  	expected_refcnt = rel->rd_isnailed ? 2 : 1;
  	if (rel->rd_refcnt != expected_refcnt)
  		ereport(ERROR,
  				(errcode(ERRCODE_OBJECT_IN_USE),
  		/* translator: first %s is a SQL command, eg ALTER TABLE */
  				 errmsg("cannot %s \"%s\" because "
  						"it is being used by active queries in this session",
  						stmt, RelationGetRelationName(rel))));
  
  	if (rel->rd_rel->relkind != RELKIND_INDEX &&
  		rel->rd_rel->relkind != RELKIND_PARTITIONED_INDEX &&
  		AfterTriggerPendingOnRel(RelationGetRelid(rel)))
  		ereport(ERROR,
  				(errcode(ERRCODE_OBJECT_IN_USE),
  		/* translator: first %s is a SQL command, eg ALTER TABLE */
  				 errmsg("cannot %s \"%s\" because "
  						"it has pending trigger events",
  						stmt, RelationGetRelationName(rel))));
  }
  
  /*
   * AlterTableLookupRelation
   *		Look up, and lock, the OID for the relation named by an alter table
   *		statement.
   */
  Oid
  AlterTableLookupRelation(AlterTableStmt *stmt, LOCKMODE lockmode)
  {
  	return RangeVarGetRelidExtended(stmt->relation, lockmode,
  									stmt->missing_ok ? RVR_MISSING_OK : 0,
  									RangeVarCallbackForAlterRelation,
  									(void *) stmt);
  }
  
  /*
   * AlterTable
   *		Execute ALTER TABLE, which can be a list of subcommands
   *
   * ALTER TABLE is performed in three phases:
   *		1. Examine subcommands and perform pre-transformation checking.
   *		2. Update system catalogs.
   *		3. Scan table(s) to check new constraints, and optionally recopy
   *		   the data into new table(s).
   * Phase 3 is not performed unless one or more of the subcommands requires
   * it.  The intention of this design is to allow multiple independent
   * updates of the table schema to be performed with only one pass over the
   * data.
   *
   * ATPrepCmd performs phase 1.  A "work queue" entry is created for
   * each table to be affected (there may be multiple affected tables if the
   * commands traverse a table inheritance hierarchy).  Also we do preliminary
   * validation of the subcommands, including parse transformation of those
   * expressions that need to be evaluated with respect to the old table
   * schema.
   *
   * ATRewriteCatalogs performs phase 2 for each affected table.  (Note that
   * phases 2 and 3 normally do no explicit recursion, since phase 1 already
   * did it --- although some subcommands have to recurse in phase 2 instead.)
   * Certain subcommands need to be performed before others to avoid
   * unnecessary conflicts; for example, DROP COLUMN should come before
   * ADD COLUMN.  Therefore phase 1 divides the subcommands into multiple
   * lists, one for each logical "pass" of phase 2.
   *
   * ATRewriteTables performs phase 3 for those tables that need it.
   *
   * Thanks to the magic of MVCC, an error anywhere along the way rolls back
   * the whole operation; we don't have to do anything special to clean up.
   *
   * The caller must lock the relation, with an appropriate lock level
   * for the subcommands requested, using AlterTableGetLockLevel(stmt->cmds)
   * or higher. We pass the lock level down
   * so that we can apply it recursively to inherited tables. Note that the
   * lock level we want as we recurse might well be higher than required for
   * that specific subcommand. So we pass down the overall lock requirement,
   * rather than reassess it at lower levels.
   */
  void
  AlterTable(Oid relid, LOCKMODE lockmode, AlterTableStmt *stmt)
  {
  	Relation	rel;
  
  	/* Caller is required to provide an adequate lock. */
  	rel = relation_open(relid, NoLock);
  
  	CheckTableNotInUse(rel, "ALTER TABLE");
  
  	ATController(stmt, rel, stmt->cmds, stmt->relation->inh, lockmode);
  }
  
  /*
   * AlterTableInternal
   *
   * ALTER TABLE with target specified by OID
   *
   * We do not reject if the relation is already open, because it's quite
   * likely that one or more layers of caller have it open.  That means it
   * is unsafe to use this entry point for alterations that could break
   * existing query plans.  On the assumption it's not used for such, we
   * don't have to reject pending AFTER triggers, either.
   */
  void
  AlterTableInternal(Oid relid, List *cmds, bool recurse)
  {
  	Relation	rel;
  	LOCKMODE	lockmode = AlterTableGetLockLevel(cmds);
  
  	rel = relation_open(relid, lockmode);
  
  	EventTriggerAlterTableRelid(relid);
  
  	ATController(NULL, rel, cmds, recurse, lockmode);
  }
  
  /*
   * AlterTableGetLockLevel
   *
   * Sets the overall lock level required for the supplied list of subcommands.
   * Policy for doing this set according to needs of AlterTable(), see
   * comments there for overall explanation.
   *
   * Function is called before and after parsing, so it must give same
   * answer each time it is called. Some subcommands are transformed
   * into other subcommand types, so the transform must never be made to a
   * lower lock level than previously assigned. All transforms are noted below.
   *
   * Since this is called before we lock the table we cannot use table metadata
   * to influence the type of lock we acquire.
   *
   * There should be no lockmodes hardcoded into the subcommand functions. All
   * lockmode decisions for ALTER TABLE are made here only. The one exception is
   * ALTER TABLE RENAME which is treated as a different statement type T_RenameStmt
   * and does not travel through this section of code and cannot be combined with
   * any of the subcommands given here.
   *
   * Note that Hot Standby only knows about AccessExclusiveLocks on the master
   * so any changes that might affect SELECTs running on standbys need to use
   * AccessExclusiveLocks even if you think a lesser lock would do, unless you
   * have a solution for that also.
   *
   * Also note that pg_dump uses only an AccessShareLock, meaning that anything
   * that takes a lock less than AccessExclusiveLock can change object definitions
   * while pg_dump is running. Be careful to check that the appropriate data is
   * derived by pg_dump using an MVCC snapshot, rather than syscache lookups,
   * otherwise we might end up with an inconsistent dump that can't restore.
   */
  LOCKMODE
  AlterTableGetLockLevel(List *cmds)
  {
  	/*
  	 * This only works if we read catalog tables using MVCC snapshots.
  	 */
  	ListCell   *lcmd;
  	LOCKMODE	lockmode = ShareUpdateExclusiveLock;
  
  	foreach(lcmd, cmds)
  	{
  		AlterTableCmd *cmd = (AlterTableCmd *) lfirst(lcmd);
  		LOCKMODE	cmd_lockmode = AccessExclusiveLock; /* default for compiler */
  
  		switch (cmd->subtype)
  		{
  				/*
  				 * These subcommands rewrite the heap, so require full locks.
  				 */
  			case AT_AddColumn:	/* may rewrite heap, in some cases and visible
  								 * to SELECT */
  			case AT_SetTableSpace:	/* must rewrite heap */
  			case AT_AlterColumnType:	/* must rewrite heap */
  			case AT_AddOids:	/* must rewrite heap */
  				cmd_lockmode = AccessExclusiveLock;
  				break;
  
  				/*
  				 * These subcommands may require addition of toast tables. If
  				 * we add a toast table to a table currently being scanned, we
  				 * might miss data added to the new toast table by concurrent
  				 * insert transactions.
  				 */
  			case AT_SetStorage: /* may add toast tables, see
  								 * ATRewriteCatalogs() */
  				cmd_lockmode = AccessExclusiveLock;
  				break;
  
  				/*
  				 * Removing constraints can affect SELECTs that have been
  				 * optimised assuming the constraint holds true.
  				 */
  			case AT_DropConstraint: /* as DROP INDEX */
  			case AT_DropNotNull:	/* may change some SQL plans */
  				cmd_lockmode = AccessExclusiveLock;
  				break;
  
  				/*
  				 * Subcommands that may be visible to concurrent SELECTs
  				 */
  			case AT_DropColumn: /* change visible to SELECT */
  			case AT_AddColumnToView:	/* CREATE VIEW */
  			case AT_DropOids:	/* calls AT_DropColumn */
  			case AT_EnableAlwaysRule:	/* may change SELECT rules */
  			case AT_EnableReplicaRule:	/* may change SELECT rules */
  			case AT_EnableRule: /* may change SELECT rules */
  			case AT_DisableRule:	/* may change SELECT rules */
  				cmd_lockmode = AccessExclusiveLock;
  				break;
  
  				/*
  				 * Changing owner may remove implicit SELECT privileges
  				 */
  			case AT_ChangeOwner:	/* change visible to SELECT */
  				cmd_lockmode = AccessExclusiveLock;
  				break;
  
  				/*
  				 * Changing foreign table options may affect optimization.
  				 */
  			case AT_GenericOptions:
  			case AT_AlterColumnGenericOptions:
  				cmd_lockmode = AccessExclusiveLock;
  				break;
  
  				/*
  				 * These subcommands affect write operations only.
  				 */
  			case AT_EnableTrig:
  			case AT_EnableAlwaysTrig:
  			case AT_EnableReplicaTrig:
  			case AT_EnableTrigAll:
  			case AT_EnableTrigUser:
  			case AT_DisableTrig:
  			case AT_DisableTrigAll:
  			case AT_DisableTrigUser:
  				cmd_lockmode = ShareRowExclusiveLock;
  				break;
  
  				/*
  				 * These subcommands affect write operations only. XXX
  				 * Theoretically, these could be ShareRowExclusiveLock.
  				 */
  			case AT_ColumnDefault:
  			case AT_AlterConstraint:
  			case AT_AddIndex:	/* from ADD CONSTRAINT */
  			case AT_AddIndexConstraint:
  			case AT_ReplicaIdentity:
  			case AT_SetNotNull:
  			case AT_EnableRowSecurity:
  			case AT_DisableRowSecurity:
  			case AT_ForceRowSecurity:
  			case AT_NoForceRowSecurity:
  			case AT_AddIdentity:
  			case AT_DropIdentity:
  			case AT_SetIdentity:
  				cmd_lockmode = AccessExclusiveLock;
  				break;
  
  			case AT_AddConstraint:
  			case AT_ProcessedConstraint:	/* becomes AT_AddConstraint */
  			case AT_AddConstraintRecurse:	/* becomes AT_AddConstraint */
  			case AT_ReAddConstraint:	/* becomes AT_AddConstraint */
  			case AT_ReAddDomainConstraint:	/* becomes AT_AddConstraint */
  				if (IsA(cmd->def, Constraint))
  				{
  					Constraint *con = (Constraint *) cmd->def;
  
  					switch (con->contype)
  					{
  						case CONSTR_EXCLUSION:
  						case CONSTR_PRIMARY:
  						case CONSTR_UNIQUE:
  
  							/*
  							 * Cases essentially the same as CREATE INDEX. We
  							 * could reduce the lock strength to ShareLock if
  							 * we can work out how to allow concurrent catalog
  							 * updates. XXX Might be set down to
  							 * ShareRowExclusiveLock but requires further
  							 * analysis.
  							 */
  							cmd_lockmode = AccessExclusiveLock;
  							break;
  						case CONSTR_FOREIGN:
  
  							/*
  							 * We add triggers to both tables when we add a
  							 * Foreign Key, so the lock level must be at least
  							 * as strong as CREATE TRIGGER.
  							 */
  							cmd_lockmode = ShareRowExclusiveLock;
  							break;
  
  						default:
  							cmd_lockmode = AccessExclusiveLock;
  					}
  				}
  				break;
  
  				/*
  				 * These subcommands affect inheritance behaviour. Queries
  				 * started before us will continue to see the old inheritance
  				 * behaviour, while queries started after we commit will see
  				 * new behaviour. No need to prevent reads or writes to the
  				 * subtable while we hook it up though. Changing the TupDesc
  				 * may be a problem, so keep highest lock.
  				 */
  			case AT_AddInherit:
  			case AT_DropInherit:
  				cmd_lockmode = AccessExclusiveLock;
  				break;
  
  				/*
  				 * These subcommands affect implicit row type conversion. They
  				 * have affects similar to CREATE/DROP CAST on queries. don't
  				 * provide for invalidating parse trees as a result of such
  				 * changes, so we keep these at AccessExclusiveLock.
  				 */
  			case AT_AddOf:
  			case AT_DropOf:
  				cmd_lockmode = AccessExclusiveLock;
  				break;
  
  				/*
  				 * Only used by CREATE OR REPLACE VIEW which must conflict
  				 * with an SELECTs currently using the view.
  				 */
  			case AT_ReplaceRelOptions:
  				cmd_lockmode = AccessExclusiveLock;
  				break;
  
  				/*
  				 * These subcommands affect general strategies for performance
  				 * and maintenance, though don't change the semantic results
  				 * from normal data reads and writes. Delaying an ALTER TABLE
  				 * behind currently active writes only delays the point where
  				 * the new strategy begins to take effect, so there is no
  				 * benefit in waiting. In this case the minimum restriction
  				 * applies: we don't currently allow concurrent catalog
  				 * updates.
  				 */
  			case AT_SetStatistics:	/* Uses MVCC in getTableAttrs() */
  			case AT_ClusterOn:	/* Uses MVCC in getIndexes() */
  			case AT_DropCluster:	/* Uses MVCC in getIndexes() */
  			case AT_SetOptions: /* Uses MVCC in getTableAttrs() */
  			case AT_ResetOptions:	/* Uses MVCC in getTableAttrs() */
  				cmd_lockmode = ShareUpdateExclusiveLock;
  				break;
  
  			case AT_SetLogged:
  			case AT_SetUnLogged:
  				cmd_lockmode = AccessExclusiveLock;
  				break;
  
  			case AT_ValidateConstraint: /* Uses MVCC in getConstraints() */
  				cmd_lockmode = ShareUpdateExclusiveLock;
  				break;
  
  				/*
  				 * Rel options are more complex than first appears. Options
  				 * are set here for tables, views and indexes; for historical
  				 * reasons these can all be used with ALTER TABLE, so we can't
  				 * decide between them using the basic grammar.
  				 */
  			case AT_SetRelOptions:	/* Uses MVCC in getIndexes() and
  									 * getTables() */
  			case AT_ResetRelOptions:	/* Uses MVCC in getIndexes() and
  										 * getTables() */
  				cmd_lockmode = AlterTableGetRelOptionsLockLevel((List *) cmd->def);
  				break;
  
  			case AT_AttachPartition:
  			case AT_DetachPartition:
  				cmd_lockmode = AccessExclusiveLock;
  				break;
  
  			default:			/* oops */
  				elog(ERROR, "unrecognized alter table type: %d",
  					 (int) cmd->subtype);
  				break;
  		}
  
  		/*
  		 * Take the greatest lockmode from any subcommand
  		 */
  		if (cmd_lockmode > lockmode)
  			lockmode = cmd_lockmode;
  	}
  
  	return lockmode;
  }
  
  /*
   * ATController provides top level control over the phases.
   *
   * parsetree is passed in to allow it to be passed to event triggers
   * when requested.
   */
  static void
  ATController(AlterTableStmt *parsetree,
  			 Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
  {
  	List	   *wqueue = NIL;
  	ListCell   *lcmd;
  
  	/* Phase 1: preliminary examination of commands, create work queue */
  	foreach(lcmd, cmds)
  	{
  		AlterTableCmd *cmd = (AlterTableCmd *) lfirst(lcmd);
  		ATPrepCmd(&wqueue, rel, cmd, recurse, false, lockmode);
  	}
  
  	/* Close the relation, but keep lock until commit */
  	relation_close(rel, NoLock);
  
  	/* Phase 2: update system catalogs */
  	YBCPgStatement rollbackHandle = NULL;
  	/*
  	 * ATRewriteCatalogs also executes changes to DocDB.
  	 * If Phase 3 fails, rollbackHandle will specify how to rollback the
  	 * changes done to DocDB.
  	*/
  	ATRewriteCatalogs(&wqueue, lockmode, &rollbackHandle);
  
  	/* Phase 3: scan/rewrite tables as needed */
  	PG_TRY();
  	{
  		ATRewriteTables(parsetree, &wqueue, lockmode);
  	}
  	PG_CATCH();
  	{
  		/* Rollback the DocDB changes. */
  		if (rollbackHandle)
  		{
  			YBCExecAlterTable(rollbackHandle, RelationGetRelid(rel));
  		}
  		PG_RE_THROW();
  	}
  	PG_END_TRY();
  }
  
  /*
   * ATPrepCmd
   *
   * Traffic cop for ALTER TABLE Phase 1 operations, including simple
   * recursion and permission checks.
   *
   * Caller must have acquired appropriate lock type on relation already.
   * This lock should be held until commit.
   */
  static void
  ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
  		  bool recurse, bool recursing, LOCKMODE lockmode)
  {
  	AlteredTableInfo *tab;
  	int			pass = AT_PASS_UNSET;
  
  	/* Find or create work queue entry for this table */
  	tab = ATGetQueueEntry(wqueue, rel);
  
  	/*
  	 * Copy the original subcommand for each table.  This avoids conflicts
  	 * when different child tables need to make different parse
  	 * transformations (for example, the same column may have different column
  	 * numbers in different children).
  	 */
  	cmd = copyObject(cmd);
  
  	/*
  	 * Do permissions checking, recursion to child tables if needed, and any
  	 * additional phase-1 processing needed.
  	 */
  	switch (cmd->subtype)
  	{
  		case AT_AddColumn:		/* ADD COLUMN */
  			ATSimplePermissions(rel,
  								ATT_TABLE | ATT_COMPOSITE_TYPE | ATT_FOREIGN_TABLE);
  			ATPrepAddColumn(wqueue, rel, recurse, recursing, false, cmd,
  							lockmode);
  			/* Recursion occurs during execution phase */
  			pass = AT_PASS_ADD_COL;
  			break;
  		case AT_AddColumnToView:	/* add column via CREATE OR REPLACE VIEW */
  			ATSimplePermissions(rel, ATT_VIEW);
  			ATPrepAddColumn(wqueue, rel, recurse, recursing, true, cmd,
  							lockmode);
  			/* Recursion occurs during execution phase */
  			pass = AT_PASS_ADD_COL;
  			break;
  		case AT_ColumnDefault:	/* ALTER COLUMN DEFAULT */
  
  			/*
  			 * We allow defaults on views so that INSERT into a view can have
  			 * default-ish behavior.  This works because the rewriter
  			 * substitutes default values into INSERTs before it expands
  			 * rules.
  			 */
  			ATSimplePermissions(rel, ATT_TABLE | ATT_VIEW | ATT_FOREIGN_TABLE);
  			ATSimpleRecursion(wqueue, rel, cmd, recurse, lockmode);
  			/* No command-specific prep needed */
  			pass = cmd->def ? AT_PASS_ADD_CONSTR : AT_PASS_DROP;
  			break;
  		case AT_AddIdentity:
  			ATSimplePermissions(rel, ATT_TABLE | ATT_VIEW | ATT_FOREIGN_TABLE);
  			pass = AT_PASS_ADD_CONSTR;
  			break;
  		case AT_DropIdentity:
  			ATSimplePermissions(rel, ATT_TABLE | ATT_VIEW | ATT_FOREIGN_TABLE);
  			pass = AT_PASS_DROP;
  			break;
  		case AT_SetIdentity:
  			ATSimplePermissions(rel, ATT_TABLE | ATT_VIEW | ATT_FOREIGN_TABLE);
  			pass = AT_PASS_COL_ATTRS;
  			break;
  		case AT_DropNotNull:	/* ALTER COLUMN DROP NOT NULL */
  			ATSimplePermissions(rel, ATT_TABLE | ATT_FOREIGN_TABLE);
  			ATPrepDropNotNull(rel, recurse, recursing);
  			ATSimpleRecursion(wqueue, rel, cmd, recurse, lockmode);
  			/* No command-specific prep needed */
  			pass = AT_PASS_DROP;
  			break;
  		case AT_SetNotNull:		/* ALTER COLUMN SET NOT NULL */
  			ATSimplePermissions(rel, ATT_TABLE | ATT_FOREIGN_TABLE);
  			ATPrepSetNotNull(rel, recurse, recursing);
  			ATSimpleRecursion(wqueue, rel, cmd, recurse, lockmode);
  			/* No command-specific prep needed */
  			pass = AT_PASS_ADD_CONSTR;
  			break;
  		case AT_SetStatistics:	/* ALTER COLUMN SET STATISTICS */
  			ATSimpleRecursion(wqueue, rel, cmd, recurse, lockmode);
  			/* Performs own permission checks */
  			ATPrepSetStatistics(rel, cmd->name, cmd->num, cmd->def, lockmode);
  			pass = AT_PASS_MISC;
  			break;
  		case AT_SetOptions:		/* ALTER COLUMN SET ( options ) */
  		case AT_ResetOptions:	/* ALTER COLUMN RESET ( options ) */
  			ATSimplePermissions(rel, ATT_TABLE | ATT_MATVIEW | ATT_INDEX | ATT_FOREIGN_TABLE);
  			/* This command never recurses */
  			pass = AT_PASS_MISC;
  			break;
  		case AT_SetStorage:		/* ALTER COLUMN SET STORAGE */
  			ATSimplePermissions(rel, ATT_TABLE | ATT_MATVIEW | ATT_FOREIGN_TABLE);
  			ATSimpleRecursion(wqueue, rel, cmd, recurse, lockmode);
  			/* No command-specific prep needed */
  			pass = AT_PASS_MISC;
  			break;
  		case AT_DropColumn:		/* DROP COLUMN */
  			ATSimplePermissions(rel,
  								ATT_TABLE | ATT_COMPOSITE_TYPE | ATT_FOREIGN_TABLE);
  			ATPrepDropColumn(wqueue, rel, recurse, recursing, cmd, lockmode);
  			/* Recursion occurs during execution phase */
  			pass = AT_PASS_DROP;
  			break;
  		case AT_AddIndex:		/* ADD INDEX */
  			ATSimplePermissions(rel, ATT_TABLE);
  			/* This command never recurses */
  			/* No command-specific prep needed */
  			pass = AT_PASS_ADD_INDEX;
  			break;
  		case AT_AddConstraint:	/* ADD CONSTRAINT */
  			ATSimplePermissions(rel, ATT_TABLE | ATT_FOREIGN_TABLE);
  			/* Recursion occurs during execution phase */
  			/* No command-specific prep needed except saving recurse flag */
  			if (recurse)
  				cmd->subtype = AT_AddConstraintRecurse;
  			pass = AT_PASS_ADD_CONSTR;
  			break;
  		case AT_AddIndexConstraint: /* ADD CONSTRAINT USING INDEX */
  			ATSimplePermissions(rel, ATT_TABLE);
  			/* This command never recurses */
  			/* No command-specific prep needed */
  			pass = AT_PASS_ADD_CONSTR;
  			break;
  		case AT_DropConstraint: /* DROP CONSTRAINT */
  			ATSimplePermissions(rel, ATT_TABLE | ATT_FOREIGN_TABLE);
  			/* Recursion occurs during execution phase */
  			/* No command-specific prep needed except saving recurse flag */
  			if (recurse)
  				cmd->subtype = AT_DropConstraintRecurse;
  			pass = AT_PASS_DROP;
  			break;
  		case AT_AlterColumnType:	/* ALTER COLUMN TYPE */
  			ATSimplePermissions(rel,
  								ATT_TABLE | ATT_COMPOSITE_TYPE | ATT_FOREIGN_TABLE);
  			/* Performs own recursion */
  			ATPrepAlterColumnType(wqueue, tab, rel, recurse, recursing, cmd, lockmode);
  			pass = AT_PASS_ALTER_TYPE;
  			break;
  		case AT_AlterColumnGenericOptions:
  			ATSimplePermissions(rel, ATT_FOREIGN_TABLE);
  			/* This command never recurses */
  			/* No command-specific prep needed */
  			pass = AT_PASS_MISC;
  			break;
  		case AT_ChangeOwner:	/* ALTER OWNER */
  			/* This command never recurses */
  			/* No command-specific prep needed */
  			pass = AT_PASS_MISC;
  			break;
  		case AT_ClusterOn:		/* CLUSTER ON */
  		case AT_DropCluster:	/* SET WITHOUT CLUSTER */
  			ATSimplePermissions(rel, ATT_TABLE | ATT_MATVIEW);
  			/* These commands never recurse */
  			/* No command-specific prep needed */
  			pass = AT_PASS_MISC;
  			break;
  		case AT_SetLogged:		/* SET LOGGED */
  			ATSimplePermissions(rel, ATT_TABLE);
  			tab->chgPersistence = ATPrepChangePersistence(rel, true);
  			/* force rewrite if necessary; see comment in ATRewriteTables */
  			if (tab->chgPersistence)
  			{
  				tab->rewrite |= AT_REWRITE_ALTER_PERSISTENCE;
  				tab->newrelpersistence = RELPERSISTENCE_PERMANENT;
  			}
  			pass = AT_PASS_MISC;
  			break;
  		case AT_SetUnLogged:	/* SET UNLOGGED */
  			ATSimplePermissions(rel, ATT_TABLE);
  			tab->chgPersistence = ATPrepChangePersistence(rel, false);
  			/* force rewrite if necessary; see comment in ATRewriteTables */
  			if (tab->chgPersistence)
  			{
  				tab->rewrite |= AT_REWRITE_ALTER_PERSISTENCE;
  				tab->newrelpersistence = RELPERSISTENCE_UNLOGGED;
  			}
  			pass = AT_PASS_MISC;
  			break;
  		case AT_AddOids:		/* SET WITH OIDS */
  			ATSimplePermissions(rel, ATT_TABLE | ATT_FOREIGN_TABLE);
  			if (!rel->rd_rel->relhasoids || recursing)
  				ATPrepAddOids(wqueue, rel, recurse, cmd, lockmode);
  			/* Recursion occurs during execution phase */
  			pass = AT_PASS_ADD_COL;
  			break;
  		case AT_DropOids:		/* SET WITHOUT OIDS */
  			ATSimplePermissions(rel, ATT_TABLE | ATT_FOREIGN_TABLE);
  			/* Performs own recursion */
  			if (rel->rd_rel->relhasoids)
  			{
  				AlterTableCmd *dropCmd = makeNode(AlterTableCmd);
  
  				dropCmd->subtype = AT_DropColumn;
  				dropCmd->name = pstrdup("oid");
  				dropCmd->behavior = cmd->behavior;
  				ATPrepCmd(wqueue, rel, dropCmd, recurse, false, lockmode);
  			}
  			pass = AT_PASS_DROP;
  			break;
  		case AT_SetTableSpace:	/* SET TABLESPACE */
  			ATSimplePermissions(rel, ATT_TABLE | ATT_MATVIEW | ATT_INDEX |
  								ATT_PARTITIONED_INDEX);
  			/* This command never recurses */
  			ATPrepSetTableSpace(tab, rel, cmd->name, lockmode);
  			pass = AT_PASS_MISC;	/* doesn't actually matter */
  			break;
  		case AT_SetRelOptions:	/* SET (...) */
  		case AT_ResetRelOptions:	/* RESET (...) */
  		case AT_ReplaceRelOptions:	/* reset them all, then set just these */
  			ATSimplePermissions(rel, ATT_TABLE | ATT_VIEW | ATT_MATVIEW | ATT_INDEX);
  			/* This command never recurses */
  			/* No command-specific prep needed */
  			pass = AT_PASS_MISC;
  			break;
  		case AT_AddInherit:		/* INHERIT */
  			ATSimplePermissions(rel, ATT_TABLE | ATT_FOREIGN_TABLE);
  			/* This command never recurses */
  			ATPrepAddInherit(rel);
  			pass = AT_PASS_MISC;
  			break;
  		case AT_DropInherit:	/* NO INHERIT */
  			ATSimplePermissions(rel, ATT_TABLE | ATT_FOREIGN_TABLE);
  			/* This command never recurses */
  			/* No command-specific prep needed */
  			pass = AT_PASS_MISC;
  			break;
  		case AT_AlterConstraint:	/* ALTER CONSTRAINT */
  			ATSimplePermissions(rel, ATT_TABLE);
  			pass = AT_PASS_MISC;
  			break;
  		case AT_ValidateConstraint: /* VALIDATE CONSTRAINT */
  			ATSimplePermissions(rel, ATT_TABLE | ATT_FOREIGN_TABLE);
  			/* Recursion occurs during execution phase */
  			/* No command-specific prep needed except saving recurse flag */
  			if (recurse)
  				cmd->subtype = AT_ValidateConstraintRecurse;
  			pass = AT_PASS_MISC;
  			break;
  		case AT_ReplicaIdentity:	/* REPLICA IDENTITY ... */
  			ATSimplePermissions(rel, ATT_TABLE | ATT_MATVIEW);
  			pass = AT_PASS_MISC;
  			/* This command never recurses */
  			/* No command-specific prep needed */
  			break;
  		case AT_EnableTrig:		/* ENABLE TRIGGER variants */
  		case AT_EnableAlwaysTrig:
  		case AT_EnableReplicaTrig:
  		case AT_EnableTrigAll:
  		case AT_EnableTrigUser:
  		case AT_DisableTrig:	/* DISABLE TRIGGER variants */
  		case AT_DisableTrigAll:
  		case AT_DisableTrigUser:
  			ATSimplePermissions(rel, ATT_TABLE | ATT_FOREIGN_TABLE);
  			pass = AT_PASS_MISC;
  			break;
  		case AT_EnableRule:		/* ENABLE/DISABLE RULE variants */
  		case AT_EnableAlwaysRule:
  		case AT_EnableReplicaRule:
  		case AT_DisableRule:
  		case AT_AddOf:			/* OF */
  		case AT_DropOf:			/* NOT OF */
  		case AT_EnableRowSecurity:
  		case AT_DisableRowSecurity:
  		case AT_ForceRowSecurity:
  		case AT_NoForceRowSecurity:
  			ATSimplePermissions(rel, ATT_TABLE);
  			/* These commands never recurse */
  			/* No command-specific prep needed */
  			pass = AT_PASS_MISC;
  			break;
  		case AT_GenericOptions:
  			ATSimplePermissions(rel, ATT_FOREIGN_TABLE);
  			/* No command-specific prep needed */
  			pass = AT_PASS_MISC;
  			break;
  		case AT_AttachPartition:
  			ATSimplePermissions(rel, ATT_TABLE | ATT_PARTITIONED_INDEX);
  			/* No command-specific prep needed */
  			pass = AT_PASS_MISC;
  			break;
  		case AT_DetachPartition:
  			ATSimplePermissions(rel, ATT_TABLE);
  			/* No command-specific prep needed */
  			pass = AT_PASS_MISC;
  			break;
  		default:				/* oops */
  			elog(ERROR, "unrecognized alter table type: %d",
  				 (int) cmd->subtype);
  			pass = AT_PASS_UNSET;	/* keep compiler quiet */
  			break;
  	}
  	Assert(pass > AT_PASS_UNSET);
  
  	/* Add the subcommand to the appropriate list for phase 2 */
  	tab->subcmds[pass] = lappend(tab->subcmds[pass], cmd);
  }
  
  /*
   * ATRewriteCatalogs
   *
   * Traffic cop for ALTER TABLE Phase 2 operations.  Subcommands are
   * dispatched in a "safe" execution order (designed to avoid unnecessary
   * conflicts).
   */
  static void
  ATRewriteCatalogs(List **wqueue,
  				  LOCKMODE lockmode,
  				  YBCPgStatement *rollbackHandle)
  {
  	int			pass;
  	ListCell   *ltab;
  
  	/*
  	 * Prepare the YB alter statement handle -- need to call this before the
  	 * system catalogs are changed below (since it looks up table metadata).
  	 *
  	 * One wqueue entry corresponds to one relation, "main" one occupying
  	 * the first slot.
  	 *
  	 * In future we might want to process all relations.
  	 */
  	AlteredTableInfo* info       = (AlteredTableInfo *) linitial(*wqueue);
  	Oid               main_relid = info->relid;
  	YBCPgStatement    handle     = YBCPrepareAlterTable(info->subcmds,
  														AT_NUM_PASSES,
  														main_relid,
  														rollbackHandle);
  
  	/*
  	 * We process all the tables "in parallel", one pass at a time.  This is
  	 * needed because we may have to propagate work from one table to another
  	 * (specifically, ALTER TYPE on a foreign key's PK has to dispatch the
  	 * re-adding of the foreign key constraint to the other table).  Work can
  	 * only be propagated into later passes, however.
  	 */
  	for (pass = 0; pass < AT_NUM_PASSES; pass++)
  	{
  		/*
  		 * Execute the YB alter table (if needed).
  		 *
  		 * Must call this after syscatalog updates succeed (e.g. dependencies are
  		 * checked) since we do not support rollback of YB alter operations yet.
  		 *
  		 * However, we must also do this before we start adding indexes because
  		 * the column in question might not be there yet.
  		 */
  		if (pass == AT_PASS_ADD_INDEX && handle)
  		{
  			YBCExecAlterTable(handle, main_relid);
  		}
  
  		/* Go through each table that needs to be processed */
  		foreach(ltab, *wqueue)
  		{
  			AlteredTableInfo *tab = (AlteredTableInfo *) lfirst(ltab);
  			List	   *subcmds = tab->subcmds[pass];
  			Relation	rel;
  			ListCell   *lcmd;
  
  			if (subcmds == NIL)
  				continue;
  
  			/*
  			 * Appropriate lock was obtained by phase 1, needn't get it again
  			 */
  			rel = relation_open(tab->relid, NoLock);
  
  			foreach(lcmd, subcmds)
  				ATExecCmd(wqueue, tab, &rel,
  						  castNode(AlterTableCmd, lfirst(lcmd)),
  						  lockmode);
  
  			/*
  			 * After the ALTER TYPE pass, do cleanup work (this is not done in
  			 * ATExecAlterColumnType since it should be done only once if
  			 * multiple columns of a table are altered).
  			 */
  			if (pass == AT_PASS_ALTER_TYPE)
  				ATPostAlterTypeCleanup(wqueue, tab, lockmode);
  
  			relation_close(rel, NoLock);
  		}
  	}
  
  	/* YugaByte doesn't support toast tables. */
  	if (IsYugaByteEnabled())
  		return;
  
  	/* Check to see if a toast table must be added. */
  	foreach(ltab, *wqueue)
  	{
  		AlteredTableInfo *tab = (AlteredTableInfo *) lfirst(ltab);
  
  		/*
  		 * If the table is source table of ATTACH PARTITION command, we did
  		 * not modify anything about it that will change its toasting
  		 * requirement, so no need to check.
  		 */
  		if (((tab->relkind == RELKIND_RELATION ||
  			  tab->relkind == RELKIND_PARTITIONED_TABLE) &&
  			 tab->partition_constraint == NULL) ||
  			tab->relkind == RELKIND_MATVIEW)
  			AlterTableCreateToastTable(tab->relid, (Datum) 0, lockmode);
  	}
  }
  
  /*
   * ATExecCmd: dispatch a subcommand to appropriate execution routine.
   *
   * YB NOTE: Will replace passed relation with another one in case it was re-created.
   */
  static void
  ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation *mutable_rel,
  		  AlterTableCmd *cmd, LOCKMODE lockmode)
  {
  	Relation      rel     = *mutable_rel;
  	ObjectAddress address = InvalidObjectAddress;
  
  	switch (cmd->subtype)
  	{
  		case AT_AddColumn:		/* ADD COLUMN */
  		case AT_AddColumnToView:	/* add column via CREATE OR REPLACE VIEW */
  			address = ATExecAddColumn(wqueue, tab, rel, (ColumnDef *) cmd->def,
  									  false, false, false,
  									  cmd->missing_ok, lockmode);
  			break;
  		case AT_AddColumnRecurse:
  			address = ATExecAddColumn(wqueue, tab, rel, (ColumnDef *) cmd->def,
  									  false, true, false,
  									  cmd->missing_ok, lockmode);
  			break;
  		case AT_ColumnDefault:	/* ALTER COLUMN DEFAULT */
  			address = ATExecColumnDefault(rel, cmd->name, cmd->def, lockmode);
  			break;
  		case AT_AddIdentity:
  			address = ATExecAddIdentity(rel, cmd->name, cmd->def, lockmode);
  			break;
  		case AT_SetIdentity:
  			address = ATExecSetIdentity(rel, cmd->name, cmd->def, lockmode);
  			break;
  		case AT_DropIdentity:
  			address = ATExecDropIdentity(rel, cmd->name, cmd->missing_ok, lockmode);
  			break;
  		case AT_DropNotNull:	/* ALTER COLUMN DROP NOT NULL */
  			address = ATExecDropNotNull(rel, cmd->name, lockmode);
  			break;
  		case AT_SetNotNull:		/* ALTER COLUMN SET NOT NULL */
  			address = ATExecSetNotNull(tab, rel, cmd->name, lockmode);
  			break;
  		case AT_SetStatistics:	/* ALTER COLUMN SET STATISTICS */
  			address = ATExecSetStatistics(rel, cmd->name, cmd->num, cmd->def, lockmode);
  			break;
  		case AT_SetOptions:		/* ALTER COLUMN SET ( options ) */
  			address = ATExecSetOptions(rel, cmd->name, cmd->def, false, lockmode);
  			break;
  		case AT_ResetOptions:	/* ALTER COLUMN RESET ( options ) */
  			address = ATExecSetOptions(rel, cmd->name, cmd->def, true, lockmode);
  			break;
  		case AT_SetStorage:		/* ALTER COLUMN SET STORAGE */
  			address = ATExecSetStorage(rel, cmd->name, cmd->def, lockmode);
  			break;
  		case AT_DropColumn:		/* DROP COLUMN */
  			address = ATExecDropColumn(wqueue, rel, cmd->name,
  									   cmd->behavior, false, false,
  									   cmd->missing_ok, lockmode);
  			break;
  		case AT_DropColumnRecurse:	/* DROP COLUMN with recursion */
  			address = ATExecDropColumn(wqueue, rel, cmd->name,
  									   cmd->behavior, true, false,
  									   cmd->missing_ok, lockmode);
  			break;
  		case AT_AddIndex:		/* ADD INDEX */
  			address = ATExecAddIndex(tab, mutable_rel, (IndexStmt *) cmd->def, false,
  									 lockmode);
  			break;
  		case AT_ReAddIndex:		/* ADD INDEX */
  			address = ATExecAddIndex(tab, mutable_rel, (IndexStmt *) cmd->def, true,
  									 lockmode);
  			break;
  		case AT_AddConstraint:	/* ADD CONSTRAINT */
  			address =
  				ATExecAddConstraint(wqueue, tab, rel, (Constraint *) cmd->def,
  									false, false, lockmode);
  			break;
  		case AT_AddConstraintRecurse:	/* ADD CONSTRAINT with recursion */
  			address =
  				ATExecAddConstraint(wqueue, tab, rel, (Constraint *) cmd->def,
  									true, false, lockmode);
  			break;
  		case AT_ReAddConstraint:	/* Re-add pre-existing check constraint */
  			address =
  				ATExecAddConstraint(wqueue, tab, rel, (Constraint *) cmd->def,
  									true, true, lockmode);
  			break;
  		case AT_ReAddDomainConstraint:	/* Re-add pre-existing domain check
  										 * constraint */
  			address =
  				AlterDomainAddConstraint(((AlterDomainStmt *) cmd->def)->typeName,
  										 ((AlterDomainStmt *) cmd->def)->def,
  										 NULL);
  			break;
  		case AT_ReAddComment:	/* Re-add existing comment */
  			address = CommentObject((CommentStmt *) cmd->def);
  			break;
  		case AT_AddIndexConstraint: /* ADD CONSTRAINT USING INDEX */
  			address = ATExecAddIndexConstraint(tab, rel, (IndexStmt *) cmd->def,
  											   lockmode);
  			break;
  		case AT_AlterConstraint:	/* ALTER CONSTRAINT */
  			address = ATExecAlterConstraint(rel, cmd, false, false, lockmode);
  			break;
  		case AT_ValidateConstraint: /* VALIDATE CONSTRAINT */
  			address = ATExecValidateConstraint(rel, cmd->name, false, false,
  											   lockmode);
  			break;
  		case AT_ValidateConstraintRecurse:	/* VALIDATE CONSTRAINT with
  											 * recursion */
  			address = ATExecValidateConstraint(rel, cmd->name, true, false,
  											   lockmode);
  			break;
  		case AT_DropConstraint: /* DROP CONSTRAINT */
  			ATExecDropConstraint(rel, cmd->name, cmd->behavior,
  								 false, false,
  								 cmd->missing_ok, lockmode);
  			break;
  		case AT_DropConstraintRecurse:	/* DROP CONSTRAINT with recursion */
  			ATExecDropConstraint(rel, cmd->name, cmd->behavior,
  								 true, false,
  								 cmd->missing_ok, lockmode);
  			break;
  		case AT_AlterColumnType:	/* ALTER COLUMN TYPE */
  			address = ATExecAlterColumnType(tab, rel, cmd, lockmode);
  			break;
  		case AT_AlterColumnGenericOptions:	/* ALTER COLUMN OPTIONS */
  			address =
  				ATExecAlterColumnGenericOptions(rel, cmd->name,
  												(List *) cmd->def, lockmode);
  			break;
  		case AT_ChangeOwner:	/* ALTER OWNER */
  			ATExecChangeOwner(RelationGetRelid(rel),
  							  get_rolespec_oid(cmd->newowner, false),
  							  false, lockmode);
  			break;
  		case AT_ClusterOn:		/* CLUSTER ON */
  			address = ATExecClusterOn(rel, cmd->name, lockmode);
  			break;
  		case AT_DropCluster:	/* SET WITHOUT CLUSTER */
  			ATExecDropCluster(rel, lockmode);
  			break;
  		case AT_SetLogged:		/* SET LOGGED */
  		case AT_SetUnLogged:	/* SET UNLOGGED */
  			break;
  		case AT_AddOids:		/* SET WITH OIDS */
  			/* Use the ADD COLUMN code, unless prep decided to do nothing */
  			if (cmd->def != NULL)
  				address =
  					ATExecAddColumn(wqueue, tab, rel, (ColumnDef *) cmd->def,
  									true, false, false,
  									cmd->missing_ok, lockmode);
  			break;
  		case AT_AddOidsRecurse: /* SET WITH OIDS */
  			/* Use the ADD COLUMN code, unless prep decided to do nothing */
  			if (cmd->def != NULL)
  				address =
  					ATExecAddColumn(wqueue, tab, rel, (ColumnDef *) cmd->def,
  									true, true, false,
  									cmd->missing_ok, lockmode);
  			break;
  		case AT_DropOids:		/* SET WITHOUT OIDS */
  
  			/*
  			 * Nothing to do here; we'll have generated a DropColumn
  			 * subcommand to do the real work
  			 */
  			break;
  		case AT_SetTableSpace:	/* SET TABLESPACE */
  			/*
  			 * Only do this for partitioned indexes, for which this is just
  			 * a catalog change.  Other relation types are handled by Phase 3.
  			 */
  			if (rel->rd_rel->relkind == RELKIND_PARTITIONED_INDEX)
  				ATExecPartedIdxSetTableSpace(rel, tab->newTableSpace);
  
  			break;
  		case AT_SetRelOptions:	/* SET (...) */
  		case AT_ResetRelOptions:	/* RESET (...) */
  		case AT_ReplaceRelOptions:	/* replace entire option list */
  			ATExecSetRelOptions(rel, (List *) cmd->def, cmd->subtype, lockmode);
  			break;
  		case AT_EnableTrig:		/* ENABLE TRIGGER name */
  			ATExecEnableDisableTrigger(rel, cmd->name,
  									   TRIGGER_FIRES_ON_ORIGIN, false, lockmode);
  			break;
  		case AT_EnableAlwaysTrig:	/* ENABLE ALWAYS TRIGGER name */
  			ATExecEnableDisableTrigger(rel, cmd->name,
  									   TRIGGER_FIRES_ALWAYS, false, lockmode);
  			break;
  		case AT_EnableReplicaTrig:	/* ENABLE REPLICA TRIGGER name */
  			ATExecEnableDisableTrigger(rel, cmd->name,
  									   TRIGGER_FIRES_ON_REPLICA, false, lockmode);
  			break;
  		case AT_DisableTrig:	/* DISABLE TRIGGER name */
  			ATExecEnableDisableTrigger(rel, cmd->name,
  									   TRIGGER_DISABLED, false, lockmode);
  			break;
  		case AT_EnableTrigAll:	/* ENABLE TRIGGER ALL */
  			ATExecEnableDisableTrigger(rel, NULL,
  									   TRIGGER_FIRES_ON_ORIGIN, false, lockmode);
  			break;
  		case AT_DisableTrigAll: /* DISABLE TRIGGER ALL */
  			ATExecEnableDisableTrigger(rel, NULL,
  									   TRIGGER_DISABLED, false, lockmode);
  			break;
  		case AT_EnableTrigUser: /* ENABLE TRIGGER USER */
  			ATExecEnableDisableTrigger(rel, NULL,
  									   TRIGGER_FIRES_ON_ORIGIN, true, lockmode);
  			break;
  		case AT_DisableTrigUser:	/* DISABLE TRIGGER USER */
  			ATExecEnableDisableTrigger(rel, NULL,
  									   TRIGGER_DISABLED, true, lockmode);
  			break;
  
  		case AT_EnableRule:		/* ENABLE RULE name */
  			ATExecEnableDisableRule(rel, cmd->name,
  									RULE_FIRES_ON_ORIGIN, lockmode);
  			break;
  		case AT_EnableAlwaysRule:	/* ENABLE ALWAYS RULE name */
  			ATExecEnableDisableRule(rel, cmd->name,
  									RULE_FIRES_ALWAYS, lockmode);
  			break;
  		case AT_EnableReplicaRule:	/* ENABLE REPLICA RULE name */
  			ATExecEnableDisableRule(rel, cmd->name,
  									RULE_FIRES_ON_REPLICA, lockmode);
  			break;
  		case AT_DisableRule:	/* DISABLE RULE name */
  			ATExecEnableDisableRule(rel, cmd->name,
  									RULE_DISABLED, lockmode);
  			break;
  
  		case AT_AddInherit:
  			address = ATExecAddInherit(rel, (RangeVar *) cmd->def, lockmode);
  			break;
  		case AT_DropInherit:
  			address = ATExecDropInherit(rel, (RangeVar *) cmd->def, lockmode);
  			break;
  		case AT_AddOf:
  			address = ATExecAddOf(rel, (TypeName *) cmd->def, lockmode);
  			break;
  		case AT_DropOf:
  			ATExecDropOf(rel, lockmode);
  			break;
  		case AT_ReplicaIdentity:
  			ATExecReplicaIdentity(rel, (ReplicaIdentityStmt *) cmd->def, lockmode);
  			break;
  		case AT_EnableRowSecurity:
  			ATExecEnableRowSecurity(rel);
  			break;
  		case AT_DisableRowSecurity:
  			ATExecDisableRowSecurity(rel);
  			break;
  		case AT_ForceRowSecurity:
  			ATExecForceNoForceRowSecurity(rel, true);
  			break;
  		case AT_NoForceRowSecurity:
  			ATExecForceNoForceRowSecurity(rel, false);
  			break;
  		case AT_GenericOptions:
  			ATExecGenericOptions(rel, (List *) cmd->def);
  			break;
  		case AT_AttachPartition:
  			if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  				ATExecAttachPartition(wqueue, rel, (PartitionCmd *) cmd->def);
  			else
  				ATExecAttachPartitionIdx(wqueue, rel,
  										 ((PartitionCmd *) cmd->def)->name);
  			break;
  		case AT_DetachPartition:
  			/* ATPrepCmd ensures it must be a table */
  			Assert(rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE);
  			ATExecDetachPartition(rel, ((PartitionCmd *) cmd->def)->name);
  			break;
  		default:				/* oops */
  			elog(ERROR, "unrecognized alter table type: %d",
  				 (int) cmd->subtype);
  			break;
  	}
  
  	/*
  	 * Report the subcommand to interested event triggers.
  	 */
  	EventTriggerCollectAlterTableSubcmd((Node *) cmd, address);
  
  	/*
  	 * Bump the command counter to ensure the next subcommand in the sequence
  	 * can see the changes so far
  	 */
  	CommandCounterIncrement();
  }
  
  /*
   * ATRewriteTables: ALTER TABLE phase 3
   */
  static void
  ATRewriteTables(AlterTableStmt *parsetree, List **wqueue, LOCKMODE lockmode)
  {
  	ListCell   *ltab;
  
  	/* Go through each table that needs to be checked or rewritten */
  	foreach(ltab, *wqueue)
  	{
  		AlteredTableInfo *tab = (AlteredTableInfo *) lfirst(ltab);
  
  		/*
  		 * Foreign tables have no storage, nor do partitioned tables and
  		 * indexes.
  		 */
  		if (tab->relkind == RELKIND_FOREIGN_TABLE ||
  			tab->relkind == RELKIND_PARTITIONED_TABLE ||
  			tab->relkind == RELKIND_PARTITIONED_INDEX)
  			continue;
  
  		/*
  		 * If we change column data types or add/remove OIDs, the operation
  		 * has to be propagated to tables that use this table's rowtype as a
  		 * column type.  tab->newvals will also be non-NULL in the case where
  		 * we're adding a column with a default.  We choose to forbid that
  		 * case as well, since composite types might eventually support
  		 * defaults.
  		 *
  		 * (Eventually we'll probably need to check for composite type
  		 * dependencies even when we're just scanning the table without a
  		 * rewrite, but at the moment a composite type does not enforce any
  		 * constraints, so it's not necessary/appropriate to enforce them just
  		 * during ALTER.)
  		 */
  		if (tab->newvals != NIL || tab->rewrite > 0)
  		{
  			Relation	rel;
  
  			rel = heap_open(tab->relid, NoLock);
  			find_composite_type_dependencies(rel->rd_rel->reltype, rel, NULL);
  			heap_close(rel, NoLock);
  		}
  
  		/*
  		 * We only need to rewrite the table if at least one column needs to
  		 * be recomputed, we are adding/removing the OID column, or we are
  		 * changing its persistence.
  		 *
  		 * There are two reasons for requiring a rewrite when changing
  		 * persistence: on one hand, we need to ensure that the buffers
  		 * belonging to each of the two relations are marked with or without
  		 * BM_PERMANENT properly.  On the other hand, since rewriting creates
  		 * and assigns a new relfilenode, we automatically create or drop an
  		 * init fork for the relation as appropriate.
  		 */
  		if (tab->rewrite > 0)
  		{
  			/* Build a temporary relation and copy data */
  			Relation	OldHeap;
  			Oid			OIDNewHeap;
  			Oid			NewTableSpace;
  			char		persistence;
  
  			OldHeap = heap_open(tab->relid, NoLock);
  
  			/*
  			 * We don't support rewriting of system catalogs; there are too
  			 * many corner cases and too little benefit.  In particular this
  			 * is certainly not going to work for mapped catalogs.
  			 */
  			if (IsSystemRelation(OldHeap))
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("cannot rewrite system relation \"%s\"",
  								RelationGetRelationName(OldHeap))));
  
  			if (RelationIsUsedAsCatalogTable(OldHeap))
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("cannot rewrite table \"%s\" used as a catalog table",
  								RelationGetRelationName(OldHeap))));
  
  			/*
  			 * Don't allow rewrite on temp tables of other backends ... their
  			 * local buffer manager is not going to cope.
  			 */
  			if (RELATION_IS_OTHER_TEMP(OldHeap))
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("cannot rewrite temporary tables of other sessions")));
  
  			/*
  			 * Select destination tablespace (same as original unless user
  			 * requested a change)
  			 */
  			if (tab->newTableSpace)
  				NewTableSpace = tab->newTableSpace;
  			else
  				NewTableSpace = OldHeap->rd_rel->reltablespace;
  
  			/*
  			 * Select persistence of transient table (same as original unless
  			 * user requested a change)
  			 */
  			persistence = tab->chgPersistence ?
  				tab->newrelpersistence : OldHeap->rd_rel->relpersistence;
  
  			heap_close(OldHeap, NoLock);
  
  			/*
  			 * Fire off an Event Trigger now, before actually rewriting the
  			 * table.
  			 *
  			 * We don't support Event Trigger for nested commands anywhere,
  			 * here included, and parsetree is given NULL when coming from
  			 * AlterTableInternal.
  			 *
  			 * And fire it only once.
  			 */
  			if (parsetree)
  				EventTriggerTableRewrite((Node *) parsetree,
  										 tab->relid,
  										 tab->rewrite);
  
  			/*
  			 * Create transient table that will receive the modified data.
  			 *
  			 * Ensure it is marked correctly as logged or unlogged.  We have
  			 * to do this here so that buffers for the new relfilenode will
  			 * have the right persistence set, and at the same time ensure
  			 * that the original filenode's buffers will get read in with the
  			 * correct setting (i.e. the original one).  Otherwise a rollback
  			 * after the rewrite would possibly result with buffers for the
  			 * original filenode having the wrong persistence setting.
  			 *
  			 * NB: This relies on swap_relation_files() also swapping the
  			 * persistence. That wouldn't work for pg_class, but that can't be
  			 * unlogged anyway.
  			 */
  			OIDNewHeap = make_new_heap(tab->relid, NewTableSpace, persistence,
  									   lockmode);
  
  			/*
  			 * Copy the heap data into the new table with the desired
  			 * modifications, and test the current data within the table
  			 * against new constraints generated by ALTER TABLE commands.
  			 */
  			ATRewriteTable(tab, OIDNewHeap, lockmode);
  
  			/*
  			 * Swap the physical files of the old and new heaps, then rebuild
  			 * indexes and discard the old heap.  We can use RecentXmin for
  			 * the table's new relfrozenxid because we rewrote all the tuples
  			 * in ATRewriteTable, so no older Xid remains in the table.  Also,
  			 * we never try to swap toast tables by content, since we have no
  			 * interest in letting this code work on system catalogs.
  			 */
  			finish_heap_swap(tab->relid, OIDNewHeap,
  							 false, false, true,
  							 !OidIsValid(tab->newTableSpace),
  							 RecentXmin,
  							 ReadNextMultiXactId(),
  							 persistence);
  		}
  		else
  		{
  			/*
  			 * Test the current data within the table against new constraints
  			 * generated by ALTER TABLE commands, but don't rebuild data.
  			 */
  			if (tab->constraints != NIL || tab->new_notnull ||
  				tab->partition_constraint != NULL)
  				ATRewriteTable(tab, InvalidOid, lockmode);
  
  			/*
  			 * If we had SET TABLESPACE but no reason to reconstruct tuples,
  			 * just do a block-by-block copy.
  			 */
  			if (tab->newTableSpace)
  				ATExecSetTableSpace(tab->relid, tab->newTableSpace, lockmode);
  		}
  	}
  
  	/*
  	 * Foreign key constraints are checked in a final pass, since (a) it's
  	 * generally best to examine each one separately, and (b) it's at least
  	 * theoretically possible that we have changed both relations of the
  	 * foreign key, and we'd better have finished both rewrites before we try
  	 * to read the tables.
  	 */
  	foreach(ltab, *wqueue)
  	{
  		AlteredTableInfo *tab = (AlteredTableInfo *) lfirst(ltab);
  		Relation	rel = NULL;
  		ListCell   *lcon;
  
  		foreach(lcon, tab->constraints)
  		{
  			NewConstraint *con = lfirst(lcon);
  
  			if (con->contype == CONSTR_FOREIGN)
  			{
  				Constraint *fkconstraint = (Constraint *) con->qual;
  				Relation	refrel;
  
  				if (rel == NULL)
  				{
  					/* Long since locked, no need for another */
  					rel = heap_open(tab->relid, NoLock);
  				}
  
  				refrel = heap_open(con->refrelid, RowShareLock);
  
  				validateForeignKeyConstraint(fkconstraint->conname, rel, refrel,
  											 con->refindid,
  											 con->conid);
  
  				/*
  				 * No need to mark the constraint row as validated, we did
  				 * that when we inserted the row earlier.
  				 */
  
  				heap_close(refrel, NoLock);
  			}
  		}
  
  		if (rel)
  			heap_close(rel, NoLock);
  	}
  }
  
  /*
   * ATRewriteTable: scan or rewrite one table
   *
   * OIDNewHeap is InvalidOid if we don't need to rewrite
   */
  static void
  ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap, LOCKMODE lockmode)
  {
  	Relation	oldrel;
  	Relation	newrel;
  	TupleDesc	oldTupDesc;
  	TupleDesc	newTupDesc;
  	bool		needscan = false;
  	List	   *notnull_attrs;
  	int			i;
  	ListCell   *l;
  	EState	   *estate;
  	CommandId	mycid;
  	BulkInsertState bistate;
  	int			hi_options;
  	ExprState  *partqualstate = NULL;
  
  	/*
  	 * Open the relation(s).  We have surely already locked the existing
  	 * table.
  	 */
  	oldrel = heap_open(tab->relid, NoLock);
  	oldTupDesc = tab->oldDesc;
  	newTupDesc = RelationGetDescr(oldrel);	/* includes all mods */
  
  	if (OidIsValid(OIDNewHeap))
  		newrel = heap_open(OIDNewHeap, lockmode);
  	else
  		newrel = NULL;
  
  	/*
  	 * Prepare a BulkInsertState and options for heap_insert. Because we're
  	 * building a new heap, we can skip WAL-logging and fsync it to disk at
  	 * the end instead (unless WAL-logging is required for archiving or
  	 * streaming replication). The FSM is empty too, so don't bother using it.
  	 */
  	if (newrel)
  	{
  		mycid = GetCurrentCommandId(true);
  		bistate = GetBulkInsertState();
  
  		hi_options = HEAP_INSERT_SKIP_FSM;
  		if (!XLogIsNeeded())
  			hi_options |= HEAP_INSERT_SKIP_WAL;
  	}
  	else
  	{
  		/* keep compiler quiet about using these uninitialized */
  		mycid = 0;
  		bistate = NULL;
  		hi_options = 0;
  	}
  
  	/*
  	 * Generate the constraint and default execution states
  	 */
  
  	estate = CreateExecutorState();
  
  	/* Build the needed expression execution states */
  	foreach(l, tab->constraints)
  	{
  		NewConstraint *con = lfirst(l);
  
  		switch (con->contype)
  		{
  			case CONSTR_CHECK:
  				needscan = true;
  				con->qualstate = ExecPrepareExpr((Expr *) con->qual, estate);
  				break;
  			case CONSTR_FOREIGN:
  				/* Nothing to do here */
  				break;
  			default:
  				elog(ERROR, "unrecognized constraint type: %d",
  					 (int) con->contype);
  		}
  	}
  
  	/* Build expression execution states for partition check quals */
  	if (tab->partition_constraint)
  	{
  		needscan = true;
  		partqualstate = ExecPrepareExpr(tab->partition_constraint, estate);
  	}
  
  	foreach(l, tab->newvals)
  	{
  		NewColumnValue *ex = lfirst(l);
  
  		/* expr already planned */
  		ex->exprstate = ExecInitExpr((Expr *) ex->expr, NULL);
  	}
  
  	notnull_attrs = NIL;
  	if (newrel || tab->new_notnull)
  	{
  		/*
  		 * If we are rebuilding the tuples OR if we added any new NOT NULL
  		 * constraints, check all not-null constraints.  This is a bit of
  		 * overkill but it minimizes risk of bugs, and heap_attisnull is a
  		 * pretty cheap test anyway.
  		 */
  		for (i = 0; i < newTupDesc->natts; i++)
  		{
  			Form_pg_attribute attr = TupleDescAttr(newTupDesc, i);
  
  			if (attr->attnotnull && !attr->attisdropped)
  				notnull_attrs = lappend_int(notnull_attrs, i);
  		}
  		if (notnull_attrs)
  			needscan = true;
  	}
  
  	if (newrel || needscan)
  	{
  		ExprContext *econtext;
  		Datum	   *values;
  		bool	   *isnull;
  		TupleTableSlot *oldslot;
  		TupleTableSlot *newslot;
  		HeapScanDesc scan;
  		HeapTuple	tuple;
  		MemoryContext oldCxt;
  		List	   *dropped_attrs = NIL;
  		ListCell   *lc;
  		Snapshot	snapshot;
  
  		if (newrel)
  			ereport(DEBUG1,
  					(errmsg("rewriting table \"%s\"",
  							RelationGetRelationName(oldrel))));
  		else
  			ereport(DEBUG1,
  					(errmsg("verifying table \"%s\"",
  							RelationGetRelationName(oldrel))));
  
  		if (newrel)
  		{
  			/*
  			 * All predicate locks on the tuples or pages are about to be made
  			 * invalid, because we move tuples around.  Promote them to
  			 * relation locks.
  			 */
  			TransferPredicateLocksToHeapRelation(oldrel);
  		}
  
  		econtext = GetPerTupleExprContext(estate);
  
  		/*
  		 * Make tuple slots for old and new tuples.  Note that even when the
  		 * tuples are the same, the tupDescs might not be (consider ADD COLUMN
  		 * without a default).
  		 */
  		oldslot = MakeSingleTupleTableSlot(oldTupDesc);
  		newslot = MakeSingleTupleTableSlot(newTupDesc);
  
  		/* Preallocate values/isnull arrays */
  		i = Max(newTupDesc->natts, oldTupDesc->natts);
  		values = (Datum *) palloc(i * sizeof(Datum));
  		isnull = (bool *) palloc(i * sizeof(bool));
  		memset(values, 0, i * sizeof(Datum));
  		memset(isnull, true, i * sizeof(bool));
  
  		/*
  		 * Any attributes that are dropped according to the new tuple
  		 * descriptor can be set to NULL. We precompute the list of dropped
  		 * attributes to avoid needing to do so in the per-tuple loop.
  		 */
  		for (i = 0; i < newTupDesc->natts; i++)
  		{
  			if (TupleDescAttr(newTupDesc, i)->attisdropped)
  				dropped_attrs = lappend_int(dropped_attrs, i);
  		}
  
  		/*
  		 * Scan through the rows, generating a new row if needed and then
  		 * checking all the constraints.
  		 */
  		snapshot = RegisterSnapshot(GetLatestSnapshot());
  		scan = heap_beginscan(oldrel, snapshot, 0, NULL);
  
  		/*
  		 * Switch to per-tuple memory context and reset it for each tuple
  		 * produced, so we don't leak memory.
  		 */
  		oldCxt = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
  
  		while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
  		{
  			if (tab->rewrite > 0)
  			{
  				Oid			tupOid = InvalidOid;
  
  				/* Extract data from old tuple */
  				heap_deform_tuple(tuple, oldTupDesc, values, isnull);
  				if (oldTupDesc->tdhasoid)
  					tupOid = HeapTupleGetOid(tuple);
  
  				/* Set dropped attributes to null in new tuple */
  				foreach(lc, dropped_attrs)
  					isnull[lfirst_int(lc)] = true;
  
  				/*
  				 * Process supplied expressions to replace selected columns.
  				 * Expression inputs come from the old tuple.
  				 */
  				ExecStoreHeapTuple(tuple, oldslot, false);
  				econtext->ecxt_scantuple = oldslot;
  
  				foreach(l, tab->newvals)
  				{
  					NewColumnValue *ex = lfirst(l);
  
  					values[ex->attnum - 1] = ExecEvalExpr(ex->exprstate,
  														  econtext,
  														  &isnull[ex->attnum - 1]);
  				}
  
  				/*
  				 * Form the new tuple. Note that we don't explicitly pfree it,
  				 * since the per-tuple memory context will be reset shortly.
  				 */
  				tuple = heap_form_tuple(newTupDesc, values, isnull);
  
  				/* Preserve OID, if any */
  				if (newTupDesc->tdhasoid)
  					HeapTupleSetOid(tuple, tupOid);
  
  				/*
  				 * Constraints might reference the tableoid column, so
  				 * initialize t_tableOid before evaluating them.
  				 */
  				tuple->t_tableOid = RelationGetRelid(oldrel);
  			}
  
  			/* Now check any constraints on the possibly-changed tuple */
  			ExecStoreHeapTuple(tuple, newslot, false);
  			econtext->ecxt_scantuple = newslot;
  
  			foreach(l, notnull_attrs)
  			{
  				int			attn = lfirst_int(l);
  
  				if (heap_attisnull(tuple, attn + 1, newTupDesc))
  				{
  					Form_pg_attribute attr = TupleDescAttr(newTupDesc, attn);
  
  					ereport(ERROR,
  							(errcode(ERRCODE_NOT_NULL_VIOLATION),
  							 errmsg("column \"%s\" contains null values",
  									NameStr(attr->attname)),
  							 errtablecol(oldrel, attn + 1)));
  				}
  			}
  
  			foreach(l, tab->constraints)
  			{
  				NewConstraint *con = lfirst(l);
  
  				switch (con->contype)
  				{
  					case CONSTR_CHECK:
  						if (!ExecCheck(con->qualstate, econtext))
  						{
  							/* If YugaByte is enabled, the add constraint operation is not atomic.
  							 * So we must delete the relevant entries from the catalog tables. */
  							if (IsYugaByteEnabled())
  							{
  								ATExecDropConstraint(oldrel, con->name, DROP_RESTRICT, true, false,
  													 false, lockmode);
  							}
  							ereport(ERROR,
  									(errcode(ERRCODE_CHECK_VIOLATION),
  									 errmsg("check constraint \"%s\" is violated by some row",
  											con->name),
  									 errtableconstraint(oldrel, con->name)));
  						}
  						break;
  					case CONSTR_FOREIGN:
  						/* Nothing to do here */
  						break;
  					default:
  						elog(ERROR, "unrecognized constraint type: %d",
  							 (int) con->contype);
  				}
  			}
  
  			if (partqualstate && !ExecCheck(partqualstate, econtext))
  			{
  				if (tab->validate_default)
  					ereport(ERROR,
  							(errcode(ERRCODE_CHECK_VIOLATION),
  							 errmsg("updated partition constraint for default partition would be violated by some row")));
  				else
  					ereport(ERROR,
  							(errcode(ERRCODE_CHECK_VIOLATION),
  							 errmsg("partition constraint is violated by some row")));
  			}
  
  			/* Write the tuple out to the new relation */
  			if (newrel)
  				heap_insert(newrel, tuple, mycid, hi_options, bistate);
  
  			ResetExprContext(econtext);
  
  			CHECK_FOR_INTERRUPTS();
  		}
  
  		MemoryContextSwitchTo(oldCxt);
  		heap_endscan(scan);
  		UnregisterSnapshot(snapshot);
  
  		ExecDropSingleTupleTableSlot(oldslot);
  		ExecDropSingleTupleTableSlot(newslot);
  	}
  
  	FreeExecutorState(estate);
  
  	heap_close(oldrel, NoLock);
  	if (newrel)
  	{
  		FreeBulkInsertState(bistate);
  
  		/* If we skipped writing WAL, then we need to sync the heap. */
  		if (hi_options & HEAP_INSERT_SKIP_WAL)
  			heap_sync(newrel);
  
  		heap_close(newrel, NoLock);
  	}
  }
  
  /*
   * ATGetQueueEntry: find or create an entry in the ALTER TABLE work queue
   */
  static AlteredTableInfo *
  ATGetQueueEntry(List **wqueue, Relation rel)
  {
  	Oid			relid = RelationGetRelid(rel);
  	AlteredTableInfo *tab;
  	ListCell   *ltab;
  
  	foreach(ltab, *wqueue)
  	{
  		tab = (AlteredTableInfo *) lfirst(ltab);
  		if (tab->relid == relid)
  			return tab;
  	}
  
  	/*
  	 * Not there, so add it.  Note that we make a copy of the relation's
  	 * existing descriptor before anything interesting can happen to it.
  	 */
  	tab = (AlteredTableInfo *) palloc0(sizeof(AlteredTableInfo));
  	tab->relid = relid;
  	tab->relkind = rel->rd_rel->relkind;
  	tab->oldDesc = CreateTupleDescCopyConstr(RelationGetDescr(rel));
  	tab->newrelpersistence = RELPERSISTENCE_PERMANENT;
  	tab->chgPersistence = false;
  
  	*wqueue = lappend(*wqueue, tab);
  
  	return tab;
  }
  
  /*
   * ATSimplePermissions
   *
   * - Ensure that it is a relation (or possibly a view)
   * - Ensure this user is the owner
   * - Ensure that it is not a system table
   */
  static void
  ATSimplePermissions(Relation rel, int allowed_targets)
  {
  	int			actual_target;
  
  	switch (rel->rd_rel->relkind)
  	{
  		case RELKIND_RELATION:
  		case RELKIND_PARTITIONED_TABLE:
  			actual_target = ATT_TABLE;
  			break;
  		case RELKIND_VIEW:
  			actual_target = ATT_VIEW;
  			break;
  		case RELKIND_MATVIEW:
  			actual_target = ATT_MATVIEW;
  			break;
  		case RELKIND_INDEX:
  			actual_target = ATT_INDEX;
  			break;
  		case RELKIND_PARTITIONED_INDEX:
  			actual_target = ATT_PARTITIONED_INDEX;
  			break;
  		case RELKIND_COMPOSITE_TYPE:
  			actual_target = ATT_COMPOSITE_TYPE;
  			break;
  		case RELKIND_FOREIGN_TABLE:
  			actual_target = ATT_FOREIGN_TABLE;
  			break;
  		default:
  			actual_target = 0;
  			break;
  	}
  
  	/* Wrong target type? */
  	if ((actual_target & allowed_targets) == 0)
  		ATWrongRelkindError(rel, allowed_targets);
  
  	/* Permissions checks */
  	if (!pg_class_ownercheck(RelationGetRelid(rel), GetUserId()))
  		aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(rel->rd_rel->relkind),
  					   RelationGetRelationName(rel));
  
  	if (!allowSystemTableMods && IsSystemRelation(rel))
  		ereport(ERROR,
  				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  				 errmsg("permission denied: \"%s\" is a system catalog",
  						RelationGetRelationName(rel))));
  }
  
  /*
   * ATWrongRelkindError
   *
   * Throw an error when a relation has been determined to be of the wrong
   * type.
   */
  static void
  ATWrongRelkindError(Relation rel, int allowed_targets)
  {
  	char	   *msg;
  
  	switch (allowed_targets)
  	{
  		case ATT_TABLE:
  			msg = _("\"%s\" is not a table");
  			break;
  		case ATT_TABLE | ATT_VIEW:
  			msg = _("\"%s\" is not a table or view");
  			break;
  		case ATT_TABLE | ATT_VIEW | ATT_FOREIGN_TABLE:
  			msg = _("\"%s\" is not a table, view, or foreign table");
  			break;
  		case ATT_TABLE | ATT_VIEW | ATT_MATVIEW | ATT_INDEX:
  			msg = _("\"%s\" is not a table, view, materialized view, or index");
  			break;
  		case ATT_TABLE | ATT_MATVIEW:
  			msg = _("\"%s\" is not a table or materialized view");
  			break;
  		case ATT_TABLE | ATT_MATVIEW | ATT_INDEX:
  			msg = _("\"%s\" is not a table, materialized view, or index");
  			break;
  		case ATT_TABLE | ATT_MATVIEW | ATT_FOREIGN_TABLE:
  			msg = _("\"%s\" is not a table, materialized view, or foreign table");
  			break;
  		case ATT_TABLE | ATT_FOREIGN_TABLE:
  			msg = _("\"%s\" is not a table or foreign table");
  			break;
  		case ATT_TABLE | ATT_COMPOSITE_TYPE | ATT_FOREIGN_TABLE:
  			msg = _("\"%s\" is not a table, composite type, or foreign table");
  			break;
  		case ATT_TABLE | ATT_MATVIEW | ATT_INDEX | ATT_FOREIGN_TABLE:
  			msg = _("\"%s\" is not a table, materialized view, index, or foreign table");
  			break;
  		case ATT_VIEW:
  			msg = _("\"%s\" is not a view");
  			break;
  		case ATT_FOREIGN_TABLE:
  			msg = _("\"%s\" is not a foreign table");
  			break;
  		default:
  			/* shouldn't get here, add all necessary cases above */
  			msg = _("\"%s\" is of the wrong type");
  			break;
  	}
  
  	ereport(ERROR,
  			(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  			 errmsg(msg, RelationGetRelationName(rel))));
  }
  
  /*
   * ATSimpleRecursion
   *
   * Simple table recursion sufficient for most ALTER TABLE operations.
   * All direct and indirect children are processed in an unspecified order.
   * Note that if a child inherits from the original table via multiple
   * inheritance paths, it will be visited just once.
   */
  static void
  ATSimpleRecursion(List **wqueue, Relation rel,
  				  AlterTableCmd *cmd, bool recurse, LOCKMODE lockmode)
  {
  	/*
  	 * Propagate to children if desired.  Only plain tables and foreign tables
  	 * have children, so no need to search for other relkinds.
  	 */
  	if (recurse &&
  		(rel->rd_rel->relkind == RELKIND_RELATION ||
  		 rel->rd_rel->relkind == RELKIND_FOREIGN_TABLE ||
  		 rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE))
  	{
  		Oid			relid = RelationGetRelid(rel);
  		ListCell   *child;
  		List	   *children;
  
  		children = find_all_inheritors(relid, lockmode, NULL);
  
  		/*
  		 * find_all_inheritors does the recursive search of the inheritance
  		 * hierarchy, so all we have to do is process all of the relids in the
  		 * list that it returns.
  		 */
  		foreach(child, children)
  		{
  			Oid			childrelid = lfirst_oid(child);
  			Relation	childrel;
  
  			if (childrelid == relid)
  				continue;
  			/* find_all_inheritors already got lock */
  			childrel = relation_open(childrelid, NoLock);
  			CheckTableNotInUse(childrel, "ALTER TABLE");
  			ATPrepCmd(wqueue, childrel, cmd, false, true, lockmode);
  			relation_close(childrel, NoLock);
  		}
  	}
  }
  
  /*
   * ATTypedTableRecursion
   *
   * Propagate ALTER TYPE operations to the typed tables of that type.
   * Also check the RESTRICT/CASCADE behavior.  Given CASCADE, also permit
   * recursion to inheritance children of the typed tables.
   */
  static void
  ATTypedTableRecursion(List **wqueue, Relation rel, AlterTableCmd *cmd,
  					  LOCKMODE lockmode)
  {
  	ListCell   *child;
  	List	   *children;
  
  	Assert(rel->rd_rel->relkind == RELKIND_COMPOSITE_TYPE);
  
  	children = find_typed_table_dependencies(rel->rd_rel->reltype,
  											 RelationGetRelationName(rel),
  											 cmd->behavior);
  
  	foreach(child, children)
  	{
  		Oid			childrelid = lfirst_oid(child);
  		Relation	childrel;
  
  		childrel = relation_open(childrelid, lockmode);
  		CheckTableNotInUse(childrel, "ALTER TABLE");
  		ATPrepCmd(wqueue, childrel, cmd, true, true, lockmode);
  		relation_close(childrel, NoLock);
  	}
  }
  
  
  /*
   * find_composite_type_dependencies
   *
   * Check to see if the type "typeOid" is being used as a column in some table
   * (possibly nested several levels deep in composite types, arrays, etc!).
   * Eventually, we'd like to propagate the check or rewrite operation
   * into such tables, but for now, just error out if we find any.
   *
   * Caller should provide either the associated relation of a rowtype,
   * or a type name (not both) for use in the error message, if any.
   *
   * Note that "typeOid" is not necessarily a composite type; it could also be
   * another container type such as an array or range, or a domain over one of
   * these things.  The name of this function is therefore somewhat historical,
   * but it's not worth changing.
   *
   * We assume that functions and views depending on the type are not reasons
   * to reject the ALTER.  (How safe is this really?)
   */
  void
  find_composite_type_dependencies(Oid typeOid, Relation origRelation,
  								 const char *origTypeName)
  {
  	Relation	depRel;
  	ScanKeyData key[2];
  	SysScanDesc depScan;
  	HeapTuple	depTup;
  
  	/* since this function recurses, it could be driven to stack overflow */
  	check_stack_depth();
  
  	/*
  	 * We scan pg_depend to find those things that depend on the given type.
  	 * (We assume we can ignore refobjsubid for a type.)
  	 */
  	depRel = heap_open(DependRelationId, AccessShareLock);
  
  	ScanKeyInit(&key[0],
  				Anum_pg_depend_refclassid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(TypeRelationId));
  	ScanKeyInit(&key[1],
  				Anum_pg_depend_refobjid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(typeOid));
  
  	depScan = systable_beginscan(depRel, DependReferenceIndexId, true,
  								 NULL, 2, key);
  
  	while (HeapTupleIsValid(depTup = systable_getnext(depScan)))
  	{
  		Form_pg_depend pg_depend = (Form_pg_depend) GETSTRUCT(depTup);
  		Relation	rel;
  		Form_pg_attribute att;
  
  		/* Check for directly dependent types */
  		if (pg_depend->classid == TypeRelationId)
  		{
  			/*
  			 * This must be an array, domain, or range containing the given
  			 * type, so recursively check for uses of this type.  Note that
  			 * any error message will mention the original type not the
  			 * container; this is intentional.
  			 */
  			find_composite_type_dependencies(pg_depend->objid,
  											 origRelation, origTypeName);
  			continue;
  		}
  
  		/* Else, ignore dependees that aren't user columns of relations */
  		/* (we assume system columns are never of interesting types) */
  		if (pg_depend->classid != RelationRelationId ||
  			pg_depend->objsubid <= 0)
  			continue;
  
  		rel = relation_open(pg_depend->objid, AccessShareLock);
  		att = TupleDescAttr(rel->rd_att, pg_depend->objsubid - 1);
  
  		if (rel->rd_rel->relkind == RELKIND_RELATION ||
  			rel->rd_rel->relkind == RELKIND_MATVIEW ||
  			rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  		{
  			if (origTypeName)
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("cannot alter type \"%s\" because column \"%s.%s\" uses it",
  								origTypeName,
  								RelationGetRelationName(rel),
  								NameStr(att->attname))));
  			else if (origRelation->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("cannot alter type \"%s\" because column \"%s.%s\" uses it",
  								RelationGetRelationName(origRelation),
  								RelationGetRelationName(rel),
  								NameStr(att->attname))));
  			else if (origRelation->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("cannot alter foreign table \"%s\" because column \"%s.%s\" uses its row type",
  								RelationGetRelationName(origRelation),
  								RelationGetRelationName(rel),
  								NameStr(att->attname))));
  			else
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("cannot alter table \"%s\" because column \"%s.%s\" uses its row type",
  								RelationGetRelationName(origRelation),
  								RelationGetRelationName(rel),
  								NameStr(att->attname))));
  		}
  		else if (OidIsValid(rel->rd_rel->reltype))
  		{
  			/*
  			 * A view or composite type itself isn't a problem, but we must
  			 * recursively check for indirect dependencies via its rowtype.
  			 */
  			find_composite_type_dependencies(rel->rd_rel->reltype,
  											 origRelation, origTypeName);
  		}
  
  		relation_close(rel, AccessShareLock);
  	}
  
  	systable_endscan(depScan);
  
  	relation_close(depRel, AccessShareLock);
  }
  
  
  /*
   * find_typed_table_dependencies
   *
   * Check to see if a composite type is being used as the type of a
   * typed table.  Abort if any are found and behavior is RESTRICT.
   * Else return the list of tables.
   */
  static List *
  find_typed_table_dependencies(Oid typeOid, const char *typeName, DropBehavior behavior)
  {
  	Relation	classRel;
  	ScanKeyData key[1];
  	HeapScanDesc scan;
  	HeapTuple	tuple;
  	List	   *result = NIL;
  
  	classRel = heap_open(RelationRelationId, AccessShareLock);
  
  	ScanKeyInit(&key[0],
  				Anum_pg_class_reloftype,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(typeOid));
  
  	scan = heap_beginscan_catalog(classRel, 1, key);
  
  	while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
  	{
  		if (behavior == DROP_RESTRICT)
  			ereport(ERROR,
  					(errcode(ERRCODE_DEPENDENT_OBJECTS_STILL_EXIST),
  					 errmsg("cannot alter type \"%s\" because it is the type of a typed table",
  							typeName),
  					 errhint("Use ALTER ... CASCADE to alter the typed tables too.")));
  		else
  			result = lappend_oid(result, HeapTupleGetOid(tuple));
  	}
  
  	heap_endscan(scan);
  	heap_close(classRel, AccessShareLock);
  
  	return result;
  }
  
  
  /*
   * check_of_type
   *
   * Check whether a type is suitable for CREATE TABLE OF/ALTER TABLE OF.  If it
   * isn't suitable, throw an error.  Currently, we require that the type
   * originated with CREATE TYPE AS.  We could support any row type, but doing so
   * would require handling a number of extra corner cases in the DDL commands.
   * (Also, allowing domain-over-composite would open up a can of worms about
   * whether and how the domain's constraints should apply to derived tables.)
   */
  void
  check_of_type(HeapTuple typetuple)
  {
  	Form_pg_type typ = (Form_pg_type) GETSTRUCT(typetuple);
  	bool		typeOk = false;
  
  	if (typ->typtype == TYPTYPE_COMPOSITE)
  	{
  		Relation	typeRelation;
  
  		Assert(OidIsValid(typ->typrelid));
  		typeRelation = relation_open(typ->typrelid, AccessShareLock);
  		typeOk = (typeRelation->rd_rel->relkind == RELKIND_COMPOSITE_TYPE);
  
  		/*
  		 * Close the parent rel, but keep our AccessShareLock on it until xact
  		 * commit.  That will prevent someone else from deleting or ALTERing
  		 * the type before the typed table creation/conversion commits.
  		 */
  		relation_close(typeRelation, NoLock);
  	}
  	if (!typeOk)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("type %s is not a composite type",
  						format_type_be(HeapTupleGetOid(typetuple)))));
  }
  
  
  /*
   * ALTER TABLE ADD COLUMN
   *
   * Adds an additional attribute to a relation making the assumption that
   * CHECK, NOT NULL, and FOREIGN KEY constraints will be removed from the
   * AT_AddColumn AlterTableCmd by parse_utilcmd.c and added as independent
   * AlterTableCmd's.
   *
   * ADD COLUMN cannot use the normal ALTER TABLE recursion mechanism, because we
   * have to decide at runtime whether to recurse or not depending on whether we
   * actually add a column or merely merge with an existing column.  (We can't
   * check this in a static pre-pass because it won't handle multiple inheritance
   * situations correctly.)
   */
  static void
  ATPrepAddColumn(List **wqueue, Relation rel, bool recurse, bool recursing,
  				bool is_view, AlterTableCmd *cmd, LOCKMODE lockmode)
  {
  	if (rel->rd_rel->reloftype && !recursing)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot add column to typed table")));
  
  	if (rel->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
  		ATTypedTableRecursion(wqueue, rel, cmd, lockmode);
  
  	if (recurse && !is_view)
  		cmd->subtype = AT_AddColumnRecurse;
  }
  
  /*
   * Add a column to a table; this handles the AT_AddOids cases as well.  The
   * return value is the address of the new column in the parent relation.
   */
  static ObjectAddress
  ATExecAddColumn(List **wqueue, AlteredTableInfo *tab, Relation rel,
  				ColumnDef *colDef, bool isOid,
  				bool recurse, bool recursing,
  				bool if_not_exists, LOCKMODE lockmode)
  {
  	Oid			myrelid = RelationGetRelid(rel);
  	Relation	pgclass,
  				attrdesc;
  	HeapTuple	reltup;
  	FormData_pg_attribute attribute;
  	int			newattnum;
  	char		relkind;
  	HeapTuple	typeTuple;
  	Oid			typeOid;
  	int32		typmod;
  	Oid			collOid;
  	Form_pg_type tform;
  	Expr	   *defval;
  	List	   *children;
  	ListCell   *child;
  	AclResult	aclresult;
  	ObjectAddress address;
  
  	/* At top level, permission check was done in ATPrepCmd, else do it */
  	if (recursing)
  		ATSimplePermissions(rel, ATT_TABLE | ATT_FOREIGN_TABLE);
  
  	if (rel->rd_rel->relispartition && !recursing)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot add column to a partition")));
  
  	attrdesc = heap_open(AttributeRelationId, RowExclusiveLock);
  
  	/*
  	 * Are we adding the column to a recursion child?  If so, check whether to
  	 * merge with an existing definition for the column.  If we do merge, we
  	 * must not recurse.  Children will already have the column, and recursing
  	 * into them would mess up attinhcount.
  	 */
  	if (colDef->inhcount > 0)
  	{
  		HeapTuple	tuple;
  
  		/* Does child already have a column by this name? */
  		tuple = SearchSysCacheCopyAttName(myrelid, colDef->colname);
  		if (HeapTupleIsValid(tuple))
  		{
  			Form_pg_attribute childatt = (Form_pg_attribute) GETSTRUCT(tuple);
  			Oid			ctypeId;
  			int32		ctypmod;
  			Oid			ccollid;
  
  			/* Child column must match on type, typmod, and collation */
  			typenameTypeIdAndMod(NULL, colDef->typeName, &ctypeId, &ctypmod);
  			if (ctypeId != childatt->atttypid ||
  				ctypmod != childatt->atttypmod)
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("child table \"%s\" has different type for column \"%s\"",
  								RelationGetRelationName(rel), colDef->colname)));
  			ccollid = GetColumnDefCollation(NULL, colDef, ctypeId);
  			if (ccollid != childatt->attcollation)
  				ereport(ERROR,
  						(errcode(ERRCODE_COLLATION_MISMATCH),
  						 errmsg("child table \"%s\" has different collation for column \"%s\"",
  								RelationGetRelationName(rel), colDef->colname),
  						 errdetail("\"%s\" versus \"%s\"",
  								   get_collation_name(ccollid),
  								   get_collation_name(childatt->attcollation))));
  
  			/* If it's OID, child column must actually be OID */
  			if (isOid && childatt->attnum != ObjectIdAttributeNumber)
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("child table \"%s\" has a conflicting \"%s\" column",
  								RelationGetRelationName(rel), colDef->colname)));
  
  			/* Bump the existing child att's inhcount */
  			childatt->attinhcount++;
  			CatalogTupleUpdate(attrdesc, &tuple->t_self, tuple);
  
  			heap_freetuple(tuple);
  
  			/* Inform the user about the merge */
  			ereport(NOTICE,
  					(errmsg("merging definition of column \"%s\" for child \"%s\"",
  							colDef->colname, RelationGetRelationName(rel))));
  
  			heap_close(attrdesc, RowExclusiveLock);
  			return InvalidObjectAddress;
  		}
  	}
  
  	pgclass = heap_open(RelationRelationId, RowExclusiveLock);
  
  	reltup = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(myrelid));
  	if (!HeapTupleIsValid(reltup))
  		elog(ERROR, "cache lookup failed for relation %u", myrelid);
  	relkind = ((Form_pg_class) GETSTRUCT(reltup))->relkind;
  
  	/*
  	 * Cannot add identity column if table has children, because identity does
  	 * not inherit.  (Adding column and identity separately will work.)
  	 */
  	if (colDef->identity &&
  		recurse &&
  		find_inheritance_children(myrelid, NoLock) != NIL)
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  				 errmsg("cannot recursively add identity column to table that has child tables")));
  
  	/* skip if the name already exists and if_not_exists is true */
  	if (!check_for_column_name_collision(rel, colDef->colname, if_not_exists))
  	{
  		heap_close(attrdesc, RowExclusiveLock);
  		heap_freetuple(reltup);
  		heap_close(pgclass, RowExclusiveLock);
  		return InvalidObjectAddress;
  	}
  
  	/* Determine the new attribute's number */
  	if (isOid)
  		newattnum = ObjectIdAttributeNumber;
  	else
  	{
  		newattnum = ((Form_pg_class) GETSTRUCT(reltup))->relnatts + 1;
  		if (newattnum > MaxHeapAttributeNumber)
  			ereport(ERROR,
  					(errcode(ERRCODE_TOO_MANY_COLUMNS),
  					 errmsg("tables can have at most %d columns",
  							MaxHeapAttributeNumber)));
  	}
  
  	typeTuple = typenameType(NULL, colDef->typeName, &typmod);
  	tform = (Form_pg_type) GETSTRUCT(typeTuple);
  	typeOid = HeapTupleGetOid(typeTuple);
  
  	aclresult = pg_type_aclcheck(typeOid, GetUserId(), ACL_USAGE);
  	if (aclresult != ACLCHECK_OK)
  		aclcheck_error_type(aclresult, typeOid);
  
  	collOid = GetColumnDefCollation(NULL, colDef, typeOid);
  
  	/* make sure datatype is legal for a column */
  	CheckAttributeType(colDef->colname, typeOid, collOid,
  					   list_make1_oid(rel->rd_rel->reltype),
  					   false);
  
  	/* construct new attribute's pg_attribute entry */
  	attribute.attrelid = myrelid;
  	namestrcpy(&(attribute.attname), colDef->colname);
  	attribute.atttypid = typeOid;
  	attribute.attstattarget = (newattnum > 0) ? -1 : 0;
  	attribute.attlen = tform->typlen;
  	attribute.attcacheoff = -1;
  	attribute.atttypmod = typmod;
  	attribute.attnum = newattnum;
  	attribute.attbyval = tform->typbyval;
  	attribute.attndims = list_length(colDef->typeName->arrayBounds);
  	attribute.attstorage = tform->typstorage;
  	attribute.attalign = tform->typalign;
  	attribute.attnotnull = colDef->is_not_null;
  	attribute.atthasdef = false;
  	attribute.atthasmissing = false;
  	attribute.attidentity = colDef->identity;
  	attribute.attisdropped = false;
  	attribute.attislocal = colDef->is_local;
  	attribute.attinhcount = colDef->inhcount;
  	attribute.attcollation = collOid;
  	/* attribute.attacl is handled by InsertPgAttributeTuple */
  
  	ReleaseSysCache(typeTuple);
  
  	InsertPgAttributeTuple(attrdesc, &attribute, NULL,
  		((Form_pg_class) GETSTRUCT(reltup))->relisshared && !IsBootstrapProcessingMode());
  
  	heap_close(attrdesc, RowExclusiveLock);
  
  	/*
  	 * Update pg_class tuple as appropriate
  	 */
  	if (isOid)
  		((Form_pg_class) GETSTRUCT(reltup))->relhasoids = true;
  	else
  		((Form_pg_class) GETSTRUCT(reltup))->relnatts = newattnum;
  
  	CatalogTupleUpdate(pgclass, &reltup->t_self, reltup);
  
  	heap_freetuple(reltup);
  
  	/* Post creation hook for new attribute */
  	InvokeObjectPostCreateHook(RelationRelationId, myrelid, newattnum);
  
  	heap_close(pgclass, RowExclusiveLock);
  
  	/* Make the attribute's catalog entry visible */
  	CommandCounterIncrement();
  
  	/*
  	 * Store the DEFAULT, if any, in the catalogs
  	 */
  	if (colDef->raw_default)
  	{
  		RawColumnDefault *rawEnt;
  
  		rawEnt = (RawColumnDefault *) palloc(sizeof(RawColumnDefault));
  		rawEnt->attnum = attribute.attnum;
  		rawEnt->raw_default = copyObject(colDef->raw_default);
  
  		/*
  		 * Attempt to skip a complete table rewrite by storing the specified
  		 * DEFAULT value outside of the heap.  This may be disabled inside
  		 * AddRelationNewConstraints if the optimization cannot be applied.
  		 */
  		rawEnt->missingMode = true;
  
  		/*
  		 * This function is intended for CREATE TABLE, so it processes a
  		 * _list_ of defaults, but we just do one.
  		 */
  		AddRelationNewConstraints(rel, list_make1(rawEnt), NIL,
  								  false, true, false, NULL);
  
  		/* Make the additional catalog changes visible */
  		CommandCounterIncrement();
  
  		/*
  		 * Did the request for a missing value work? If not we'll have to do a
  		 * rewrite
  		 */
  		if (!rawEnt->missingMode)
  			tab->rewrite |= AT_REWRITE_DEFAULT_VAL;
  	}
  
  	/*
  	 * Tell Phase 3 to fill in the default expression, if there is one.
  	 *
  	 * If there is no default, Phase 3 doesn't have to do anything, because
  	 * that effectively means that the default is NULL.  The heap tuple access
  	 * routines always check for attnum > # of attributes in tuple, and return
  	 * NULL if so, so without any modification of the tuple data we will get
  	 * the effect of NULL values in the new column.
  	 *
  	 * An exception occurs when the new column is of a domain type: the domain
  	 * might have a NOT NULL constraint, or a check constraint that indirectly
  	 * rejects nulls.  If there are any domain constraints then we construct
  	 * an explicit NULL default value that will be passed through
  	 * CoerceToDomain processing.  (This is a tad inefficient, since it causes
  	 * rewriting the table which we really don't have to do, but the present
  	 * design of domain processing doesn't offer any simple way of checking
  	 * the constraints more directly.)
  	 *
  	 * Note: we use build_column_default, and not just the cooked default
  	 * returned by AddRelationNewConstraints, so that the right thing happens
  	 * when a datatype's default applies.
  	 *
  	 * We skip this step completely for views and foreign tables.  For a view,
  	 * we can only get here from CREATE OR REPLACE VIEW, which historically
  	 * doesn't set up defaults, not even for domain-typed columns.  And in any
  	 * case we mustn't invoke Phase 3 on a view or foreign table, since they
  	 * have no storage.
  	 */
  	if (relkind != RELKIND_VIEW && relkind != RELKIND_COMPOSITE_TYPE
  		&& relkind != RELKIND_FOREIGN_TABLE && attribute.attnum > 0)
  	{
  		/*
  		 * For an identity column, we can't use build_column_default(),
  		 * because the sequence ownership isn't set yet.  So do it manually.
  		 */
  		if (colDef->identity)
  		{
  			NextValueExpr *nve = makeNode(NextValueExpr);
  
  			nve->seqid = RangeVarGetRelid(colDef->identitySequence, NoLock, false);
  			nve->typeId = typeOid;
  
  			defval = (Expr *) nve;
  
  			/* must do a rewrite for identity columns */
  			tab->rewrite |= AT_REWRITE_DEFAULT_VAL;
  		}
  		else
  			defval = (Expr *) build_column_default(rel, attribute.attnum);
  
  		if (!defval && DomainHasConstraints(typeOid))
  		{
  			Oid			baseTypeId;
  			int32		baseTypeMod;
  			Oid			baseTypeColl;
  
  			baseTypeMod = typmod;
  			baseTypeId = getBaseTypeAndTypmod(typeOid, &baseTypeMod);
  			baseTypeColl = get_typcollation(baseTypeId);
  			defval = (Expr *) makeNullConst(baseTypeId, baseTypeMod, baseTypeColl);
  			defval = (Expr *) coerce_to_target_type(NULL,
  													(Node *) defval,
  													baseTypeId,
  													typeOid,
  													typmod,
  													COERCION_ASSIGNMENT,
  													COERCE_IMPLICIT_CAST,
  													-1);
  			if (defval == NULL) /* should not happen */
  				elog(ERROR, "failed to coerce base type to domain");
  		}
  
  		if (defval)
  		{
  			NewColumnValue *newval;
  
  			newval = (NewColumnValue *) palloc0(sizeof(NewColumnValue));
  			newval->attnum = attribute.attnum;
  			newval->expr = expression_planner(defval);
  
  			tab->newvals = lappend(tab->newvals, newval);
  		}
  
  		if (DomainHasConstraints(typeOid))
  			tab->rewrite |= AT_REWRITE_DEFAULT_VAL;
  
  		if (!TupleDescAttr(rel->rd_att, attribute.attnum - 1)->atthasmissing)
  		{
  			/*
  			 * If the new column is NOT NULL, and there is no missing value,
  			 * tell Phase 3 it needs to test that. (Note we don't do this for
  			 * an OID column.  OID will be marked not null, but since it's
  			 * filled specially, there's no need to test anything.)
  			 */
  			tab->new_notnull |= colDef->is_not_null;
  		}
  	}
  
  	/*
  	 * If we are adding an OID column, we have to tell Phase 3 to rewrite the
  	 * table to fix that.
  	 */
  	if (isOid)
  		tab->rewrite |= AT_REWRITE_ALTER_OID;
  
  	/*
  	 * Add needed dependency entries for the new column.
  	 */
  	add_column_datatype_dependency(myrelid, newattnum, attribute.atttypid);
  	add_column_collation_dependency(myrelid, newattnum, attribute.attcollation);
  
  	/*
  	 * Propagate to children as appropriate.  Unlike most other ALTER
  	 * routines, we have to do this one level of recursion at a time; we can't
  	 * use find_all_inheritors to do it in one pass.
  	 */
  	children = find_inheritance_children(RelationGetRelid(rel), lockmode);
  
  	/*
  	 * If we are told not to recurse, there had better not be any child
  	 * tables; else the addition would put them out of step.
  	 */
  	if (children && !recurse)
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  				 errmsg("column must be added to child tables too")));
  
  	/* Children should see column as singly inherited */
  	if (!recursing)
  	{
  		colDef = copyObject(colDef);
  		colDef->inhcount = 1;
  		colDef->is_local = false;
  	}
  
  	foreach(child, children)
  	{
  		Oid			childrelid = lfirst_oid(child);
  		Relation	childrel;
  		AlteredTableInfo *childtab;
  
  		/* find_inheritance_children already got lock */
  		childrel = heap_open(childrelid, NoLock);
  		CheckTableNotInUse(childrel, "ALTER TABLE");
  
  		/* Find or create work queue entry for this table */
  		childtab = ATGetQueueEntry(wqueue, childrel);
  
  		/* Recurse to child; return value is ignored */
  		ATExecAddColumn(wqueue, childtab, childrel,
  						colDef, isOid, recurse, true,
  						if_not_exists, lockmode);
  
  		heap_close(childrel, NoLock);
  	}
  
  	ObjectAddressSubSet(address, RelationRelationId, myrelid, newattnum);
  	return address;
  }
  
  /*
   * If a new or renamed column will collide with the name of an existing
   * column and if_not_exists is false then error out, else do nothing.
   */
  static bool
  check_for_column_name_collision(Relation rel, const char *colname,
  								bool if_not_exists)
  {
  	HeapTuple	attTuple;
  	int			attnum;
  
  	/*
  	 * this test is deliberately not attisdropped-aware, since if one tries to
  	 * add a column matching a dropped column name, it's gonna fail anyway.
  	 */
  	attTuple = SearchSysCache2(ATTNAME,
  							   ObjectIdGetDatum(RelationGetRelid(rel)),
  							   PointerGetDatum(colname));
  	if (!HeapTupleIsValid(attTuple))
  		return true;
  
  	attnum = ((Form_pg_attribute) GETSTRUCT(attTuple))->attnum;
  	ReleaseSysCache(attTuple);
  
  	/*
  	 * We throw a different error message for conflicts with system column
  	 * names, since they are normally not shown and the user might otherwise
  	 * be confused about the reason for the conflict.
  	 */
  	if (attnum <= 0)
  		ereport(ERROR,
  				(errcode(ERRCODE_DUPLICATE_COLUMN),
  				 errmsg("column name \"%s\" conflicts with a system column name",
  						colname)));
  	else
  	{
  		if (if_not_exists)
  		{
  			ereport(NOTICE,
  					(errcode(ERRCODE_DUPLICATE_COLUMN),
  					 errmsg("column \"%s\" of relation \"%s\" already exists, skipping",
  							colname, RelationGetRelationName(rel))));
  			return false;
  		}
  
  		ereport(ERROR,
  				(errcode(ERRCODE_DUPLICATE_COLUMN),
  				 errmsg("column \"%s\" of relation \"%s\" already exists",
  						colname, RelationGetRelationName(rel))));
  	}
  
  	return true;
  }
  
  /*
   * Install a column's dependency on its datatype.
   */
  static void
  add_column_datatype_dependency(Oid relid, int32 attnum, Oid typid)
  {
  	ObjectAddress myself,
  				referenced;
  
  	myself.classId = RelationRelationId;
  	myself.objectId = relid;
  	myself.objectSubId = attnum;
  	referenced.classId = TypeRelationId;
  	referenced.objectId = typid;
  	referenced.objectSubId = 0;
  	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
  }
  
  /*
   * Install a column's dependency on its collation.
   */
  static void
  add_column_collation_dependency(Oid relid, int32 attnum, Oid collid)
  {
  	ObjectAddress myself,
  				referenced;
  
  	/* We know the default collation is pinned, so don't bother recording it */
  	if (OidIsValid(collid) && collid != DEFAULT_COLLATION_OID)
  	{
  		myself.classId = RelationRelationId;
  		myself.objectId = relid;
  		myself.objectSubId = attnum;
  		referenced.classId = CollationRelationId;
  		referenced.objectId = collid;
  		referenced.objectSubId = 0;
  		recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
  	}
  }
  
  /*
   * ALTER TABLE SET WITH OIDS
   *
   * Basically this is an ADD COLUMN for the special OID column.  We have
   * to cons up a ColumnDef node because the ADD COLUMN code needs one.
   */
  static void
  ATPrepAddOids(List **wqueue, Relation rel, bool recurse, AlterTableCmd *cmd, LOCKMODE lockmode)
  {
  	/* If we're recursing to a child table, the ColumnDef is already set up */
  	if (cmd->def == NULL)
  	{
  		ColumnDef  *cdef = makeNode(ColumnDef);
  
  		cdef->colname = pstrdup("oid");
  		cdef->typeName = makeTypeNameFromOid(OIDOID, -1);
  		cdef->inhcount = 0;
  		cdef->is_local = true;
  		cdef->is_not_null = true;
  		cdef->storage = 0;
  		cdef->location = -1;
  		cmd->def = (Node *) cdef;
  	}
  	ATPrepAddColumn(wqueue, rel, recurse, false, false, cmd, lockmode);
  
  	if (recurse)
  		cmd->subtype = AT_AddOidsRecurse;
  }
  
  /*
   * ALTER TABLE ALTER COLUMN DROP NOT NULL
   *
   * Return the address of the modified column.  If the column was already
   * nullable, InvalidObjectAddress is returned.
   */
  
  static void
  ATPrepDropNotNull(Relation rel, bool recurse, bool recursing)
  {
  	/*
  	 * If the parent is a partitioned table, like check constraints, we do not
  	 * support removing the NOT NULL while partitions exist.
  	 */
  	if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  	{
  		PartitionDesc partdesc = RelationGetPartitionDesc(rel);
  
  		Assert(partdesc != NULL);
  		if (partdesc->nparts > 0 && !recurse && !recursing)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  					 errmsg("cannot remove constraint from only the partitioned table when partitions exist"),
  					 errhint("Do not specify the ONLY keyword.")));
  	}
  }
  static ObjectAddress
  ATExecDropNotNull(Relation rel, const char *colName, LOCKMODE lockmode)
  {
  	HeapTuple	tuple;
  	AttrNumber	attnum;
  	Relation	attr_rel;
  	List	   *indexoidlist;
  	ListCell   *indexoidscan;
  	ObjectAddress address;
  
  	/*
  	 * lookup the attribute
  	 */
  	attr_rel = heap_open(AttributeRelationId, RowExclusiveLock);
  
  	tuple = SearchSysCacheCopyAttName(RelationGetRelid(rel), colName);
  
  	if (!HeapTupleIsValid(tuple))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_COLUMN),
  				 errmsg("column \"%s\" of relation \"%s\" does not exist",
  						colName, RelationGetRelationName(rel))));
  
  	attnum = ((Form_pg_attribute) GETSTRUCT(tuple))->attnum;
  
  	/* Prevent them from altering a system attribute */
  	if (attnum <= 0)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot alter system column \"%s\"",
  						colName)));
  
  	if (get_attidentity(RelationGetRelid(rel), attnum))
  		ereport(ERROR,
  				(errcode(ERRCODE_SYNTAX_ERROR),
  				 errmsg("column \"%s\" of relation \"%s\" is an identity column",
  						colName, RelationGetRelationName(rel))));
  
  	/*
  	 * Check that the attribute is not in a primary key
  	 *
  	 * Note: we'll throw error even if the pkey index is not valid.
  	 */
  
  	/* Loop over all indexes on the relation */
  	indexoidlist = RelationGetIndexList(rel);
  
  	foreach(indexoidscan, indexoidlist)
  	{
  		Oid			indexoid = lfirst_oid(indexoidscan);
  		HeapTuple	indexTuple;
  		Form_pg_index indexStruct;
  		int			i;
  
  		indexTuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(indexoid));
  		if (!HeapTupleIsValid(indexTuple))
  			elog(ERROR, "cache lookup failed for index %u", indexoid);
  		indexStruct = (Form_pg_index) GETSTRUCT(indexTuple);
  
  		/* If the index is not a primary key, skip the check */
  		if (indexStruct->indisprimary)
  		{
  			/*
  			 * Loop over each attribute in the primary key and see if it
  			 * matches the to-be-altered attribute
  			 */
  			for (i = 0; i < indexStruct->indnkeyatts; i++)
  			{
  				if (indexStruct->indkey.values[i] == attnum)
  					ereport(ERROR,
  							(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  							 errmsg("column \"%s\" is in a primary key",
  									colName)));
  			}
  		}
  
  		ReleaseSysCache(indexTuple);
  	}
  
  	list_free(indexoidlist);
  
  	/* If rel is partition, shouldn't drop NOT NULL if parent has the same */
  	if (rel->rd_rel->relispartition)
  	{
  		Oid			parentId = get_partition_parent(RelationGetRelid(rel));
  		Relation	parent = heap_open(parentId, AccessShareLock);
  		TupleDesc	tupDesc = RelationGetDescr(parent);
  		AttrNumber	parent_attnum;
  
  		parent_attnum = get_attnum(parentId, colName);
  		if (TupleDescAttr(tupDesc, parent_attnum - 1)->attnotnull)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  					 errmsg("column \"%s\" is marked NOT NULL in parent table",
  							colName)));
  		heap_close(parent, AccessShareLock);
  	}
  
  	/*
  	 * Okay, actually perform the catalog change ... if needed
  	 */
  	if (((Form_pg_attribute) GETSTRUCT(tuple))->attnotnull)
  	{
  		((Form_pg_attribute) GETSTRUCT(tuple))->attnotnull = false;
  
  		CatalogTupleUpdate(attr_rel, &tuple->t_self, tuple);
  
  		ObjectAddressSubSet(address, RelationRelationId,
  							RelationGetRelid(rel), attnum);
  	}
  	else
  		address = InvalidObjectAddress;
  
  	InvokeObjectPostAlterHook(RelationRelationId,
  							  RelationGetRelid(rel), attnum);
  
  	heap_close(attr_rel, RowExclusiveLock);
  
  	return address;
  }
  
  /*
   * ALTER TABLE ALTER COLUMN SET NOT NULL
   */
  
  static void
  ATPrepSetNotNull(Relation rel, bool recurse, bool recursing)
  {
  	/*
  	 * If the parent is a partitioned table, like check constraints, NOT NULL
  	 * constraints must be added to the child tables.  Complain if requested
  	 * otherwise and partitions exist.
  	 */
  	if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  	{
  		PartitionDesc partdesc = RelationGetPartitionDesc(rel);
  
  		if (partdesc && partdesc->nparts > 0 && !recurse && !recursing)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  					 errmsg("cannot add constraint to only the partitioned table when partitions exist"),
  					 errhint("Do not specify the ONLY keyword.")));
  	}
  }
  
  /*
   * Return the address of the modified column.  If the column was already NOT
   * NULL, InvalidObjectAddress is returned.
   */
  static ObjectAddress
  ATExecSetNotNull(AlteredTableInfo *tab, Relation rel,
  				 const char *colName, LOCKMODE lockmode)
  {
  	HeapTuple	tuple;
  	AttrNumber	attnum;
  	Relation	attr_rel;
  	ObjectAddress address;
  
  	/*
  	 * lookup the attribute
  	 */
  	attr_rel = heap_open(AttributeRelationId, RowExclusiveLock);
  
  	tuple = SearchSysCacheCopyAttName(RelationGetRelid(rel), colName);
  
  	if (!HeapTupleIsValid(tuple))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_COLUMN),
  				 errmsg("column \"%s\" of relation \"%s\" does not exist",
  						colName, RelationGetRelationName(rel))));
  
  	attnum = ((Form_pg_attribute) GETSTRUCT(tuple))->attnum;
  
  	/* Prevent them from altering a system attribute */
  	if (attnum <= 0)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot alter system column \"%s\"",
  						colName)));
  
  	/*
  	 * Okay, actually perform the catalog change ... if needed
  	 */
  	if (!((Form_pg_attribute) GETSTRUCT(tuple))->attnotnull)
  	{
  		((Form_pg_attribute) GETSTRUCT(tuple))->attnotnull = true;
  
  		CatalogTupleUpdate(attr_rel, &tuple->t_self, tuple);
  
  		/* Tell Phase 3 it needs to test the constraint */
  		tab->new_notnull = true;
  
  		ObjectAddressSubSet(address, RelationRelationId,
  							RelationGetRelid(rel), attnum);
  	}
  	else
  		address = InvalidObjectAddress;
  
  	InvokeObjectPostAlterHook(RelationRelationId,
  							  RelationGetRelid(rel), attnum);
  
  	heap_close(attr_rel, RowExclusiveLock);
  
  	return address;
  }
  
  /*
   * ALTER TABLE ALTER COLUMN SET/DROP DEFAULT
   *
   * Return the address of the affected column.
   */
  static ObjectAddress
  ATExecColumnDefault(Relation rel, const char *colName,
  					Node *newDefault, LOCKMODE lockmode)
  {
  	AttrNumber	attnum;
  	ObjectAddress address;
  
  	/*
  	 * get the number of the attribute
  	 */
  	attnum = get_attnum(RelationGetRelid(rel), colName);
  	if (attnum == InvalidAttrNumber)
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_COLUMN),
  				 errmsg("column \"%s\" of relation \"%s\" does not exist",
  						colName, RelationGetRelationName(rel))));
  
  	/* Prevent them from altering a system attribute */
  	if (attnum <= 0)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot alter system column \"%s\"",
  						colName)));
  
  	if (get_attidentity(RelationGetRelid(rel), attnum))
  		ereport(ERROR,
  				(errcode(ERRCODE_SYNTAX_ERROR),
  				 errmsg("column \"%s\" of relation \"%s\" is an identity column",
  						colName, RelationGetRelationName(rel)),
  				 newDefault ? 0 : errhint("Use ALTER TABLE ... ALTER COLUMN ... DROP IDENTITY instead.")));
  
  	/*
  	 * Remove any old default for the column.  We use RESTRICT here for
  	 * safety, but at present we do not expect anything to depend on the
  	 * default.
  	 *
  	 * We treat removing the existing default as an internal operation when it
  	 * is preparatory to adding a new default, but as a user-initiated
  	 * operation when the user asked for a drop.
  	 */
  	RemoveAttrDefault(RelationGetRelid(rel), attnum, DROP_RESTRICT, false,
  					  newDefault == NULL ? false : true);
  
  	if (newDefault)
  	{
  		/* SET DEFAULT */
  		RawColumnDefault *rawEnt;
  
  		rawEnt = (RawColumnDefault *) palloc(sizeof(RawColumnDefault));
  		rawEnt->attnum = attnum;
  		rawEnt->raw_default = newDefault;
  		rawEnt->missingMode = false;
  
  		/*
  		 * This function is intended for CREATE TABLE, so it processes a
  		 * _list_ of defaults, but we just do one.
  		 */
  		AddRelationNewConstraints(rel, list_make1(rawEnt), NIL,
  								  false, true, false, NULL);
  	}
  
  	ObjectAddressSubSet(address, RelationRelationId,
  						RelationGetRelid(rel), attnum);
  	return address;
  }
  
  /*
   * ALTER TABLE ALTER COLUMN ADD IDENTITY
   *
   * Return the address of the affected column.
   */
  static ObjectAddress
  ATExecAddIdentity(Relation rel, const char *colName,
  				  Node *def, LOCKMODE lockmode)
  {
  	Relation	attrelation;
  	HeapTuple	tuple;
  	Form_pg_attribute attTup;
  	AttrNumber	attnum;
  	ObjectAddress address;
  	ColumnDef  *cdef = castNode(ColumnDef, def);
  
  	attrelation = heap_open(AttributeRelationId, RowExclusiveLock);
  
  	tuple = SearchSysCacheCopyAttName(RelationGetRelid(rel), colName);
  	if (!HeapTupleIsValid(tuple))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_COLUMN),
  				 errmsg("column \"%s\" of relation \"%s\" does not exist",
  						colName, RelationGetRelationName(rel))));
  	attTup = (Form_pg_attribute) GETSTRUCT(tuple);
  	attnum = attTup->attnum;
  
  	/* Can't alter a system attribute */
  	if (attnum <= 0)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot alter system column \"%s\"",
  						colName)));
  
  	/*
  	 * Creating a column as identity implies NOT NULL, so adding the identity
  	 * to an existing column that is not NOT NULL would create a state that
  	 * cannot be reproduced without contortions.
  	 */
  	if (!attTup->attnotnull)
  		ereport(ERROR,
  				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  				 errmsg("column \"%s\" of relation \"%s\" must be declared NOT NULL before identity can be added",
  						colName, RelationGetRelationName(rel))));
  
  	if (attTup->attidentity)
  		ereport(ERROR,
  				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  				 errmsg("column \"%s\" of relation \"%s\" is already an identity column",
  						colName, RelationGetRelationName(rel))));
  
  	if (attTup->atthasdef)
  		ereport(ERROR,
  				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  				 errmsg("column \"%s\" of relation \"%s\" already has a default value",
  						colName, RelationGetRelationName(rel))));
  
  	attTup->attidentity = cdef->identity;
  	CatalogTupleUpdate(attrelation, &tuple->t_self, tuple);
  
  	InvokeObjectPostAlterHook(RelationRelationId,
  							  RelationGetRelid(rel),
  							  attTup->attnum);
  	ObjectAddressSubSet(address, RelationRelationId,
  						RelationGetRelid(rel), attnum);
  	heap_freetuple(tuple);
  
  	heap_close(attrelation, RowExclusiveLock);
  
  	return address;
  }
  
  /*
   * ALTER TABLE ALTER COLUMN SET { GENERATED or sequence options }
   *
   * Return the address of the affected column.
   */
  static ObjectAddress
  ATExecSetIdentity(Relation rel, const char *colName, Node *def, LOCKMODE lockmode)
  {
  	ListCell   *option;
  	DefElem    *generatedEl = NULL;
  	HeapTuple	tuple;
  	Form_pg_attribute attTup;
  	AttrNumber	attnum;
  	Relation	attrelation;
  	ObjectAddress address;
  
  	foreach(option, castNode(List, def))
  	{
  		DefElem    *defel = lfirst_node(DefElem, option);
  
  		if (strcmp(defel->defname, "generated") == 0)
  		{
  			if (generatedEl)
  				ereport(ERROR,
  						(errcode(ERRCODE_SYNTAX_ERROR),
  						 errmsg("conflicting or redundant options")));
  			generatedEl = defel;
  		}
  		else
  			elog(ERROR, "option \"%s\" not recognized",
  				 defel->defname);
  	}
  
  	/*
  	 * Even if there is nothing to change here, we run all the checks.  There
  	 * will be a subsequent ALTER SEQUENCE that relies on everything being
  	 * there.
  	 */
  
  	attrelation = heap_open(AttributeRelationId, RowExclusiveLock);
  	tuple = SearchSysCacheCopyAttName(RelationGetRelid(rel), colName);
  	if (!HeapTupleIsValid(tuple))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_COLUMN),
  				 errmsg("column \"%s\" of relation \"%s\" does not exist",
  						colName, RelationGetRelationName(rel))));
  
  	attTup = (Form_pg_attribute) GETSTRUCT(tuple);
  	attnum = attTup->attnum;
  
  	if (attnum <= 0)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot alter system column \"%s\"",
  						colName)));
  
  	if (!attTup->attidentity)
  		ereport(ERROR,
  				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  				 errmsg("column \"%s\" of relation \"%s\" is not an identity column",
  						colName, RelationGetRelationName(rel))));
  
  	if (generatedEl)
  	{
  		attTup->attidentity = defGetInt32(generatedEl);
  		CatalogTupleUpdate(attrelation, &tuple->t_self, tuple);
  
  		InvokeObjectPostAlterHook(RelationRelationId,
  								  RelationGetRelid(rel),
  								  attTup->attnum);
  		ObjectAddressSubSet(address, RelationRelationId,
  							RelationGetRelid(rel), attnum);
  	}
  	else
  		address = InvalidObjectAddress;
  
  	heap_freetuple(tuple);
  	heap_close(attrelation, RowExclusiveLock);
  
  	return address;
  }
  
  /*
   * ALTER TABLE ALTER COLUMN DROP IDENTITY
   *
   * Return the address of the affected column.
   */
  static ObjectAddress
  ATExecDropIdentity(Relation rel, const char *colName, bool missing_ok, LOCKMODE lockmode)
  {
  	HeapTuple	tuple;
  	Form_pg_attribute attTup;
  	AttrNumber	attnum;
  	Relation	attrelation;
  	ObjectAddress address;
  	Oid			seqid;
  	ObjectAddress seqaddress;
  
  	attrelation = heap_open(AttributeRelationId, RowExclusiveLock);
  	tuple = SearchSysCacheCopyAttName(RelationGetRelid(rel), colName);
  	if (!HeapTupleIsValid(tuple))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_COLUMN),
  				 errmsg("column \"%s\" of relation \"%s\" does not exist",
  						colName, RelationGetRelationName(rel))));
  
  	attTup = (Form_pg_attribute) GETSTRUCT(tuple);
  	attnum = attTup->attnum;
  
  	if (attnum <= 0)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot alter system column \"%s\"",
  						colName)));
  
  	if (!attTup->attidentity)
  	{
  		if (!missing_ok)
  			ereport(ERROR,
  					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  					 errmsg("column \"%s\" of relation \"%s\" is not an identity column",
  							colName, RelationGetRelationName(rel))));
  		else
  		{
  			ereport(NOTICE,
  					(errmsg("column \"%s\" of relation \"%s\" is not an identity column, skipping",
  							colName, RelationGetRelationName(rel))));
  			heap_freetuple(tuple);
  			heap_close(attrelation, RowExclusiveLock);
  			return InvalidObjectAddress;
  		}
  	}
  
  	attTup->attidentity = '\0';
  	CatalogTupleUpdate(attrelation, &tuple->t_self, tuple);
  
  	InvokeObjectPostAlterHook(RelationRelationId,
  							  RelationGetRelid(rel),
  							  attTup->attnum);
  	ObjectAddressSubSet(address, RelationRelationId,
  						RelationGetRelid(rel), attnum);
  	heap_freetuple(tuple);
  
  	heap_close(attrelation, RowExclusiveLock);
  
  	/* drop the internal sequence */
  	seqid = getOwnedSequence(RelationGetRelid(rel), attnum);
  	deleteDependencyRecordsForClass(RelationRelationId, seqid,
  									RelationRelationId, DEPENDENCY_INTERNAL);
  	CommandCounterIncrement();
  	seqaddress.classId = RelationRelationId;
  	seqaddress.objectId = seqid;
  	seqaddress.objectSubId = 0;
  	performDeletion(&seqaddress, DROP_RESTRICT, PERFORM_DELETION_INTERNAL);
  
  	return address;
  }
  
  /*
   * ALTER TABLE ALTER COLUMN SET STATISTICS
   */
  static void
  ATPrepSetStatistics(Relation rel, const char *colName, int16 colNum, Node *newValue, LOCKMODE lockmode)
  {
  	/*
  	 * We do our own permission checking because (a) we want to allow SET
  	 * STATISTICS on indexes (for expressional index columns), and (b) we want
  	 * to allow SET STATISTICS on system catalogs without requiring
  	 * allowSystemTableMods to be turned on.
  	 */
  	if (rel->rd_rel->relkind != RELKIND_RELATION &&
  		rel->rd_rel->relkind != RELKIND_MATVIEW &&
  		rel->rd_rel->relkind != RELKIND_INDEX &&
  		rel->rd_rel->relkind != RELKIND_PARTITIONED_INDEX &&
  		rel->rd_rel->relkind != RELKIND_FOREIGN_TABLE &&
  		rel->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is not a table, materialized view, index, or foreign table",
  						RelationGetRelationName(rel))));
  
  	/*
  	 * We allow referencing columns by numbers only for indexes, since table
  	 * column numbers could contain gaps if columns are later dropped.
  	 */
  	if (rel->rd_rel->relkind != RELKIND_INDEX &&
  		rel->rd_rel->relkind != RELKIND_PARTITIONED_INDEX &&
  		!colName)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot refer to non-index column by number")));
  
  	/* Permissions checks */
  	if (!pg_class_ownercheck(RelationGetRelid(rel), GetUserId()))
  		aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(rel->rd_rel->relkind),
  					   RelationGetRelationName(rel));
  }
  
  /*
   * Return value is the address of the modified column
   */
  static ObjectAddress
  ATExecSetStatistics(Relation rel, const char *colName, int16 colNum, Node *newValue, LOCKMODE lockmode)
  {
  	int			newtarget;
  	Relation	attrelation;
  	HeapTuple	tuple;
  	Form_pg_attribute attrtuple;
  	AttrNumber	attnum;
  	ObjectAddress address;
  
  	Assert(IsA(newValue, Integer));
  	newtarget = intVal(newValue);
  
  	/*
  	 * Limit target to a sane range
  	 */
  	if (newtarget < -1)
  	{
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  				 errmsg("statistics target %d is too low",
  						newtarget)));
  	}
  	else if (newtarget > 10000)
  	{
  		newtarget = 10000;
  		ereport(WARNING,
  				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  				 errmsg("lowering statistics target to %d",
  						newtarget)));
  	}
  
  	attrelation = heap_open(AttributeRelationId, RowExclusiveLock);
  
  	if (colName)
  	{
  		tuple = SearchSysCacheCopyAttName(RelationGetRelid(rel), colName);
  
  		if (!HeapTupleIsValid(tuple))
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_COLUMN),
  					 errmsg("column \"%s\" of relation \"%s\" does not exist",
  							colName, RelationGetRelationName(rel))));
  	}
  	else
  	{
  		tuple = SearchSysCacheCopyAttNum(RelationGetRelid(rel), colNum);
  
  		if (!HeapTupleIsValid(tuple))
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_COLUMN),
  					 errmsg("column number %d of relation \"%s\" does not exist",
  							colNum, RelationGetRelationName(rel))));
  	}
  
  	attrtuple = (Form_pg_attribute) GETSTRUCT(tuple);
  
  	attnum = attrtuple->attnum;
  	if (attnum <= 0)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot alter system column \"%s\"",
  						colName)));
  
  	if (rel->rd_rel->relkind == RELKIND_INDEX ||
  		rel->rd_rel->relkind == RELKIND_PARTITIONED_INDEX)
  	{
  		if (attnum > rel->rd_index->indnkeyatts)
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("cannot alter statistics on included column \"%s\" of index \"%s\"",
  							NameStr(attrtuple->attname), RelationGetRelationName(rel))));
  		else if (rel->rd_index->indkey.values[attnum - 1] != 0)
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("cannot alter statistics on non-expression column \"%s\" of index \"%s\"",
  							NameStr(attrtuple->attname), RelationGetRelationName(rel)),
  					 errhint("Alter statistics on table column instead.")));
  	}
  
  	attrtuple->attstattarget = newtarget;
  
  	CatalogTupleUpdate(attrelation, &tuple->t_self, tuple);
  
  	InvokeObjectPostAlterHook(RelationRelationId,
  							  RelationGetRelid(rel),
  							  attrtuple->attnum);
  	ObjectAddressSubSet(address, RelationRelationId,
  						RelationGetRelid(rel), attnum);
  	heap_freetuple(tuple);
  
  	heap_close(attrelation, RowExclusiveLock);
  
  	return address;
  }
  
  /*
   * Return value is the address of the modified column
   */
  static ObjectAddress
  ATExecSetOptions(Relation rel, const char *colName, Node *options,
  				 bool isReset, LOCKMODE lockmode)
  {
  	Relation	attrelation;
  	HeapTuple	tuple,
  				newtuple;
  	Form_pg_attribute attrtuple;
  	AttrNumber	attnum;
  	Datum		datum,
  				newOptions;
  	bool		isnull;
  	ObjectAddress address;
  	Datum		repl_val[Natts_pg_attribute];
  	bool		repl_null[Natts_pg_attribute];
  	bool		repl_repl[Natts_pg_attribute];
  
  	attrelation = heap_open(AttributeRelationId, RowExclusiveLock);
  
  	tuple = SearchSysCacheAttName(RelationGetRelid(rel), colName);
  
  	if (!HeapTupleIsValid(tuple))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_COLUMN),
  				 errmsg("column \"%s\" of relation \"%s\" does not exist",
  						colName, RelationGetRelationName(rel))));
  	attrtuple = (Form_pg_attribute) GETSTRUCT(tuple);
  
  	attnum = attrtuple->attnum;
  	if (attnum <= 0)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot alter system column \"%s\"",
  						colName)));
  
  	/* Generate new proposed attoptions (text array) */
  	datum = SysCacheGetAttr(ATTNAME, tuple, Anum_pg_attribute_attoptions,
  							&isnull);
  	newOptions = transformRelOptions(isnull ? (Datum) 0 : datum,
  									 castNode(List, options), NULL, NULL,
  									 false, isReset);
  	/* Validate new options */
  	(void) attribute_reloptions(newOptions, true);
  
  	/* Build new tuple. */
  	memset(repl_null, false, sizeof(repl_null));
  	memset(repl_repl, false, sizeof(repl_repl));
  	if (newOptions != (Datum) 0)
  		repl_val[Anum_pg_attribute_attoptions - 1] = newOptions;
  	else
  		repl_null[Anum_pg_attribute_attoptions - 1] = true;
  	repl_repl[Anum_pg_attribute_attoptions - 1] = true;
  	newtuple = heap_modify_tuple(tuple, RelationGetDescr(attrelation),
  								 repl_val, repl_null, repl_repl);
  
  	/* Update system catalog. */
  	CatalogTupleUpdate(attrelation, &newtuple->t_self, newtuple);
  
  	InvokeObjectPostAlterHook(RelationRelationId,
  							  RelationGetRelid(rel),
  							  attrtuple->attnum);
  	ObjectAddressSubSet(address, RelationRelationId,
  						RelationGetRelid(rel), attnum);
  
  	heap_freetuple(newtuple);
  
  	ReleaseSysCache(tuple);
  
  	heap_close(attrelation, RowExclusiveLock);
  
  	return address;
  }
  
  /*
   * ALTER TABLE ALTER COLUMN SET STORAGE
   *
   * Return value is the address of the modified column
   */
  static ObjectAddress
  ATExecSetStorage(Relation rel, const char *colName, Node *newValue, LOCKMODE lockmode)
  {
  	char	   *storagemode;
  	char		newstorage;
  	Relation	attrelation;
  	HeapTuple	tuple;
  	Form_pg_attribute attrtuple;
  	AttrNumber	attnum;
  	ObjectAddress address;
  
  	Assert(IsA(newValue, String));
  	storagemode = strVal(newValue);
  
  	if (pg_strcasecmp(storagemode, "plain") == 0)
  		newstorage = 'p';
  	else if (pg_strcasecmp(storagemode, "external") == 0)
  		newstorage = 'e';
  	else if (pg_strcasecmp(storagemode, "extended") == 0)
  		newstorage = 'x';
  	else if (pg_strcasecmp(storagemode, "main") == 0)
  		newstorage = 'm';
  	else
  	{
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  				 errmsg("invalid storage type \"%s\"",
  						storagemode)));
  		newstorage = 0;			/* keep compiler quiet */
  	}
  
  	attrelation = heap_open(AttributeRelationId, RowExclusiveLock);
  
  	tuple = SearchSysCacheCopyAttName(RelationGetRelid(rel), colName);
  
  	if (!HeapTupleIsValid(tuple))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_COLUMN),
  				 errmsg("column \"%s\" of relation \"%s\" does not exist",
  						colName, RelationGetRelationName(rel))));
  	attrtuple = (Form_pg_attribute) GETSTRUCT(tuple);
  
  	attnum = attrtuple->attnum;
  	if (attnum <= 0)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot alter system column \"%s\"",
  						colName)));
  
  	/*
  	 * safety check: do not allow toasted storage modes unless column datatype
  	 * is TOAST-aware.
  	 */
  	if (newstorage == 'p' || TypeIsToastable(attrtuple->atttypid))
  		attrtuple->attstorage = newstorage;
  	else
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("column data type %s can only have storage PLAIN",
  						format_type_be(attrtuple->atttypid))));
  
  	CatalogTupleUpdate(attrelation, &tuple->t_self, tuple);
  
  	InvokeObjectPostAlterHook(RelationRelationId,
  							  RelationGetRelid(rel),
  							  attrtuple->attnum);
  
  	heap_freetuple(tuple);
  
  	heap_close(attrelation, RowExclusiveLock);
  
  	ObjectAddressSubSet(address, RelationRelationId,
  						RelationGetRelid(rel), attnum);
  	return address;
  }
  
  
  /*
   * ALTER TABLE DROP COLUMN
   *
   * DROP COLUMN cannot use the normal ALTER TABLE recursion mechanism,
   * because we have to decide at runtime whether to recurse or not depending
   * on whether attinhcount goes to zero or not.  (We can't check this in a
   * static pre-pass because it won't handle multiple inheritance situations
   * correctly.)
   */
  static void
  ATPrepDropColumn(List **wqueue, Relation rel, bool recurse, bool recursing,
  				 AlterTableCmd *cmd, LOCKMODE lockmode)
  {
  	if (rel->rd_rel->reloftype && !recursing)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot drop column from typed table")));
  
  	if (rel->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
  		ATTypedTableRecursion(wqueue, rel, cmd, lockmode);
  
  	if (recurse)
  		cmd->subtype = AT_DropColumnRecurse;
  }
  
  /*
   * Return value is the address of the dropped column.
   */
  static ObjectAddress
  ATExecDropColumn(List **wqueue, Relation rel, const char *colName,
  				 DropBehavior behavior,
  				 bool recurse, bool recursing,
  				 bool missing_ok, LOCKMODE lockmode)
  {
  	HeapTuple	tuple;
  	Form_pg_attribute targetatt;
  	AttrNumber	attnum;
  	List	   *children;
  	ObjectAddress object;
  	bool		is_expr;
  
  	/* At top level, permission check was done in ATPrepCmd, else do it */
  	if (recursing)
  		ATSimplePermissions(rel, ATT_TABLE | ATT_FOREIGN_TABLE);
  
  	/*
  	 * get the number of the attribute
  	 */
  	tuple = SearchSysCacheAttName(RelationGetRelid(rel), colName);
  	if (!HeapTupleIsValid(tuple))
  	{
  		if (!missing_ok)
  		{
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_COLUMN),
  					 errmsg("column \"%s\" of relation \"%s\" does not exist",
  							colName, RelationGetRelationName(rel))));
  		}
  		else
  		{
  			ereport(NOTICE,
  					(errmsg("column \"%s\" of relation \"%s\" does not exist, skipping",
  							colName, RelationGetRelationName(rel))));
  			return InvalidObjectAddress;
  		}
  	}
  	targetatt = (Form_pg_attribute) GETSTRUCT(tuple);
  
  	attnum = targetatt->attnum;
  
  	/* Can't drop a system attribute, except OID */
  	if (attnum <= 0 && attnum != ObjectIdAttributeNumber)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot drop system column \"%s\"",
  						colName)));
  
  	/* Don't drop inherited columns */
  	if (targetatt->attinhcount > 0 && !recursing)
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  				 errmsg("cannot drop inherited column \"%s\"",
  						colName)));
  
  	/* Don't drop columns used in the partition key */
  	if (has_partition_attrs(rel,
  							bms_make_singleton(attnum - YBGetFirstLowInvalidAttributeNumber(rel)),
  							&is_expr))
  	{
  		if (!is_expr)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  					 errmsg("cannot drop column named in partition key")));
  		else
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  					 errmsg("cannot drop column referenced in partition key expression")));
  	}
  
  	ReleaseSysCache(tuple);
  
  	/*
  	 * Propagate to children as appropriate.  Unlike most other ALTER
  	 * routines, we have to do this one level of recursion at a time; we can't
  	 * use find_all_inheritors to do it in one pass.
  	 */
  	children = find_inheritance_children(RelationGetRelid(rel), lockmode);
  
  	if (children)
  	{
  		Relation	attr_rel;
  		ListCell   *child;
  
  		/*
  		 * In case of a partitioned table, the column must be dropped from the
  		 * partitions as well.
  		 */
  		if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE && !recurse)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  					 errmsg("cannot drop column from only the partitioned table when partitions exist"),
  					 errhint("Do not specify the ONLY keyword.")));
  
  		attr_rel = heap_open(AttributeRelationId, RowExclusiveLock);
  		foreach(child, children)
  		{
  			Oid			childrelid = lfirst_oid(child);
  			Relation	childrel;
  			Form_pg_attribute childatt;
  
  			/* find_inheritance_children already got lock */
  			childrel = heap_open(childrelid, NoLock);
  			CheckTableNotInUse(childrel, "ALTER TABLE");
  
  			tuple = SearchSysCacheCopyAttName(childrelid, colName);
  			if (!HeapTupleIsValid(tuple))	/* shouldn't happen */
  				elog(ERROR, "cache lookup failed for attribute \"%s\" of relation %u",
  					 colName, childrelid);
  			childatt = (Form_pg_attribute) GETSTRUCT(tuple);
  
  			if (childatt->attinhcount <= 0) /* shouldn't happen */
  				elog(ERROR, "relation %u has non-inherited attribute \"%s\"",
  					 childrelid, colName);
  
  			if (recurse)
  			{
  				/*
  				 * If the child column has other definition sources, just
  				 * decrement its inheritance count; if not, recurse to delete
  				 * it.
  				 */
  				if (childatt->attinhcount == 1 && !childatt->attislocal)
  				{
  					/* Time to delete this child column, too */
  					ATExecDropColumn(wqueue, childrel, colName,
  									 behavior, true, true,
  									 false, lockmode);
  				}
  				else
  				{
  					/* Child column must survive my deletion */
  					childatt->attinhcount--;
  
  					CatalogTupleUpdate(attr_rel, &tuple->t_self, tuple);
  
  					/* Make update visible */
  					CommandCounterIncrement();
  				}
  			}
  			else
  			{
  				/*
  				 * If we were told to drop ONLY in this table (no recursion),
  				 * we need to mark the inheritors' attributes as locally
  				 * defined rather than inherited.
  				 */
  				childatt->attinhcount--;
  				childatt->attislocal = true;
  
  				CatalogTupleUpdate(attr_rel, &tuple->t_self, tuple);
  
  				/* Make update visible */
  				CommandCounterIncrement();
  			}
  
  			heap_freetuple(tuple);
  
  			heap_close(childrel, NoLock);
  		}
  		heap_close(attr_rel, RowExclusiveLock);
  	}
  
  	/*
  	 * Perform the actual column deletion
  	 */
  	object.classId = RelationRelationId;
  	object.objectId = RelationGetRelid(rel);
  	object.objectSubId = attnum;
  
  	performDeletion(&object, behavior, 0);
  
  	/*
  	 * If we dropped the OID column, must adjust pg_class.relhasoids and tell
  	 * Phase 3 to physically get rid of the column.  We formerly left the
  	 * column in place physically, but this caused subtle problems.  See
  	 * http://archives.postgresql.org/pgsql-hackers/2009-02/msg00363.php
  	 */
  	if (attnum == ObjectIdAttributeNumber)
  	{
  		Relation	class_rel;
  		Form_pg_class tuple_class;
  		AlteredTableInfo *tab;
  
  		class_rel = heap_open(RelationRelationId, RowExclusiveLock);
  
  		tuple = SearchSysCacheCopy1(RELOID,
  									ObjectIdGetDatum(RelationGetRelid(rel)));
  		if (!HeapTupleIsValid(tuple))
  			elog(ERROR, "cache lookup failed for relation %u",
  				 RelationGetRelid(rel));
  		tuple_class = (Form_pg_class) GETSTRUCT(tuple);
  
  		tuple_class->relhasoids = false;
  		CatalogTupleUpdate(class_rel, &tuple->t_self, tuple);
  
  		heap_close(class_rel, RowExclusiveLock);
  
  		/* Find or create work queue entry for this table */
  		tab = ATGetQueueEntry(wqueue, rel);
  
  		/* Tell Phase 3 to physically remove the OID column */
  		tab->rewrite |= AT_REWRITE_ALTER_OID;
  	}
  
  	return object;
  }
  
  /*
   * Retrieve attribute from pg_constraint sys cache, ensure it's not null and save it
   * to a variable provided in the first argument.
   */
  #define YBGetNotNullConstraintAttr(tuple, attname) \
  	__extension__ ({ \
  		bool isnull; \
  		Datum result = SysCacheGetAttr(CONSTROID, \
  		                               tuple, \
  		                               Anum_pg_constraint_##attname, \
  		                               &isnull); \
  		if (isnull) \
  			elog(ERROR, "null " #attname " for constraint %u", HeapTupleGetOid(tuple)); \
  		result; \
  	});
  
  /*
   * Copy all rows from one table to the other.
   * Does not perform any constraint checks.
   *
   * This is a based on ATRewriteTable, but adopted for YB and with attribute
   * remapping, accounting for oldrel columns dropped in newrel (we don't expect
   * any dropped columns in newrel).
   */
  static void
  YBCopyTableRowsUnchecked(Relation oldrel, Relation newrel, AttrNumber* attmap)
  {
  	TupleDesc       oldTupDesc, newTupDesc;
  	Datum*          old_values;
  	bool*           old_isnull;
  	Datum*          new_values;
  	bool*           new_isnull;
  	TupleTableSlot* newslot;
  	HeapScanDesc    scan;
  	HeapTuple       tuple;
  	MemoryContext   oldcxt, per_tup_cxt;
  	Snapshot        snapshot;
  
  	Assert(IsYBRelation(newrel));
  
  	oldTupDesc = RelationGetDescr(oldrel);
  	newTupDesc = RelationGetDescr(newrel);
  
  	newslot = MakeSingleTupleTableSlot(newTupDesc);
  
  	/* Preallocate values/isnull arrays */
  	old_values = (Datum *) palloc(oldTupDesc->natts * sizeof(Datum));
  	old_isnull = (bool *)  palloc(oldTupDesc->natts * sizeof(bool));
  	new_values = (Datum *) palloc(newTupDesc->natts * sizeof(Datum));
  	new_isnull = (bool *)  palloc(newTupDesc->natts * sizeof(bool));
  
  	/*
  	 * Scan through the rows, generating a new row if needed and then
  	 * checking all the constraints.
  	 */
  	snapshot = RegisterSnapshot(GetLatestSnapshot());
  	scan = heap_beginscan(oldrel, snapshot, 0, NULL);
  
  	/*
  	 * Switch to per-tuple memory context and reset it for each tuple
  	 * produced, so we don't leak memory.
  	 */
  	per_tup_cxt = AllocSetContextCreate(GetCurrentMemoryContext(),
  	                                    "copy table rows",
  	                                    ALLOCSET_DEFAULT_SIZES);
  	oldcxt = MemoryContextSwitchTo(per_tup_cxt);
  
  	while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
  	{
  		Oid tupOid = InvalidOid;
  
  		/* Extract data from old tuple */
  		heap_deform_tuple(tuple, oldTupDesc, old_values, old_isnull);
  		if (oldTupDesc->tdhasoid)
  			tupOid = HeapTupleGetOid(tuple);
  
  		/* Remap the attribute numbers. */
  		for (int i = 0; i < newTupDesc->natts; ++i)
  		{
  			new_values[i] = old_values[attmap[i] - 1];
  			new_isnull[i] = old_isnull[attmap[i] - 1];
  		}
  
  		/*
  		 * Form the new tuple. Note that we don't explicitly pfree it,
  		 * since the per-tuple memory context will be reset shortly.
  		 */
  		tuple = heap_form_tuple(newTupDesc, new_values, new_isnull);
  
  		/* Preserve OID, if any */
  		if (newTupDesc->tdhasoid)
  			HeapTupleSetOid(tuple, tupOid);
  
  		ExecStoreHeapTuple(tuple, newslot, false);
  
  		/* Write the tuple out to the new relation */
  		YBCExecuteInsert(newrel, newslot->tts_tupleDescriptor, tuple);
  
  		MemoryContextReset(per_tup_cxt);
  
  		CHECK_FOR_INTERRUPTS();
  	}
  
  	MemoryContextSwitchTo(oldcxt);
  	MemoryContextDelete(per_tup_cxt);
  
  	heap_endscan(scan);
  	UnregisterSnapshot(snapshot);
  
  	ExecDropSingleTupleTableSlot(newslot);
  }
  
  /*
   * Create a FK constraint similar to the one in the given pg_constraint HeapTuple.
   * Will use different name, base/FK relations, and will remap attribute numbers
   * if mapping is provided.
   */
  static void
  YBCreateSimilarForeignKey(HeapTuple tuple,
                            const char* fk_name,
                            Relation base_rel,
                            Relation fk_rel,
                            AttrNumber* conkey_attmap,
                            AttrNumber* confkey_attmap)
  {
  	Form_pg_constraint con_form = (Form_pg_constraint) GETSTRUCT(tuple);
  
  	/* attnums of constrained columns. */
  	Datum conkey_val = YBGetNotNullConstraintAttr(tuple, conkey);
  	/* attnums of referenced columns. */
  	Datum confkey_val= YBGetNotNullConstraintAttr(tuple, confkey);
  	/* equality operators for PK = FK comparisons */
  	Datum pfeqop_val = YBGetNotNullConstraintAttr(tuple, conpfeqop);
  	/* equality operators for PK = PK comparisons */
  	Datum ppeqop_val = YBGetNotNullConstraintAttr(tuple, conppeqop);
  	/* equality operators for FK = FK comparisons */
  	Datum ffeqop_val = YBGetNotNullConstraintAttr(tuple, conffeqop);
  
  	int numkeys = ARR_DIMS(DatumGetArrayTypeP(conkey_val))[0];
  
  	int16 conkey[numkeys];
  	int16 confkey[numkeys];
  	Oid   pfeqop[numkeys];
  	Oid   ppeqop[numkeys];
  	Oid   ffeqop[numkeys];
  
  	Oid index_oid;
  	Oid index_opclasses[numkeys];
  
  	memcpy(conkey,
  	       ARR_DATA_PTR(DatumGetArrayTypeP(conkey_val)),
  	       numkeys * sizeof(int16));
  	memcpy(confkey,
  	       ARR_DATA_PTR(DatumGetArrayTypeP(confkey_val)),
  	       numkeys * sizeof(int16));
  	memcpy(pfeqop,
  	       ARR_DATA_PTR(DatumGetArrayTypeP(pfeqop_val)),
  	       numkeys * sizeof(Oid));
  	memcpy(ppeqop,
  	       ARR_DATA_PTR(DatumGetArrayTypeP(ppeqop_val)),
  	       numkeys * sizeof(Oid));
  	memcpy(ffeqop,
  	       ARR_DATA_PTR(DatumGetArrayTypeP(ffeqop_val)),
  	       numkeys * sizeof(Oid));
  
  	/* Remap the attribute numbers. */
  	for (int i = 0; i < numkeys; ++i)
  	{
  		if (conkey_attmap)
  			conkey[i]  = conkey_attmap[conkey[i] - 1];
  		if (confkey_attmap)
  			confkey[i] = confkey_attmap[confkey[i] - 1];
  	}
  
  
  	/* Look for an index matching the column list */
  	index_oid = transformFkeyCheckAttrs(fk_rel, numkeys, confkey, index_opclasses);
  
  	/* Record the FK constraint in pg_constraint. */
  	Oid constr_oid = CreateConstraintEntry(
  	    fk_name,
  	    con_form->connamespace,
  	    CONSTRAINT_FOREIGN,
  	    con_form->condeferrable,
  	    con_form->condeferred,
  	    con_form->convalidated,
  	    con_form->conparentid,
  	    RelationGetRelid(base_rel),
  	    conkey,
  	    numkeys,
  	    numkeys,
  	    InvalidOid /* not a domain constraint */,
  	    index_oid,
  	    RelationGetRelid(fk_rel),
  	    confkey,
  	    pfeqop,
  	    ppeqop,
  	    ffeqop,
  	    numkeys,
  	    con_form->confupdtype,
  	    con_form->confdeltype,
  	    con_form->confmatchtype,
  	    NULL /* exclOp - not an exclusion constraint */,
  	    NULL /* conExpr - not a check constraint */,
  	    NULL /* conBin - not a check constraint */,
  	    NULL /* conSrc - not a check constraint */,
  	    true  /* islocal */,
  	    0 /* inhcount */,
  	    con_form->connoinherit /* conNoInherit */,
  	    false /* is_internal */);
  
  	Constraint* entity = makeNode(Constraint);
  	entity->deferrable      = con_form->condeferrable;
  	entity->initdeferred    = con_form->condeferred;
  	entity->location        = -1;
  	entity->skip_validation = !con_form->convalidated;
  	entity->initially_valid = con_form->convalidated;
  	entity->is_no_inherit   = con_form->connoinherit;
  	entity->fk_matchtype    = con_form->confmatchtype;
  	entity->fk_upd_action   = con_form->confupdtype;
  	entity->fk_del_action   = con_form->confdeltype;
  
  	/*
  	 * Create the triggers that will enforce the constraint.
  	 * Note that this calls CommandCounterIncrement().
  	 */
  	createForeignKeyTriggers(base_rel,
  	                         RelationGetRelid(fk_rel),
  	                         entity,
  	                         constr_oid,
  	                         index_oid,
  	                         true /* create_action */);
  }
  
  /*
   * Make sequences and FKs referencing old_rel refer to new_rel instead.
   * FK referenced columns will be remapped according to the given attmap (if any).
   */
  static void
  YBMoveRelDependencies(Relation old_rel, Relation new_rel,
                        Relation pg_depend, Relation pg_constraint,
                        AttrNumber* attmap)
  {
  	ScanKeyData key[2];
  	SysScanDesc scan;
  	HeapTuple   dep_tuple, con_tuple;
  	ListCell*   cell;
  	List*       cons_to_drop = NIL; /* list of pairs (ConOid, ConstraintedRelOid) */
  
  	/* Move sequences dependencies. */
  	ScanKeyInit(&key[0], Anum_pg_depend_refclassid, BTEqualStrategyNumber,
  	            F_OIDEQ, ObjectIdGetDatum(RelationRelationId));
  	ScanKeyInit(&key[1], Anum_pg_depend_refobjid, BTEqualStrategyNumber,
  	            F_OIDEQ, ObjectIdGetDatum(RelationGetRelid(old_rel)));
  	scan = systable_beginscan(pg_depend,
  	                          DependReferenceIndexId,
  	                          true /* indexOK */,
  	                          NULL /* snapshot */,
  	                          2 /* nkeys */,
  	                          key);
  
  	while (HeapTupleIsValid(dep_tuple = systable_getnext(scan)))
  	{
  		Form_pg_depend dep_form = (Form_pg_depend) GETSTRUCT(dep_tuple);
  
  		if (get_rel_relkind(dep_form->objid) != RELKIND_SEQUENCE)
  			continue;
  
  		/* make a modifiable copy */
  		dep_tuple = heap_copytuple(dep_tuple);
  		dep_form  = (Form_pg_depend) GETSTRUCT(dep_tuple);
  		dep_form->refobjid = RelationGetRelid(new_rel);
  
  		CatalogTupleUpdate(pg_depend, &dep_tuple->t_self, dep_tuple);
  
  		heap_freetuple(dep_tuple);
  	}
  	systable_endscan(scan);
  	CommandCounterIncrement();
  
  	/* Move FKs referencing old_rel. */
  	ScanKeyInit(&key[0], Anum_pg_constraint_confrelid, BTEqualStrategyNumber,
  	            F_OIDEQ, ObjectIdGetDatum(RelationGetRelid(old_rel)));
  	ScanKeyInit(&key[1], Anum_pg_constraint_contype, BTEqualStrategyNumber,
  	            F_OIDEQ, CharGetDatum(CONSTRAINT_FOREIGN));
  	scan = systable_beginscan(pg_constraint,
  	                          InvalidOid /* no index */,
  	                          true /* indexOK */,
  	                          NULL /* snapshot */,
  	                          2 /* nkeys */,
  	                          key);
  	while (HeapTupleIsValid(con_tuple = systable_getnext(scan)))
  	{
  		Form_pg_constraint con_form = (Form_pg_constraint) GETSTRUCT(con_tuple);
  
  		/*
  		 * We need to rename this FK constraint and create a new one in its stead.
  		 * Dropping old constraints will be postponed until the end of the scan.
  		 */
  
  		const char* con_origname = pstrdup(NameStr(con_form->conname));
  		const char* con_tempname =
  		    ChooseConstraintName(NameStr(con_form->conname),
  		                         NULL /* name2 */,
  		                         "temp_old" /* label */,
  		                         con_form->connamespace,
  		                         NIL /* others */);
  
  		con_tuple = heap_copytuple(con_tuple);
  		con_form  = (Form_pg_constraint) GETSTRUCT(con_tuple);
  		namestrcpy(&(con_form->conname), con_tempname);
  		CatalogTupleUpdate(pg_constraint, &con_tuple->t_self, con_tuple);
  		CommandCounterIncrement();
  
  		cons_to_drop = lappend(cons_to_drop,
  		  list_make2_oid(HeapTupleGetOid(con_tuple), con_form->conrelid));
  
  		/*
  		 * We don't need AccessExclusiveLock since old constraint
  		 * can't be violated at any point.
  		 */
  		Relation base_rel = heap_open(con_form->conrelid, ShareUpdateExclusiveLock);
  
  		YBCreateSimilarForeignKey(con_tuple,
  		                          con_origname,
  		                          base_rel,
  		                          new_rel,
  		                          NULL,
  		                          attmap);
  
  		heap_freetuple(con_tuple);
  		heap_close(base_rel, ShareUpdateExclusiveLock);
  	}
  	systable_endscan(scan);
  
  	foreach(cell, cons_to_drop)
  	{
  		List* cell_list   = lfirst(cell);
  		Oid   conoid      = linitial_oid(cell_list);
  		Oid   base_relid  = lsecond_oid(cell_list);
  
  		ObjectAddress con_objaddr;
  		con_objaddr.classId     = ConstraintRelationId;
  		con_objaddr.objectId    = conoid;
  		con_objaddr.objectSubId = 0;
  
  		Relation base_rel = heap_open(base_relid, ShareUpdateExclusiveLock);
  		performDeletion(&con_objaddr, DROP_CASCADE, 0);
  		heap_close(base_rel, ShareUpdateExclusiveLock);
  	}
  }
  
  /*
   * Primary key is an inherent part of a DocDB table, we can't literally "add"
   * a primary key to an existing table.
   * As a workaround, we create a new table with the desired schema and replace
   * the old table with it.
   * Returns an address of the new primary key (dummy) index.
   */
  static ObjectAddress
  YBCloneRelationSetPrimaryKey(Relation* mutable_rel, IndexStmt* stmt)
  {
  	CreateStmt*  create_stmt;
  	RenameStmt*  rename_stmt;
  	DropStmt*    drop_stmt;
  	ListCell*    cell;
  	Relation     new_rel;
  	TupleConstr* constr;
  	AttrNumber*  old2new_attmap;
  	AttrNumber*  new2old_attmap;
  	Oid          old_relid, new_relid;
  
  	Relation     pg_constraint, pg_trigger, pg_depend;
  	ScanKeyData  key;
  	SysScanDesc  scan;
  	HeapTuple    tuple;
  
  	MemoryContext oldcxt, per_tup_cxt;
  	ObjectAddress result = InvalidObjectAddress, address;
  
  	YBCPgTableDesc       yb_table_desc;
  	YBCPgTableProperties yb_table_props;
  
  	old_relid = RelationGetRelid(*mutable_rel);
  
  	constr = RelationGetDescr(*mutable_rel)->constr;
  
  	/*
  	 * Recreating a table will change its OID, which is not tolerable
  	 * for system tables.
  	 */
  	if (IsCatalogRelation(*mutable_rel))
  		elog(ERROR, "cannot add a primary key to a system table");
  
  	if ((*mutable_rel)->rd_partkey != NULL || (*mutable_rel)->rd_rel->relispartition)
  		elog(ERROR, "adding primary key to a partitioned table "
  		            "is not yet implemented");
  
  	if ((*mutable_rel)->rd_rel->relhasrules)
  		elog(ERROR, "adding primary key to a table with rules "
  		            "is not yet implemented");
  
  	HandleYBStatus(YBCPgGetTableDesc(MyDatabaseId, old_relid, &yb_table_desc));
  	HandleYBStatus(YBCPgGetTableProperties(yb_table_desc, &yb_table_props));
  
  	/*
  	 * TODO: This works as a sanity check for now, but after we support inheritance
  	 *       we'd need to check for the presence of actual children.
  	 *       If we decide to support ALTER ADD PK for inherited tables, there will be
  	 *       issues with inherited constraints being recreated.
  	 *       Also note that partitioned tables have relhassubclass set as well.
  	 */
  	if ((*mutable_rel)->rd_rel->relhassubclass)
  		elog(ERROR, "adding primary key to a table having children tables "
  		            "is not yet implemented");
  
  	const Oid   namespace_oid   = RelationGetNamespace(*mutable_rel);
  	const char* namespace_name  = get_namespace_name(namespace_oid);
  
  	const char* temp_old_suffix     = "temp_old";
  
  	const char* orig_table_name     = pstrdup(RelationGetRelationName(*mutable_rel));
  	const char* temp_old_table_name = ChooseRelationName(orig_table_name,
  	                                                     NULL /* name2 */,
  	                                                     temp_old_suffix /* label */,
  	                                                     namespace_oid,
  	                                                     false /* isconstraint */);
  
  	/*
  	 * PHASE 1
  	 * -------
  	 * Rename the old table to free up the name.
  	 */
  
  	rename_stmt = makeNode(RenameStmt);
  	rename_stmt->renameType = OBJECT_TABLE;
  	rename_stmt->relation   = makeRangeVar(pstrdup(namespace_name),
  	                                       pstrdup(orig_table_name),
  	                                       -1 /* location */);
  	rename_stmt->subname    = NULL;
  	rename_stmt->newname    = pstrdup(temp_old_table_name);
  	rename_stmt->missing_ok = false;
  	RenameRelation(rename_stmt);
  
  	/* Make caches changes visible. */
  	CommandCounterIncrement();
  
  	/*
  	 * PHASE 2
  	 * -------
  	 * Create a replacement table with a correct PK.
  	 */
  
  	create_stmt = makeNode(CreateStmt);
  	create_stmt->relation      = makeRangeVar(pstrdup(namespace_name),
                                                pstrdup(orig_table_name),
  	                                          -1 /* location */);
  	create_stmt->ofTypename    = (OidIsValid((*mutable_rel)->rd_rel->reloftype)
  	        ? makeTypeNameFromOid((*mutable_rel)->rd_rel->reloftype, -1 /* typmod */)
  	        : NULL);
  	create_stmt->tablespacename = get_tablespace_name((*mutable_rel)->rd_rel->reltablespace);
  	create_stmt->tablegroup     = NULL;
  
  	/*
  	 * Colocation support is further complicated by the fact that we can't
  	 * verify it via pure SQL, see #6159.
  	 */
  	const Oid tablegroup_id = RelationGetTablegroup(*mutable_rel);
  	if (OidIsValid(tablegroup_id))
  	{
  		create_stmt->tablegroup = makeNode(OptTableGroup);
  		create_stmt->tablegroup->has_tablegroup = true;
  		create_stmt->tablegroup->tablegroup_name = get_tablegroup_name(tablegroup_id);
  		Assert(create_stmt->tablegroup->tablegroup_name);
  	} else if ((*mutable_rel)->rd_options) {
  		const bool colocated = RelationGetColocated(*mutable_rel);
  		create_stmt->options = lappend(create_stmt->options,
  			makeDefElem("colocated", (Node *) makeInteger(colocated), -1));
  	}
  
  	/*
  	 * While there is little to no sense for a user to be doing
  	 * CREATE TABLE ... SPLIT INTO x TABLETS without defining a primary key,
  	 * we're still going to preserve it.
  	 * It might come in handy if once we start supporting DROP PK as well.
  	 */
  	if (yb_table_props.num_hash_key_columns > 0)
  	{
  		create_stmt->split_options = makeNode(OptSplit);
  		create_stmt->split_options->split_type   = NUM_TABLETS;
  		create_stmt->split_options->num_tablets  = yb_table_props.num_tablets;
  		create_stmt->split_options->split_points = NULL;
  	}
  
  	/*
  	 * Set attributes and their defaults.
  	 */
  	AttrDefault* attrdef = constr ? constr->defval : NULL;
  	for (int attno = 1; attno <= RelationGetDescr(*mutable_rel)->natts; attno++)
  	{
  		Form_pg_attribute attr_form = TupleDescAttr(RelationGetDescr(*mutable_rel), attno - 1);
  
  		if (attr_form->attisdropped)
  			continue;
  
  		/*
  		 * Non-default collations are not supported yet (#1127) so we can't test it.
  		 * This acts as a safeguard.
  		 */
  		if (OidIsValid(attr_form->attcollation))
  		{
  			tuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(attr_form->atttypid));
  			if (!HeapTupleIsValid(tuple))
  				elog(ERROR, "cache lookup failed for type %u", attr_form->atttypid);
  			Form_pg_type attr_type_form = (Form_pg_type) GETSTRUCT(tuple);
  
  			if (attr_form->attcollation != attr_type_form->typcollation)
  				elog(ERROR, "adding primary key to a table with collated columns "
  				            "is not yet implemented");
  
  			ReleaseSysCache(tuple);
  		}
  
  		ColumnDef* col_def = makeColumnDef(NameStr(attr_form->attname),
  		                                   attr_form->atttypid,
  		                                   attr_form->atttypmod,
  		                                   attr_form->attcollation);
  		col_def->inhcount    = attr_form->attinhcount;
  		col_def->is_local    = attr_form->attislocal;
  		col_def->storage     = attr_form->attstorage;
  		col_def->identity    = attr_form->attidentity;
  		col_def->is_not_null = attr_form->attnotnull;
  		/* If this is a PK column now, is should be made non-nullable */
  		foreach(cell, stmt->indexParams)
  		{
  			IndexElem* ielem = lfirst(cell);
  			if (strcmp(NameStr(attr_form->attname), ielem->name) == 0)
  				col_def->is_not_null = true;
  		}
  		for (int j = 0; j < (constr ? constr->num_defval : 0); j++)
  		{
  			if (attrdef[j].adnum == attno)
  			{
  				col_def->cooked_default = stringToNode(attrdef[j].adbin);
  				break;
  			}
  		}
  		for (int j = 0; j < attr_form->attndims; j++)
  		{
  			/*
  			 * Individual elements of arrayBounds do not matter, see
  			 * https://www.postgresql.org/docs/11/arrays.html#ARRAYS-DECLARATION
  			 */
  			col_def->typeName->arrayBounds =
  			    lappend(col_def->typeName->arrayBounds, makeInteger(-1));
  		}
  
  		create_stmt->tableElts = lappend(create_stmt->tableElts, col_def);
  	}
  
  	/* The only constraint we care about here is the PK constraint needed for YB. */
  	Constraint* pk_constr = makeNode(Constraint);
  	pk_constr->contype      = CONSTR_PRIMARY;
  	pk_constr->conname      = stmt->idxname;
  	pk_constr->options      = stmt->options;
  	pk_constr->indexspace   = stmt->tableSpace;
  	foreach(cell, stmt->indexParams)
  	{
  		IndexElem* ielem = lfirst(cell);
  		pk_constr->keys            = lappend(pk_constr->keys, makeString(ielem->name));
  		pk_constr->yb_index_params = lappend(pk_constr->yb_index_params, ielem);
  	}
  	create_stmt->constraints = lappend(create_stmt->constraints, pk_constr);
  
  	/*
  	 * Create an altered table and open it.
  	 */
  	address = DefineRelation(create_stmt,
  	                         RELKIND_RELATION,
  	                         (*mutable_rel)->rd_rel->relowner,
  	                         NULL /* typaddress */,
  	                         "" /* queryString */);
  	new_relid = address.objectId;
  	new_rel = heap_open(new_relid, AccessExclusiveLock);
  
  	old2new_attmap =
  	    convert_tuples_by_name_map(RelationGetDescr(*mutable_rel),
  	                               RelationGetDescr(new_rel),
  	                               gettext_noop("could not convert row type"));
  
  	new2old_attmap =
  	    convert_tuples_by_name_map(RelationGetDescr(new_rel),
  	                               RelationGetDescr(*mutable_rel),
  	                               gettext_noop("could not convert row type"));
  
  	/*
  	 * PHASE 3
  	 * -------
  	 * Copy constraints.
  	 *
  	 * Only CHECK and FK constraints are copied here.
  	 */
  
  	pg_constraint = heap_open(ConstraintRelationId, RowExclusiveLock);
  	ScanKeyInit(&key, Anum_pg_constraint_conrelid, BTEqualStrategyNumber,
  	            F_OIDEQ, ObjectIdGetDatum(old_relid));
  	scan = systable_beginscan(pg_constraint,
  	                          ConstraintRelidTypidNameIndexId,
  	                          true /* indexOK */,
  	                          NULL /* snapshot */,
  	                          1 /* nkeys */,
  	                          &key);
  	bool has_dummy_pk = false; /* Sanity check that dummy PK index is already defined. */
  	List* checks_list = NIL;
  	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
  	{
  		Form_pg_constraint con_form = (Form_pg_constraint) GETSTRUCT(tuple);
  
  		/* Sanity check, should never happen as we've already checked for inheritance. */
  		if (con_form->coninhcount > 0)
  			elog(ERROR, "constraint '%s' is inherited!", NameStr(con_form->conname));
  
  		switch (con_form->contype)
  		{
  			case CONSTRAINT_CHECK:
  			{
  				Node* expr;
  				bool  found_whole_row;
  				Datum conbin_val = YBGetNotNullConstraintAttr(tuple, conbin);
  
  				// NOTE: Expression diverges, locations are -1
  				char* conbin = TextDatumGetCString(conbin_val);
  
  				/*
  				 * An alternative would be to directly use
  				 * StoreRelCheck + SetRelationNumChecks which is more straightforward
  				 * and incurs slightly less overhead, but those are private to heap.c
  				 * and that's probably not a good enough reason to change it.
  				 */
  
  				/* Same-named CHECK constraints on different relations do not conflict. */
  				Constraint* entity = makeNode(Constraint);
  				entity->contype         = CONSTR_CHECK;
  				entity->conname         = NameStr(con_form->conname);
  				entity->deferrable      = false;
  				entity->initdeferred    = false;
  				entity->location        = -1;
  				entity->skip_validation = !con_form->convalidated;
  				entity->initially_valid = con_form->convalidated;
  				entity->is_no_inherit   = con_form->connoinherit;
  
  				expr = (Node*) map_variable_attnos(stringToNode(conbin),
  				                                   1 /* fromrel_varno */,
  				                                   0 /* sublevels_up */,
  				                                   new2old_attmap,
  				                                   RelationGetDescr(*mutable_rel)->natts,
  				                                   RelationGetForm(new_rel)->reltype,
  				                                   &found_whole_row);
  				if (found_whole_row)
  					elog(ERROR, "unexpected whole-row reference found in CHECK constraint %s",
  					            entity->conname);
  
  				entity->raw_expr    = NULL;
  				entity->cooked_expr = nodeToString(expr);
  
  				checks_list = lappend(checks_list, entity);
  
  				break;
  			}
  			case CONSTRAINT_FOREIGN:
  			{
  				Relation fk_rel = heap_open(con_form->confrelid, ShareRowExclusiveLock);
  
  				/* Same-named FK constraints on different relations do not conflict. */
  
  				YBCreateSimilarForeignKey(tuple,
  				                          NameStr(con_form->conname),
  				                          new_rel,
  				                          fk_rel,
  				                          new2old_attmap,
  				                          NULL);
  
  				heap_close(fk_rel, ShareRowExclusiveLock);
  				break;
  			}
  			case CONSTRAINT_PRIMARY:
  				has_dummy_pk = true;
  				break;
  			case CONSTRAINT_UNIQUE:
  				/* UNIQUE constraints are indexes and will be copied as such. */
  				break;
  			case CONSTRAINT_TRIGGER:
  				/* Triggers are processed separately later on. */
  				break;
  			case CONSTRAINT_EXCLUSION:
  				/*
  				 * EXCLUDE constraints are not yet implemented, see #3944 - so
  				 * we can't test them.
  				 */
  				elog(ERROR, "adding primary key to a table with EXCLUDE constraints "
  				            "is not yet implemented");
  				break;
  			default:
  				elog(ERROR, "invalid constraint type \"%c\"", con_form->contype);
  				break;
  		}
  	}
  	systable_endscan(scan);
  	if (!has_dummy_pk)
  		elog(ERROR, "expected dummy primary key index to be defined");
  	/* We don't close pg_constraint just yet. */
  	AddRelationNewConstraints(new_rel,
  	                          NULL /* newColDefaults - they are already in place */,
  	                          checks_list,
  	                          false /* allow_merge */,
  	                          true /* is_local */,
  	                          true /* is_internal */,
  	                          NULL /* queryString - not available here */);
  	list_free(checks_list);
  
  	/* Make caches changes visible. */
  	CommandCounterIncrement();
  
  	/*
  	 * PHASE 4
  	 * -------
  	 * Copy table content.
  	 */
  
  	YBCopyTableRowsUnchecked(*mutable_rel, new_rel, old2new_attmap);
  
  	/*
  	 * PHASE 5
  	 * -------
  	 * Copy indexes (including constraint indexes).
  	 *
  	 * We're doing this after data migration to not bother populating
  	 * indexes manually.
  	 * Index names on different tables conflict with each other, so
  	 * we also rename old indexes as we go.
  	 */
  
  	pg_depend = heap_open(DependRelationId, RowExclusiveLock);
  
  	List* idx_list = RelationGetIndexList(*mutable_rel);
  	foreach(cell, idx_list)
  	{
  		ObjectAddress idx_addr;
  		Relation      idx_rel = index_open(lfirst_oid(cell), AccessExclusiveLock);
  
  		IndexStmt* idx_stmt =
  		    generateClonedIndexStmt(NULL /* heapRel, we provide an oid instead */,
  		                            new_relid,
  		                            idx_rel,
  		                            new2old_attmap,
  		                            RelationGetDescr(*mutable_rel)->natts,
  		                            NULL /* parent constraint OID pointer */);
  
  		const char* idx_orig_name = pstrdup(RelationGetRelationName(idx_rel));
  		const char* idx_temp_old_name =
  		    ChooseRelationName(idx_orig_name,
  		                       NULL /* name2 */,
  		                       temp_old_suffix /* label */,
  		                       namespace_oid,
  		                       idx_stmt->isconstraint);
  
  		/* Free up original index name. */
  		rename_stmt->relation = makeRangeVar(pstrdup(namespace_name),
  		                                     pstrdup(idx_orig_name),
  		                                     -1 /* location */);
  		rename_stmt->newname  = pstrdup(idx_temp_old_name);
  		RenameRelation(rename_stmt);
  		CommandCounterIncrement();
  
  		/* The tablegroup attribute of a table is not a reloption at syntax level
  		 * but it is recorded as a reloption by DefineIndex (which makes a special
  		 * case only for "tablegroup" to convert it to a reloption). As a result,
  		 * if the old table has a tablegroup, then every index on the old table
  		 * including the dummy pkey index has also stored a reloption for the
  		 * tablegroup when DefineIndex was called for it.
  		 *
  		 * When generateClonedIndexStmt is called to make a new index statement, it
  		 * will have cloned the old index's reloptions, which includes the special
  		 * reloption for "tablegroup".
  		 *
  		 * Next we will call DefineIndex for each cloned index statement. DefineIndex
  		 * will again make a special case for "tablegroup" and convert "tablegroup"
  		 * to another reloption. This means that the new index statement gets two
  		 * "tablegroup" reloption instances and caused postgres error:
  		 *   ERROR: parameter "tablegroup" specified more than once
  		 * To prevent this error, remove "tablegroup" reloption if there is one.
  		 */
  		if (idx_stmt->options)
  		{
  			ListCell   *option;
  			ListCell   *prev;
  
  			prev = NULL;
  			foreach(option, idx_stmt->options)
  			{
  				DefElem *elem = lfirst_node(DefElem, option);
  				if (strcmp(elem->defname, "tablegroup") == 0)
  				{
  					idx_stmt->options = list_delete_cell(idx_stmt->options, option, prev);
  					break;
  				}
  				else
  					prev = option;
  			}
  		}
  
  		/* Create a new index taking up the freed name. */
  		idx_stmt->idxname = pstrdup(idx_orig_name);
  		idx_addr = DefineIndex(new_relid,
  		                       idx_stmt,
  		                       InvalidOid, /* no predefined OID */
  		                       InvalidOid, /* no parent index */
  		                       InvalidOid, /* no parent constraint */
  		                       false, /* is_alter_table */
  		                       false, /* check_rights */
  		                       false, /* check_not_in_use */
  		                       false, /* skip_build */
  		                       true /* quiet */);
  
  		if (idx_rel->rd_index->indisprimary)
  			result = idx_addr;
  
  		index_close(idx_rel,  AccessExclusiveLock);
  	}
  	list_free(idx_list);
  	Assert(OidIsValid(result.objectId));
  
  	/*
  	 * PHASE 6
  	 * -------
  	 * Migrate dependencies: owned sequences and external FK constraints.
  	 *
  	 * FK constraints referencing the old table will be dropped and re-created
  	 * as the results.
  	 */
  
  	YBMoveRelDependencies(*mutable_rel, new_rel, pg_depend, pg_constraint, new2old_attmap);
  	heap_close(pg_depend, RowExclusiveLock);
  	heap_close(pg_constraint, RowExclusiveLock);
  
  	/*
  	 * PHASE 7
  	 * -------
  	 * Copy triggers.
  	 */
  
  	pg_trigger = heap_open(TriggerRelationId, RowExclusiveLock);
  	ScanKeyInit(&key, Anum_pg_trigger_tgrelid, BTEqualStrategyNumber,
  	            F_OIDEQ, ObjectIdGetDatum(old_relid));
  	scan = systable_beginscan(pg_trigger,
  	                          TriggerRelidNameIndexId,
  	                          true /* indexOK */,
  	                          NULL /* snapshot */,
  	                          1 /* nkeys */,
  	                          &key);
  
  	per_tup_cxt = AllocSetContextCreate(GetCurrentMemoryContext(),
  	                                    "copy triggers",
  	                                    ALLOCSET_SMALL_SIZES);
  	oldcxt = MemoryContextSwitchTo(per_tup_cxt);
  
  	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
  	{
  		Form_pg_trigger trig_form = (Form_pg_trigger) GETSTRUCT(tuple);
  		CreateTrigStmt* trig_stmt;
  		Node*           qual = NULL;
  		Datum           value;
  		bool            isnull;
  		List*           cols = NIL;
  
  		/*
  		 * Don't copy internal triggers as they are constraint-related
  		 * and have already been copied.
  		 */
  		if (trig_form->tgisinternal)
  			continue;
  
  		/*
  		 * If there is a WHEN clause, generate a 'cooked' version of it that's
  		 * appropriate for the new attnums.
  		 */
  		value = heap_getattr(tuple,
  		                     Anum_pg_trigger_tgqual,
  		                     RelationGetDescr(pg_trigger),
  		                     &isnull);
  		if (!isnull)
  		{
  			bool found_whole_row;
  			qual = stringToNode(TextDatumGetCString(value));
  			/* 'OLD' is guaranteed to have varno equal to 1 and 'NEW' equal to 2. */
  			for (int fromrel_varno = 1; fromrel_varno <= 2; ++fromrel_varno)
  			{
  				qual = (Node*) map_variable_attnos(qual,
  				                                   fromrel_varno,
  				                                   0 /* sublevels_up */,
  				                                   new2old_attmap,
  				                                   RelationGetDescr(*mutable_rel)->natts,
  				                                   RelationGetForm(new_rel)->reltype,
  				                                   &found_whole_row);
  				if (found_whole_row)
  					elog(ERROR, "unexpected whole-row reference found in WHEN clause "
  					            "of trigger %s",
  					            NameStr(trig_form->tgname));
  			}
  		}
  
  		/*
  		 * If there is a column list, transform it to a list of column names.
  		 */
  		for (int i = 0; i < trig_form->tgattr.dim1; i++)
  		{
  			AttrNumber attnum = trig_form->tgattr.values[i];
  			Form_pg_attribute col_form =
  			    TupleDescAttr((*mutable_rel)->rd_att, attnum - 1);
  			cols = lappend(cols, makeString(pstrdup(NameStr(col_form->attname))));
  		}
  
  		/* Same-named triggers on different relations do not conflict. */
  		trig_stmt = makeNode(CreateTrigStmt);
  		trig_stmt->trigname       = NameStr(trig_form->tgname);
  		trig_stmt->relation       = NULL; /* passed separately (as OID) */
  		trig_stmt->funcname       = NULL; /* passed separately */
  		trig_stmt->args           = NULL; /* no args for trigger funcs */
  		trig_stmt->row            = TRIGGER_FOR_ROW(trig_form->tgtype);
  		trig_stmt->timing         = trig_form->tgtype & TRIGGER_TYPE_TIMING_MASK;
  		trig_stmt->events         = trig_form->tgtype & TRIGGER_TYPE_EVENT_MASK;
  		trig_stmt->columns        = cols;
  		trig_stmt->whenClause     = NULL; /* passed separately */
  		trig_stmt->isconstraint   = OidIsValid(trig_form->tgconstraint);
  		trig_stmt->deferrable     = trig_form->tgdeferrable;
  		trig_stmt->initdeferred   = trig_form->tginitdeferred;
  		trig_stmt->constrrel      = NULL; /* passed separately */
  
  		CreateTrigger(trig_stmt,
  		              NULL /* queryString */,
  		              new_relid,
  		              InvalidOid /* refRelOid */,
  		              InvalidOid /* constraintOid */,
  		              InvalidOid /* indexOid */,
  		              trig_form->tgfoid,
  		              InvalidOid /* parentTriggerOid */,
  		              qual,
  		              false /* isInternal */,
  		              false /* in_partition */);
  
  		MemoryContextReset(per_tup_cxt);
  	}
  
  	MemoryContextSwitchTo(oldcxt);
  	MemoryContextDelete(per_tup_cxt);
  
  	systable_endscan(scan);
  	heap_close(pg_trigger, RowExclusiveLock);
  
  	/*
  	 * PHASE 8
  	 * -------
  	 * Drop the old table.
  	 *
  	 * This will drop everything associated with it except sequences
  	 * (which we migrated) and external FK constraints referencing it
  	 * (which we already dropped in phase 6).
  	 */
  
  	/* "Close" a relation (decrement the refcount) to allow removing it, and do so. */
  	RelationClose(*mutable_rel);
  
  	/* Drop the old table. */
  	drop_stmt = makeNode(DropStmt);
  	drop_stmt->removeType = OBJECT_TABLE;
  	drop_stmt->missing_ok = false;
  	drop_stmt->objects    = list_make1(list_make2(
  	    makeString(pstrdup(namespace_name)),
  	    makeString(pstrdup(temp_old_table_name))));
  	drop_stmt->behavior   = DROP_CASCADE;
  	drop_stmt->concurrent = false;
  	RemoveRelations(drop_stmt);
  
  	/* Re-target old relation to point to the new one. */
  	*mutable_rel = new_rel;
  
  	return result;
  }
  
  /*
   * ALTER TABLE ADD INDEX
   *
   * There is no such command in the grammar, but parse_utilcmd.c converts
   * UNIQUE and PRIMARY KEY constraints into AT_AddIndex subcommands.  This lets
   * us schedule creation of the index at the appropriate time during ALTER.
   *
   * Return value is the address of the new index.
   *
   * YB NOTE: Will replace passed relation with another one in case it was re-created.
   */
  static ObjectAddress
  ATExecAddIndex(AlteredTableInfo *tab, Relation *mutable_rel,
  			   IndexStmt *stmt, bool is_rebuild, LOCKMODE lockmode)
  {
  	bool		check_rights;
  	bool		skip_build;
  	bool		quiet;
  	ObjectAddress address;
  
  	Assert(IsA(stmt, IndexStmt));
  	Assert(!stmt->concurrent);
  
  	/* The IndexStmt has already been through transformIndexStmt */
  	Assert(stmt->transformed);
  
  	/* suppress schema rights check when rebuilding existing index */
  	check_rights = !is_rebuild;
  	/* skip index build if phase 3 will do it or we're reusing an old one */
  	skip_build = tab->rewrite > 0 || OidIsValid(stmt->oldNode);
  	/* suppress notices when rebuilding existing index */
  	quiet = is_rebuild;
  
  	/*
  	 * YB note:
  	 * For a PRIMARY KEY index creation, this will create a dummy index.
  	 * We're doing this before YBCloneRelationSetPrimaryKey for it to run
  	 * all necessary checks - columns existence and types, absence of nulls, etc.
  	 */
  	address = DefineIndex(RelationGetRelid(*mutable_rel),
  						  stmt,
  						  InvalidOid,	/* no predefined OID */
  						  InvalidOid,	/* no parent index */
  						  InvalidOid,	/* no parent constraint */
  						  true, /* is_alter_table */
  						  check_rights,
  						  false,	/* check_not_in_use - we did it already */
  						  skip_build,
  						  quiet);
  	if (IsYBRelation(*mutable_rel) && stmt->primary)
  	{
  		/* Table will be re-created, along with the dummy PK index. */
  		address = YBCloneRelationSetPrimaryKey(mutable_rel, stmt);
  	}
  
  	/*
  	 * If TryReuseIndex() stashed a relfilenode for us, we used it for the new
  	 * index instead of building from scratch.  The DROP of the old edition of
  	 * this index will have scheduled the storage for deletion at commit, so
  	 * cancel that pending deletion.
  	 */
  	if (OidIsValid(stmt->oldNode))
  	{
  		Relation	irel = index_open(address.objectId, NoLock);
  
  		RelationPreserveStorage(irel->rd_node, true);
  		index_close(irel, NoLock);
  	}
  
  	return address;
  }
  
  /*
   * ALTER TABLE ADD CONSTRAINT USING INDEX
   *
   * Returns the address of the new constraint.
   */
  static ObjectAddress
  ATExecAddIndexConstraint(AlteredTableInfo *tab, Relation rel,
  						 IndexStmt *stmt, LOCKMODE lockmode)
  {
  	Oid			index_oid = stmt->indexOid;
  	Relation	indexRel;
  	char	   *indexName;
  	IndexInfo  *indexInfo;
  	char	   *constraintName;
  	char		constraintType;
  	ObjectAddress address;
  	bits16		flags;
  
  	Assert(IsA(stmt, IndexStmt));
  	Assert(OidIsValid(index_oid));
  	Assert(stmt->isconstraint);
  
  	/*
  	 * Doing this on partitioned tables is not a simple feature to implement,
  	 * so let's punt for now.
  	 */
  	if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("ALTER TABLE / ADD CONSTRAINT USING INDEX is not supported on partitioned tables")));
  
  	if (IsYugaByteEnabled() && stmt->primary)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("ALTER TABLE / ADD CONSTRAINT PRIMARY KEY USING INDEX is not supported")));
  
  	indexRel = index_open(index_oid, AccessShareLock);
  
  	indexName = pstrdup(RelationGetRelationName(indexRel));
  
  	indexInfo = BuildIndexInfo(indexRel);
  
  	/* this should have been checked at parse time */
  	if (!indexInfo->ii_Unique)
  		elog(ERROR, "index \"%s\" is not unique", indexName);
  
  	/*
  	 * Determine name to assign to constraint.  We require a constraint to
  	 * have the same name as the underlying index; therefore, use the index's
  	 * existing name as the default constraint name, and if the user
  	 * explicitly gives some other name for the constraint, rename the index
  	 * to match.
  	 */
  	constraintName = stmt->idxname;
  	if (constraintName == NULL)
  		constraintName = indexName;
  	else if (strcmp(constraintName, indexName) != 0)
  	{
  		ereport(NOTICE,
  				(errmsg("ALTER TABLE / ADD CONSTRAINT USING INDEX will rename index \"%s\" to \"%s\"",
  						indexName, constraintName)));
  		RenameRelationInternal(index_oid, constraintName, false);
  	}
  
  	/* Extra checks needed if making primary key */
  	if (stmt->primary)
  		index_check_primary_key(rel, indexInfo, true, stmt);
  
  	/* Note we currently don't support EXCLUSION constraints here */
  	if (stmt->primary)
  		constraintType = CONSTRAINT_PRIMARY;
  	else
  		constraintType = CONSTRAINT_UNIQUE;
  
  	/* Create the catalog entries for the constraint */
  	flags = INDEX_CONSTR_CREATE_UPDATE_INDEX |
  		INDEX_CONSTR_CREATE_REMOVE_OLD_DEPS |
  		(stmt->initdeferred ? INDEX_CONSTR_CREATE_INIT_DEFERRED : 0) |
  		(stmt->deferrable ? INDEX_CONSTR_CREATE_DEFERRABLE : 0) |
  		(stmt->primary ? INDEX_CONSTR_CREATE_MARK_AS_PRIMARY : 0);
  
  	address = index_constraint_create(rel,
  									  index_oid,
  									  InvalidOid,
  									  indexInfo,
  									  constraintName,
  									  constraintType,
  									  flags,
  									  allowSystemTableMods,
  									  false);	/* is_internal */
  
  	index_close(indexRel, NoLock);
  
  	return address;
  }
  
  /*
   * ALTER TABLE ADD CONSTRAINT
   *
   * Return value is the address of the new constraint; if no constraint was
   * added, InvalidObjectAddress is returned.
   */
  static ObjectAddress
  ATExecAddConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
  					Constraint *newConstraint, bool recurse, bool is_readd,
  					LOCKMODE lockmode)
  {
  	ObjectAddress address = InvalidObjectAddress;
  
  	Assert(IsA(newConstraint, Constraint));
  
  	/*
  	 * Currently, we only expect to see CONSTR_CHECK and CONSTR_FOREIGN nodes
  	 * arriving here (see the preprocessing done in parse_utilcmd.c).  Use a
  	 * switch anyway to make it easier to add more code later.
  	 */
  	switch (newConstraint->contype)
  	{
  		case CONSTR_CHECK:
  			address =
  				ATAddCheckConstraint(wqueue, tab, rel,
  									 newConstraint, recurse, false, is_readd,
  									 lockmode);
  			break;
  
  		case CONSTR_FOREIGN:
  
  			/*
  			 * Note that we currently never recurse for FK constraints, so the
  			 * "recurse" flag is silently ignored.
  			 *
  			 * Assign or validate constraint name
  			 */
  			if (newConstraint->conname)
  			{
  				if (ConstraintNameIsUsed(CONSTRAINT_RELATION,
  										 RelationGetRelid(rel),
  										 newConstraint->conname))
  					ereport(ERROR,
  							(errcode(ERRCODE_DUPLICATE_OBJECT),
  							 errmsg("constraint \"%s\" for relation \"%s\" already exists",
  									newConstraint->conname,
  									RelationGetRelationName(rel))));
  			}
  			else
  				newConstraint->conname =
  					ChooseConstraintName(RelationGetRelationName(rel),
  										 strVal(linitial(newConstraint->fk_attrs)),
  										 "fkey",
  										 RelationGetNamespace(rel),
  										 NIL);
  
  			address = ATAddForeignKeyConstraint(wqueue, tab, rel,
  												newConstraint, InvalidOid,
  												recurse, false,
  												lockmode);
  			break;
  
  		default:
  			elog(ERROR, "unrecognized constraint type: %d",
  				 (int) newConstraint->contype);
  	}
  
  	return address;
  }
  
  /*
   * Add a check constraint to a single table and its children.  Returns the
   * address of the constraint added to the parent relation, if one gets added,
   * or InvalidObjectAddress otherwise.
   *
   * Subroutine for ATExecAddConstraint.
   *
   * We must recurse to child tables during execution, rather than using
   * ALTER TABLE's normal prep-time recursion.  The reason is that all the
   * constraints *must* be given the same name, else they won't be seen as
   * related later.  If the user didn't explicitly specify a name, then
   * AddRelationNewConstraints would normally assign different names to the
   * child constraints.  To fix that, we must capture the name assigned at
   * the parent table and pass that down.
   */
  static ObjectAddress
  ATAddCheckConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
  					 Constraint *constr, bool recurse, bool recursing,
  					 bool is_readd, LOCKMODE lockmode)
  {
  	List	   *newcons;
  	ListCell   *lcon;
  	List	   *children;
  	ListCell   *child;
  	ObjectAddress address = InvalidObjectAddress;
  
  	/* At top level, permission check was done in ATPrepCmd, else do it */
  	if (recursing)
  		ATSimplePermissions(rel, ATT_TABLE | ATT_FOREIGN_TABLE);
  
  	/*
  	 * Call AddRelationNewConstraints to do the work, making sure it works on
  	 * a copy of the Constraint so transformExpr can't modify the original. It
  	 * returns a list of cooked constraints.
  	 *
  	 * If the constraint ends up getting merged with a pre-existing one, it's
  	 * omitted from the returned list, which is what we want: we do not need
  	 * to do any validation work.  That can only happen at child tables,
  	 * though, since we disallow merging at the top level.
  	 */
  	newcons = AddRelationNewConstraints(rel, NIL,
  										list_make1(copyObject(constr)),
  										recursing | is_readd,	/* allow_merge */
  										!recursing, /* is_local */
  										is_readd,	/* is_internal */
  										NULL);		/* queryString not available here */
  
  	/* we don't expect more than one constraint here */
  	Assert(list_length(newcons) <= 1);
  
  	/* Add each to-be-validated constraint to Phase 3's queue */
  	foreach(lcon, newcons)
  	{
  		CookedConstraint *ccon = (CookedConstraint *) lfirst(lcon);
  
  		if (!ccon->skip_validation)
  		{
  			NewConstraint *newcon;
  
  			newcon = (NewConstraint *) palloc0(sizeof(NewConstraint));
  			newcon->name = ccon->name;
  			newcon->contype = ccon->contype;
  			newcon->qual = ccon->expr;
  
  			tab->constraints = lappend(tab->constraints, newcon);
  		}
  
  		/* Save the actually assigned name if it was defaulted */
  		if (constr->conname == NULL)
  			constr->conname = ccon->name;
  
  		ObjectAddressSet(address, ConstraintRelationId, ccon->conoid);
  	}
  
  	/* At this point we must have a locked-down name to use */
  	Assert(constr->conname != NULL);
  
  	/* Advance command counter in case same table is visited multiple times */
  	CommandCounterIncrement();
  
  	/*
  	 * If the constraint got merged with an existing constraint, we're done.
  	 * We mustn't recurse to child tables in this case, because they've
  	 * already got the constraint, and visiting them again would lead to an
  	 * incorrect value for coninhcount.
  	 */
  	if (newcons == NIL)
  		return address;
  
  	/*
  	 * If adding a NO INHERIT constraint, no need to find our children.
  	 */
  	if (constr->is_no_inherit)
  		return address;
  
  	/*
  	 * Propagate to children as appropriate.  Unlike most other ALTER
  	 * routines, we have to do this one level of recursion at a time; we can't
  	 * use find_all_inheritors to do it in one pass.
  	 */
  	children = find_inheritance_children(RelationGetRelid(rel), lockmode);
  
  	/*
  	 * Check if ONLY was specified with ALTER TABLE.  If so, allow the
  	 * constraint creation only if there are no children currently.  Error out
  	 * otherwise.
  	 */
  	if (!recurse && children != NIL)
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  				 errmsg("constraint must be added to child tables too")));
  
  	foreach(child, children)
  	{
  		Oid			childrelid = lfirst_oid(child);
  		Relation	childrel;
  		AlteredTableInfo *childtab;
  
  		/* find_inheritance_children already got lock */
  		childrel = heap_open(childrelid, NoLock);
  		CheckTableNotInUse(childrel, "ALTER TABLE");
  
  		/* Find or create work queue entry for this table */
  		childtab = ATGetQueueEntry(wqueue, childrel);
  
  		/* Recurse to child */
  		ATAddCheckConstraint(wqueue, childtab, childrel,
  							 constr, recurse, true, is_readd, lockmode);
  
  		heap_close(childrel, NoLock);
  	}
  
  	return address;
  }
  
  /*
   * Add a foreign-key constraint to a single table; return the new constraint's
   * address.
   *
   * Subroutine for ATExecAddConstraint.  Must already hold exclusive
   * lock on the rel, and have done appropriate validity checks for it.
   * We do permissions checks here, however.
   */
  static ObjectAddress
  ATAddForeignKeyConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
  						  Constraint *fkconstraint, Oid parentConstr,
  						  bool recurse, bool recursing, LOCKMODE lockmode)
  {
  	Relation	pkrel;
  	int16		pkattnum[INDEX_MAX_KEYS];
  	int16		fkattnum[INDEX_MAX_KEYS];
  	Oid			pktypoid[INDEX_MAX_KEYS];
  	Oid			fktypoid[INDEX_MAX_KEYS];
  	Oid			opclasses[INDEX_MAX_KEYS];
  	Oid			pfeqoperators[INDEX_MAX_KEYS];
  	Oid			ppeqoperators[INDEX_MAX_KEYS];
  	Oid			ffeqoperators[INDEX_MAX_KEYS];
  	bool		connoinherit;
  	int			i;
  	int			numfks,
  				numpks;
  	Oid			indexOid;
  	Oid			constrOid;
  	bool		old_check_ok;
  	ObjectAddress address;
  	ListCell   *old_pfeqop_item = list_head(fkconstraint->old_conpfeqop);
  
  	/*
  	 * Grab ShareRowExclusiveLock on the pk table, so that someone doesn't
  	 * delete rows out from under us.
  	 */
  	if (OidIsValid(fkconstraint->old_pktable_oid))
  		pkrel = heap_open(fkconstraint->old_pktable_oid, ShareRowExclusiveLock);
  	else
  		pkrel = heap_openrv(fkconstraint->pktable, ShareRowExclusiveLock);
  
  	/*
  	 * Validity checks (permission checks wait till we have the column
  	 * numbers)
  	 */
  	if (pkrel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot reference partitioned table \"%s\"",
  						RelationGetRelationName(pkrel))));
  
  	if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  	{
  		if (!recurse)
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("cannot use ONLY for foreign key on partitioned table \"%s\" referencing relation \"%s\"",
  							RelationGetRelationName(rel),
  							RelationGetRelationName(pkrel))));
  		if (fkconstraint->skip_validation && !fkconstraint->initially_valid)
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("cannot add NOT VALID foreign key on partitioned table \"%s\" referencing relation \"%s\"",
  							RelationGetRelationName(rel),
  							RelationGetRelationName(pkrel)),
  					 errdetail("This feature is not yet supported on partitioned tables.")));
  	}
  
  	if (pkrel->rd_rel->relkind != RELKIND_RELATION)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("referenced relation \"%s\" is not a table",
  						RelationGetRelationName(pkrel))));
  
  	if (!allowSystemTableMods && IsSystemRelation(pkrel))
  		ereport(ERROR,
  				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  				 errmsg("permission denied: \"%s\" is a system catalog",
  						RelationGetRelationName(pkrel))));
  
  	/*
  	 * References from permanent or unlogged tables to temp tables, and from
  	 * permanent tables to unlogged tables, are disallowed because the
  	 * referenced data can vanish out from under us.  References from temp
  	 * tables to any other table type are also disallowed, because other
  	 * backends might need to run the RI triggers on the perm table, but they
  	 * can't reliably see tuples in the local buffers of other backends.
  	 */
  	switch (rel->rd_rel->relpersistence)
  	{
  		case RELPERSISTENCE_PERMANENT:
  			if (pkrel->rd_rel->relpersistence != RELPERSISTENCE_PERMANENT)
  				ereport(ERROR,
  						(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  						 errmsg("constraints on permanent tables may reference only permanent tables")));
  			break;
  		case RELPERSISTENCE_UNLOGGED:
  			if (pkrel->rd_rel->relpersistence != RELPERSISTENCE_PERMANENT
  				&& pkrel->rd_rel->relpersistence != RELPERSISTENCE_UNLOGGED)
  				ereport(ERROR,
  						(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  						 errmsg("constraints on unlogged tables may reference only permanent or unlogged tables")));
  			break;
  		case RELPERSISTENCE_TEMP:
  			if (pkrel->rd_rel->relpersistence != RELPERSISTENCE_TEMP)
  				ereport(ERROR,
  						(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  						 errmsg("constraints on temporary tables may reference only temporary tables")));
  			if (!pkrel->rd_islocaltemp || !rel->rd_islocaltemp)
  				ereport(ERROR,
  						(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  						 errmsg("constraints on temporary tables must involve temporary tables of this session")));
  			break;
  	}
  
  	/*
  	 * Look up the referencing attributes to make sure they exist, and record
  	 * their attnums and type OIDs.
  	 */
  	MemSet(pkattnum, 0, sizeof(pkattnum));
  	MemSet(fkattnum, 0, sizeof(fkattnum));
  	MemSet(pktypoid, 0, sizeof(pktypoid));
  	MemSet(fktypoid, 0, sizeof(fktypoid));
  	MemSet(opclasses, 0, sizeof(opclasses));
  	MemSet(pfeqoperators, 0, sizeof(pfeqoperators));
  	MemSet(ppeqoperators, 0, sizeof(ppeqoperators));
  	MemSet(ffeqoperators, 0, sizeof(ffeqoperators));
  
  	numfks = transformColumnNameList(RelationGetRelid(rel),
  									 fkconstraint->fk_attrs,
  									 fkattnum, fktypoid);
  
  	/*
  	 * If the attribute list for the referenced table was omitted, lookup the
  	 * definition of the primary key and use it.  Otherwise, validate the
  	 * supplied attribute list.  In either case, discover the index OID and
  	 * index opclasses, and the attnums and type OIDs of the attributes.
  	 */
  	if (fkconstraint->pk_attrs == NIL)
  	{
  		numpks = transformFkeyGetPrimaryKey(pkrel, &indexOid,
  											&fkconstraint->pk_attrs,
  											pkattnum, pktypoid,
  											opclasses);
  	}
  	else
  	{
  		numpks = transformColumnNameList(RelationGetRelid(pkrel),
  										 fkconstraint->pk_attrs,
  										 pkattnum, pktypoid);
  		/* Look for an index matching the column list */
  		indexOid = transformFkeyCheckAttrs(pkrel, numpks, pkattnum,
  										   opclasses);
  	}
  
  	/*
  	 * Now we can check permissions.
  	 */
  	checkFkeyPermissions(pkrel, pkattnum, numpks);
  
  	/*
  	 * Look up the equality operators to use in the constraint.
  	 *
  	 * Note that we have to be careful about the difference between the actual
  	 * PK column type and the opclass' declared input type, which might be
  	 * only binary-compatible with it.  The declared opcintype is the right
  	 * thing to probe pg_amop with.
  	 */
  	if (numfks != numpks)
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_FOREIGN_KEY),
  				 errmsg("number of referencing and referenced columns for foreign key disagree")));
  
  	/*
  	 * On the strength of a previous constraint, we might avoid scanning
  	 * tables to validate this one.  See below.
  	 */
  	old_check_ok = (fkconstraint->old_conpfeqop != NIL);
  	Assert(!old_check_ok || numfks == list_length(fkconstraint->old_conpfeqop));
  
  	for (i = 0; i < numpks; i++)
  	{
  		Oid			pktype = pktypoid[i];
  		Oid			fktype = fktypoid[i];
  		Oid			fktyped;
  		HeapTuple	cla_ht;
  		Form_pg_opclass cla_tup;
  		Oid			amid;
  		Oid			opfamily;
  		Oid			opcintype;
  		Oid			pfeqop;
  		Oid			ppeqop;
  		Oid			ffeqop;
  		int16		eqstrategy;
  		Oid			pfeqop_right;
  
  		/* We need several fields out of the pg_opclass entry */
  		cla_ht = SearchSysCache1(CLAOID, ObjectIdGetDatum(opclasses[i]));
  		if (!HeapTupleIsValid(cla_ht))
  			elog(ERROR, "cache lookup failed for opclass %u", opclasses[i]);
  		cla_tup = (Form_pg_opclass) GETSTRUCT(cla_ht);
  		amid = cla_tup->opcmethod;
  		opfamily = cla_tup->opcfamily;
  		opcintype = cla_tup->opcintype;
  		ReleaseSysCache(cla_ht);
  
  		/*
  		 * Check it's a btree; currently this can never fail since no other
  		 * index AMs support unique indexes.  If we ever did have other types
  		 * of unique indexes, we'd need a way to determine which operator
  		 * strategy number is equality.  (Is it reasonable to insist that
  		 * every such index AM use btree's number for equality?)
  		 */
  		if (amid != BTREE_AM_OID && amid != LSM_AM_OID)
  			elog(ERROR, "only b-tree and lsm indexes are supported for foreign keys");
  		eqstrategy = BTEqualStrategyNumber;
  
  		/*
  		 * There had better be a primary equality operator for the index.
  		 * We'll use it for PK = PK comparisons.
  		 */
  		ppeqop = get_opfamily_member(opfamily, opcintype, opcintype,
  									 eqstrategy);
  
  		if (!OidIsValid(ppeqop))
  			elog(ERROR, "missing operator %d(%u,%u) in opfamily %u",
  				 eqstrategy, opcintype, opcintype, opfamily);
  
  		/*
  		 * Are there equality operators that take exactly the FK type? Assume
  		 * we should look through any domain here.
  		 */
  		fktyped = getBaseType(fktype);
  
  		pfeqop = get_opfamily_member(opfamily, opcintype, fktyped,
  									 eqstrategy);
  		if (OidIsValid(pfeqop))
  		{
  			pfeqop_right = fktyped;
  			ffeqop = get_opfamily_member(opfamily, fktyped, fktyped,
  										 eqstrategy);
  		}
  		else
  		{
  			/* keep compiler quiet */
  			pfeqop_right = InvalidOid;
  			ffeqop = InvalidOid;
  		}
  
  		if (!(OidIsValid(pfeqop) && OidIsValid(ffeqop)))
  		{
  			/*
  			 * Otherwise, look for an implicit cast from the FK type to the
  			 * opcintype, and if found, use the primary equality operator.
  			 * This is a bit tricky because opcintype might be a polymorphic
  			 * type such as ANYARRAY or ANYENUM; so what we have to test is
  			 * whether the two actual column types can be concurrently cast to
  			 * that type.  (Otherwise, we'd fail to reject combinations such
  			 * as int[] and point[].)
  			 */
  			Oid			input_typeids[2];
  			Oid			target_typeids[2];
  
  			input_typeids[0] = pktype;
  			input_typeids[1] = fktype;
  			target_typeids[0] = opcintype;
  			target_typeids[1] = opcintype;
  			if (can_coerce_type(2, input_typeids, target_typeids,
  								COERCION_IMPLICIT))
  			{
  				pfeqop = ffeqop = ppeqop;
  				pfeqop_right = opcintype;
  			}
  		}
  
  		if (!(OidIsValid(pfeqop) && OidIsValid(ffeqop)))
  			ereport(ERROR,
  					(errcode(ERRCODE_DATATYPE_MISMATCH),
  					 errmsg("foreign key constraint \"%s\" "
  							"cannot be implemented",
  							fkconstraint->conname),
  					 errdetail("Key columns \"%s\" and \"%s\" "
  							   "are of incompatible types: %s and %s.",
  							   strVal(list_nth(fkconstraint->fk_attrs, i)),
  							   strVal(list_nth(fkconstraint->pk_attrs, i)),
  							   format_type_be(fktype),
  							   format_type_be(pktype))));
  
  		if (old_check_ok)
  		{
  			/*
  			 * When a pfeqop changes, revalidate the constraint.  We could
  			 * permit intra-opfamily changes, but that adds subtle complexity
  			 * without any concrete benefit for core types.  We need not
  			 * assess ppeqop or ffeqop, which RI_Initial_Check() does not use.
  			 */
  			old_check_ok = (pfeqop == lfirst_oid(old_pfeqop_item));
  			old_pfeqop_item = lnext(old_pfeqop_item);
  		}
  		if (old_check_ok)
  		{
  			Oid			old_fktype;
  			Oid			new_fktype;
  			CoercionPathType old_pathtype;
  			CoercionPathType new_pathtype;
  			Oid			old_castfunc;
  			Oid			new_castfunc;
  			Form_pg_attribute attr = TupleDescAttr(tab->oldDesc,
  												   fkattnum[i] - 1);
  
  			/*
  			 * Identify coercion pathways from each of the old and new FK-side
  			 * column types to the right (foreign) operand type of the pfeqop.
  			 * We may assume that pg_constraint.conkey is not changing.
  			 */
  			old_fktype = attr->atttypid;
  			new_fktype = fktype;
  			old_pathtype = findFkeyCast(pfeqop_right, old_fktype,
  										&old_castfunc);
  			new_pathtype = findFkeyCast(pfeqop_right, new_fktype,
  										&new_castfunc);
  
  			/*
  			 * Upon a change to the cast from the FK column to its pfeqop
  			 * operand, revalidate the constraint.  For this evaluation, a
  			 * binary coercion cast is equivalent to no cast at all.  While
  			 * type implementors should design implicit casts with an eye
  			 * toward consistency of operations like equality, we cannot
  			 * assume here that they have done so.
  			 *
  			 * A function with a polymorphic argument could change behavior
  			 * arbitrarily in response to get_fn_expr_argtype().  Therefore,
  			 * when the cast destination is polymorphic, we only avoid
  			 * revalidation if the input type has not changed at all.  Given
  			 * just the core data types and operator classes, this requirement
  			 * prevents no would-be optimizations.
  			 *
  			 * If the cast converts from a base type to a domain thereon, then
  			 * that domain type must be the opcintype of the unique index.
  			 * Necessarily, the primary key column must then be of the domain
  			 * type.  Since the constraint was previously valid, all values on
  			 * the foreign side necessarily exist on the primary side and in
  			 * turn conform to the domain.  Consequently, we need not treat
  			 * domains specially here.
  			 *
  			 * Since we require that all collations share the same notion of
  			 * equality (which they do, because texteq reduces to bitwise
  			 * equality), we don't compare collation here.
  			 *
  			 * We need not directly consider the PK type.  It's necessarily
  			 * binary coercible to the opcintype of the unique index column,
  			 * and ri_triggers.c will only deal with PK datums in terms of
  			 * that opcintype.  Changing the opcintype also changes pfeqop.
  			 */
  			old_check_ok = (new_pathtype == old_pathtype &&
  							new_castfunc == old_castfunc &&
  							(!IsPolymorphicType(pfeqop_right) ||
  							 new_fktype == old_fktype));
  
  		}
  
  		pfeqoperators[i] = pfeqop;
  		ppeqoperators[i] = ppeqop;
  		ffeqoperators[i] = ffeqop;
  	}
  
  	/*
  	 * FKs always inherit for partitioned tables, and never for legacy
  	 * inheritance.
  	 */
  	connoinherit = rel->rd_rel->relkind != RELKIND_PARTITIONED_TABLE;
  
  	/*
  	 * Record the FK constraint in pg_constraint.
  	 */
  	constrOid = CreateConstraintEntry(fkconstraint->conname,
  									  RelationGetNamespace(rel),
  									  CONSTRAINT_FOREIGN,
  									  fkconstraint->deferrable,
  									  fkconstraint->initdeferred,
  									  fkconstraint->initially_valid,
  									  parentConstr,
  									  RelationGetRelid(rel),
  									  fkattnum,
  									  numfks,
  									  numfks,
  									  InvalidOid,	/* not a domain constraint */
  									  indexOid,
  									  RelationGetRelid(pkrel),
  									  pkattnum,
  									  pfeqoperators,
  									  ppeqoperators,
  									  ffeqoperators,
  									  numpks,
  									  fkconstraint->fk_upd_action,
  									  fkconstraint->fk_del_action,
  									  fkconstraint->fk_matchtype,
  									  NULL, /* no exclusion constraint */
  									  NULL, /* no check constraint */
  									  NULL,
  									  NULL,
  									  true, /* islocal */
  									  0,	/* inhcount */
  									  connoinherit,	/* conNoInherit */
  									  false);	/* is_internal */
  	ObjectAddressSet(address, ConstraintRelationId, constrOid);
  
  	/*
  	 * Create the triggers that will enforce the constraint.  We only want the
  	 * action triggers to appear for the parent partitioned relation, even
  	 * though the constraints also exist below.
  	 */
  	createForeignKeyTriggers(rel, RelationGetRelid(pkrel), fkconstraint,
  							 constrOid, indexOid, !recursing);
  
  	/*
  	 * Tell Phase 3 to check that the constraint is satisfied by existing
  	 * rows. We can skip this during table creation, when requested explicitly
  	 * by specifying NOT VALID in an ADD FOREIGN KEY command, and when we're
  	 * recreating a constraint following a SET DATA TYPE operation that did
  	 * not impugn its validity.
  	 */
  	if (!old_check_ok && !fkconstraint->skip_validation)
  	{
  		NewConstraint *newcon;
  
  		newcon = (NewConstraint *) palloc0(sizeof(NewConstraint));
  		newcon->name = fkconstraint->conname;
  		newcon->contype = CONSTR_FOREIGN;
  		newcon->refrelid = RelationGetRelid(pkrel);
  		newcon->refindid = indexOid;
  		newcon->conid = constrOid;
  		newcon->qual = (Node *) fkconstraint;
  
  		tab->constraints = lappend(tab->constraints, newcon);
  	}
  
  	/*
  	 * When called on a partitioned table, recurse to create the constraint on
  	 * the partitions also.
  	 */
  	if (recurse && rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  	{
  		PartitionDesc partdesc;
  		Relation	pg_constraint;
  		List	   *cloned = NIL;
  		ListCell   *cell;
  
  		pg_constraint = heap_open(ConstraintRelationId, RowExclusiveLock);
  		partdesc = RelationGetPartitionDesc(rel);
  
  		for (i = 0; i < partdesc->nparts; i++)
  		{
  			Oid			partitionId = partdesc->oids[i];
  			Relation	partition = heap_open(partitionId, lockmode);
  
  			CheckTableNotInUse(partition, "ALTER TABLE");
  
  			CloneFkReferencing(pg_constraint, rel, partition,
  							   list_make1_oid(constrOid),
  							   &cloned);
  
  			heap_close(partition, NoLock);
  		}
  		heap_close(pg_constraint, RowExclusiveLock);
  
  		foreach(cell, cloned)
  		{
  			ClonedConstraint *cc = (ClonedConstraint *) lfirst(cell);
  			Relation    partition = heap_open(cc->relid, lockmode);
  			AlteredTableInfo *childtab;
  			NewConstraint *newcon;
  
  			/* Find or create work queue entry for this partition */
  			childtab = ATGetQueueEntry(wqueue, partition);
  
  			newcon = (NewConstraint *) palloc0(sizeof(NewConstraint));
  			newcon->name = cc->constraint->conname;
  			newcon->contype = CONSTR_FOREIGN;
  			newcon->refrelid = cc->refrelid;
  			newcon->refindid = cc->conindid;
  			newcon->conid = cc->conid;
  			newcon->qual = (Node *) fkconstraint;
  
  			childtab->constraints = lappend(childtab->constraints, newcon);
  
  			heap_close(partition, lockmode);
  		}
  	}
  
  	/*
  	 * Close pk table, but keep lock until we've committed.
  	 */
  	heap_close(pkrel, NoLock);
  
  	return address;
  }
  
  /*
   * CloneForeignKeyConstraints
   *		Clone foreign keys from a partitioned table to a newly acquired
   *		partition.
   *
   * relationId is a partition of parentId, so we can be certain that it has the
   * same columns with the same datatypes.  The columns may be in different
   * order, though.
   *
   * The *cloned list is appended ClonedConstraint elements describing what was
   * created, for the purposes of validating the constraint in ALTER TABLE's
   * Phase 3.
   */
  void
  CloneForeignKeyConstraints(Oid parentId, Oid relationId, List **cloned)
  {
  	Relation	pg_constraint;
  	Relation	parentRel;
  	Relation	rel;
  	ScanKeyData key;
  	SysScanDesc scan;
  	HeapTuple	tuple;
  	List	   *clone = NIL;
  
  	parentRel = heap_open(parentId, NoLock);	/* already got lock */
  	/* see ATAddForeignKeyConstraint about lock level */
  	rel = heap_open(relationId, AccessExclusiveLock);
  	pg_constraint = heap_open(ConstraintRelationId, RowShareLock);
  
  	/* Obtain the list of constraints to clone or attach */
  	ScanKeyInit(&key,
  				Anum_pg_constraint_conrelid, BTEqualStrategyNumber,
  				F_OIDEQ, ObjectIdGetDatum(parentId));
  	scan = systable_beginscan(pg_constraint, ConstraintRelidTypidNameIndexId, true,
  							  NULL, 1, &key);
  	while ((tuple = systable_getnext(scan)) != NULL)
  	{
  		Oid		oid = HeapTupleGetOid(tuple);
  
  		clone = lappend_oid(clone, oid);
  	}
  	systable_endscan(scan);
  
  	/* Do the actual work, recursing to partitions as needed */
  	CloneFkReferencing(pg_constraint, parentRel, rel, clone, cloned);
  
  	/* We're done.  Clean up */
  	heap_close(parentRel, NoLock);
  	heap_close(rel, NoLock);	/* keep lock till commit */
  	heap_close(pg_constraint, RowShareLock);
  }
  
  /*
   * CloneFkReferencing
   *		Recursive subroutine for CloneForeignKeyConstraints, referencing side
   *
   * Clone the given list of FK constraints when a partition is attached on the
   * referencing side of those constraints.
   *
   * When cloning foreign keys to a partition, it may happen that equivalent
   * constraints already exist in the partition for some of them.  We can skip
   * creating a clone in that case, and instead just attach the existing
   * constraint to the one in the parent.
   *
   * This function recurses to partitions, if the new partition is partitioned;
   * of course, only do this for FKs that were actually cloned.
   */
  static void
  CloneFkReferencing(Relation pg_constraint, Relation parentRel,
  				   Relation partRel, List *clone, List **cloned)
  {
  	AttrNumber *attmap;
  	List	   *partFKs;
  	List	   *subclone = NIL;
  	ListCell   *cell;
  
  	/*
  	 * The constraint key may differ, if the columns in the partition are
  	 * different.  This map is used to convert them.
  	 */
  	attmap = convert_tuples_by_name_map(RelationGetDescr(partRel),
  										RelationGetDescr(parentRel),
  										gettext_noop("could not convert row type"));
  
  	partFKs = copyObject(RelationGetFKeyList(partRel));
  
  	foreach(cell, clone)
  	{
  		Oid			parentConstrOid = lfirst_oid(cell);
  		Form_pg_constraint constrForm;
  		HeapTuple	tuple;
  		int			numfks;
  		AttrNumber	conkey[INDEX_MAX_KEYS];
  		AttrNumber	mapped_conkey[INDEX_MAX_KEYS];
  		AttrNumber	confkey[INDEX_MAX_KEYS];
  		Oid			conpfeqop[INDEX_MAX_KEYS];
  		Oid			conppeqop[INDEX_MAX_KEYS];
  		Oid			conffeqop[INDEX_MAX_KEYS];
  		Constraint *fkconstraint;
  		bool		attach_it;
  		Oid			constrOid;
  		ObjectAddress parentAddr,
  					childAddr;
  		ListCell   *cell;
  		int			i;
  
  		tuple = SearchSysCache1(CONSTROID, parentConstrOid);
  		if (!tuple)
  			elog(ERROR, "cache lookup failed for constraint %u",
  				 parentConstrOid);
  		constrForm = (Form_pg_constraint) GETSTRUCT(tuple);
  
  		/* only foreign keys */
  		if (constrForm->contype != CONSTRAINT_FOREIGN)
  		{
  			ReleaseSysCache(tuple);
  			continue;
  		}
  
  		ObjectAddressSet(parentAddr, ConstraintRelationId, parentConstrOid);
  
  		DeconstructFkConstraintRow(tuple, &numfks, conkey, confkey,
  								   conpfeqop, conppeqop, conffeqop);
  		for (i = 0; i < numfks; i++)
  			mapped_conkey[i] = attmap[conkey[i] - 1];
  
  		/*
  		 * Before creating a new constraint, see whether any existing FKs are
  		 * fit for the purpose.  If one is, attach the parent constraint to it,
  		 * and don't clone anything.  This way we avoid the expensive
  		 * verification step and don't end up with a duplicate FK.  This also
  		 * means we don't consider this constraint when recursing to
  		 * partitions.
  		 */
  		attach_it = false;
  		foreach(cell, partFKs)
  		{
  			ForeignKeyCacheInfo *fk = lfirst_node(ForeignKeyCacheInfo, cell);
  			Form_pg_constraint partConstr;
  			HeapTuple	partcontup;
  			Relation	trigrel;
  			HeapTuple	trigtup;
  			SysScanDesc scan;
  			ScanKeyData key;
  
  			attach_it = true;
  
  			/*
  			 * Do some quick & easy initial checks.  If any of these fail, we
  			 * cannot use this constraint, but keep looking.
  			 */
  			if (fk->confrelid != constrForm->confrelid || fk->nkeys != numfks)
  			{
  				attach_it = false;
  				continue;
  			}
  			for (i = 0; i < numfks; i++)
  			{
  				if (fk->conkey[i] != mapped_conkey[i] ||
  					fk->confkey[i] != confkey[i] ||
  					fk->conpfeqop[i] != conpfeqop[i])
  				{
  					attach_it = false;
  					break;
  				}
  			}
  			if (!attach_it)
  				continue;
  
  			/*
  			 * Looks good so far; do some more extensive checks.  Presumably
  			 * the check for 'convalidated' could be dropped, since we don't
  			 * really care about that, but let's be careful for now.
  			 */
  			partcontup = SearchSysCache1(CONSTROID,
  										 ObjectIdGetDatum(fk->conoid));
  			if (!partcontup)
  				elog(ERROR, "cache lookup failed for constraint %u",
  					 fk->conoid);
  			partConstr = (Form_pg_constraint) GETSTRUCT(partcontup);
  			if (OidIsValid(partConstr->conparentid) ||
  				!partConstr->convalidated ||
  				partConstr->condeferrable != constrForm->condeferrable ||
  				partConstr->condeferred != constrForm->condeferred ||
  				partConstr->confupdtype != constrForm->confupdtype ||
  				partConstr->confdeltype != constrForm->confdeltype ||
  				partConstr->confmatchtype != constrForm->confmatchtype)
  			{
  				ReleaseSysCache(partcontup);
  				attach_it = false;
  				continue;
  			}
  
  			ReleaseSysCache(partcontup);
  
  			/*
  			 * Looks good!  Attach this constraint.  The action triggers in
  			 * the new partition become redundant -- the parent table already
  			 * has equivalent ones, and those will be able to reach the
  			 * partition.  Remove the ones in the partition.  We identify them
  			 * because they have our constraint OID, as well as being on the
  			 * referenced rel.
  			 */
  			trigrel = heap_open(TriggerRelationId, RowExclusiveLock);
  			ScanKeyInit(&key,
  						Anum_pg_trigger_tgconstraint,
  						BTEqualStrategyNumber, F_OIDEQ,
  						ObjectIdGetDatum(fk->conoid));
  
  			scan = systable_beginscan(trigrel, TriggerConstraintIndexId, true,
  									  NULL, 1, &key);
  			while ((trigtup = systable_getnext(scan)) != NULL)
  			{
  				Form_pg_trigger	trgform = (Form_pg_trigger) GETSTRUCT(trigtup);
  				ObjectAddress	trigger;
  
  				if (trgform->tgconstrrelid != fk->conrelid)
  					continue;
  				if (trgform->tgrelid != fk->confrelid)
  					continue;
  
  				/*
  				 * The constraint is originally set up to contain this trigger
  				 * as an implementation object, so there's a dependency record
  				 * that links the two; however, since the trigger is no longer
  				 * needed, we remove the dependency link in order to be able
  				 * to drop the trigger while keeping the constraint intact.
  				 */
  				deleteDependencyRecordsFor(TriggerRelationId,
  										   HeapTupleGetOid(trigtup),
  										   false);
  				/* make dependency deletion visible to performDeletion */
  				CommandCounterIncrement();
  				ObjectAddressSet(trigger, TriggerRelationId,
  								 HeapTupleGetOid(trigtup));
  				performDeletion(&trigger, DROP_RESTRICT, 0);
  				/* make trigger drop visible, in case the loop iterates */
  				CommandCounterIncrement();
  			}
  
  			systable_endscan(scan);
  			heap_close(trigrel, RowExclusiveLock);
  
  			ConstraintSetParentConstraint(fk->conoid, parentConstrOid);
  			CommandCounterIncrement();
  			attach_it = true;
  			break;
  		}
  
  		/*
  		 * If we attached to an existing constraint, there is no need to
  		 * create a new one.  In fact, there's no need to recurse for this
  		 * constraint to partitions, either.
  		 */
  		if (attach_it)
  		{
  			ReleaseSysCache(tuple);
  			continue;
  		}
  
  		constrOid =
  			CreateConstraintEntry(NameStr(constrForm->conname),
  								  constrForm->connamespace,
  								  CONSTRAINT_FOREIGN,
  								  constrForm->condeferrable,
  								  constrForm->condeferred,
  								  constrForm->convalidated,
  								  parentConstrOid,
  								  RelationGetRelid(partRel),
  								  mapped_conkey,
  								  numfks,
  								  numfks,
  								  InvalidOid,	/* not a domain constraint */
  								  constrForm->conindid, /* same index */
  								  constrForm->confrelid,	/* same foreign rel */
  								  confkey,
  								  conpfeqop,
  								  conppeqop,
  								  conffeqop,
  								  numfks,
  								  constrForm->confupdtype,
  								  constrForm->confdeltype,
  								  constrForm->confmatchtype,
  								  NULL,
  								  NULL,
  								  NULL,
  								  NULL,
  								  false,
  								  1, false, true);
  		subclone = lappend_oid(subclone, constrOid);
  
  		ObjectAddressSet(childAddr, ConstraintRelationId, constrOid);
  		recordDependencyOn(&childAddr, &parentAddr, DEPENDENCY_INTERNAL_AUTO);
  
  		fkconstraint = makeNode(Constraint);
  		/* for now this is all we need */
  		fkconstraint->conname = pstrdup(NameStr(constrForm->conname));
  		fkconstraint->fk_upd_action = constrForm->confupdtype;
  		fkconstraint->fk_del_action = constrForm->confdeltype;
  		fkconstraint->deferrable = constrForm->condeferrable;
  		fkconstraint->initdeferred = constrForm->condeferred;
  
  		createForeignKeyTriggers(partRel, constrForm->confrelid, fkconstraint,
  								 constrOid, constrForm->conindid, false);
  
  		if (cloned)
  		{
  			ClonedConstraint *newc;
  
  			/*
  			 * Feed back caller about the constraints we created, so that they
  			 * can set up constraint verification.
  			 */
  			newc = palloc(sizeof(ClonedConstraint));
  			newc->relid = RelationGetRelid(partRel);
  			newc->refrelid = constrForm->confrelid;
  			newc->conindid = constrForm->conindid;
  			newc->conid = constrOid;
  			newc->constraint = fkconstraint;
  
  			*cloned = lappend(*cloned, newc);
  		}
  
  		ReleaseSysCache(tuple);
  	}
  
  	pfree(attmap);
  	list_free_deep(partFKs);
  
  	/*
  	 * If the partition is partitioned, recurse to handle any constraints that
  	 * were cloned.
  	 */
  	if (partRel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE &&
  		subclone != NIL)
  	{
  		PartitionDesc partdesc = RelationGetPartitionDesc(partRel);
  		int			i;
  
  		for (i = 0; i < partdesc->nparts; i++)
  		{
  			Relation	childRel;
  
  			childRel = heap_open(partdesc->oids[i], AccessExclusiveLock);
  			CloneFkReferencing(pg_constraint,
  							   partRel,
  							   childRel,
  							   subclone,
  							   cloned);
  			heap_close(childRel, NoLock);	/* keep lock till commit */
  		}
  	}
  }
  
  /*
   * ALTER TABLE ALTER CONSTRAINT
   *
   * Update the attributes of a constraint.
   *
   * Currently only works for Foreign Key constraints.
   * Foreign keys do not inherit, so we purposely ignore the
   * recursion bit here, but we keep the API the same for when
   * other constraint types are supported.
   *
   * If the constraint is modified, returns its address; otherwise, return
   * InvalidObjectAddress.
   */
  static ObjectAddress
  ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
  					  bool recurse, bool recursing, LOCKMODE lockmode)
  {
  	Constraint *cmdcon;
  	Relation	conrel;
  	SysScanDesc scan;
  	ScanKeyData skey[3];
  	HeapTuple	contuple;
  	Form_pg_constraint currcon;
  	ObjectAddress address;
  
  	cmdcon = castNode(Constraint, cmd->def);
  
  	conrel = heap_open(ConstraintRelationId, RowExclusiveLock);
  
  	/*
  	 * Find and check the target constraint
  	 */
  	ScanKeyInit(&skey[0],
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(rel)));
  	ScanKeyInit(&skey[1],
  				Anum_pg_constraint_contypid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(InvalidOid));
  	ScanKeyInit(&skey[2],
  				Anum_pg_constraint_conname,
  				BTEqualStrategyNumber, F_NAMEEQ,
  				CStringGetDatum(cmdcon->conname));
  	scan = systable_beginscan(conrel, ConstraintRelidTypidNameIndexId,
  							  true, NULL, 3, skey);
  
  	/* There can be at most one matching row */
  	if (!HeapTupleIsValid(contuple = systable_getnext(scan)))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_OBJECT),
  				 errmsg("constraint \"%s\" of relation \"%s\" does not exist",
  						cmdcon->conname, RelationGetRelationName(rel))));
  
  	currcon = (Form_pg_constraint) GETSTRUCT(contuple);
  	if (currcon->contype != CONSTRAINT_FOREIGN)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("constraint \"%s\" of relation \"%s\" is not a foreign key constraint",
  						cmdcon->conname, RelationGetRelationName(rel))));
  
  	if (currcon->condeferrable != cmdcon->deferrable ||
  		currcon->condeferred != cmdcon->initdeferred)
  	{
  		HeapTuple	copyTuple;
  		HeapTuple	tgtuple;
  		Form_pg_constraint copy_con;
  		List	   *otherrelids = NIL;
  		ScanKeyData tgkey;
  		SysScanDesc tgscan;
  		Relation	tgrel;
  		ListCell   *lc;
  
  		/*
  		 * Now update the catalog, while we have the door open.
  		 */
  		copyTuple = heap_copytuple(contuple);
  		copy_con = (Form_pg_constraint) GETSTRUCT(copyTuple);
  		copy_con->condeferrable = cmdcon->deferrable;
  		copy_con->condeferred = cmdcon->initdeferred;
  		CatalogTupleUpdate(conrel, &copyTuple->t_self, copyTuple);
  
  		InvokeObjectPostAlterHook(ConstraintRelationId,
  								  HeapTupleGetOid(contuple), 0);
  
  		heap_freetuple(copyTuple);
  
  		/*
  		 * Now we need to update the multiple entries in pg_trigger that
  		 * implement the constraint.
  		 */
  		tgrel = heap_open(TriggerRelationId, RowExclusiveLock);
  
  		ScanKeyInit(&tgkey,
  					Anum_pg_trigger_tgconstraint,
  					BTEqualStrategyNumber, F_OIDEQ,
  					ObjectIdGetDatum(HeapTupleGetOid(contuple)));
  
  		tgscan = systable_beginscan(tgrel, TriggerConstraintIndexId, true,
  									NULL, 1, &tgkey);
  
  		while (HeapTupleIsValid(tgtuple = systable_getnext(tgscan)))
  		{
  			Form_pg_trigger tgform = (Form_pg_trigger) GETSTRUCT(tgtuple);
  			Form_pg_trigger copy_tg;
  
  			/*
  			 * Remember OIDs of other relation(s) involved in FK constraint.
  			 * (Note: it's likely that we could skip forcing a relcache inval
  			 * for other rels that don't have a trigger whose properties
  			 * change, but let's be conservative.)
  			 */
  			if (tgform->tgrelid != RelationGetRelid(rel))
  				otherrelids = list_append_unique_oid(otherrelids,
  													 tgform->tgrelid);
  
  			/*
  			 * Update deferrability of RI_FKey_noaction_del,
  			 * RI_FKey_noaction_upd, RI_FKey_check_ins and RI_FKey_check_upd
  			 * triggers, but not others; see createForeignKeyTriggers and
  			 * CreateFKCheckTrigger.
  			 */
  			if (tgform->tgfoid != F_RI_FKEY_NOACTION_DEL &&
  				tgform->tgfoid != F_RI_FKEY_NOACTION_UPD &&
  				tgform->tgfoid != F_RI_FKEY_CHECK_INS &&
  				tgform->tgfoid != F_RI_FKEY_CHECK_UPD)
  				continue;
  
  			copyTuple = heap_copytuple(tgtuple);
  			copy_tg = (Form_pg_trigger) GETSTRUCT(copyTuple);
  
  			copy_tg->tgdeferrable = cmdcon->deferrable;
  			copy_tg->tginitdeferred = cmdcon->initdeferred;
  			CatalogTupleUpdate(tgrel, &copyTuple->t_self, copyTuple);
  
  			InvokeObjectPostAlterHook(TriggerRelationId,
  									  HeapTupleGetOid(tgtuple), 0);
  
  			heap_freetuple(copyTuple);
  		}
  
  		systable_endscan(tgscan);
  
  		heap_close(tgrel, RowExclusiveLock);
  
  		/*
  		 * Invalidate relcache so that others see the new attributes.  We must
  		 * inval both the named rel and any others having relevant triggers.
  		 * (At present there should always be exactly one other rel, but
  		 * there's no need to hard-wire such an assumption here.)
  		 */
  		CacheInvalidateRelcache(rel);
  		foreach(lc, otherrelids)
  		{
  			CacheInvalidateRelcacheByRelid(lfirst_oid(lc));
  		}
  
  		ObjectAddressSet(address, ConstraintRelationId,
  						 HeapTupleGetOid(contuple));
  	}
  	else
  		address = InvalidObjectAddress;
  
  	systable_endscan(scan);
  
  	heap_close(conrel, RowExclusiveLock);
  
  	return address;
  }
  
  /*
   * ALTER TABLE VALIDATE CONSTRAINT
   *
   * XXX The reason we handle recursion here rather than at Phase 1 is because
   * there's no good way to skip recursing when handling foreign keys: there is
   * no need to lock children in that case, yet we wouldn't be able to avoid
   * doing so at that level.
   *
   * Return value is the address of the validated constraint.  If the constraint
   * was already validated, InvalidObjectAddress is returned.
   */
  static ObjectAddress
  ATExecValidateConstraint(Relation rel, char *constrName, bool recurse,
  						 bool recursing, LOCKMODE lockmode)
  {
  	Relation	conrel;
  	SysScanDesc scan;
  	ScanKeyData skey[3];
  	HeapTuple	tuple;
  	Form_pg_constraint con;
  	ObjectAddress address;
  
  	conrel = heap_open(ConstraintRelationId, RowExclusiveLock);
  
  	/*
  	 * Find and check the target constraint
  	 */
  	ScanKeyInit(&skey[0],
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(rel)));
  	ScanKeyInit(&skey[1],
  				Anum_pg_constraint_contypid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(InvalidOid));
  	ScanKeyInit(&skey[2],
  				Anum_pg_constraint_conname,
  				BTEqualStrategyNumber, F_NAMEEQ,
  				CStringGetDatum(constrName));
  	scan = systable_beginscan(conrel, ConstraintRelidTypidNameIndexId,
  							  true, NULL, 3, skey);
  
  	/* There can be at most one matching row */
  	if (!HeapTupleIsValid(tuple = systable_getnext(scan)))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_OBJECT),
  				 errmsg("constraint \"%s\" of relation \"%s\" does not exist",
  						constrName, RelationGetRelationName(rel))));
  
  	con = (Form_pg_constraint) GETSTRUCT(tuple);
  	if (con->contype != CONSTRAINT_FOREIGN &&
  		con->contype != CONSTRAINT_CHECK)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("constraint \"%s\" of relation \"%s\" is not a foreign key or check constraint",
  						constrName, RelationGetRelationName(rel))));
  
  	if (!con->convalidated)
  	{
  		HeapTuple	copyTuple;
  		Form_pg_constraint copy_con;
  
  		if (con->contype == CONSTRAINT_FOREIGN)
  		{
  			Relation	refrel;
  
  			/*
  			 * Triggers are already in place on both tables, so a concurrent
  			 * write that alters the result here is not possible. Normally we
  			 * can run a query here to do the validation, which would only
  			 * require AccessShareLock. In some cases, it is possible that we
  			 * might need to fire triggers to perform the check, so we take a
  			 * lock at RowShareLock level just in case.
  			 */
  			refrel = heap_open(con->confrelid, RowShareLock);
  
  			validateForeignKeyConstraint(constrName, rel, refrel,
  										 con->conindid,
  										 HeapTupleGetOid(tuple));
  			heap_close(refrel, NoLock);
  
  			/*
  			 * We disallow creating invalid foreign keys to or from
  			 * partitioned tables, so ignoring the recursion bit is okay.
  			 */
  		}
  		else if (con->contype == CONSTRAINT_CHECK)
  		{
  			List	   *children = NIL;
  			ListCell   *child;
  
  			/*
  			 * If we're recursing, the parent has already done this, so skip
  			 * it.  Also, if the constraint is a NO INHERIT constraint, we
  			 * shouldn't try to look for it in the children.
  			 */
  			if (!recursing && !con->connoinherit)
  				children = find_all_inheritors(RelationGetRelid(rel),
  											   lockmode, NULL);
  
  			/*
  			 * For CHECK constraints, we must ensure that we only mark the
  			 * constraint as validated on the parent if it's already validated
  			 * on the children.
  			 *
  			 * We recurse before validating on the parent, to reduce risk of
  			 * deadlocks.
  			 */
  			foreach(child, children)
  			{
  				Oid			childoid = lfirst_oid(child);
  				Relation	childrel;
  
  				if (childoid == RelationGetRelid(rel))
  					continue;
  
  				/*
  				 * If we are told not to recurse, there had better not be any
  				 * child tables, because we can't mark the constraint on the
  				 * parent valid unless it is valid for all child tables.
  				 */
  				if (!recurse)
  					ereport(ERROR,
  							(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  							 errmsg("constraint must be validated on child tables too")));
  
  				/* find_all_inheritors already got lock */
  				childrel = heap_open(childoid, NoLock);
  
  				ATExecValidateConstraint(childrel, constrName, false,
  										 true, lockmode);
  				heap_close(childrel, NoLock);
  			}
  
  			validateCheckConstraint(rel, tuple);
  
  			/*
  			 * Invalidate relcache so that others see the new validated
  			 * constraint.
  			 */
  			CacheInvalidateRelcache(rel);
  		}
  
  		/*
  		 * Now update the catalog, while we have the door open.
  		 */
  		copyTuple = heap_copytuple(tuple);
  		copy_con = (Form_pg_constraint) GETSTRUCT(copyTuple);
  		copy_con->convalidated = true;
  		CatalogTupleUpdate(conrel, &copyTuple->t_self, copyTuple);
  
  		InvokeObjectPostAlterHook(ConstraintRelationId,
  								  HeapTupleGetOid(tuple), 0);
  
  		heap_freetuple(copyTuple);
  
  		ObjectAddressSet(address, ConstraintRelationId,
  						 HeapTupleGetOid(tuple));
  	}
  	else
  		address = InvalidObjectAddress; /* already validated */
  
  	systable_endscan(scan);
  
  	heap_close(conrel, RowExclusiveLock);
  
  	return address;
  }
  
  
  /*
   * transformColumnNameList - transform list of column names
   *
   * Lookup each name and return its attnum and type OID
   */
  static int
  transformColumnNameList(Oid relId, List *colList,
  						int16 *attnums, Oid *atttypids)
  {
  	ListCell   *l;
  	int			attnum;
  
  	attnum = 0;
  	foreach(l, colList)
  	{
  		char	   *attname = strVal(lfirst(l));
  		HeapTuple	atttuple;
  
  		atttuple = SearchSysCacheAttName(relId, attname);
  		if (!HeapTupleIsValid(atttuple))
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_COLUMN),
  					 errmsg("column \"%s\" referenced in foreign key constraint does not exist",
  							attname)));
  		if (attnum >= INDEX_MAX_KEYS)
  			ereport(ERROR,
  					(errcode(ERRCODE_TOO_MANY_COLUMNS),
  					 errmsg("cannot have more than %d keys in a foreign key",
  							INDEX_MAX_KEYS)));
  		attnums[attnum] = ((Form_pg_attribute) GETSTRUCT(atttuple))->attnum;
  		atttypids[attnum] = ((Form_pg_attribute) GETSTRUCT(atttuple))->atttypid;
  		ReleaseSysCache(atttuple);
  		attnum++;
  	}
  
  	return attnum;
  }
  
  /*
   * transformFkeyGetPrimaryKey -
   *
   *	Look up the names, attnums, and types of the primary key attributes
   *	for the pkrel.  Also return the index OID and index opclasses of the
   *	index supporting the primary key.
   *
   *	All parameters except pkrel are output parameters.  Also, the function
   *	return value is the number of attributes in the primary key.
   *
   *	Used when the column list in the REFERENCES specification is omitted.
   */
  static int
  transformFkeyGetPrimaryKey(Relation pkrel, Oid *indexOid,
  						   List **attnamelist,
  						   int16 *attnums, Oid *atttypids,
  						   Oid *opclasses)
  {
  	List	   *indexoidlist;
  	ListCell   *indexoidscan;
  	HeapTuple	indexTuple = NULL;
  	Form_pg_index indexStruct = NULL;
  	Datum		indclassDatum;
  	bool		isnull;
  	oidvector  *indclass;
  	int			i;
  
  	/*
  	 * Get the list of index OIDs for the table from the relcache, and look up
  	 * each one in the pg_index syscache until we find one marked primary key
  	 * (hopefully there isn't more than one such).  Insist it's valid, too.
  	 */
  	*indexOid = InvalidOid;
  
  	indexoidlist = RelationGetIndexList(pkrel);
  
  	foreach(indexoidscan, indexoidlist)
  	{
  		Oid			indexoid = lfirst_oid(indexoidscan);
  
  		indexTuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(indexoid));
  		if (!HeapTupleIsValid(indexTuple))
  			elog(ERROR, "cache lookup failed for index %u", indexoid);
  		indexStruct = (Form_pg_index) GETSTRUCT(indexTuple);
  		if (indexStruct->indisprimary && IndexIsValid(indexStruct))
  		{
  			/*
  			 * Refuse to use a deferrable primary key.  This is per SQL spec,
  			 * and there would be a lot of interesting semantic problems if we
  			 * tried to allow it.
  			 */
  			if (!indexStruct->indimmediate)
  				ereport(ERROR,
  						(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  						 errmsg("cannot use a deferrable primary key for referenced table \"%s\"",
  								RelationGetRelationName(pkrel))));
  
  			*indexOid = indexoid;
  			break;
  		}
  		ReleaseSysCache(indexTuple);
  	}
  
  	list_free(indexoidlist);
  
  	/*
  	 * Check that we found it
  	 */
  	if (!OidIsValid(*indexOid))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_OBJECT),
  				 errmsg("there is no primary key for referenced table \"%s\"",
  						RelationGetRelationName(pkrel))));
  
  	/* Must get indclass the hard way */
  	indclassDatum = SysCacheGetAttr(INDEXRELID, indexTuple,
  									Anum_pg_index_indclass, &isnull);
  	Assert(!isnull);
  	indclass = (oidvector *) DatumGetPointer(indclassDatum);
  
  	/*
  	 * Now build the list of PK attributes from the indkey definition (we
  	 * assume a primary key cannot have expressional elements)
  	 */
  	*attnamelist = NIL;
  	for (i = 0; i < indexStruct->indnkeyatts; i++)
  	{
  		int			pkattno = indexStruct->indkey.values[i];
  
  		attnums[i] = pkattno;
  		atttypids[i] = attnumTypeId(pkrel, pkattno);
  		opclasses[i] = indclass->values[i];
  		*attnamelist = lappend(*attnamelist,
  							   makeString(pstrdup(NameStr(*attnumAttName(pkrel, pkattno)))));
  	}
  
  	ReleaseSysCache(indexTuple);
  
  	return i;
  }
  
  /*
   * transformFkeyCheckAttrs -
   *
   *	Make sure that the attributes of a referenced table belong to a unique
   *	(or primary key) constraint.  Return the OID of the index supporting
   *	the constraint, as well as the opclasses associated with the index
   *	columns.
   */
  static Oid
  transformFkeyCheckAttrs(Relation pkrel,
  						int numattrs, int16 *attnums,
  						Oid *opclasses) /* output parameter */
  {
  	Oid			indexoid = InvalidOid;
  	bool		found = false;
  	bool		found_deferrable = false;
  	List	   *indexoidlist;
  	ListCell   *indexoidscan;
  	int			i,
  				j;
  
  	/*
  	 * Reject duplicate appearances of columns in the referenced-columns list.
  	 * Such a case is forbidden by the SQL standard, and even if we thought it
  	 * useful to allow it, there would be ambiguity about how to match the
  	 * list to unique indexes (in particular, it'd be unclear which index
  	 * opclass goes with which FK column).
  	 */
  	for (i = 0; i < numattrs; i++)
  	{
  		for (j = i + 1; j < numattrs; j++)
  		{
  			if (attnums[i] == attnums[j])
  				ereport(ERROR,
  						(errcode(ERRCODE_INVALID_FOREIGN_KEY),
  						 errmsg("foreign key referenced-columns list must not contain duplicates")));
  		}
  	}
  
  	/*
  	 * Get the list of index OIDs for the table from the relcache, and look up
  	 * each one in the pg_index syscache, and match unique indexes to the list
  	 * of attnums we are given.
  	 */
  	indexoidlist = RelationGetIndexList(pkrel);
  
  	foreach(indexoidscan, indexoidlist)
  	{
  		HeapTuple	indexTuple;
  		Form_pg_index indexStruct;
  
  		indexoid = lfirst_oid(indexoidscan);
  		indexTuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(indexoid));
  		if (!HeapTupleIsValid(indexTuple))
  			elog(ERROR, "cache lookup failed for index %u", indexoid);
  		indexStruct = (Form_pg_index) GETSTRUCT(indexTuple);
  
  		/*
  		 * Must have the right number of columns; must be unique and not a
  		 * partial index; forget it if there are any expressions, too. Invalid
  		 * indexes are out as well.
  		 */
  		if (indexStruct->indnkeyatts == numattrs &&
  			indexStruct->indisunique &&
  			IndexIsValid(indexStruct) &&
  			heap_attisnull(indexTuple, Anum_pg_index_indpred, NULL) &&
  			heap_attisnull(indexTuple, Anum_pg_index_indexprs, NULL))
  		{
  			Datum		indclassDatum;
  			bool		isnull;
  			oidvector  *indclass;
  
  			/* Must get indclass the hard way */
  			indclassDatum = SysCacheGetAttr(INDEXRELID, indexTuple,
  											Anum_pg_index_indclass, &isnull);
  			Assert(!isnull);
  			indclass = (oidvector *) DatumGetPointer(indclassDatum);
  
  			/*
  			 * The given attnum list may match the index columns in any order.
  			 * Check for a match, and extract the appropriate opclasses while
  			 * we're at it.
  			 *
  			 * We know that attnums[] is duplicate-free per the test at the
  			 * start of this function, and we checked above that the number of
  			 * index columns agrees, so if we find a match for each attnums[]
  			 * entry then we must have a one-to-one match in some order.
  			 */
  			for (i = 0; i < numattrs; i++)
  			{
  				found = false;
  				for (j = 0; j < numattrs; j++)
  				{
  					if (attnums[i] == indexStruct->indkey.values[j])
  					{
  						opclasses[i] = indclass->values[j];
  						found = true;
  						break;
  					}
  				}
  				if (!found)
  					break;
  			}
  
  			/*
  			 * Refuse to use a deferrable unique/primary key.  This is per SQL
  			 * spec, and there would be a lot of interesting semantic problems
  			 * if we tried to allow it.
  			 */
  			if (found && !indexStruct->indimmediate)
  			{
  				/*
  				 * Remember that we found an otherwise matching index, so that
  				 * we can generate a more appropriate error message.
  				 */
  				found_deferrable = true;
  				found = false;
  			}
  		}
  		ReleaseSysCache(indexTuple);
  		if (found)
  			break;
  	}
  
  	if (!found)
  	{
  		if (found_deferrable)
  			ereport(ERROR,
  					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  					 errmsg("cannot use a deferrable unique constraint for referenced table \"%s\"",
  							RelationGetRelationName(pkrel))));
  		else
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_FOREIGN_KEY),
  					 errmsg("there is no unique constraint matching given keys for referenced table \"%s\"",
  							RelationGetRelationName(pkrel))));
  	}
  
  	list_free(indexoidlist);
  
  	return indexoid;
  }
  
  /*
   * findFkeyCast -
   *
   *	Wrapper around find_coercion_pathway() for ATAddForeignKeyConstraint().
   *	Caller has equal regard for binary coercibility and for an exact match.
  */
  static CoercionPathType
  findFkeyCast(Oid targetTypeId, Oid sourceTypeId, Oid *funcid)
  {
  	CoercionPathType ret;
  
  	if (targetTypeId == sourceTypeId)
  	{
  		ret = COERCION_PATH_RELABELTYPE;
  		*funcid = InvalidOid;
  	}
  	else
  	{
  		ret = find_coercion_pathway(targetTypeId, sourceTypeId,
  									COERCION_IMPLICIT, funcid);
  		if (ret == COERCION_PATH_NONE)
  			/* A previously-relied-upon cast is now gone. */
  			elog(ERROR, "could not find cast from %u to %u",
  				 sourceTypeId, targetTypeId);
  	}
  
  	return ret;
  }
  
  /*
   * Permissions checks on the referenced table for ADD FOREIGN KEY
   *
   * Note: we have already checked that the user owns the referencing table,
   * else we'd have failed much earlier; no additional checks are needed for it.
   */
  static void
  checkFkeyPermissions(Relation rel, int16 *attnums, int natts)
  {
  	Oid			roleid = GetUserId();
  	AclResult	aclresult;
  	int			i;
  
  	/* Okay if we have relation-level REFERENCES permission */
  	aclresult = pg_class_aclcheck(RelationGetRelid(rel), roleid,
  								  ACL_REFERENCES);
  	if (aclresult == ACLCHECK_OK)
  		return;
  	/* Else we must have REFERENCES on each column */
  	for (i = 0; i < natts; i++)
  	{
  		aclresult = pg_attribute_aclcheck(RelationGetRelid(rel), attnums[i],
  										  roleid, ACL_REFERENCES);
  		if (aclresult != ACLCHECK_OK)
  			aclcheck_error(aclresult, get_relkind_objtype(rel->rd_rel->relkind),
  						   RelationGetRelationName(rel));
  	}
  }
  
  /*
   * Scan the existing rows in a table to verify they meet a proposed
   * CHECK constraint.
   *
   * The caller must have opened and locked the relation appropriately.
   */
  static void
  validateCheckConstraint(Relation rel, HeapTuple constrtup)
  {
  	EState	   *estate;
  	Datum		val;
  	char	   *conbin;
  	Expr	   *origexpr;
  	ExprState  *exprstate;
  	TupleDesc	tupdesc;
  	HeapScanDesc scan;
  	HeapTuple	tuple;
  	ExprContext *econtext;
  	MemoryContext oldcxt;
  	TupleTableSlot *slot;
  	Form_pg_constraint constrForm;
  	bool		isnull;
  	Snapshot	snapshot;
  
  	/*
  	 * VALIDATE CONSTRAINT is a no-op for foreign tables and partitioned
  	 * tables.
  	 */
  	if (rel->rd_rel->relkind == RELKIND_FOREIGN_TABLE ||
  		rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  		return;
  
  	constrForm = (Form_pg_constraint) GETSTRUCT(constrtup);
  
  	estate = CreateExecutorState();
  
  	/*
  	 * XXX this tuple doesn't really come from a syscache, but this doesn't
  	 * matter to SysCacheGetAttr, because it only wants to be able to fetch
  	 * the tupdesc
  	 */
  	val = SysCacheGetAttr(CONSTROID, constrtup, Anum_pg_constraint_conbin,
  						  &isnull);
  	if (isnull)
  		elog(ERROR, "null conbin for constraint %u",
  			 HeapTupleGetOid(constrtup));
  	conbin = TextDatumGetCString(val);
  	origexpr = (Expr *) stringToNode(conbin);
  	exprstate = ExecPrepareExpr(origexpr, estate);
  
  	econtext = GetPerTupleExprContext(estate);
  	tupdesc = RelationGetDescr(rel);
  	slot = MakeSingleTupleTableSlot(tupdesc);
  	econtext->ecxt_scantuple = slot;
  
  	snapshot = RegisterSnapshot(GetLatestSnapshot());
  	scan = heap_beginscan(rel, snapshot, 0, NULL);
  
  	/*
  	 * Switch to per-tuple memory context and reset it for each tuple
  	 * produced, so we don't leak memory.
  	 */
  	oldcxt = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
  
  	while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
  	{
  		ExecStoreHeapTuple(tuple, slot, false);
  
  		if (!ExecCheck(exprstate, econtext))
  			ereport(ERROR,
  					(errcode(ERRCODE_CHECK_VIOLATION),
  					 errmsg("check constraint \"%s\" is violated by some row",
  							NameStr(constrForm->conname)),
  					 errtableconstraint(rel, NameStr(constrForm->conname))));
  
  		ResetExprContext(econtext);
  	}
  
  	MemoryContextSwitchTo(oldcxt);
  	heap_endscan(scan);
  	UnregisterSnapshot(snapshot);
  	ExecDropSingleTupleTableSlot(slot);
  	FreeExecutorState(estate);
  }
  
  /*
   * Scan the existing rows in a table to verify they meet a proposed FK
   * constraint.
   *
   * Caller must have opened and locked both relations appropriately.
   */
  static void
  validateForeignKeyConstraint(char *conname,
  							 Relation rel,
  							 Relation pkrel,
  							 Oid pkindOid,
  							 Oid constraintOid)
  {
  	HeapScanDesc scan;
  	HeapTuple	tuple;
  	Trigger		trig;
  	Snapshot	snapshot;
  
  	ereport(DEBUG1,
  			(errmsg("validating foreign key constraint \"%s\"", conname)));
  
  	/*
  	 * Build a trigger call structure; we'll need it either way.
  	 */
  	MemSet(&trig, 0, sizeof(trig));
  	trig.tgoid = InvalidOid;
  	trig.tgname = conname;
  	trig.tgenabled = TRIGGER_FIRES_ON_ORIGIN;
  	trig.tgisinternal = true;
  	trig.tgconstrrelid = RelationGetRelid(pkrel);
  	trig.tgconstrindid = pkindOid;
  	trig.tgconstraint = constraintOid;
  	trig.tgdeferrable = false;
  	trig.tginitdeferred = false;
  	/* we needn't fill in remaining fields */
  
  	/*
  	 * See if we can do it with a single LEFT JOIN query.  A false result
  	 * indicates we must proceed with the fire-the-trigger method.
  	 */
  	if (RI_Initial_Check(&trig, rel, pkrel))
  		return;
  
  	/*
  	 * Scan through each tuple, calling RI_FKey_check_ins (insert trigger) as
  	 * if that tuple had just been inserted.  If any of those fail, it should
  	 * ereport(ERROR) and that's that.
  	 */
  	snapshot = RegisterSnapshot(GetLatestSnapshot());
  	scan = heap_beginscan(rel, snapshot, 0, NULL);
  
  	while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
  	{
  		LOCAL_FCINFO(fcinfo, 0);
  		TriggerData trigdata;
  
  		/*
  		 * Make a call to the trigger function
  		 *
  		 * No parameters are passed, but we do set a context
  		 */
  		MemSet(fcinfo, 0, SizeForFunctionCallInfo(0));
  
  		/*
  		 * We assume RI_FKey_check_ins won't look at flinfo...
  		 */
  		trigdata.type = T_TriggerData;
  		trigdata.tg_event = TRIGGER_EVENT_INSERT | TRIGGER_EVENT_ROW;
  		trigdata.tg_relation = rel;
  		trigdata.tg_trigtuple = tuple;
  		trigdata.tg_newtuple = NULL;
  		trigdata.tg_trigger = &trig;
  		trigdata.tg_trigtuplebuf = scan->rs_cbuf;
  		trigdata.tg_newtuplebuf = InvalidBuffer;
  
  		fcinfo->context = (Node *) &trigdata;
  
  		RI_FKey_check_ins(fcinfo);
  	}
  
  	heap_endscan(scan);
  	UnregisterSnapshot(snapshot);
  }
  
  static void
  CreateFKCheckTrigger(Oid myRelOid, Oid refRelOid, Constraint *fkconstraint,
  					 Oid constraintOid, Oid indexOid, bool on_insert)
  {
  	CreateTrigStmt *fk_trigger;
  
  	/*
  	 * Note: for a self-referential FK (referencing and referenced tables are
  	 * the same), it is important that the ON UPDATE action fires before the
  	 * CHECK action, since both triggers will fire on the same row during an
  	 * UPDATE event; otherwise the CHECK trigger will be checking a non-final
  	 * state of the row.  Triggers fire in name order, so we ensure this by
  	 * using names like "RI_ConstraintTrigger_a_NNNN" for the action triggers
  	 * and "RI_ConstraintTrigger_c_NNNN" for the check triggers.
  	 */
  	fk_trigger = makeNode(CreateTrigStmt);
  	fk_trigger->trigname = "RI_ConstraintTrigger_c";
  	fk_trigger->relation = NULL;
  	fk_trigger->row = true;
  	fk_trigger->timing = TRIGGER_TYPE_AFTER;
  
  	/* Either ON INSERT or ON UPDATE */
  	if (on_insert)
  	{
  		fk_trigger->funcname = SystemFuncName("RI_FKey_check_ins");
  		fk_trigger->events = TRIGGER_TYPE_INSERT;
  	}
  	else
  	{
  		fk_trigger->funcname = SystemFuncName("RI_FKey_check_upd");
  		fk_trigger->events = TRIGGER_TYPE_UPDATE;
  	}
  
  	fk_trigger->columns = NIL;
  	fk_trigger->transitionRels = NIL;
  	fk_trigger->whenClause = NULL;
  	fk_trigger->isconstraint = true;
  	fk_trigger->deferrable = fkconstraint->deferrable;
  	fk_trigger->initdeferred = fkconstraint->initdeferred;
  	fk_trigger->constrrel = NULL;
  	fk_trigger->args = NIL;
  
  	(void) CreateTrigger(fk_trigger, NULL, myRelOid, refRelOid, constraintOid,
  						 indexOid, InvalidOid, InvalidOid, NULL, true, false);
  
  	/* Make changes-so-far visible */
  	CommandCounterIncrement();
  }
  
  /*
   * createForeignKeyActionTriggers
   *		Create the referenced-side "action" triggers that implement a foreign
   *		key.
   */
  static void
  createForeignKeyActionTriggers(Relation rel, Oid refRelOid, Constraint *fkconstraint,
  							   Oid constraintOid, Oid indexOid)
  {
  	CreateTrigStmt *fk_trigger;
  
  	/*
  	 * Build and execute a CREATE CONSTRAINT TRIGGER statement for the ON
  	 * DELETE action on the referenced table.
  	 */
  	fk_trigger = makeNode(CreateTrigStmt);
  	fk_trigger->trigname = "RI_ConstraintTrigger_a";
  	fk_trigger->relation = NULL;
  	fk_trigger->row = true;
  	fk_trigger->timing = TRIGGER_TYPE_AFTER;
  	fk_trigger->events = TRIGGER_TYPE_DELETE;
  	fk_trigger->columns = NIL;
  	fk_trigger->transitionRels = NIL;
  	fk_trigger->whenClause = NULL;
  	fk_trigger->isconstraint = true;
  	fk_trigger->constrrel = NULL;
  	switch (fkconstraint->fk_del_action)
  	{
  		case FKCONSTR_ACTION_NOACTION:
  			fk_trigger->deferrable = fkconstraint->deferrable;
  			fk_trigger->initdeferred = fkconstraint->initdeferred;
  			fk_trigger->funcname = SystemFuncName("RI_FKey_noaction_del");
  			break;
  		case FKCONSTR_ACTION_RESTRICT:
  			fk_trigger->deferrable = false;
  			fk_trigger->initdeferred = false;
  			fk_trigger->funcname = SystemFuncName("RI_FKey_restrict_del");
  			break;
  		case FKCONSTR_ACTION_CASCADE:
  			fk_trigger->deferrable = false;
  			fk_trigger->initdeferred = false;
  			fk_trigger->funcname = SystemFuncName("RI_FKey_cascade_del");
  			break;
  		case FKCONSTR_ACTION_SETNULL:
  			fk_trigger->deferrable = false;
  			fk_trigger->initdeferred = false;
  			fk_trigger->funcname = SystemFuncName("RI_FKey_setnull_del");
  			break;
  		case FKCONSTR_ACTION_SETDEFAULT:
  			fk_trigger->deferrable = false;
  			fk_trigger->initdeferred = false;
  			fk_trigger->funcname = SystemFuncName("RI_FKey_setdefault_del");
  			break;
  		default:
  			elog(ERROR, "unrecognized FK action type: %d",
  				 (int) fkconstraint->fk_del_action);
  			break;
  	}
  	fk_trigger->args = NIL;
  
  	(void) CreateTrigger(fk_trigger, NULL, refRelOid, RelationGetRelid(rel),
  						 constraintOid,
  						 indexOid, InvalidOid, InvalidOid, NULL, true, false);
  
  	/* Make changes-so-far visible */
  	CommandCounterIncrement();
  
  	/*
  	 * Build and execute a CREATE CONSTRAINT TRIGGER statement for the ON
  	 * UPDATE action on the referenced table.
  	 */
  	fk_trigger = makeNode(CreateTrigStmt);
  	fk_trigger->trigname = "RI_ConstraintTrigger_a";
  	fk_trigger->relation = NULL;
  	fk_trigger->row = true;
  	fk_trigger->timing = TRIGGER_TYPE_AFTER;
  	fk_trigger->events = TRIGGER_TYPE_UPDATE;
  	fk_trigger->columns = NIL;
  	fk_trigger->transitionRels = NIL;
  	fk_trigger->whenClause = NULL;
  	fk_trigger->isconstraint = true;
  	fk_trigger->constrrel = NULL;
  	switch (fkconstraint->fk_upd_action)
  	{
  		case FKCONSTR_ACTION_NOACTION:
  			fk_trigger->deferrable = fkconstraint->deferrable;
  			fk_trigger->initdeferred = fkconstraint->initdeferred;
  			fk_trigger->funcname = SystemFuncName("RI_FKey_noaction_upd");
  			break;
  		case FKCONSTR_ACTION_RESTRICT:
  			fk_trigger->deferrable = false;
  			fk_trigger->initdeferred = false;
  			fk_trigger->funcname = SystemFuncName("RI_FKey_restrict_upd");
  			break;
  		case FKCONSTR_ACTION_CASCADE:
  			fk_trigger->deferrable = false;
  			fk_trigger->initdeferred = false;
  			fk_trigger->funcname = SystemFuncName("RI_FKey_cascade_upd");
  			break;
  		case FKCONSTR_ACTION_SETNULL:
  			fk_trigger->deferrable = false;
  			fk_trigger->initdeferred = false;
  			fk_trigger->funcname = SystemFuncName("RI_FKey_setnull_upd");
  			break;
  		case FKCONSTR_ACTION_SETDEFAULT:
  			fk_trigger->deferrable = false;
  			fk_trigger->initdeferred = false;
  			fk_trigger->funcname = SystemFuncName("RI_FKey_setdefault_upd");
  			break;
  		default:
  			elog(ERROR, "unrecognized FK action type: %d",
  				 (int) fkconstraint->fk_upd_action);
  			break;
  	}
  	fk_trigger->args = NIL;
  
  	(void) CreateTrigger(fk_trigger, NULL, refRelOid, RelationGetRelid(rel),
  						 constraintOid,
  						 indexOid, InvalidOid, InvalidOid, NULL, true, false);
  }
  
  /*
   * createForeignKeyCheckTriggers
   *		Create the referencing-side "check" triggers that implement a foreign
   *		key.
   */
  static void
  createForeignKeyCheckTriggers(Oid myRelOid, Oid refRelOid,
  							  Constraint *fkconstraint, Oid constraintOid,
  							  Oid indexOid)
  {
  	CreateFKCheckTrigger(myRelOid, refRelOid, fkconstraint, constraintOid,
  						 indexOid, true);
  	CreateFKCheckTrigger(myRelOid, refRelOid, fkconstraint, constraintOid,
  						 indexOid, false);
  }
  
  /*
   * Create the triggers that implement an FK constraint.
   *
   * NB: if you change any trigger properties here, see also
   * ATExecAlterConstraint.
   */
  void
  createForeignKeyTriggers(Relation rel, Oid refRelOid, Constraint *fkconstraint,
  						 Oid constraintOid, Oid indexOid, bool create_action)
  {
  	/*
  	 * For the referenced side, create action triggers, if requested.  (If the
  	 * referencing side is partitioned, there is still only one trigger, which
  	 * runs on the referenced side and points to the top of the referencing
  	 * hierarchy.)
  	 */
  	if (create_action)
  		createForeignKeyActionTriggers(rel, refRelOid, fkconstraint, constraintOid,
  									   indexOid);
  
  	/*
  	 * For the referencing side, create the check triggers.  We only need
  	 * these on the partitions.
  	 */
  	if (rel->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
  		createForeignKeyCheckTriggers(RelationGetRelid(rel), refRelOid,
  									  fkconstraint, constraintOid, indexOid);
  
  	CommandCounterIncrement();
  }
  
  /*
   * ALTER TABLE DROP CONSTRAINT
   *
   * Like DROP COLUMN, we can't use the normal ALTER TABLE recursion mechanism.
   */
  static void
  ATExecDropConstraint(Relation rel, const char *constrName,
  					 DropBehavior behavior,
  					 bool recurse, bool recursing,
  					 bool missing_ok, LOCKMODE lockmode)
  {
  	List	   *children;
  	ListCell   *child;
  	Relation	conrel;
  	Form_pg_constraint con;
  	SysScanDesc scan;
  	ScanKeyData skey[3];
  	HeapTuple	tuple;
  	bool		found = false;
  	bool		is_no_inherit_constraint = false;
  	char		contype;
  
  	/* At top level, permission check was done in ATPrepCmd, else do it */
  	if (recursing)
  		ATSimplePermissions(rel, ATT_TABLE | ATT_FOREIGN_TABLE);
  
  	conrel = heap_open(ConstraintRelationId, RowExclusiveLock);
  
  	/*
  	 * Find and drop the target constraint
  	 */
  	ScanKeyInit(&skey[0],
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(rel)));
  	ScanKeyInit(&skey[1],
  				Anum_pg_constraint_contypid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(InvalidOid));
  	ScanKeyInit(&skey[2],
  				Anum_pg_constraint_conname,
  				BTEqualStrategyNumber, F_NAMEEQ,
  				CStringGetDatum(constrName));
  	scan = systable_beginscan(conrel, ConstraintRelidTypidNameIndexId,
  							  true, NULL, 3, skey);
  
  	/* There can be at most one matching row */
  	if (HeapTupleIsValid(tuple = systable_getnext(scan)))
  	{
  		ObjectAddress conobj;
  
  		con = (Form_pg_constraint) GETSTRUCT(tuple);
  
  		/* Don't drop inherited constraints */
  		if (con->coninhcount > 0 && !recursing)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  					 errmsg("cannot drop inherited constraint \"%s\" of relation \"%s\"",
  							constrName, RelationGetRelationName(rel))));
  
  		is_no_inherit_constraint = con->connoinherit;
  		contype = con->contype;
  
  		/*
  		 * If it's a foreign-key constraint, we'd better lock the referenced
  		 * table and check that that's not in use, just as we've already done
  		 * for the constrained table (else we might, eg, be dropping a trigger
  		 * that has unfired events).  But we can/must skip that in the
  		 * self-referential case.
  		 */
  		if (contype == CONSTRAINT_FOREIGN &&
  			con->confrelid != RelationGetRelid(rel))
  		{
  			Relation	frel;
  
  			/* Must match lock taken by RemoveTriggerById: */
  			frel = heap_open(con->confrelid, AccessExclusiveLock);
  			CheckTableNotInUse(frel, "ALTER TABLE");
  			heap_close(frel, NoLock);
  		}
  
  		if (IsYugaByteEnabled() &&
  			contype == CONSTRAINT_PRIMARY)
  		{
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("dropping a primary key constraint is not yet supported")));
  		}
  
  		/*
  		 * Perform the actual constraint deletion
  		 */
  		conobj.classId = ConstraintRelationId;
  		conobj.objectId = HeapTupleGetOid(tuple);
  		conobj.objectSubId = 0;
  
  		performDeletion(&conobj, behavior, 0);
  
  		found = true;
  	}
  
  	systable_endscan(scan);
  
  	if (!found)
  	{
  		if (!missing_ok)
  		{
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_OBJECT),
  					 errmsg("constraint \"%s\" of relation \"%s\" does not exist",
  							constrName, RelationGetRelationName(rel))));
  		}
  		else
  		{
  			ereport(NOTICE,
  					(errmsg("constraint \"%s\" of relation \"%s\" does not exist, skipping",
  							constrName, RelationGetRelationName(rel))));
  			heap_close(conrel, RowExclusiveLock);
  			return;
  		}
  	}
  
  	/*
  	 * For partitioned tables, non-CHECK inherited constraints are dropped via
  	 * the dependency mechanism, so we're done here.
  	 */
  	if (contype != CONSTRAINT_CHECK &&
  		rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  	{
  		heap_close(conrel, RowExclusiveLock);
  		return;
  	}
  
  	/*
  	 * Propagate to children as appropriate.  Unlike most other ALTER
  	 * routines, we have to do this one level of recursion at a time; we can't
  	 * use find_all_inheritors to do it in one pass.
  	 */
  	if (!is_no_inherit_constraint)
  		children = find_inheritance_children(RelationGetRelid(rel), lockmode);
  	else
  		children = NIL;
  
  	/*
  	 * For a partitioned table, if partitions exist and we are told not to
  	 * recurse, it's a user error.  It doesn't make sense to have a constraint
  	 * be defined only on the parent, especially if it's a partitioned table.
  	 */
  	if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE &&
  		children != NIL && !recurse)
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  				 errmsg("cannot remove constraint from only the partitioned table when partitions exist"),
  				 errhint("Do not specify the ONLY keyword.")));
  
  	foreach(child, children)
  	{
  		Oid			childrelid = lfirst_oid(child);
  		Relation	childrel;
  		HeapTuple	copy_tuple;
  
  		/* find_inheritance_children already got lock */
  		childrel = heap_open(childrelid, NoLock);
  		CheckTableNotInUse(childrel, "ALTER TABLE");
  
  		ScanKeyInit(&skey[0],
  					Anum_pg_constraint_conrelid,
  					BTEqualStrategyNumber, F_OIDEQ,
  					ObjectIdGetDatum(childrelid));
  		ScanKeyInit(&skey[1],
  					Anum_pg_constraint_contypid,
  					BTEqualStrategyNumber, F_OIDEQ,
  					ObjectIdGetDatum(InvalidOid));
  		ScanKeyInit(&skey[2],
  					Anum_pg_constraint_conname,
  					BTEqualStrategyNumber, F_NAMEEQ,
  					CStringGetDatum(constrName));
  		scan = systable_beginscan(conrel, ConstraintRelidTypidNameIndexId,
  								  true, NULL, 3, skey);
  
  		/* There can be at most one matching row */
  		if (!HeapTupleIsValid(tuple = systable_getnext(scan)))
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_OBJECT),
  					 errmsg("constraint \"%s\" of relation \"%s\" does not exist",
  							constrName,
  							RelationGetRelationName(childrel))));
  
  		copy_tuple = heap_copytuple(tuple);
  
  		systable_endscan(scan);
  
  		con = (Form_pg_constraint) GETSTRUCT(copy_tuple);
  
  		/* Right now only CHECK constraints can be inherited */
  		if (con->contype != CONSTRAINT_CHECK)
  			elog(ERROR, "inherited constraint is not a CHECK constraint");
  
  		if (con->coninhcount <= 0)	/* shouldn't happen */
  			elog(ERROR, "relation %u has non-inherited constraint \"%s\"",
  				 childrelid, constrName);
  
  		if (recurse)
  		{
  			/*
  			 * If the child constraint has other definition sources, just
  			 * decrement its inheritance count; if not, recurse to delete it.
  			 */
  			if (con->coninhcount == 1 && !con->conislocal)
  			{
  				/* Time to delete this child constraint, too */
  				ATExecDropConstraint(childrel, constrName, behavior,
  									 true, true,
  									 false, lockmode);
  			}
  			else
  			{
  				/* Child constraint must survive my deletion */
  				con->coninhcount--;
  				CatalogTupleUpdate(conrel, &copy_tuple->t_self, copy_tuple);
  
  				/* Make update visible */
  				CommandCounterIncrement();
  			}
  		}
  		else
  		{
  			/*
  			 * If we were told to drop ONLY in this table (no recursion), we
  			 * need to mark the inheritors' constraints as locally defined
  			 * rather than inherited.
  			 */
  			con->coninhcount--;
  			con->conislocal = true;
  
  			CatalogTupleUpdate(conrel, &copy_tuple->t_self, copy_tuple);
  
  			/* Make update visible */
  			CommandCounterIncrement();
  		}
  
  		heap_freetuple(copy_tuple);
  
  		heap_close(childrel, NoLock);
  	}
  
  	heap_close(conrel, RowExclusiveLock);
  }
  
  /*
   * ALTER COLUMN TYPE
   */
  static void
  ATPrepAlterColumnType(List **wqueue,
  					  AlteredTableInfo *tab, Relation rel,
  					  bool recurse, bool recursing,
  					  AlterTableCmd *cmd, LOCKMODE lockmode)
  {
  	char	   *colName = cmd->name;
  	ColumnDef  *def = (ColumnDef *) cmd->def;
  	TypeName   *typeName = def->typeName;
  	Node	   *transform = def->cooked_default;
  	HeapTuple	tuple;
  	Form_pg_attribute attTup;
  	AttrNumber	attnum;
  	Oid			targettype;
  	int32		targettypmod;
  	Oid			targetcollid;
  	NewColumnValue *newval;
  	ParseState *pstate = make_parsestate(NULL);
  	AclResult	aclresult;
  	bool		is_expr;
  
  	if (rel->rd_rel->reloftype && !recursing)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot alter column type of typed table")));
  
  	/* lookup the attribute so we can check inheritance status */
  	tuple = SearchSysCacheAttName(RelationGetRelid(rel), colName);
  	if (!HeapTupleIsValid(tuple))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_COLUMN),
  				 errmsg("column \"%s\" of relation \"%s\" does not exist",
  						colName, RelationGetRelationName(rel))));
  	attTup = (Form_pg_attribute) GETSTRUCT(tuple);
  	attnum = attTup->attnum;
  
  	/* Can't alter a system attribute */
  	if (attnum <= 0)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot alter system column \"%s\"",
  						colName)));
  
  	/* Don't alter inherited columns */
  	if (attTup->attinhcount > 0 && !recursing)
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  				 errmsg("cannot alter inherited column \"%s\"",
  						colName)));
  
  	/* Don't alter columns used in the partition key */
  	if (has_partition_attrs(rel,
  							bms_make_singleton(attnum - YBGetFirstLowInvalidAttributeNumber(rel)),
  							&is_expr))
  	{
  		if (!is_expr)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  					 errmsg("cannot alter type of column named in partition key")));
  		else
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  					 errmsg("cannot alter type of column referenced in partition key expression")));
  	}
  
  	/* Look up the target type */
  	typenameTypeIdAndMod(NULL, typeName, &targettype, &targettypmod);
  
  	aclresult = pg_type_aclcheck(targettype, GetUserId(), ACL_USAGE);
  	if (aclresult != ACLCHECK_OK)
  		aclcheck_error_type(aclresult, targettype);
  
  	/* And the collation */
  	targetcollid = GetColumnDefCollation(NULL, def, targettype);
  
  	/* make sure datatype is legal for a column */
  	CheckAttributeType(colName, targettype, targetcollid,
  					   list_make1_oid(rel->rd_rel->reltype),
  					   false);
  
  	if (tab->relkind == RELKIND_RELATION ||
  		tab->relkind == RELKIND_PARTITIONED_TABLE)
  	{
  		/*
  		 * Set up an expression to transform the old data value to the new
  		 * type. If a USING option was given, use the expression as
  		 * transformed by transformAlterTableStmt, else just take the old
  		 * value and try to coerce it.  We do this first so that type
  		 * incompatibility can be detected before we waste effort, and because
  		 * we need the expression to be parsed against the original table row
  		 * type.
  		 */
  		if (!transform)
  		{
  			transform = (Node *) makeVar(1, attnum,
  										 attTup->atttypid, attTup->atttypmod,
  										 attTup->attcollation,
  										 0);
  		}
  
  		transform = coerce_to_target_type(pstate,
  										  transform, exprType(transform),
  										  targettype, targettypmod,
  										  COERCION_ASSIGNMENT,
  										  COERCE_IMPLICIT_CAST,
  										  -1);
  		if (transform == NULL)
  		{
  			/* error text depends on whether USING was specified or not */
  			if (def->cooked_default != NULL)
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("result of USING clause for column \"%s\""
  								" cannot be cast automatically to type %s",
  								colName, format_type_be(targettype)),
  						 errhint("You might need to add an explicit cast.")));
  			else
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("column \"%s\" cannot be cast automatically to type %s",
  								colName, format_type_be(targettype)),
  				/* translator: USING is SQL, don't translate it */
  						 errhint("You might need to specify \"USING %s::%s\".",
  								 quote_identifier(colName),
  								 format_type_with_typemod(targettype,
  														  targettypmod))));
  		}
  
  		/* Fix collations after all else */
  		assign_expr_collations(pstate, transform);
  
  		/* Plan the expr now so we can accurately assess the need to rewrite. */
  		transform = (Node *) expression_planner((Expr *) transform);
  
  		/*
  		 * Add a work queue item to make ATRewriteTable update the column
  		 * contents.
  		 */
  		newval = (NewColumnValue *) palloc0(sizeof(NewColumnValue));
  		newval->attnum = attnum;
  		newval->expr = (Expr *) transform;
  
  		tab->newvals = lappend(tab->newvals, newval);
  		if (ATColumnChangeRequiresRewrite(transform, attnum))
  			tab->rewrite |= AT_REWRITE_COLUMN_REWRITE;
  	}
  	else if (transform)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is not a table",
  						RelationGetRelationName(rel))));
  
  	if (tab->relkind == RELKIND_COMPOSITE_TYPE ||
  		tab->relkind == RELKIND_FOREIGN_TABLE)
  	{
  		/*
  		 * For composite types, do this check now.  Tables will check it later
  		 * when the table is being rewritten.
  		 */
  		find_composite_type_dependencies(rel->rd_rel->reltype, rel, NULL);
  	}
  
  	ReleaseSysCache(tuple);
  
  	/*
  	 * Recurse manually by queueing a new command for each child, if
  	 * necessary. We cannot apply ATSimpleRecursion here because we need to
  	 * remap attribute numbers in the USING expression, if any.
  	 *
  	 * If we are told not to recurse, there had better not be any child
  	 * tables; else the alter would put them out of step.
  	 */
  	if (recurse)
  	{
  		Oid			relid = RelationGetRelid(rel);
  		ListCell   *child;
  		List	   *children;
  
  		children = find_all_inheritors(relid, lockmode, NULL);
  
  		/*
  		 * find_all_inheritors does the recursive search of the inheritance
  		 * hierarchy, so all we have to do is process all of the relids in the
  		 * list that it returns.
  		 */
  		foreach(child, children)
  		{
  			Oid			childrelid = lfirst_oid(child);
  			Relation	childrel;
  
  			if (childrelid == relid)
  				continue;
  
  			/* find_all_inheritors already got lock */
  			childrel = relation_open(childrelid, NoLock);
  			CheckTableNotInUse(childrel, "ALTER TABLE");
  
  			/*
  			 * Remap the attribute numbers.  If no USING expression was
  			 * specified, there is no need for this step.
  			 */
  			if (def->cooked_default)
  			{
  				AttrNumber *attmap;
  				bool		found_whole_row;
  
  				/* create a copy to scribble on */
  				cmd = copyObject(cmd);
  
  				attmap = convert_tuples_by_name_map(RelationGetDescr(childrel),
  													RelationGetDescr(rel),
  													gettext_noop("could not convert row type"));
  				((ColumnDef *) cmd->def)->cooked_default =
  					map_variable_attnos(def->cooked_default,
  										1, 0,
  										attmap, RelationGetDescr(rel)->natts,
  										InvalidOid, &found_whole_row);
  				if (found_whole_row)
  					ereport(ERROR,
  							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  							 errmsg("cannot convert whole-row table reference"),
  							 errdetail("USING expression contains a whole-row table reference.")));
  				pfree(attmap);
  			}
  			ATPrepCmd(wqueue, childrel, cmd, false, true, lockmode);
  			relation_close(childrel, NoLock);
  		}
  	}
  	else if (!recursing &&
  			 find_inheritance_children(RelationGetRelid(rel), NoLock) != NIL)
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  				 errmsg("type of inherited column \"%s\" must be changed in child tables too",
  						colName)));
  
  	if (tab->relkind == RELKIND_COMPOSITE_TYPE)
  		ATTypedTableRecursion(wqueue, rel, cmd, lockmode);
  }
  
  /*
   * When the data type of a column is changed, a rewrite might not be required
   * if the new type is sufficiently identical to the old one, and the USING
   * clause isn't trying to insert some other value.  It's safe to skip the
   * rewrite in these cases:
   *
   * - the old type is binary coercible to the new type
   * - the new type is an unconstrained domain over the old type
   * - {NEW,OLD} or {OLD,NEW} is {timestamptz,timestamp} and the timezone is UTC
   *
   * In the case of a constrained domain, we could get by with scanning the
   * table and checking the constraint rather than actually rewriting it, but we
   * don't currently try to do that.
   */
  static bool
  ATColumnChangeRequiresRewrite(Node *expr, AttrNumber varattno)
  {
  	Assert(expr != NULL);
  
  	for (;;)
  	{
  		/* only one varno, so no need to check that */
  		if (IsA(expr, Var) &&((Var *) expr)->varattno == varattno)
  			return false;
  		else if (IsA(expr, RelabelType))
  			expr = (Node *) ((RelabelType *) expr)->arg;
  		else if (IsA(expr, CoerceToDomain))
  		{
  			CoerceToDomain *d = (CoerceToDomain *) expr;
  
  			if (DomainHasConstraints(d->resulttype))
  				return true;
  			expr = (Node *) d->arg;
  		}
  		else if (IsA(expr, FuncExpr))
  		{
  			FuncExpr   *f = (FuncExpr *) expr;
  
  			switch (f->funcid)
  			{
  				case F_TIMESTAMPTZ_TIMESTAMP:
  				case F_TIMESTAMP_TIMESTAMPTZ:
  					if (TimestampTimestampTzRequiresRewrite())
  						return true;
  					else
  						expr = linitial(f->args);
  					break;
  				default:
  					return true;
  			}
  		}
  		else
  			return true;
  	}
  }
  
  /*
   * ALTER COLUMN .. SET DATA TYPE
   *
   * Return the address of the modified column.
   */
  static ObjectAddress
  ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
  					  AlterTableCmd *cmd, LOCKMODE lockmode)
  {
  	char	   *colName = cmd->name;
  	ColumnDef  *def = (ColumnDef *) cmd->def;
  	TypeName   *typeName = def->typeName;
  	HeapTuple	heapTup;
  	Form_pg_attribute attTup,
  				attOldTup;
  	AttrNumber	attnum;
  	HeapTuple	typeTuple;
  	Form_pg_type tform;
  	Oid			targettype;
  	int32		targettypmod;
  	Oid			targetcollid;
  	Node	   *defaultexpr;
  	Relation	attrelation;
  	Relation	depRel;
  	ScanKeyData key[3];
  	SysScanDesc scan;
  	HeapTuple	depTup;
  	ObjectAddress address;
  
  	/*
  	 * Clear all the missing values if we're rewriting the table, since this
  	 * renders them pointless.
  	 */
  	if (tab->rewrite)
  	{
  		Relation    newrel;
  
  		newrel = heap_open(RelationGetRelid(rel), NoLock);
  		RelationClearMissing(newrel);
  		relation_close(newrel, NoLock);
  		/* make sure we don't conflict with later attribute modifications */
  		CommandCounterIncrement();
  	}
  
  	attrelation = heap_open(AttributeRelationId, RowExclusiveLock);
  
  	/* Look up the target column */
  	heapTup = SearchSysCacheCopyAttName(RelationGetRelid(rel), colName);
  	if (!HeapTupleIsValid(heapTup)) /* shouldn't happen */
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_COLUMN),
  				 errmsg("column \"%s\" of relation \"%s\" does not exist",
  						colName, RelationGetRelationName(rel))));
  	attTup = (Form_pg_attribute) GETSTRUCT(heapTup);
  	attnum = attTup->attnum;
  	attOldTup = TupleDescAttr(tab->oldDesc, attnum - 1);
  
  	/* Check for multiple ALTER TYPE on same column --- can't cope */
  	if (attTup->atttypid != attOldTup->atttypid ||
  		attTup->atttypmod != attOldTup->atttypmod)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot alter type of column \"%s\" twice",
  						colName)));
  
  	/* Look up the target type (should not fail, since prep found it) */
  	typeTuple = typenameType(NULL, typeName, &targettypmod);
  	tform = (Form_pg_type) GETSTRUCT(typeTuple);
  	targettype = HeapTupleGetOid(typeTuple);
  	/* And the collation */
  	targetcollid = GetColumnDefCollation(NULL, def, targettype);
  
  	/*
  	 * If there is a default expression for the column, get it and ensure we
  	 * can coerce it to the new datatype.  (We must do this before changing
  	 * the column type, because build_column_default itself will try to
  	 * coerce, and will not issue the error message we want if it fails.)
  	 *
  	 * We remove any implicit coercion steps at the top level of the old
  	 * default expression; this has been agreed to satisfy the principle of
  	 * least surprise.  (The conversion to the new column type should act like
  	 * it started from what the user sees as the stored expression, and the
  	 * implicit coercions aren't going to be shown.)
  	 */
  	if (attTup->atthasdef)
  	{
  		defaultexpr = build_column_default(rel, attnum);
  		Assert(defaultexpr);
  		defaultexpr = strip_implicit_coercions(defaultexpr);
  		defaultexpr = coerce_to_target_type(NULL,	/* no UNKNOWN params */
  											defaultexpr, exprType(defaultexpr),
  											targettype, targettypmod,
  											COERCION_ASSIGNMENT,
  											COERCE_IMPLICIT_CAST,
  											-1);
  		if (defaultexpr == NULL)
  			ereport(ERROR,
  					(errcode(ERRCODE_DATATYPE_MISMATCH),
  					 errmsg("default for column \"%s\" cannot be cast automatically to type %s",
  							colName, format_type_be(targettype))));
  	}
  	else
  		defaultexpr = NULL;
  
  	/*
  	 * Find everything that depends on the column (constraints, indexes, etc),
  	 * and record enough information to let us recreate the objects.
  	 *
  	 * The actual recreation does not happen here, but only after we have
  	 * performed all the individual ALTER TYPE operations.  We have to save
  	 * the info before executing ALTER TYPE, though, else the deparser will
  	 * get confused.
  	 *
  	 * There could be multiple entries for the same object, so we must check
  	 * to ensure we process each one only once.  Note: we assume that an index
  	 * that implements a constraint will not show a direct dependency on the
  	 * column.
  	 */
  	depRel = heap_open(DependRelationId, RowExclusiveLock);
  
  	ScanKeyInit(&key[0],
  				Anum_pg_depend_refclassid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationRelationId));
  	ScanKeyInit(&key[1],
  				Anum_pg_depend_refobjid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(rel)));
  	ScanKeyInit(&key[2],
  				Anum_pg_depend_refobjsubid,
  				BTEqualStrategyNumber, F_INT4EQ,
  				Int32GetDatum((int32) attnum));
  
  	scan = systable_beginscan(depRel, DependReferenceIndexId, true,
  							  NULL, 3, key);
  
  	while (HeapTupleIsValid(depTup = systable_getnext(scan)))
  	{
  		Form_pg_depend foundDep = (Form_pg_depend) GETSTRUCT(depTup);
  		ObjectAddress foundObject;
  
  		/* We don't expect any PIN dependencies on columns */
  		if (foundDep->deptype == DEPENDENCY_PIN)
  			elog(ERROR, "cannot alter type of a pinned column");
  
  		foundObject.classId = foundDep->classid;
  		foundObject.objectId = foundDep->objid;
  		foundObject.objectSubId = foundDep->objsubid;
  
  		switch (getObjectClass(&foundObject))
  		{
  			case OCLASS_CLASS:
  				{
  					char		relKind = get_rel_relkind(foundObject.objectId);
  
  					if (relKind == RELKIND_INDEX ||
  						relKind == RELKIND_PARTITIONED_INDEX)
  					{
  						Assert(foundObject.objectSubId == 0);
  						if (!list_member_oid(tab->changedIndexOids, foundObject.objectId))
  						{
  							tab->changedIndexOids = lappend_oid(tab->changedIndexOids,
  																foundObject.objectId);
  							tab->changedIndexDefs = lappend(tab->changedIndexDefs,
  											pg_get_indexdef_string(foundObject.objectId));
  						}
  					}
  					else if (relKind == RELKIND_SEQUENCE)
  					{
  						/*
  						 * This must be a SERIAL column's sequence.  We need
  						 * not do anything to it.
  						 */
  						Assert(foundObject.objectSubId == 0);
  					}
  					else
  					{
  						/* Not expecting any other direct dependencies... */
  						elog(ERROR, "unexpected object depending on column: %s",
  							 getObjectDescription(&foundObject));
  					}
  					break;
  				}
  
  			case OCLASS_CONSTRAINT:
  				Assert(foundObject.objectSubId == 0);
  				if (!list_member_oid(tab->changedConstraintOids,
  									 foundObject.objectId))
  				{
  					char	   *defstring = pg_get_constraintdef_command(foundObject.objectId);
  
  					tab->changedConstraintOids =
  						lappend_oid(tab->changedConstraintOids,
  									foundObject.objectId);
  					tab->changedConstraintDefs =
  						lappend(tab->changedConstraintDefs,
  								defstring);
  				}
  				break;
  
  			case OCLASS_REWRITE:
  				/* XXX someday see if we can cope with revising views */
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("cannot alter type of a column used by a view or rule"),
  						 errdetail("%s depends on column \"%s\"",
  								   getObjectDescription(&foundObject),
  								   colName)));
  				break;
  
  			case OCLASS_TRIGGER:
  
  				/*
  				 * A trigger can depend on a column because the column is
  				 * specified as an update target, or because the column is
  				 * used in the trigger's WHEN condition.  The first case would
  				 * not require any extra work, but the second case would
  				 * require updating the WHEN expression, which will take a
  				 * significant amount of new code.  Since we can't easily tell
  				 * which case applies, we punt for both.  FIXME someday.
  				 */
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("cannot alter type of a column used in a trigger definition"),
  						 errdetail("%s depends on column \"%s\"",
  								   getObjectDescription(&foundObject),
  								   colName)));
  				break;
  
  			case OCLASS_POLICY:
  
  				/*
  				 * A policy can depend on a column because the column is
  				 * specified in the policy's USING or WITH CHECK qual
  				 * expressions.  It might be possible to rewrite and recheck
  				 * the policy expression, but punt for now.  It's certainly
  				 * easy enough to remove and recreate the policy; still, FIXME
  				 * someday.
  				 */
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("cannot alter type of a column used in a policy definition"),
  						 errdetail("%s depends on column \"%s\"",
  								   getObjectDescription(&foundObject),
  								   colName)));
  				break;
  
  			case OCLASS_DEFAULT:
  
  				/*
  				 * Ignore the column's default expression, since we will fix
  				 * it below.
  				 */
  				Assert(defaultexpr);
  				break;
  
  			case OCLASS_STATISTIC_EXT:
  
  				/*
  				 * Give the extended-stats machinery a chance to fix anything
  				 * that this column type change would break.
  				 */
  				UpdateStatisticsForTypeChange(foundObject.objectId,
  											  RelationGetRelid(rel), attnum,
  											  attTup->atttypid, targettype);
  				break;
  
  			case OCLASS_PROC:
  			case OCLASS_TYPE:
  			case OCLASS_CAST:
  			case OCLASS_COLLATION:
  			case OCLASS_CONVERSION:
  			case OCLASS_LANGUAGE:
  			case OCLASS_LARGEOBJECT:
  			case OCLASS_OPERATOR:
  			case OCLASS_OPCLASS:
  			case OCLASS_OPFAMILY:
  			case OCLASS_AM:
  			case OCLASS_AMOP:
  			case OCLASS_AMPROC:
  			case OCLASS_SCHEMA:
  			case OCLASS_TSPARSER:
  			case OCLASS_TSDICT:
  			case OCLASS_TSTEMPLATE:
  			case OCLASS_TSCONFIG:
  			case OCLASS_ROLE:
  			case OCLASS_DATABASE:
  			case OCLASS_TBLGROUP:
  			case OCLASS_TBLSPACE:
  			case OCLASS_FDW:
  			case OCLASS_FOREIGN_SERVER:
  			case OCLASS_USER_MAPPING:
  			case OCLASS_DEFACL:
  			case OCLASS_EXTENSION:
  			case OCLASS_EVENT_TRIGGER:
  			case OCLASS_PUBLICATION:
  			case OCLASS_PUBLICATION_REL:
  			case OCLASS_SUBSCRIPTION:
  			case OCLASS_TRANSFORM:
  
  				/*
  				 * We don't expect any of these sorts of objects to depend on
  				 * a column.
  				 */
  				elog(ERROR, "unexpected object depending on column: %s",
  					 getObjectDescription(&foundObject));
  				break;
  
  				/*
  				 * There's intentionally no default: case here; we want the
  				 * compiler to warn if a new OCLASS hasn't been handled above.
  				 */
  		}
  	}
  
  	systable_endscan(scan);
  
  	/*
  	 * Now scan for dependencies of this column on other things.  The only
  	 * thing we should find is the dependency on the column datatype, which we
  	 * want to remove, and possibly a collation dependency.
  	 */
  	ScanKeyInit(&key[0],
  				Anum_pg_depend_classid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationRelationId));
  	ScanKeyInit(&key[1],
  				Anum_pg_depend_objid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(rel)));
  	ScanKeyInit(&key[2],
  				Anum_pg_depend_objsubid,
  				BTEqualStrategyNumber, F_INT4EQ,
  				Int32GetDatum((int32) attnum));
  
  	scan = systable_beginscan(depRel, DependDependerIndexId, true,
  							  NULL, 3, key);
  
  	while (HeapTupleIsValid(depTup = systable_getnext(scan)))
  	{
  		Form_pg_depend foundDep = (Form_pg_depend) GETSTRUCT(depTup);
  
  		if (foundDep->deptype != DEPENDENCY_NORMAL)
  			elog(ERROR, "found unexpected dependency type '%c'",
  				 foundDep->deptype);
  		if (!(foundDep->refclassid == TypeRelationId &&
  			  foundDep->refobjid == attTup->atttypid) &&
  			!(foundDep->refclassid == CollationRelationId &&
  			  foundDep->refobjid == attTup->attcollation))
  			elog(ERROR, "found unexpected dependency for column");
  
  		CatalogTupleDelete(depRel, depTup);
  	}
  
  	systable_endscan(scan);
  
  	heap_close(depRel, RowExclusiveLock);
  
  	/*
  	 * Here we go --- change the recorded column type and collation.  (Note
  	 * heapTup is a copy of the syscache entry, so okay to scribble on.)
  	 * First fix up the missing value if any.
  	 */
  	if (attTup->atthasmissing)
  	{
  		Datum       missingval;
  		bool        missingNull;
  
  		/* if rewrite is true the missing value should already be cleared */
  		Assert(tab->rewrite == 0);
  
  		/* Get the missing value datum */
  		missingval = heap_getattr(heapTup,
  								  Anum_pg_attribute_attmissingval,
  								  attrelation->rd_att,
  								  &missingNull);
  
  		/* if it's a null array there is nothing to do */
  
  		if (! missingNull)
  		{
  			/*
  			 * Get the datum out of the array and repack it in a new array
  			 * built with the new type data. We assume that since the table
  			 * doesn't need rewriting, the actual Datum doesn't need to be
  			 * changed, only the array metadata.
  			 */
  
  			int one = 1;
  			bool isNull;
  			Datum       valuesAtt[Natts_pg_attribute];
  			bool        nullsAtt[Natts_pg_attribute];
  			bool        replacesAtt[Natts_pg_attribute];
  			HeapTuple   newTup;
  
  			MemSet(valuesAtt, 0, sizeof(valuesAtt));
  			MemSet(nullsAtt, false, sizeof(nullsAtt));
  			MemSet(replacesAtt, false, sizeof(replacesAtt));
  
  			missingval = array_get_element(missingval,
  										   1,
  										   &one,
  										   0,
  										   attTup->attlen,
  										   attTup->attbyval,
  										   attTup->attalign,
  										   &isNull);
  			missingval = PointerGetDatum(
  				construct_array(&missingval,
  								1,
  								targettype,
  								tform->typlen,
  								tform->typbyval,
  								tform->typalign));
  
  			valuesAtt[Anum_pg_attribute_attmissingval - 1] = missingval;
  			replacesAtt[Anum_pg_attribute_attmissingval - 1] = true;
  			nullsAtt[Anum_pg_attribute_attmissingval - 1] = false;
  
  			newTup = heap_modify_tuple(heapTup, RelationGetDescr(attrelation),
  									   valuesAtt, nullsAtt, replacesAtt);
  			heap_freetuple(heapTup);
  			heapTup = newTup;
  			attTup = (Form_pg_attribute) GETSTRUCT(heapTup);
  		}
  	}
  
  	attTup->atttypid = targettype;
  	attTup->atttypmod = targettypmod;
  	attTup->attcollation = targetcollid;
  	attTup->attndims = list_length(typeName->arrayBounds);
  	attTup->attlen = tform->typlen;
  	attTup->attbyval = tform->typbyval;
  	attTup->attalign = tform->typalign;
  	attTup->attstorage = tform->typstorage;
  
  	ReleaseSysCache(typeTuple);
  
  	CatalogTupleUpdate(attrelation, &heapTup->t_self, heapTup);
  
  	heap_close(attrelation, RowExclusiveLock);
  
  	/* Install dependencies on new datatype and collation */
  	add_column_datatype_dependency(RelationGetRelid(rel), attnum, targettype);
  	add_column_collation_dependency(RelationGetRelid(rel), attnum, targetcollid);
  
  	/*
  	 * Drop any pg_statistic entry for the column, since it's now wrong type
  	 */
  	RemoveStatistics(RelationGetRelid(rel), attnum);
  
  	InvokeObjectPostAlterHook(RelationRelationId,
  							  RelationGetRelid(rel), attnum);
  
  	/*
  	 * Update the default, if present, by brute force --- remove and re-add
  	 * the default.  Probably unsafe to take shortcuts, since the new version
  	 * may well have additional dependencies.  (It's okay to do this now,
  	 * rather than after other ALTER TYPE commands, since the default won't
  	 * depend on other column types.)
  	 */
  	if (defaultexpr)
  	{
  		/* Must make new row visible since it will be updated again */
  		CommandCounterIncrement();
  
  		/*
  		 * We use RESTRICT here for safety, but at present we do not expect
  		 * anything to depend on the default.
  		 */
  		RemoveAttrDefault(RelationGetRelid(rel), attnum, DROP_RESTRICT, true,
  						  true);
  
  		StoreAttrDefault(rel, attnum, defaultexpr, true, false);
  	}
  
  	ObjectAddressSubSet(address, RelationRelationId,
  						RelationGetRelid(rel), attnum);
  
  	/* Cleanup */
  	heap_freetuple(heapTup);
  
  	return address;
  }
  
  /*
   * Returns the address of the modified column
   */
  static ObjectAddress
  ATExecAlterColumnGenericOptions(Relation rel,
  								const char *colName,
  								List *options,
  								LOCKMODE lockmode)
  {
  	Relation	ftrel;
  	Relation	attrel;
  	ForeignServer *server;
  	ForeignDataWrapper *fdw;
  	HeapTuple	tuple;
  	HeapTuple	newtuple;
  	bool		isnull;
  	Datum		repl_val[Natts_pg_attribute];
  	bool		repl_null[Natts_pg_attribute];
  	bool		repl_repl[Natts_pg_attribute];
  	Datum		datum;
  	Form_pg_foreign_table fttableform;
  	Form_pg_attribute atttableform;
  	AttrNumber	attnum;
  	ObjectAddress address;
  
  	if (options == NIL)
  		return InvalidObjectAddress;
  
  	/* First, determine FDW validator associated to the foreign table. */
  	ftrel = heap_open(ForeignTableRelationId, AccessShareLock);
  	tuple = SearchSysCache1(FOREIGNTABLEREL, rel->rd_id);
  	if (!HeapTupleIsValid(tuple))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_OBJECT),
  				 errmsg("foreign table \"%s\" does not exist",
  						RelationGetRelationName(rel))));
  	fttableform = (Form_pg_foreign_table) GETSTRUCT(tuple);
  	server = GetForeignServer(fttableform->ftserver);
  	fdw = GetForeignDataWrapper(server->fdwid);
  
  	heap_close(ftrel, AccessShareLock);
  	ReleaseSysCache(tuple);
  
  	attrel = heap_open(AttributeRelationId, RowExclusiveLock);
  	tuple = SearchSysCacheAttName(RelationGetRelid(rel), colName);
  	if (!HeapTupleIsValid(tuple))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_COLUMN),
  				 errmsg("column \"%s\" of relation \"%s\" does not exist",
  						colName, RelationGetRelationName(rel))));
  
  	/* Prevent them from altering a system attribute */
  	atttableform = (Form_pg_attribute) GETSTRUCT(tuple);
  	attnum = atttableform->attnum;
  	if (attnum <= 0)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot alter system column \"%s\"", colName)));
  
  
  	/* Initialize buffers for new tuple values */
  	memset(repl_val, 0, sizeof(repl_val));
  	memset(repl_null, false, sizeof(repl_null));
  	memset(repl_repl, false, sizeof(repl_repl));
  
  	/* Extract the current options */
  	datum = SysCacheGetAttr(ATTNAME,
  							tuple,
  							Anum_pg_attribute_attfdwoptions,
  							&isnull);
  	if (isnull)
  		datum = PointerGetDatum(NULL);
  
  	/* Transform the options */
  	datum = transformGenericOptions(AttributeRelationId,
  									datum,
  									options,
  									fdw->fdwvalidator);
  
  	if (PointerIsValid(DatumGetPointer(datum)))
  		repl_val[Anum_pg_attribute_attfdwoptions - 1] = datum;
  	else
  		repl_null[Anum_pg_attribute_attfdwoptions - 1] = true;
  
  	repl_repl[Anum_pg_attribute_attfdwoptions - 1] = true;
  
  	/* Everything looks good - update the tuple */
  
  	newtuple = heap_modify_tuple(tuple, RelationGetDescr(attrel),
  								 repl_val, repl_null, repl_repl);
  
  	CatalogTupleUpdate(attrel, &newtuple->t_self, newtuple);
  
  	InvokeObjectPostAlterHook(RelationRelationId,
  							  RelationGetRelid(rel),
  							  atttableform->attnum);
  	ObjectAddressSubSet(address, RelationRelationId,
  						RelationGetRelid(rel), attnum);
  
  	ReleaseSysCache(tuple);
  
  	heap_close(attrel, RowExclusiveLock);
  
  	heap_freetuple(newtuple);
  
  	return address;
  }
  
  /*
   * Cleanup after we've finished all the ALTER TYPE operations for a
   * particular relation.  We have to drop and recreate all the indexes
   * and constraints that depend on the altered columns.
   */
  static void
  ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab, LOCKMODE lockmode)
  {
  	ObjectAddress obj;
  	ObjectAddresses *objects;
  	ListCell   *def_item;
  	ListCell   *oid_item;
  
  	/*
  	 * Collect all the constraints and indexes to drop so we can process them
  	 * in a single call.  That way we don't have to worry about dependencies
  	 * among them.
  	 */
  	objects = new_object_addresses();
  
  	/*
  	 * Re-parse the index and constraint definitions, and attach them to the
  	 * appropriate work queue entries.  We do this before dropping because in
  	 * the case of a FOREIGN KEY constraint, we might not yet have exclusive
  	 * lock on the table the constraint is attached to, and we need to get
  	 * that before reparsing/dropping.
  	 *
  	 * We can't rely on the output of deparsing to tell us which relation to
  	 * operate on, because concurrent activity might have made the name
  	 * resolve differently.  Instead, we've got to use the OID of the
  	 * constraint or index we're processing to figure out which relation to
  	 * operate on.
  	 */
  	forboth(oid_item, tab->changedConstraintOids,
  			def_item, tab->changedConstraintDefs)
  	{
  		Oid			oldId = lfirst_oid(oid_item);
  		HeapTuple	tup;
  		Form_pg_constraint con;
  		Oid			relid;
  		Oid			confrelid;
  		char		contype;
  		bool		conislocal;
  
  		tup = SearchSysCache1(CONSTROID, ObjectIdGetDatum(oldId));
  		if (!HeapTupleIsValid(tup)) /* should not happen */
  			elog(ERROR, "cache lookup failed for constraint %u", oldId);
  		con = (Form_pg_constraint) GETSTRUCT(tup);
  		if (OidIsValid(con->conrelid))
  			relid = con->conrelid;
  		else
  		{
  			/* must be a domain constraint */
  			relid = get_typ_typrelid(getBaseType(con->contypid));
  			if (!OidIsValid(relid))
  				elog(ERROR, "could not identify relation associated with constraint %u", oldId);
  		}
  		confrelid = con->confrelid;
  		contype = con->contype;
  		conislocal = con->conislocal;
  		ReleaseSysCache(tup);
  
  		ObjectAddressSet(obj, ConstraintRelationId, oldId);
  		add_exact_object_address(&obj, objects);
  
  		/*
  		 * If the constraint is inherited (only), we don't want to inject a
  		 * new definition here; it'll get recreated when ATAddCheckConstraint
  		 * recurses from adding the parent table's constraint.  But we had to
  		 * carry the info this far so that we can drop the constraint below.
  		 */
  		if (!conislocal)
  			continue;
  
  		/*
  		 * When rebuilding an FK constraint that references the table we're
  		 * modifying, we might not yet have any lock on the FK's table, so get
  		 * one now.  We'll need AccessExclusiveLock for the DROP CONSTRAINT
  		 * step, so there's no value in asking for anything weaker.
  		 */
  		if (relid != tab->relid && contype == CONSTRAINT_FOREIGN)
  			LockRelationOid(relid, AccessExclusiveLock);
  
  		ATPostAlterTypeParse(oldId, relid, confrelid,
  							 (char *) lfirst(def_item),
  							 wqueue, lockmode, tab->rewrite);
  	}
  	forboth(oid_item, tab->changedIndexOids,
  			def_item, tab->changedIndexDefs)
  	{
  		Oid			oldId = lfirst_oid(oid_item);
  		Oid			relid;
  
  		relid = IndexGetRelation(oldId, false);
  		ATPostAlterTypeParse(oldId, relid, InvalidOid,
  							 (char *) lfirst(def_item),
  							 wqueue, lockmode, tab->rewrite);
  
  		ObjectAddressSet(obj, RelationRelationId, oldId);
  		add_exact_object_address(&obj, objects);
  	}
  
  	/*
  	 * It should be okay to use DROP_RESTRICT here, since nothing else should
  	 * be depending on these objects.
  	 */
  	performMultipleDeletions(objects, DROP_RESTRICT, PERFORM_DELETION_INTERNAL);
  
  	free_object_addresses(objects);
  
  	/*
  	 * The objects will get recreated during subsequent passes over the work
  	 * queue.
  	 */
  }
  
  static void
  ATPostAlterTypeParse(Oid oldId, Oid oldRelId, Oid refRelId, char *cmd,
  					 List **wqueue, LOCKMODE lockmode, bool rewrite)
  {
  	List	   *raw_parsetree_list;
  	List	   *querytree_list;
  	ListCell   *list_item;
  	Relation	rel;
  
  	/*
  	 * We expect that we will get only ALTER TABLE and CREATE INDEX
  	 * statements. Hence, there is no need to pass them through
  	 * parse_analyze() or the rewriter, but instead we need to pass them
  	 * through parse_utilcmd.c to make them ready for execution.
  	 */
  	raw_parsetree_list = raw_parser(cmd);
  	querytree_list = NIL;
  	foreach(list_item, raw_parsetree_list)
  	{
  		RawStmt    *rs = lfirst_node(RawStmt, list_item);
  		Node	   *stmt = rs->stmt;
  
  		if (IsA(stmt, IndexStmt))
  			querytree_list = lappend(querytree_list,
  									 transformIndexStmt(oldRelId,
  														(IndexStmt *) stmt,
  														cmd));
  		else if (IsA(stmt, AlterTableStmt))
  			querytree_list = list_concat(querytree_list,
  										 transformAlterTableStmt(oldRelId,
  																 (AlterTableStmt *) stmt,
  																 cmd));
  		else
  			querytree_list = lappend(querytree_list, stmt);
  	}
  
  	/* Caller should already have acquired whatever lock we need. */
  	rel = relation_open(oldRelId, NoLock);
  
  	/*
  	 * Attach each generated command to the proper place in the work queue.
  	 * Note this could result in creation of entirely new work-queue entries.
  	 *
  	 * Also note that we have to tweak the command subtypes, because it turns
  	 * out that re-creation of indexes and constraints has to act a bit
  	 * differently from initial creation.
  	 */
  	foreach(list_item, querytree_list)
  	{
  		Node	   *stm = (Node *) lfirst(list_item);
  		AlteredTableInfo *tab;
  
  		tab = ATGetQueueEntry(wqueue, rel);
  
  		if (IsA(stm, IndexStmt))
  		{
  			IndexStmt  *stmt = (IndexStmt *) stm;
  			AlterTableCmd *newcmd;
  
  			if (!rewrite)
  				TryReuseIndex(oldId, stmt);
  			/* keep the index's comment */
  			stmt->idxcomment = GetComment(oldId, RelationRelationId, 0);
  
  			newcmd = makeNode(AlterTableCmd);
  			newcmd->subtype = AT_ReAddIndex;
  			newcmd->def = (Node *) stmt;
  			tab->subcmds[AT_PASS_OLD_INDEX] =
  				lappend(tab->subcmds[AT_PASS_OLD_INDEX], newcmd);
  		}
  		else if (IsA(stm, AlterTableStmt))
  		{
  			AlterTableStmt *stmt = (AlterTableStmt *) stm;
  			ListCell   *lcmd;
  
  			foreach(lcmd, stmt->cmds)
  			{
  				AlterTableCmd *cmd = castNode(AlterTableCmd, lfirst(lcmd));
  
  				if (cmd->subtype == AT_AddIndex)
  				{
  					IndexStmt  *indstmt;
  					Oid			indoid;
  
  					indstmt = castNode(IndexStmt, cmd->def);
  					indoid = get_constraint_index(oldId);
  
  					if (!rewrite)
  						TryReuseIndex(indoid, indstmt);
  					/* keep any comment on the index */
  					indstmt->idxcomment = GetComment(indoid,
  													 RelationRelationId, 0);
  
  					cmd->subtype = AT_ReAddIndex;
  					tab->subcmds[AT_PASS_OLD_INDEX] =
  						lappend(tab->subcmds[AT_PASS_OLD_INDEX], cmd);
  
  					/* recreate any comment on the constraint */
  					RebuildConstraintComment(tab,
  											 AT_PASS_OLD_INDEX,
  											 oldId,
  											 rel,
  											 NIL,
  											 indstmt->idxname);
  				}
  				else if (cmd->subtype == AT_AddConstraint)
  				{
  					Constraint *con = castNode(Constraint, cmd->def);
  
  					con->old_pktable_oid = refRelId;
  					/* rewriting neither side of a FK */
  					if (con->contype == CONSTR_FOREIGN &&
  						!rewrite && tab->rewrite == 0)
  						TryReuseForeignKey(oldId, con);
  					cmd->subtype = AT_ReAddConstraint;
  					tab->subcmds[AT_PASS_OLD_CONSTR] =
  						lappend(tab->subcmds[AT_PASS_OLD_CONSTR], cmd);
  
  					/* recreate any comment on the constraint */
  					RebuildConstraintComment(tab,
  											 AT_PASS_OLD_CONSTR,
  											 oldId,
  											 rel,
  											 NIL,
  											 con->conname);
  				}
  				else
  					elog(ERROR, "unexpected statement subtype: %d",
  						 (int) cmd->subtype);
  			}
  		}
  		else if (IsA(stm, AlterDomainStmt))
  		{
  			AlterDomainStmt *stmt = (AlterDomainStmt *) stm;
  
  			if (stmt->subtype == 'C')	/* ADD CONSTRAINT */
  			{
  				Constraint *con = castNode(Constraint, stmt->def);
  				AlterTableCmd *cmd = makeNode(AlterTableCmd);
  
  				cmd->subtype = AT_ReAddDomainConstraint;
  				cmd->def = (Node *) stmt;
  				tab->subcmds[AT_PASS_OLD_CONSTR] =
  					lappend(tab->subcmds[AT_PASS_OLD_CONSTR], cmd);
  
  				/* recreate any comment on the constraint */
  				RebuildConstraintComment(tab,
  										 AT_PASS_OLD_CONSTR,
  										 oldId,
  										 NULL,
  										 stmt->typeName,
  										 con->conname);
  			}
  			else
  				elog(ERROR, "unexpected statement subtype: %d",
  					 (int) stmt->subtype);
  		}
  		else
  			elog(ERROR, "unexpected statement type: %d",
  				 (int) nodeTag(stm));
  	}
  
  	relation_close(rel, NoLock);
  }
  
  /*
   * Subroutine for ATPostAlterTypeParse() to recreate any existing comment
   * for a table or domain constraint that is being rebuilt.
   *
   * objid is the OID of the constraint.
   * Pass "rel" for a table constraint, or "domname" (domain's qualified name
   * as a string list) for a domain constraint.
   * (We could dig that info, as well as the conname, out of the pg_constraint
   * entry; but callers already have them so might as well pass them.)
   */
  static void
  RebuildConstraintComment(AlteredTableInfo *tab, int pass, Oid objid,
  						 Relation rel, List *domname,
  						 const char *conname)
  {
  	CommentStmt *cmd;
  	char	   *comment_str;
  	AlterTableCmd *newcmd;
  
  	/* Look for comment for object wanted, and leave if none */
  	comment_str = GetComment(objid, ConstraintRelationId, 0);
  	if (comment_str == NULL)
  		return;
  
  	/* Build CommentStmt node, copying all input data for safety */
  	cmd = makeNode(CommentStmt);
  	if (rel)
  	{
  		cmd->objtype = OBJECT_TABCONSTRAINT;
  		cmd->object = (Node *)
  			list_make3(makeString(get_namespace_name(RelationGetNamespace(rel))),
  					   makeString(pstrdup(RelationGetRelationName(rel))),
  					   makeString(pstrdup(conname)));
  	}
  	else
  	{
  		cmd->objtype = OBJECT_DOMCONSTRAINT;
  		cmd->object = (Node *)
  			list_make2(makeTypeNameFromNameList(copyObject(domname)),
  					   makeString(pstrdup(conname)));
  	}
  	cmd->comment = comment_str;
  
  	/* Append it to list of commands */
  	newcmd = makeNode(AlterTableCmd);
  	newcmd->subtype = AT_ReAddComment;
  	newcmd->def = (Node *) cmd;
  	tab->subcmds[pass] = lappend(tab->subcmds[pass], newcmd);
  }
  
  /*
   * Subroutine for ATPostAlterTypeParse().  Calls out to CheckIndexCompatible()
   * for the real analysis, then mutates the IndexStmt based on that verdict.
   */
  static void
  TryReuseIndex(Oid oldId, IndexStmt *stmt)
  {
  	if (CheckIndexCompatible(oldId,
  							 stmt->accessMethod,
  							 stmt->indexParams,
  							 stmt->excludeOpNames))
  	{
  		Relation	irel = index_open(oldId, NoLock);
  
  		stmt->oldNode = irel->rd_node.relNode;
  		index_close(irel, NoLock);
  	}
  }
  
  /*
   * Subroutine for ATPostAlterTypeParse().
   *
   * Stash the old P-F equality operator into the Constraint node, for possible
   * use by ATAddForeignKeyConstraint() in determining whether revalidation of
   * this constraint can be skipped.
   */
  static void
  TryReuseForeignKey(Oid oldId, Constraint *con)
  {
  	HeapTuple	tup;
  	Datum		adatum;
  	bool		isNull;
  	ArrayType  *arr;
  	Oid		   *rawarr;
  	int			numkeys;
  	int			i;
  
  	Assert(con->contype == CONSTR_FOREIGN);
  	Assert(con->old_conpfeqop == NIL);	/* already prepared this node */
  
  	tup = SearchSysCache1(CONSTROID, ObjectIdGetDatum(oldId));
  	if (!HeapTupleIsValid(tup)) /* should not happen */
  		elog(ERROR, "cache lookup failed for constraint %u", oldId);
  
  	adatum = SysCacheGetAttr(CONSTROID, tup,
  							 Anum_pg_constraint_conpfeqop, &isNull);
  	if (isNull)
  		elog(ERROR, "null conpfeqop for constraint %u", oldId);
  	arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
  	numkeys = ARR_DIMS(arr)[0];
  	/* test follows the one in ri_FetchConstraintInfo() */
  	if (ARR_NDIM(arr) != 1 ||
  		ARR_HASNULL(arr) ||
  		ARR_ELEMTYPE(arr) != OIDOID)
  		elog(ERROR, "conpfeqop is not a 1-D Oid array");
  	rawarr = (Oid *) ARR_DATA_PTR(arr);
  
  	/* stash a List of the operator Oids in our Constraint node */
  	for (i = 0; i < numkeys; i++)
  		con->old_conpfeqop = lcons_oid(rawarr[i], con->old_conpfeqop);
  
  	ReleaseSysCache(tup);
  }
  
  /*
   * ALTER TABLE OWNER
   *
   * recursing is true if we are recursing from a table to its indexes,
   * sequences, or toast table.  We don't allow the ownership of those things to
   * be changed separately from the parent table.  Also, we can skip permission
   * checks (this is necessary not just an optimization, else we'd fail to
   * handle toast tables properly).
   *
   * recursing is also true if ALTER TYPE OWNER is calling us to fix up a
   * free-standing composite type.
   */
  void
  ATExecChangeOwner(Oid relationOid, Oid newOwnerId, bool recursing, LOCKMODE lockmode)
  {
  	Relation	target_rel;
  	Relation	class_rel;
  	HeapTuple	tuple;
  	Form_pg_class tuple_class;
  
  	/*
  	 * Get exclusive lock till end of transaction on the target table. Use
  	 * relation_open so that we can work on indexes and sequences.
  	 */
  	target_rel = relation_open(relationOid, lockmode);
  
  	/* Get its pg_class tuple, too */
  	class_rel = heap_open(RelationRelationId, RowExclusiveLock);
  
  	tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relationOid));
  	if (!HeapTupleIsValid(tuple))
  		elog(ERROR, "cache lookup failed for relation %u", relationOid);
  	tuple_class = (Form_pg_class) GETSTRUCT(tuple);
  
  	/* Can we change the ownership of this tuple? */
  	switch (tuple_class->relkind)
  	{
  		case RELKIND_RELATION:
  		case RELKIND_VIEW:
  		case RELKIND_MATVIEW:
  		case RELKIND_FOREIGN_TABLE:
  		case RELKIND_PARTITIONED_TABLE:
  			/* ok to change owner */
  			break;
  		case RELKIND_INDEX:
  			if (!recursing)
  			{
  				/*
  				 * Because ALTER INDEX OWNER used to be allowed, and in fact
  				 * is generated by old versions of pg_dump, we give a warning
  				 * and do nothing rather than erroring out.  Also, to avoid
  				 * unnecessary chatter while restoring those old dumps, say
  				 * nothing at all if the command would be a no-op anyway.
  				 */
  				if (tuple_class->relowner != newOwnerId)
  					ereport(WARNING,
  							(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  							 errmsg("cannot change owner of index \"%s\"",
  									NameStr(tuple_class->relname)),
  							 errhint("Change the ownership of the index's table, instead.")));
  				/* quick hack to exit via the no-op path */
  				newOwnerId = tuple_class->relowner;
  			}
  			break;
  		case RELKIND_PARTITIONED_INDEX:
  			if (recursing)
  				break;
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("cannot change owner of index \"%s\"",
  							NameStr(tuple_class->relname)),
  					 errhint("Change the ownership of the index's table, instead.")));
  			break;
  		case RELKIND_SEQUENCE:
  			if (!recursing &&
  				tuple_class->relowner != newOwnerId)
  			{
  				/* if it's an owned sequence, disallow changing it by itself */
  				Oid			tableId;
  				int32		colId;
  
  				if (sequenceIsOwned(relationOid, DEPENDENCY_AUTO, &tableId, &colId) ||
  					sequenceIsOwned(relationOid, DEPENDENCY_INTERNAL, &tableId, &colId))
  					ereport(ERROR,
  							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  							 errmsg("cannot change owner of sequence \"%s\"",
  									NameStr(tuple_class->relname)),
  							 errdetail("Sequence \"%s\" is linked to table \"%s\".",
  									   NameStr(tuple_class->relname),
  									   get_rel_name(tableId))));
  			}
  			break;
  		case RELKIND_COMPOSITE_TYPE:
  			if (recursing)
  				break;
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("\"%s\" is a composite type",
  							NameStr(tuple_class->relname)),
  					 errhint("Use ALTER TYPE instead.")));
  			break;
  		case RELKIND_TOASTVALUE:
  			if (recursing)
  				break;
  			switch_fallthrough();
  		default:
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("\"%s\" is not a table, view, sequence, or foreign table",
  							NameStr(tuple_class->relname))));
  	}
  
  	/*
  	 * If the new owner is the same as the existing owner, consider the
  	 * command to have succeeded.  This is for dump restoration purposes.
  	 */
  	if (tuple_class->relowner != newOwnerId)
  	{
  		Datum		repl_val[Natts_pg_class];
  		bool		repl_null[Natts_pg_class];
  		bool		repl_repl[Natts_pg_class];
  		Acl		   *newAcl;
  		Datum		aclDatum;
  		bool		isNull;
  		HeapTuple	newtuple;
  
  		/* skip permission checks when recursing to index or toast table */
  		if (!recursing)
  		{
  			/* Superusers can always do it */
  			if (!superuser())
  			{
  				Oid			namespaceOid = tuple_class->relnamespace;
  				AclResult	aclresult;
  
  				/* Otherwise, must be owner of the existing object */
  				if (!pg_class_ownercheck(relationOid, GetUserId()))
  					aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(get_rel_relkind(relationOid)),
  								   RelationGetRelationName(target_rel));
  
  				/* Must be able to become new owner */
  				check_is_member_of_role(GetUserId(), newOwnerId);
  
  				/* New owner must have CREATE privilege on namespace */
  				aclresult = pg_namespace_aclcheck(namespaceOid, newOwnerId,
  												  ACL_CREATE);
  				if (aclresult != ACLCHECK_OK)
  					aclcheck_error(aclresult, OBJECT_SCHEMA,
  								   get_namespace_name(namespaceOid));
  			}
  		}
  
  		memset(repl_null, false, sizeof(repl_null));
  		memset(repl_repl, false, sizeof(repl_repl));
  
  		repl_repl[Anum_pg_class_relowner - 1] = true;
  		repl_val[Anum_pg_class_relowner - 1] = ObjectIdGetDatum(newOwnerId);
  
  		/*
  		 * Determine the modified ACL for the new owner.  This is only
  		 * necessary when the ACL is non-null.
  		 */
  		aclDatum = SysCacheGetAttr(RELOID, tuple,
  								   Anum_pg_class_relacl,
  								   &isNull);
  		if (!isNull)
  		{
  			newAcl = aclnewowner(DatumGetAclP(aclDatum),
  								 tuple_class->relowner, newOwnerId);
  			repl_repl[Anum_pg_class_relacl - 1] = true;
  			repl_val[Anum_pg_class_relacl - 1] = PointerGetDatum(newAcl);
  		}
  
  		newtuple = heap_modify_tuple(tuple, RelationGetDescr(class_rel), repl_val, repl_null, repl_repl);
  
  		CatalogTupleUpdate(class_rel, &newtuple->t_self, newtuple);
  
  		heap_freetuple(newtuple);
  
  		/*
  		 * We must similarly update any per-column ACLs to reflect the new
  		 * owner; for neatness reasons that's split out as a subroutine.
  		 */
  		change_owner_fix_column_acls(relationOid,
  									 tuple_class->relowner,
  									 newOwnerId);
  
  		/*
  		 * Update owner dependency reference, if any.  A composite type has
  		 * none, because it's tracked for the pg_type entry instead of here;
  		 * indexes and TOAST tables don't have their own entries either.
  		 */
  		if (tuple_class->relkind != RELKIND_COMPOSITE_TYPE &&
  			tuple_class->relkind != RELKIND_INDEX &&
  			tuple_class->relkind != RELKIND_PARTITIONED_INDEX &&
  			tuple_class->relkind != RELKIND_TOASTVALUE)
  			changeDependencyOnOwner(RelationRelationId, relationOid,
  									newOwnerId);
  
  		/*
  		 * Also change the ownership of the table's row type, if it has one
  		 */
  		if (tuple_class->relkind != RELKIND_INDEX &&
  			tuple_class->relkind != RELKIND_PARTITIONED_INDEX)
  			AlterTypeOwnerInternal(tuple_class->reltype, newOwnerId);
  
  		/*
  		 * If we are operating on a table or materialized view, also change
  		 * the ownership of any indexes and sequences that belong to the
  		 * relation, as well as its toast table (if it has one).
  		 */
  		if (tuple_class->relkind == RELKIND_RELATION ||
  			tuple_class->relkind == RELKIND_PARTITIONED_TABLE ||
  			tuple_class->relkind == RELKIND_MATVIEW ||
  			tuple_class->relkind == RELKIND_TOASTVALUE)
  		{
  			List	   *index_oid_list;
  			ListCell   *i;
  
  			/* Find all the indexes belonging to this relation */
  			index_oid_list = RelationGetIndexList(target_rel);
  
  			/* For each index, recursively change its ownership */
  			foreach(i, index_oid_list)
  				ATExecChangeOwner(lfirst_oid(i), newOwnerId, true, lockmode);
  
  			list_free(index_oid_list);
  		}
  
  		/* If it has a toast table, recurse to change its ownership */
  		if (tuple_class->reltoastrelid != InvalidOid)
  			ATExecChangeOwner(tuple_class->reltoastrelid, newOwnerId,
  							  true, lockmode);
  
  		/* If it has dependent sequences, recurse to change them too */
  		change_owner_recurse_to_sequences(relationOid, newOwnerId, lockmode);
  	}
  
  	InvokeObjectPostAlterHook(RelationRelationId, relationOid, 0);
  
  	ReleaseSysCache(tuple);
  	heap_close(class_rel, RowExclusiveLock);
  	relation_close(target_rel, NoLock);
  }
  
  /*
   * change_owner_fix_column_acls
   *
   * Helper function for ATExecChangeOwner.  Scan the columns of the table
   * and fix any non-null column ACLs to reflect the new owner.
   */
  static void
  change_owner_fix_column_acls(Oid relationOid, Oid oldOwnerId, Oid newOwnerId)
  {
  	Relation	attRelation;
  	SysScanDesc scan;
  	ScanKeyData key[1];
  	HeapTuple	attributeTuple;
  
  	attRelation = heap_open(AttributeRelationId, RowExclusiveLock);
  	ScanKeyInit(&key[0],
  				Anum_pg_attribute_attrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(relationOid));
  	scan = systable_beginscan(attRelation, AttributeRelidNumIndexId,
  							  true, NULL, 1, key);
  	while (HeapTupleIsValid(attributeTuple = systable_getnext(scan)))
  	{
  		Form_pg_attribute att = (Form_pg_attribute) GETSTRUCT(attributeTuple);
  		Datum		repl_val[Natts_pg_attribute];
  		bool		repl_null[Natts_pg_attribute];
  		bool		repl_repl[Natts_pg_attribute];
  		Acl		   *newAcl;
  		Datum		aclDatum;
  		bool		isNull;
  		HeapTuple	newtuple;
  
  		/* Ignore dropped columns */
  		if (att->attisdropped)
  			continue;
  
  		aclDatum = heap_getattr(attributeTuple,
  								Anum_pg_attribute_attacl,
  								RelationGetDescr(attRelation),
  								&isNull);
  		/* Null ACLs do not require changes */
  		if (isNull)
  			continue;
  
  		memset(repl_null, false, sizeof(repl_null));
  		memset(repl_repl, false, sizeof(repl_repl));
  
  		newAcl = aclnewowner(DatumGetAclP(aclDatum),
  							 oldOwnerId, newOwnerId);
  		repl_repl[Anum_pg_attribute_attacl - 1] = true;
  		repl_val[Anum_pg_attribute_attacl - 1] = PointerGetDatum(newAcl);
  
  		newtuple = heap_modify_tuple(attributeTuple,
  									 RelationGetDescr(attRelation),
  									 repl_val, repl_null, repl_repl);
  
  		CatalogTupleUpdate(attRelation, &newtuple->t_self, newtuple);
  
  		heap_freetuple(newtuple);
  	}
  	systable_endscan(scan);
  	heap_close(attRelation, RowExclusiveLock);
  }
  
  /*
   * change_owner_recurse_to_sequences
   *
   * Helper function for ATExecChangeOwner.  Examines pg_depend searching
   * for sequences that are dependent on serial columns, and changes their
   * ownership.
   */
  static void
  change_owner_recurse_to_sequences(Oid relationOid, Oid newOwnerId, LOCKMODE lockmode)
  {
  	Relation	depRel;
  	SysScanDesc scan;
  	ScanKeyData key[2];
  	HeapTuple	tup;
  
  	/*
  	 * SERIAL sequences are those having an auto dependency on one of the
  	 * table's columns (we don't care *which* column, exactly).
  	 */
  	depRel = heap_open(DependRelationId, AccessShareLock);
  
  	ScanKeyInit(&key[0],
  				Anum_pg_depend_refclassid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationRelationId));
  	ScanKeyInit(&key[1],
  				Anum_pg_depend_refobjid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(relationOid));
  	/* we leave refobjsubid unspecified */
  
  	scan = systable_beginscan(depRel, DependReferenceIndexId, true,
  							  NULL, 2, key);
  
  	while (HeapTupleIsValid(tup = systable_getnext(scan)))
  	{
  		Form_pg_depend depForm = (Form_pg_depend) GETSTRUCT(tup);
  		Relation	seqRel;
  
  		/* skip dependencies other than auto dependencies on columns */
  		if (depForm->refobjsubid == 0 ||
  			depForm->classid != RelationRelationId ||
  			depForm->objsubid != 0 ||
  			!(depForm->deptype == DEPENDENCY_AUTO || depForm->deptype == DEPENDENCY_INTERNAL))
  			continue;
  
  		/* Use relation_open just in case it's an index */
  		seqRel = relation_open(depForm->objid, lockmode);
  
  		/* skip non-sequence relations */
  		if (RelationGetForm(seqRel)->relkind != RELKIND_SEQUENCE)
  		{
  			/* No need to keep the lock */
  			relation_close(seqRel, lockmode);
  			continue;
  		}
  
  		/* We don't need to close the sequence while we alter it. */
  		ATExecChangeOwner(depForm->objid, newOwnerId, true, lockmode);
  
  		/* Now we can close it.  Keep the lock till end of transaction. */
  		relation_close(seqRel, NoLock);
  	}
  
  	systable_endscan(scan);
  
  	relation_close(depRel, AccessShareLock);
  }
  
  /*
   * ALTER TABLE CLUSTER ON
   *
   * The only thing we have to do is to change the indisclustered bits.
   *
   * Return the address of the new clustering index.
   */
  static ObjectAddress
  ATExecClusterOn(Relation rel, const char *indexName, LOCKMODE lockmode)
  {
  	Oid			indexOid;
  	ObjectAddress address;
  
  	indexOid = get_relname_relid(indexName, rel->rd_rel->relnamespace);
  
  	if (!OidIsValid(indexOid))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_OBJECT),
  				 errmsg("index \"%s\" for table \"%s\" does not exist",
  						indexName, RelationGetRelationName(rel))));
  
  	/* Check index is valid to cluster on */
  	check_index_is_clusterable(rel, indexOid, false, lockmode);
  
  	/* And do the work */
  	mark_index_clustered(rel, indexOid, false);
  
  	ObjectAddressSet(address,
  					 RelationRelationId, indexOid);
  
  	return address;
  }
  
  /*
   * ALTER TABLE SET WITHOUT CLUSTER
   *
   * We have to find any indexes on the table that have indisclustered bit
   * set and turn it off.
   */
  static void
  ATExecDropCluster(Relation rel, LOCKMODE lockmode)
  {
  	mark_index_clustered(rel, InvalidOid, false);
  }
  
  /*
   * ALTER TABLE SET TABLESPACE
   */
  static void
  ATPrepSetTableSpace(AlteredTableInfo *tab, Relation rel, const char *tablespacename, LOCKMODE lockmode)
  {
  	Oid			tablespaceId;
  
  	/* Check that the tablespace exists */
  	tablespaceId = get_tablespace_oid(tablespacename, false);
  
  	/* Check permissions except when moving to database's default */
  	if (OidIsValid(tablespaceId) && tablespaceId != MyDatabaseTableSpace)
  	{
  		AclResult	aclresult;
  
  		aclresult = pg_tablespace_aclcheck(tablespaceId, GetUserId(), ACL_CREATE);
  		if (aclresult != ACLCHECK_OK)
  			aclcheck_error(aclresult, OBJECT_TABLESPACE, tablespacename);
  	}
  
  	/* Save info for Phase 3 to do the real work */
  	if (OidIsValid(tab->newTableSpace))
  		ereport(ERROR,
  				(errcode(ERRCODE_SYNTAX_ERROR),
  				 errmsg("cannot have multiple SET TABLESPACE subcommands")));
  
  	tab->newTableSpace = tablespaceId;
  }
  
  /*
   * Set, reset, or replace reloptions.
   */
  static void
  ATExecSetRelOptions(Relation rel, List *defList, AlterTableType operation,
  					LOCKMODE lockmode)
  {
  	Oid			relid;
  	Relation	pgclass;
  	HeapTuple	tuple;
  	HeapTuple	newtuple;
  	Datum		datum;
  	bool		isnull;
  	Datum		newOptions;
  	Datum		repl_val[Natts_pg_class];
  	bool		repl_null[Natts_pg_class];
  	bool		repl_repl[Natts_pg_class];
  	static char *validnsps[] = HEAP_RELOPT_NAMESPACES;
  
  	if (defList == NIL && operation != AT_ReplaceRelOptions)
  		return;					/* nothing to do */
  
  	pgclass = heap_open(RelationRelationId, RowExclusiveLock);
  
  	/* Fetch heap tuple */
  	relid = RelationGetRelid(rel);
  	tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
  	if (!HeapTupleIsValid(tuple))
  		elog(ERROR, "cache lookup failed for relation %u", relid);
  
  	if (operation == AT_ReplaceRelOptions)
  	{
  		/*
  		 * If we're supposed to replace the reloptions list, we just pretend
  		 * there were none before.
  		 */
  		datum = (Datum) 0;
  		isnull = true;
  	}
  	else
  	{
  		/* Get the old reloptions */
  		datum = SysCacheGetAttr(RELOID, tuple, Anum_pg_class_reloptions,
  								&isnull);
  	}
  
  	/* Generate new proposed reloptions (text array) */
  	newOptions = transformRelOptions(isnull ? (Datum) 0 : datum,
  									 defList, NULL, validnsps, false,
  									 operation == AT_ResetRelOptions);
  
  	/* Validate */
  	switch (rel->rd_rel->relkind)
  	{
  		case RELKIND_RELATION:
  		case RELKIND_TOASTVALUE:
  		case RELKIND_MATVIEW:
  		case RELKIND_PARTITIONED_TABLE:
  			(void) heap_reloptions(rel->rd_rel->relkind, newOptions, true);
  			break;
  		case RELKIND_VIEW:
  			(void) view_reloptions(newOptions, true);
  			break;
  		case RELKIND_INDEX:
  		case RELKIND_PARTITIONED_INDEX:
  			(void) index_reloptions(rel->rd_amroutine->amoptions, newOptions, true);
  			break;
  		default:
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("\"%s\" is not a table, view, materialized view, index, or TOAST table",
  							RelationGetRelationName(rel))));
  			break;
  	}
  
  	/* Special-case validation of view options */
  	if (rel->rd_rel->relkind == RELKIND_VIEW)
  	{
  		Query	   *view_query = get_view_query(rel);
  		List	   *view_options = untransformRelOptions(newOptions);
  		ListCell   *cell;
  		bool		check_option = false;
  
  		foreach(cell, view_options)
  		{
  			DefElem    *defel = (DefElem *) lfirst(cell);
  
  			if (strcmp(defel->defname, "check_option") == 0)
  				check_option = true;
  		}
  
  		/*
  		 * If the check option is specified, look to see if the view is
  		 * actually auto-updatable or not.
  		 */
  		if (check_option)
  		{
  			const char *view_updatable_error =
  			view_query_is_auto_updatable(view_query, true);
  
  			if (view_updatable_error)
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("WITH CHECK OPTION is supported only on automatically updatable views"),
  						 errhint("%s", _(view_updatable_error))));
  		}
  	}
  
  	/*
  	 * All we need do here is update the pg_class row; the new options will be
  	 * propagated into relcaches during post-commit cache inval.
  	 */
  	memset(repl_val, 0, sizeof(repl_val));
  	memset(repl_null, false, sizeof(repl_null));
  	memset(repl_repl, false, sizeof(repl_repl));
  
  	if (newOptions != (Datum) 0)
  		repl_val[Anum_pg_class_reloptions - 1] = newOptions;
  	else
  		repl_null[Anum_pg_class_reloptions - 1] = true;
  
  	repl_repl[Anum_pg_class_reloptions - 1] = true;
  
  	newtuple = heap_modify_tuple(tuple, RelationGetDescr(pgclass),
  								 repl_val, repl_null, repl_repl);
  
  	CatalogTupleUpdate(pgclass, &newtuple->t_self, newtuple);
  
  	InvokeObjectPostAlterHook(RelationRelationId, RelationGetRelid(rel), 0);
  
  	heap_freetuple(newtuple);
  
  	ReleaseSysCache(tuple);
  
  	/* repeat the whole exercise for the toast table, if there's one */
  	if (OidIsValid(rel->rd_rel->reltoastrelid))
  	{
  		Relation	toastrel;
  		Oid			toastid = rel->rd_rel->reltoastrelid;
  
  		toastrel = heap_open(toastid, lockmode);
  
  		/* Fetch heap tuple */
  		tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(toastid));
  		if (!HeapTupleIsValid(tuple))
  			elog(ERROR, "cache lookup failed for relation %u", toastid);
  
  		if (operation == AT_ReplaceRelOptions)
  		{
  			/*
  			 * If we're supposed to replace the reloptions list, we just
  			 * pretend there were none before.
  			 */
  			datum = (Datum) 0;
  			isnull = true;
  		}
  		else
  		{
  			/* Get the old reloptions */
  			datum = SysCacheGetAttr(RELOID, tuple, Anum_pg_class_reloptions,
  									&isnull);
  		}
  
  		newOptions = transformRelOptions(isnull ? (Datum) 0 : datum,
  										 defList, "toast", validnsps, false,
  										 operation == AT_ResetRelOptions);
  
  		(void) heap_reloptions(RELKIND_TOASTVALUE, newOptions, true);
  
  		memset(repl_val, 0, sizeof(repl_val));
  		memset(repl_null, false, sizeof(repl_null));
  		memset(repl_repl, false, sizeof(repl_repl));
  
  		if (newOptions != (Datum) 0)
  			repl_val[Anum_pg_class_reloptions - 1] = newOptions;
  		else
  			repl_null[Anum_pg_class_reloptions - 1] = true;
  
  		repl_repl[Anum_pg_class_reloptions - 1] = true;
  
  		newtuple = heap_modify_tuple(tuple, RelationGetDescr(pgclass),
  									 repl_val, repl_null, repl_repl);
  
  		CatalogTupleUpdate(pgclass, &newtuple->t_self, newtuple);
  
  		InvokeObjectPostAlterHookArg(RelationRelationId,
  									 RelationGetRelid(toastrel), 0,
  									 InvalidOid, true);
  
  		heap_freetuple(newtuple);
  
  		ReleaseSysCache(tuple);
  
  		heap_close(toastrel, NoLock);
  	}
  
  	heap_close(pgclass, RowExclusiveLock);
  }
  
  /*
   * Execute ALTER TABLE SET TABLESPACE for cases where there is no tuple
   * rewriting to be done, so we just want to copy the data as fast as possible.
   */
  static void
  ATExecSetTableSpace(Oid tableOid, Oid newTableSpace, LOCKMODE lockmode)
  {
  	Relation	rel;
  	Oid			oldTableSpace;
  	Oid			reltoastrelid;
  	Oid			newrelfilenode;
  	RelFileNode newrnode;
  	SMgrRelation dstrel;
  	Relation	pg_class;
  	HeapTuple	tuple;
  	Form_pg_class rd_rel;
  	ForkNumber	forkNum;
  	List	   *reltoastidxids = NIL;
  	ListCell   *lc;
  
  	/*
  	 * Need lock here in case we are recursing to toast table or index
  	 */
  	rel = relation_open(tableOid, lockmode);
  
  	/*
  	 * No work if no change in tablespace.
  	 */
  	oldTableSpace = rel->rd_rel->reltablespace;
  	if (newTableSpace == oldTableSpace ||
  		(newTableSpace == MyDatabaseTableSpace && oldTableSpace == 0))
  	{
  		InvokeObjectPostAlterHook(RelationRelationId,
  								  RelationGetRelid(rel), 0);
  
  		relation_close(rel, NoLock);
  		return;
  	}
  
  	/*
  	 * We cannot support moving mapped relations into different tablespaces.
  	 * (In particular this eliminates all shared catalogs.)
  	 */
  	if (RelationIsMapped(rel))
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot move system relation \"%s\"",
  						RelationGetRelationName(rel))));
  
  	/* Can't move a non-shared relation into pg_global */
  	if (newTableSpace == GLOBALTABLESPACE_OID)
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  				 errmsg("only shared relations can be placed in pg_global tablespace")));
  
  	/*
  	 * Don't allow moving temp tables of other backends ... their local buffer
  	 * manager is not going to cope.
  	 */
  	if (RELATION_IS_OTHER_TEMP(rel))
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot move temporary tables of other sessions")));
  
  	reltoastrelid = rel->rd_rel->reltoastrelid;
  	/* Fetch the list of indexes on toast relation if necessary */
  	if (OidIsValid(reltoastrelid))
  	{
  		Relation	toastRel = relation_open(reltoastrelid, lockmode);
  
  		reltoastidxids = RelationGetIndexList(toastRel);
  		relation_close(toastRel, lockmode);
  	}
  
  	/* Get a modifiable copy of the relation's pg_class row */
  	pg_class = heap_open(RelationRelationId, RowExclusiveLock);
  
  	tuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(tableOid));
  	if (!HeapTupleIsValid(tuple))
  		elog(ERROR, "cache lookup failed for relation %u", tableOid);
  	rd_rel = (Form_pg_class) GETSTRUCT(tuple);
  
  	/*
  	 * Since we copy the file directly without looking at the shared buffers,
  	 * we'd better first flush out any pages of the source relation that are
  	 * in shared buffers.  We assume no new changes will be made while we are
  	 * holding exclusive lock on the rel.
  	 */
  	FlushRelationBuffers(rel);
  
  	/*
  	 * Relfilenodes are not unique in databases across tablespaces, so we need
  	 * to allocate a new one in the new tablespace.
  	 */
  	newrelfilenode = GetNewRelFileNode(newTableSpace, NULL,
  									   rel->rd_rel->relpersistence);
  
  	/* Open old and new relation */
  	newrnode = rel->rd_node;
  	newrnode.relNode = newrelfilenode;
  	newrnode.spcNode = newTableSpace;
  	dstrel = smgropen(newrnode, rel->rd_backend);
  
  	RelationOpenSmgr(rel);
  
  	/*
  	 * Create and copy all forks of the relation, and schedule unlinking of
  	 * old physical files.
  	 *
  	 * NOTE: any conflict in relfilenode value will be caught in
  	 * RelationCreateStorage().
  	 */
  	RelationCreateStorage(newrnode, rel->rd_rel->relpersistence);
  
  	/* copy main fork */
  	copy_relation_data(rel->rd_smgr, dstrel, MAIN_FORKNUM,
  					   rel->rd_rel->relpersistence);
  
  	/* copy those extra forks that exist */
  	for (forkNum = MAIN_FORKNUM + 1; forkNum <= MAX_FORKNUM; forkNum++)
  	{
  		if (smgrexists(rel->rd_smgr, forkNum))
  		{
  			smgrcreate(dstrel, forkNum, false);
  
  			/*
  			 * WAL log creation if the relation is persistent, or this is the
  			 * init fork of an unlogged relation.
  			 */
  			if (rel->rd_rel->relpersistence == RELPERSISTENCE_PERMANENT ||
  				(rel->rd_rel->relpersistence == RELPERSISTENCE_UNLOGGED &&
  				 forkNum == INIT_FORKNUM))
  				log_smgrcreate(&newrnode, forkNum);
  			copy_relation_data(rel->rd_smgr, dstrel, forkNum,
  							   rel->rd_rel->relpersistence);
  		}
  	}
  
  	/* drop old relation, and close new one */
  	RelationDropStorage(rel);
  	smgrclose(dstrel);
  
  	/* update the pg_class row */
  	rd_rel->reltablespace = (newTableSpace == MyDatabaseTableSpace) ? InvalidOid : newTableSpace;
  	rd_rel->relfilenode = newrelfilenode;
  	CatalogTupleUpdate(pg_class, &tuple->t_self, tuple);
  
  	InvokeObjectPostAlterHook(RelationRelationId, RelationGetRelid(rel), 0);
  
  	heap_freetuple(tuple);
  
  	heap_close(pg_class, RowExclusiveLock);
  
  	relation_close(rel, NoLock);
  
  	/* Make sure the reltablespace change is visible */
  	CommandCounterIncrement();
  
  	/* Move associated toast relation and/or indexes, too */
  	if (OidIsValid(reltoastrelid))
  		ATExecSetTableSpace(reltoastrelid, newTableSpace, lockmode);
  	foreach(lc, reltoastidxids)
  		ATExecSetTableSpace(lfirst_oid(lc), newTableSpace, lockmode);
  
  	/* Clean up */
  	list_free(reltoastidxids);
  }
  
  /*
   * Special handling of ALTER TABLE SET TABLESPACE for partitioned indexes,
   * which have no storage (so not handled in Phase 3 like other relation types)
   */
  static void
  ATExecPartedIdxSetTableSpace(Relation rel, Oid newTableSpace)
  {
  	HeapTuple	tuple;
  	Oid			oldTableSpace;
  	Relation	pg_class;
  	Form_pg_class rd_rel;
  	Oid			indexOid = RelationGetRelid(rel);
  
  	Assert(rel->rd_rel->relkind == RELKIND_PARTITIONED_INDEX);
  
  	/* Can't allow a non-shared relation in pg_global */
  	if (newTableSpace == GLOBALTABLESPACE_OID)
  		ereport(ERROR,
  		(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  			errmsg("only shared relations can be placed in pg_global tablespace")));
  
  	/*
  	 * No work if no change in tablespace.
  	 */
  	oldTableSpace = rel->rd_rel->reltablespace;
  	if (newTableSpace == oldTableSpace ||
  		(newTableSpace == MyDatabaseTableSpace && oldTableSpace == 0))
  	{
  		InvokeObjectPostAlterHook(RelationRelationId,
  								  indexOid, 0);
  		return;
  	}
  
  	/* Get a modifiable copy of the relation's pg_class row */
  	pg_class = heap_open(RelationRelationId, RowExclusiveLock);
  
  	tuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(indexOid));
  	if (!HeapTupleIsValid(tuple))
  		elog(ERROR, "cache lookup failed for relation %u", indexOid);
  	rd_rel = (Form_pg_class) GETSTRUCT(tuple);
  
  	/* update the pg_class row */
  	rd_rel->reltablespace = (newTableSpace == MyDatabaseTableSpace) ? InvalidOid : newTableSpace;
  	CatalogTupleUpdate(pg_class, &tuple->t_self, tuple);
  
  	InvokeObjectPostAlterHook(RelationRelationId, indexOid, 0);
  
  	heap_freetuple(tuple);
  
  	heap_close(pg_class, RowExclusiveLock);
  
  	/* Make sure the reltablespace change is visible */
  	CommandCounterIncrement();
  }
  
  /*
   * Alter Table ALL ... SET TABLESPACE
   *
   * Allows a user to move all objects of some type in a given tablespace in the
   * current database to another tablespace.  Objects can be chosen based on the
   * owner of the object also, to allow users to move only their objects.
   * The user must have CREATE rights on the new tablespace, as usual.   The main
   * permissions handling is done by the lower-level table move function.
   *
   * All to-be-moved objects are locked first. If NOWAIT is specified and the
   * lock can't be acquired then we ereport(ERROR).
   */
  Oid
  AlterTableMoveAll(AlterTableMoveAllStmt *stmt)
  {
  	List	   *relations = NIL;
  	ListCell   *l;
  	ScanKeyData key[1];
  	Relation	rel;
  	HeapScanDesc scan;
  	HeapTuple	tuple;
  	Oid			orig_tablespaceoid;
  	Oid			new_tablespaceoid;
  	List	   *role_oids = roleSpecsToIds(stmt->roles);
  
  	/* Ensure we were not asked to move something we can't */
  	if (stmt->objtype != OBJECT_TABLE && stmt->objtype != OBJECT_INDEX &&
  		stmt->objtype != OBJECT_MATVIEW)
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  				 errmsg("only tables, indexes, and materialized views exist in tablespaces")));
  
  	/* Get the orig and new tablespace OIDs */
  	orig_tablespaceoid = get_tablespace_oid(stmt->orig_tablespacename, false);
  	new_tablespaceoid = get_tablespace_oid(stmt->new_tablespacename, false);
  
  	/* Can't move shared relations in to or out of pg_global */
  	/* This is also checked by ATExecSetTableSpace, but nice to stop earlier */
  	if (orig_tablespaceoid == GLOBALTABLESPACE_OID ||
  		new_tablespaceoid == GLOBALTABLESPACE_OID)
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  				 errmsg("cannot move relations in to or out of pg_global tablespace")));
  
  	/*
  	 * Must have CREATE rights on the new tablespace, unless it is the
  	 * database default tablespace (which all users implicitly have CREATE
  	 * rights on).
  	 */
  	if (OidIsValid(new_tablespaceoid) && new_tablespaceoid != MyDatabaseTableSpace)
  	{
  		AclResult	aclresult;
  
  		aclresult = pg_tablespace_aclcheck(new_tablespaceoid, GetUserId(),
  										   ACL_CREATE);
  		if (aclresult != ACLCHECK_OK)
  			aclcheck_error(aclresult, OBJECT_TABLESPACE,
  						   get_tablespace_name(new_tablespaceoid));
  	}
  
  	/*
  	 * Now that the checks are done, check if we should set either to
  	 * InvalidOid because it is our database's default tablespace.
  	 */
  	if (orig_tablespaceoid == MyDatabaseTableSpace)
  		orig_tablespaceoid = InvalidOid;
  
  	if (new_tablespaceoid == MyDatabaseTableSpace)
  		new_tablespaceoid = InvalidOid;
  
  	/* no-op */
  	if (orig_tablespaceoid == new_tablespaceoid)
  		return new_tablespaceoid;
  
  	/*
  	 * Walk the list of objects in the tablespace and move them. This will
  	 * only find objects in our database, of course.
  	 */
  	ScanKeyInit(&key[0],
  				Anum_pg_class_reltablespace,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(orig_tablespaceoid));
  
  	rel = heap_open(RelationRelationId, AccessShareLock);
  	scan = heap_beginscan_catalog(rel, 1, key);
  	while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
  	{
  		Oid			relOid = HeapTupleGetOid(tuple);
  		Form_pg_class relForm;
  
  		relForm = (Form_pg_class) GETSTRUCT(tuple);
  
  		/*
  		 * Do not move objects in pg_catalog as part of this, if an admin
  		 * really wishes to do so, they can issue the individual ALTER
  		 * commands directly.
  		 *
  		 * Also, explicitly avoid any shared tables, temp tables, or TOAST
  		 * (TOAST will be moved with the main table).
  		 */
  		if (IsSystemNamespace(relForm->relnamespace) || relForm->relisshared ||
  			isAnyTempNamespace(relForm->relnamespace) ||
  			relForm->relnamespace == PG_TOAST_NAMESPACE)
  			continue;
  
  		/* Only move the object type requested */
  		if ((stmt->objtype == OBJECT_TABLE &&
  			 relForm->relkind != RELKIND_RELATION &&
  			 relForm->relkind != RELKIND_PARTITIONED_TABLE) ||
  			(stmt->objtype == OBJECT_INDEX &&
  			 relForm->relkind != RELKIND_INDEX &&
  			 relForm->relkind != RELKIND_PARTITIONED_INDEX) ||
  			(stmt->objtype == OBJECT_MATVIEW &&
  			 relForm->relkind != RELKIND_MATVIEW))
  			continue;
  
  		/* Check if we are only moving objects owned by certain roles */
  		if (role_oids != NIL && !list_member_oid(role_oids, relForm->relowner))
  			continue;
  
  		/*
  		 * Handle permissions-checking here since we are locking the tables
  		 * and also to avoid doing a bunch of work only to fail part-way. Note
  		 * that permissions will also be checked by AlterTableInternal().
  		 *
  		 * Caller must be considered an owner on the table to move it.
  		 */
  		if (!pg_class_ownercheck(relOid, GetUserId()))
  			aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(get_rel_relkind(relOid)),
  						   NameStr(relForm->relname));
  
  		if (stmt->nowait &&
  			!ConditionalLockRelationOid(relOid, AccessExclusiveLock))
  			ereport(ERROR,
  					(errcode(ERRCODE_OBJECT_IN_USE),
  					 errmsg("aborting because lock on relation \"%s.%s\" is not available",
  							get_namespace_name(relForm->relnamespace),
  							NameStr(relForm->relname))));
  		else
  			LockRelationOid(relOid, AccessExclusiveLock);
  
  		/* Add to our list of objects to move */
  		relations = lappend_oid(relations, relOid);
  	}
  
  	heap_endscan(scan);
  	heap_close(rel, AccessShareLock);
  
  	if (relations == NIL)
  		ereport(NOTICE,
  				(errcode(ERRCODE_NO_DATA_FOUND),
  				 errmsg("no matching relations in tablespace \"%s\" found",
  						orig_tablespaceoid == InvalidOid ? "(database default)" :
  						get_tablespace_name(orig_tablespaceoid))));
  
  	/* Everything is locked, loop through and move all of the relations. */
  	foreach(l, relations)
  	{
  		List	   *cmds = NIL;
  		AlterTableCmd *cmd = makeNode(AlterTableCmd);
  
  		cmd->subtype = AT_SetTableSpace;
  		cmd->name = stmt->new_tablespacename;
  
  		cmds = lappend(cmds, cmd);
  
  		EventTriggerAlterTableStart((Node *) stmt);
  		/* OID is set by AlterTableInternal */
  		AlterTableInternal(lfirst_oid(l), cmds, false);
  		EventTriggerAlterTableEnd();
  	}
  
  	return new_tablespaceoid;
  }
  
  /*
   * Copy data, block by block
   */
  static void
  copy_relation_data(SMgrRelation src, SMgrRelation dst,
  				   ForkNumber forkNum, char relpersistence)
  {
  	PGAlignedBlock buf;
  	Page		page;
  	bool		use_wal;
  	bool		copying_initfork;
  	BlockNumber nblocks;
  	BlockNumber blkno;
  
  	page = (Page) buf.data;
  
  	/*
  	 * The init fork for an unlogged relation in many respects has to be
  	 * treated the same as normal relation, changes need to be WAL logged and
  	 * it needs to be synced to disk.
  	 */
  	copying_initfork = relpersistence == RELPERSISTENCE_UNLOGGED &&
  		forkNum == INIT_FORKNUM;
  
  	/*
  	 * We need to log the copied data in WAL iff WAL archiving/streaming is
  	 * enabled AND it's a permanent relation.
  	 */
  	use_wal = XLogIsNeeded() &&
  		(relpersistence == RELPERSISTENCE_PERMANENT || copying_initfork);
  
  	nblocks = smgrnblocks(src, forkNum);
  
  	for (blkno = 0; blkno < nblocks; blkno++)
  	{
  		/* If we got a cancel signal during the copy of the data, quit */
  		CHECK_FOR_INTERRUPTS();
  
  		smgrread(src, forkNum, blkno, buf.data);
  
  		if (!PageIsVerified(page, blkno))
  			ereport(ERROR,
  					(errcode(ERRCODE_DATA_CORRUPTED),
  					 errmsg("invalid page in block %u of relation %s",
  							blkno,
  							relpathbackend(src->smgr_rnode.node,
  										   src->smgr_rnode.backend,
  										   forkNum))));
  
  		/*
  		 * WAL-log the copied page. Unfortunately we don't know what kind of a
  		 * page this is, so we have to log the full page including any unused
  		 * space.
  		 */
  		if (use_wal)
  			log_newpage(&dst->smgr_rnode.node, forkNum, blkno, page, false);
  
  		PageSetChecksumInplace(page, blkno);
  
  		/*
  		 * Now write the page.  We say isTemp = true even if it's not a temp
  		 * rel, because there's no need for smgr to schedule an fsync for this
  		 * write; we'll do it ourselves below.
  		 */
  		smgrextend(dst, forkNum, blkno, buf.data, true);
  	}
  
  	/*
  	 * If the rel is WAL-logged, must fsync before commit.  We use heap_sync
  	 * to ensure that the toast table gets fsync'd too.  (For a temp or
  	 * unlogged rel we don't care since the data will be gone after a crash
  	 * anyway.)
  	 *
  	 * It's obvious that we must do this when not WAL-logging the copy. It's
  	 * less obvious that we have to do it even if we did WAL-log the copied
  	 * pages. The reason is that since we're copying outside shared buffers, a
  	 * CHECKPOINT occurring during the copy has no way to flush the previously
  	 * written data to disk (indeed it won't know the new rel even exists).  A
  	 * crash later on would replay WAL from the checkpoint, therefore it
  	 * wouldn't replay our earlier WAL entries. If we do not fsync those pages
  	 * here, they might still not be on disk when the crash occurs.
  	 */
  	if (relpersistence == RELPERSISTENCE_PERMANENT || copying_initfork)
  		smgrimmedsync(dst, forkNum);
  }
  
  /*
   * ALTER TABLE ENABLE/DISABLE TRIGGER
   *
   * We just pass this off to trigger.c.
   */
  static void
  ATExecEnableDisableTrigger(Relation rel, const char *trigname,
  						   char fires_when, bool skip_system, LOCKMODE lockmode)
  {
  	EnableDisableTrigger(rel, trigname, fires_when, skip_system, lockmode);
  }
  
  /*
   * ALTER TABLE ENABLE/DISABLE RULE
   *
   * We just pass this off to rewriteDefine.c.
   */
  static void
  ATExecEnableDisableRule(Relation rel, const char *rulename,
  						char fires_when, LOCKMODE lockmode)
  {
  	EnableDisableRule(rel, rulename, fires_when);
  }
  
  /*
   * ALTER TABLE INHERIT
   *
   * Add a parent to the child's parents. This verifies that all the columns and
   * check constraints of the parent appear in the child and that they have the
   * same data types and expressions.
   */
  static void
  ATPrepAddInherit(Relation child_rel)
  {
  	if (child_rel->rd_rel->reloftype)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot change inheritance of typed table")));
  
  	if (child_rel->rd_rel->relispartition)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot change inheritance of a partition")));
  
  	if (child_rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot change inheritance of partitioned table")));
  }
  
  /*
   * Return the address of the new parent relation.
   */
  static ObjectAddress
  ATExecAddInherit(Relation child_rel, RangeVar *parent, LOCKMODE lockmode)
  {
  	Relation	parent_rel;
  	List	   *children;
  	ObjectAddress address;
  	const char *trigger_name;
  
  	/*
  	 * A self-exclusive lock is needed here.  See the similar case in
  	 * MergeAttributes() for a full explanation.
  	 */
  	parent_rel = heap_openrv(parent, ShareUpdateExclusiveLock);
  
  	/*
  	 * Must be owner of both parent and child -- child was checked by
  	 * ATSimplePermissions call in ATPrepCmd
  	 */
  	ATSimplePermissions(parent_rel, ATT_TABLE | ATT_FOREIGN_TABLE);
  
  	/* Permanent rels cannot inherit from temporary ones */
  	if (parent_rel->rd_rel->relpersistence == RELPERSISTENCE_TEMP &&
  		child_rel->rd_rel->relpersistence != RELPERSISTENCE_TEMP)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot inherit from temporary relation \"%s\"",
  						RelationGetRelationName(parent_rel))));
  
  	/* If parent rel is temp, it must belong to this session */
  	if (parent_rel->rd_rel->relpersistence == RELPERSISTENCE_TEMP &&
  		!parent_rel->rd_islocaltemp)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot inherit from temporary relation of another session")));
  
  	/* Ditto for the child */
  	if (child_rel->rd_rel->relpersistence == RELPERSISTENCE_TEMP &&
  		!child_rel->rd_islocaltemp)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot inherit to temporary relation of another session")));
  
  	/* Prevent partitioned tables from becoming inheritance parents */
  	if (parent_rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot inherit from partitioned table \"%s\"",
  						parent->relname)));
  
  	/* Likewise for partitions */
  	if (parent_rel->rd_rel->relispartition)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot inherit from a partition")));
  
  	/*
  	 * Prevent circularity by seeing if proposed parent inherits from child.
  	 * (In particular, this disallows making a rel inherit from itself.)
  	 *
  	 * This is not completely bulletproof because of race conditions: in
  	 * multi-level inheritance trees, someone else could concurrently be
  	 * making another inheritance link that closes the loop but does not join
  	 * either of the rels we have locked.  Preventing that seems to require
  	 * exclusive locks on the entire inheritance tree, which is a cure worse
  	 * than the disease.  find_all_inheritors() will cope with circularity
  	 * anyway, so don't sweat it too much.
  	 *
  	 * We use weakest lock we can on child's children, namely AccessShareLock.
  	 */
  	children = find_all_inheritors(RelationGetRelid(child_rel),
  								   AccessShareLock, NULL);
  
  	if (list_member_oid(children, RelationGetRelid(parent_rel)))
  		ereport(ERROR,
  				(errcode(ERRCODE_DUPLICATE_TABLE),
  				 errmsg("circular inheritance not allowed"),
  				 errdetail("\"%s\" is already a child of \"%s\".",
  						   parent->relname,
  						   RelationGetRelationName(child_rel))));
  
  	/* If parent has OIDs then child must have OIDs */
  	if (parent_rel->rd_rel->relhasoids && !child_rel->rd_rel->relhasoids)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("table \"%s\" without OIDs cannot inherit from table \"%s\" with OIDs",
  						RelationGetRelationName(child_rel),
  						RelationGetRelationName(parent_rel))));
  
  	/*
  	 * If child_rel has row-level triggers with transition tables, we
  	 * currently don't allow it to become an inheritance child.  See also
  	 * prohibitions in ATExecAttachPartition() and CreateTrigger().
  	 */
  	trigger_name = FindTriggerIncompatibleWithInheritance(child_rel->trigdesc);
  	if (trigger_name != NULL)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("trigger \"%s\" prevents table \"%s\" from becoming an inheritance child",
  						trigger_name, RelationGetRelationName(child_rel)),
  				 errdetail("ROW triggers with transition tables are not supported in inheritance hierarchies")));
  
  	/* OK to create inheritance */
  	CreateInheritance(child_rel, parent_rel);
  
  	ObjectAddressSet(address, RelationRelationId,
  					 RelationGetRelid(parent_rel));
  
  	/* keep our lock on the parent relation until commit */
  	heap_close(parent_rel, NoLock);
  
  	return address;
  }
  
  /*
   * CreateInheritance
   *		Catalog manipulation portion of creating inheritance between a child
   *		table and a parent table.
   *
   * Common to ATExecAddInherit() and ATExecAttachPartition().
   */
  static void
  CreateInheritance(Relation child_rel, Relation parent_rel)
  {
  	Relation	catalogRelation;
  	SysScanDesc scan;
  	ScanKeyData key;
  	HeapTuple	inheritsTuple;
  	int32		inhseqno;
  
  	/* Note: get RowExclusiveLock because we will write pg_inherits below. */
  	catalogRelation = heap_open(InheritsRelationId, RowExclusiveLock);
  
  	/*
  	 * Check for duplicates in the list of parents, and determine the highest
  	 * inhseqno already present; we'll use the next one for the new parent.
  	 * Also, if proposed child is a partition, it cannot already be
  	 * inheriting.
  	 *
  	 * Note: we do not reject the case where the child already inherits from
  	 * the parent indirectly; CREATE TABLE doesn't reject comparable cases.
  	 */
  	ScanKeyInit(&key,
  				Anum_pg_inherits_inhrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(child_rel)));
  	scan = systable_beginscan(catalogRelation, InheritsRelidSeqnoIndexId,
  							  true, NULL, 1, &key);
  
  	/* inhseqno sequences start at 1 */
  	inhseqno = 0;
  	while (HeapTupleIsValid(inheritsTuple = systable_getnext(scan)))
  	{
  		Form_pg_inherits inh = (Form_pg_inherits) GETSTRUCT(inheritsTuple);
  
  		if (inh->inhparent == RelationGetRelid(parent_rel))
  			ereport(ERROR,
  					(errcode(ERRCODE_DUPLICATE_TABLE),
  					 errmsg("relation \"%s\" would be inherited from more than once",
  							RelationGetRelationName(parent_rel))));
  
  		if (inh->inhseqno > inhseqno)
  			inhseqno = inh->inhseqno;
  	}
  	systable_endscan(scan);
  
  	/* Match up the columns and bump attinhcount as needed */
  	MergeAttributesIntoExisting(child_rel, parent_rel);
  
  	/* Match up the constraints and bump coninhcount as needed */
  	MergeConstraintsIntoExisting(child_rel, parent_rel);
  
  	/*
  	 * OK, it looks valid.  Make the catalog entries that show inheritance.
  	 */
  	StoreCatalogInheritance1(RelationGetRelid(child_rel),
  							 RelationGetRelid(parent_rel),
  							 inhseqno + 1,
  							 catalogRelation,
  							 parent_rel->rd_rel->relkind ==
  							 RELKIND_PARTITIONED_TABLE);
  
  	/* Now we're done with pg_inherits */
  	heap_close(catalogRelation, RowExclusiveLock);
  }
  
  /*
   * Obtain the source-text form of the constraint expression for a check
   * constraint, given its pg_constraint tuple
   */
  static char *
  decompile_conbin(HeapTuple contup, TupleDesc tupdesc)
  {
  	Form_pg_constraint con;
  	bool		isnull;
  	Datum		attr;
  	Datum		expr;
  
  	con = (Form_pg_constraint) GETSTRUCT(contup);
  	attr = heap_getattr(contup, Anum_pg_constraint_conbin, tupdesc, &isnull);
  	if (isnull)
  		elog(ERROR, "null conbin for constraint %u", HeapTupleGetOid(contup));
  
  	expr = DirectFunctionCall2(pg_get_expr, attr,
  							   ObjectIdGetDatum(con->conrelid));
  	return TextDatumGetCString(expr);
  }
  
  /*
   * Determine whether two check constraints are functionally equivalent
   *
   * The test we apply is to see whether they reverse-compile to the same
   * source string.  This insulates us from issues like whether attributes
   * have the same physical column numbers in parent and child relations.
   */
  static bool
  constraints_equivalent(HeapTuple a, HeapTuple b, TupleDesc tupleDesc)
  {
  	Form_pg_constraint acon = (Form_pg_constraint) GETSTRUCT(a);
  	Form_pg_constraint bcon = (Form_pg_constraint) GETSTRUCT(b);
  
  	if (acon->condeferrable != bcon->condeferrable ||
  		acon->condeferred != bcon->condeferred ||
  		strcmp(decompile_conbin(a, tupleDesc),
  			   decompile_conbin(b, tupleDesc)) != 0)
  		return false;
  	else
  		return true;
  }
  
  /*
   * Check columns in child table match up with columns in parent, and increment
   * their attinhcount.
   *
   * Called by CreateInheritance
   *
   * Currently all parent columns must be found in child. Missing columns are an
   * error.  One day we might consider creating new columns like CREATE TABLE
   * does.  However, that is widely unpopular --- in the common use case of
   * partitioned tables it's a foot-gun.
   *
   * The data type must match exactly. If the parent column is NOT NULL then
   * the child must be as well. Defaults are not compared, however.
   */
  static void
  MergeAttributesIntoExisting(Relation child_rel, Relation parent_rel)
  {
  	Relation	attrrel;
  	AttrNumber	parent_attno;
  	int			parent_natts;
  	TupleDesc	tupleDesc;
  	HeapTuple	tuple;
  	bool		child_is_partition = false;
  
  	attrrel = heap_open(AttributeRelationId, RowExclusiveLock);
  
  	tupleDesc = RelationGetDescr(parent_rel);
  	parent_natts = tupleDesc->natts;
  
  	/* If parent_rel is a partitioned table, child_rel must be a partition */
  	if (parent_rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  		child_is_partition = true;
  
  	for (parent_attno = 1; parent_attno <= parent_natts; parent_attno++)
  	{
  		Form_pg_attribute attribute = TupleDescAttr(tupleDesc,
  													parent_attno - 1);
  		char	   *attributeName = NameStr(attribute->attname);
  
  		/* Ignore dropped columns in the parent. */
  		if (attribute->attisdropped)
  			continue;
  
  		/* Find same column in child (matching on column name). */
  		tuple = SearchSysCacheCopyAttName(RelationGetRelid(child_rel),
  										  attributeName);
  		if (HeapTupleIsValid(tuple))
  		{
  			/* Check they are same type, typmod, and collation */
  			Form_pg_attribute childatt = (Form_pg_attribute) GETSTRUCT(tuple);
  
  			if (attribute->atttypid != childatt->atttypid ||
  				attribute->atttypmod != childatt->atttypmod)
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("child table \"%s\" has different type for column \"%s\"",
  								RelationGetRelationName(child_rel),
  								attributeName)));
  
  			if (attribute->attcollation != childatt->attcollation)
  				ereport(ERROR,
  						(errcode(ERRCODE_COLLATION_MISMATCH),
  						 errmsg("child table \"%s\" has different collation for column \"%s\"",
  								RelationGetRelationName(child_rel),
  								attributeName)));
  
  			/*
  			 * Check child doesn't discard NOT NULL property.  (Other
  			 * constraints are checked elsewhere.)
  			 */
  			if (attribute->attnotnull && !childatt->attnotnull)
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("column \"%s\" in child table must be marked NOT NULL",
  								attributeName)));
  
  			/*
  			 * OK, bump the child column's inheritance count.  (If we fail
  			 * later on, this change will just roll back.)
  			 */
  			childatt->attinhcount++;
  
  			/*
  			 * In case of partitions, we must enforce that value of attislocal
  			 * is same in all partitions. (Note: there are only inherited
  			 * attributes in partitions)
  			 */
  			if (child_is_partition)
  			{
  				Assert(childatt->attinhcount == 1);
  				childatt->attislocal = false;
  			}
  
  			CatalogTupleUpdate(attrrel, &tuple->t_self, tuple);
  			heap_freetuple(tuple);
  		}
  		else
  		{
  			ereport(ERROR,
  					(errcode(ERRCODE_DATATYPE_MISMATCH),
  					 errmsg("child table is missing column \"%s\"",
  							attributeName)));
  		}
  	}
  
  	/*
  	 * If the parent has an OID column, so must the child, and we'd better
  	 * update the child's attinhcount and attislocal the same as for normal
  	 * columns.  We needn't check data type or not-nullness though.
  	 */
  	if (tupleDesc->tdhasoid)
  	{
  		/*
  		 * Here we match by column number not name; the match *must* be the
  		 * system column, not some random column named "oid".
  		 */
  		tuple = SearchSysCacheCopy2(ATTNUM,
  									ObjectIdGetDatum(RelationGetRelid(child_rel)),
  									Int16GetDatum(ObjectIdAttributeNumber));
  		if (HeapTupleIsValid(tuple))
  		{
  			Form_pg_attribute childatt = (Form_pg_attribute) GETSTRUCT(tuple);
  
  			/* See comments above; these changes should be the same */
  			childatt->attinhcount++;
  
  			if (child_is_partition)
  			{
  				Assert(childatt->attinhcount == 1);
  				childatt->attislocal = false;
  			}
  
  			CatalogTupleUpdate(attrrel, &tuple->t_self, tuple);
  			heap_freetuple(tuple);
  		}
  		else
  		{
  			ereport(ERROR,
  					(errcode(ERRCODE_DATATYPE_MISMATCH),
  					 errmsg("child table is missing column \"%s\"",
  							"oid")));
  		}
  	}
  
  	heap_close(attrrel, RowExclusiveLock);
  }
  
  /*
   * Check constraints in child table match up with constraints in parent,
   * and increment their coninhcount.
   *
   * Constraints that are marked ONLY in the parent are ignored.
   *
   * Called by CreateInheritance
   *
   * Currently all constraints in parent must be present in the child. One day we
   * may consider adding new constraints like CREATE TABLE does.
   *
   * XXX This is O(N^2) which may be an issue with tables with hundreds of
   * constraints. As long as tables have more like 10 constraints it shouldn't be
   * a problem though. Even 100 constraints ought not be the end of the world.
   *
   * XXX See MergeWithExistingConstraint too if you change this code.
   */
  static void
  MergeConstraintsIntoExisting(Relation child_rel, Relation parent_rel)
  {
  	Relation	catalog_relation;
  	TupleDesc	tuple_desc;
  	SysScanDesc parent_scan;
  	ScanKeyData parent_key;
  	HeapTuple	parent_tuple;
  	bool		child_is_partition = false;
  
  	catalog_relation = heap_open(ConstraintRelationId, RowExclusiveLock);
  	tuple_desc = RelationGetDescr(catalog_relation);
  
  	/* If parent_rel is a partitioned table, child_rel must be a partition */
  	if (parent_rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  		child_is_partition = true;
  
  	/* Outer loop scans through the parent's constraint definitions */
  	ScanKeyInit(&parent_key,
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(parent_rel)));
  	parent_scan = systable_beginscan(catalog_relation, ConstraintRelidTypidNameIndexId,
  									 true, NULL, 1, &parent_key);
  
  	while (HeapTupleIsValid(parent_tuple = systable_getnext(parent_scan)))
  	{
  		Form_pg_constraint parent_con = (Form_pg_constraint) GETSTRUCT(parent_tuple);
  		SysScanDesc child_scan;
  		ScanKeyData child_key;
  		HeapTuple	child_tuple;
  		bool		found = false;
  
  		if (parent_con->contype != CONSTRAINT_CHECK)
  			continue;
  
  		/* if the parent's constraint is marked NO INHERIT, it's not inherited */
  		if (parent_con->connoinherit)
  			continue;
  
  		/* Search for a child constraint matching this one */
  		ScanKeyInit(&child_key,
  					Anum_pg_constraint_conrelid,
  					BTEqualStrategyNumber, F_OIDEQ,
  					ObjectIdGetDatum(RelationGetRelid(child_rel)));
  		child_scan = systable_beginscan(catalog_relation, ConstraintRelidTypidNameIndexId,
  										true, NULL, 1, &child_key);
  
  		while (HeapTupleIsValid(child_tuple = systable_getnext(child_scan)))
  		{
  			Form_pg_constraint child_con = (Form_pg_constraint) GETSTRUCT(child_tuple);
  			HeapTuple	child_copy;
  
  			if (child_con->contype != CONSTRAINT_CHECK)
  				continue;
  
  			if (strcmp(NameStr(parent_con->conname),
  					   NameStr(child_con->conname)) != 0)
  				continue;
  
  			if (!constraints_equivalent(parent_tuple, child_tuple, tuple_desc))
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("child table \"%s\" has different definition for check constraint \"%s\"",
  								RelationGetRelationName(child_rel),
  								NameStr(parent_con->conname))));
  
  			/* If the child constraint is "no inherit" then cannot merge */
  			if (child_con->connoinherit)
  				ereport(ERROR,
  						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  						 errmsg("constraint \"%s\" conflicts with non-inherited constraint on child table \"%s\"",
  								NameStr(child_con->conname),
  								RelationGetRelationName(child_rel))));
  
  			/*
  			 * If the child constraint is "not valid" then cannot merge with a
  			 * valid parent constraint
  			 */
  			if (parent_con->convalidated && !child_con->convalidated)
  				ereport(ERROR,
  						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  						 errmsg("constraint \"%s\" conflicts with NOT VALID constraint on child table \"%s\"",
  								NameStr(child_con->conname),
  								RelationGetRelationName(child_rel))));
  
  			/*
  			 * OK, bump the child constraint's inheritance count.  (If we fail
  			 * later on, this change will just roll back.)
  			 */
  			child_copy = heap_copytuple(child_tuple);
  			child_con = (Form_pg_constraint) GETSTRUCT(child_copy);
  			child_con->coninhcount++;
  
  			/*
  			 * In case of partitions, an inherited constraint must be
  			 * inherited only once since it cannot have multiple parents and
  			 * it is never considered local.
  			 */
  			if (child_is_partition)
  			{
  				Assert(child_con->coninhcount == 1);
  				child_con->conislocal = false;
  			}
  
  			CatalogTupleUpdate(catalog_relation, &child_copy->t_self, child_copy);
  			heap_freetuple(child_copy);
  
  			found = true;
  			break;
  		}
  
  		systable_endscan(child_scan);
  
  		if (!found)
  			ereport(ERROR,
  					(errcode(ERRCODE_DATATYPE_MISMATCH),
  					 errmsg("child table is missing constraint \"%s\"",
  							NameStr(parent_con->conname))));
  	}
  
  	systable_endscan(parent_scan);
  	heap_close(catalog_relation, RowExclusiveLock);
  }
  
  /*
   * ALTER TABLE NO INHERIT
   *
   * Return value is the address of the relation that is no longer parent.
   */
  static ObjectAddress
  ATExecDropInherit(Relation rel, RangeVar *parent, LOCKMODE lockmode)
  {
  	ObjectAddress address;
  	Relation	parent_rel;
  
  	if (rel->rd_rel->relispartition)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot change inheritance of a partition")));
  
  	/*
  	 * AccessShareLock on the parent is probably enough, seeing that DROP
  	 * TABLE doesn't lock parent tables at all.  We need some lock since we'll
  	 * be inspecting the parent's schema.
  	 */
  	parent_rel = heap_openrv(parent, AccessShareLock);
  
  	/*
  	 * We don't bother to check ownership of the parent table --- ownership of
  	 * the child is presumed enough rights.
  	 */
  
  	/* Off to RemoveInheritance() where most of the work happens */
  	RemoveInheritance(rel, parent_rel);
  
  	ObjectAddressSet(address, RelationRelationId,
  					 RelationGetRelid(parent_rel));
  
  	/* keep our lock on the parent relation until commit */
  	heap_close(parent_rel, NoLock);
  
  	return address;
  }
  
  /*
   * RemoveInheritance
   *
   * Drop a parent from the child's parents. This just adjusts the attinhcount
   * and attislocal of the columns and removes the pg_inherit and pg_depend
   * entries.
   *
   * If attinhcount goes to 0 then attislocal gets set to true. If it goes back
   * up attislocal stays true, which means if a child is ever removed from a
   * parent then its columns will never be automatically dropped which may
   * surprise. But at least we'll never surprise by dropping columns someone
   * isn't expecting to be dropped which would actually mean data loss.
   *
   * coninhcount and conislocal for inherited constraints are adjusted in
   * exactly the same way.
   *
   * Common to ATExecDropInherit() and ATExecDetachPartition().
   */
  static void
  RemoveInheritance(Relation child_rel, Relation parent_rel)
  {
  	Relation	catalogRelation;
  	SysScanDesc scan;
  	ScanKeyData key[3];
  	HeapTuple	attributeTuple,
  				constraintTuple;
  	List	   *connames;
  	bool		found;
  	bool		child_is_partition = false;
  
  	/* If parent_rel is a partitioned table, child_rel must be a partition */
  	if (parent_rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  		child_is_partition = true;
  
  	found = DeleteInheritsTuple(RelationGetRelid(child_rel),
  								RelationGetRelid(parent_rel));
  	if (!found)
  	{
  		if (child_is_partition)
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_TABLE),
  					 errmsg("relation \"%s\" is not a partition of relation \"%s\"",
  							RelationGetRelationName(child_rel),
  							RelationGetRelationName(parent_rel))));
  		else
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_TABLE),
  					 errmsg("relation \"%s\" is not a parent of relation \"%s\"",
  							RelationGetRelationName(parent_rel),
  							RelationGetRelationName(child_rel))));
  	}
  
  	/*
  	 * Search through child columns looking for ones matching parent rel
  	 */
  	catalogRelation = heap_open(AttributeRelationId, RowExclusiveLock);
  	ScanKeyInit(&key[0],
  				Anum_pg_attribute_attrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(child_rel)));
  	scan = systable_beginscan(catalogRelation, AttributeRelidNumIndexId,
  							  true, NULL, 1, key);
  	while (HeapTupleIsValid(attributeTuple = systable_getnext(scan)))
  	{
  		Form_pg_attribute att = (Form_pg_attribute) GETSTRUCT(attributeTuple);
  
  		/* Ignore if dropped or not inherited */
  		if (att->attisdropped)
  			continue;
  		if (att->attinhcount <= 0)
  			continue;
  
  		if (SearchSysCacheExistsAttName(RelationGetRelid(parent_rel),
  										NameStr(att->attname)))
  		{
  			/* Decrement inhcount and possibly set islocal to true */
  			HeapTuple	copyTuple = heap_copytuple(attributeTuple);
  			Form_pg_attribute copy_att = (Form_pg_attribute) GETSTRUCT(copyTuple);
  
  			copy_att->attinhcount--;
  			if (copy_att->attinhcount == 0)
  				copy_att->attislocal = true;
  
  			CatalogTupleUpdate(catalogRelation, &copyTuple->t_self, copyTuple);
  			heap_freetuple(copyTuple);
  		}
  	}
  	systable_endscan(scan);
  	heap_close(catalogRelation, RowExclusiveLock);
  
  	/*
  	 * Likewise, find inherited check constraints and disinherit them. To do
  	 * this, we first need a list of the names of the parent's check
  	 * constraints.  (We cheat a bit by only checking for name matches,
  	 * assuming that the expressions will match.)
  	 */
  	catalogRelation = heap_open(ConstraintRelationId, RowExclusiveLock);
  	ScanKeyInit(&key[0],
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(parent_rel)));
  	scan = systable_beginscan(catalogRelation, ConstraintRelidTypidNameIndexId,
  							  true, NULL, 1, key);
  
  	connames = NIL;
  
  	while (HeapTupleIsValid(constraintTuple = systable_getnext(scan)))
  	{
  		Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(constraintTuple);
  
  		if (con->contype == CONSTRAINT_CHECK)
  			connames = lappend(connames, pstrdup(NameStr(con->conname)));
  	}
  
  	systable_endscan(scan);
  
  	/* Now scan the child's constraints */
  	ScanKeyInit(&key[0],
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(child_rel)));
  	scan = systable_beginscan(catalogRelation, ConstraintRelidTypidNameIndexId,
  							  true, NULL, 1, key);
  
  	while (HeapTupleIsValid(constraintTuple = systable_getnext(scan)))
  	{
  		Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(constraintTuple);
  		bool		match;
  		ListCell   *lc;
  
  		if (con->contype != CONSTRAINT_CHECK)
  			continue;
  
  		match = false;
  		foreach(lc, connames)
  		{
  			if (strcmp(NameStr(con->conname), (char *) lfirst(lc)) == 0)
  			{
  				match = true;
  				break;
  			}
  		}
  
  		if (match)
  		{
  			/* Decrement inhcount and possibly set islocal to true */
  			HeapTuple	copyTuple = heap_copytuple(constraintTuple);
  			Form_pg_constraint copy_con = (Form_pg_constraint) GETSTRUCT(copyTuple);
  
  			if (copy_con->coninhcount <= 0) /* shouldn't happen */
  				elog(ERROR, "relation %u has non-inherited constraint \"%s\"",
  					 RelationGetRelid(child_rel), NameStr(copy_con->conname));
  
  			copy_con->coninhcount--;
  			if (copy_con->coninhcount == 0)
  				copy_con->conislocal = true;
  
  			CatalogTupleUpdate(catalogRelation, &copyTuple->t_self, copyTuple);
  			heap_freetuple(copyTuple);
  		}
  	}
  
  	systable_endscan(scan);
  	heap_close(catalogRelation, RowExclusiveLock);
  
  	drop_parent_dependency(RelationGetRelid(child_rel),
  						   RelationRelationId,
  						   RelationGetRelid(parent_rel),
  						   child_dependency_type(child_is_partition));
  
  	/*
  	 * Post alter hook of this inherits. Since object_access_hook doesn't take
  	 * multiple object identifiers, we relay oid of parent relation using
  	 * auxiliary_id argument.
  	 */
  	InvokeObjectPostAlterHookArg(InheritsRelationId,
  								 RelationGetRelid(child_rel), 0,
  								 RelationGetRelid(parent_rel), false);
  }
  
  /*
   * Drop the dependency created by StoreCatalogInheritance1 (CREATE TABLE
   * INHERITS/ALTER TABLE INHERIT -- refclassid will be RelationRelationId) or
   * heap_create_with_catalog (CREATE TABLE OF/ALTER TABLE OF -- refclassid will
   * be TypeRelationId).  There's no convenient way to do this, so go trawling
   * through pg_depend.
   */
  static void
  drop_parent_dependency(Oid relid, Oid refclassid, Oid refobjid,
  					   DependencyType deptype)
  {
  	Relation	catalogRelation;
  	SysScanDesc scan;
  	ScanKeyData key[3];
  	HeapTuple	depTuple;
  
  	catalogRelation = heap_open(DependRelationId, RowExclusiveLock);
  
  	ScanKeyInit(&key[0],
  				Anum_pg_depend_classid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationRelationId));
  	ScanKeyInit(&key[1],
  				Anum_pg_depend_objid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(relid));
  	ScanKeyInit(&key[2],
  				Anum_pg_depend_objsubid,
  				BTEqualStrategyNumber, F_INT4EQ,
  				Int32GetDatum(0));
  
  	scan = systable_beginscan(catalogRelation, DependDependerIndexId, true,
  							  NULL, 3, key);
  
  	while (HeapTupleIsValid(depTuple = systable_getnext(scan)))
  	{
  		Form_pg_depend dep = (Form_pg_depend) GETSTRUCT(depTuple);
  
  		if (dep->refclassid == refclassid &&
  			dep->refobjid == refobjid &&
  			dep->refobjsubid == 0 &&
  			dep->deptype == deptype)
  			CatalogTupleDelete(catalogRelation, depTuple);
  	}
  
  	systable_endscan(scan);
  	heap_close(catalogRelation, RowExclusiveLock);
  }
  
  /*
   * ALTER TABLE OF
   *
   * Attach a table to a composite type, as though it had been created with CREATE
   * TABLE OF.  All attname, atttypid, atttypmod and attcollation must match.  The
   * subject table must not have inheritance parents.  These restrictions ensure
   * that you cannot create a configuration impossible with CREATE TABLE OF alone.
   *
   * The address of the type is returned.
   */
  static ObjectAddress
  ATExecAddOf(Relation rel, const TypeName *ofTypename, LOCKMODE lockmode)
  {
  	Oid			relid = RelationGetRelid(rel);
  	Type		typetuple;
  	Oid			typeid;
  	Relation	inheritsRelation,
  				relationRelation;
  	SysScanDesc scan;
  	ScanKeyData key;
  	AttrNumber	table_attno,
  				type_attno;
  	TupleDesc	typeTupleDesc,
  				tableTupleDesc;
  	ObjectAddress tableobj,
  				typeobj;
  	HeapTuple	classtuple;
  
  	/* Validate the type. */
  	typetuple = typenameType(NULL, ofTypename, NULL);
  	check_of_type(typetuple);
  	typeid = HeapTupleGetOid(typetuple);
  
  	/* Fail if the table has any inheritance parents. */
  	inheritsRelation = heap_open(InheritsRelationId, AccessShareLock);
  	ScanKeyInit(&key,
  				Anum_pg_inherits_inhrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(relid));
  	scan = systable_beginscan(inheritsRelation, InheritsRelidSeqnoIndexId,
  							  true, NULL, 1, &key);
  	if (HeapTupleIsValid(systable_getnext(scan)))
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("typed tables cannot inherit")));
  	systable_endscan(scan);
  	heap_close(inheritsRelation, AccessShareLock);
  
  	/*
  	 * Check the tuple descriptors for compatibility.  Unlike inheritance, we
  	 * require that the order also match.  However, attnotnull need not match.
  	 * Also unlike inheritance, we do not require matching relhasoids.
  	 */
  	typeTupleDesc = lookup_rowtype_tupdesc(typeid, -1);
  	tableTupleDesc = RelationGetDescr(rel);
  	table_attno = 1;
  	for (type_attno = 1; type_attno <= typeTupleDesc->natts; type_attno++)
  	{
  		Form_pg_attribute type_attr,
  					table_attr;
  		const char *type_attname,
  				   *table_attname;
  
  		/* Get the next non-dropped type attribute. */
  		type_attr = TupleDescAttr(typeTupleDesc, type_attno - 1);
  		if (type_attr->attisdropped)
  			continue;
  		type_attname = NameStr(type_attr->attname);
  
  		/* Get the next non-dropped table attribute. */
  		do
  		{
  			if (table_attno > tableTupleDesc->natts)
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("table is missing column \"%s\"",
  								type_attname)));
  			table_attr = TupleDescAttr(tableTupleDesc, table_attno - 1);
  			table_attno++;
  		} while (table_attr->attisdropped);
  		table_attname = NameStr(table_attr->attname);
  
  		/* Compare name. */
  		if (strncmp(table_attname, type_attname, NAMEDATALEN) != 0)
  			ereport(ERROR,
  					(errcode(ERRCODE_DATATYPE_MISMATCH),
  					 errmsg("table has column \"%s\" where type requires \"%s\"",
  							table_attname, type_attname)));
  
  		/* Compare type. */
  		if (table_attr->atttypid != type_attr->atttypid ||
  			table_attr->atttypmod != type_attr->atttypmod ||
  			table_attr->attcollation != type_attr->attcollation)
  			ereport(ERROR,
  					(errcode(ERRCODE_DATATYPE_MISMATCH),
  					 errmsg("table \"%s\" has different type for column \"%s\"",
  							RelationGetRelationName(rel), type_attname)));
  	}
  	DecrTupleDescRefCount(typeTupleDesc);
  
  	/* Any remaining columns at the end of the table had better be dropped. */
  	for (; table_attno <= tableTupleDesc->natts; table_attno++)
  	{
  		Form_pg_attribute table_attr = TupleDescAttr(tableTupleDesc,
  													 table_attno - 1);
  
  		if (!table_attr->attisdropped)
  			ereport(ERROR,
  					(errcode(ERRCODE_DATATYPE_MISMATCH),
  					 errmsg("table has extra column \"%s\"",
  							NameStr(table_attr->attname))));
  	}
  
  	/* If the table was already typed, drop the existing dependency. */
  	if (rel->rd_rel->reloftype)
  		drop_parent_dependency(relid, TypeRelationId, rel->rd_rel->reloftype,
  							   DEPENDENCY_NORMAL);
  
  	/* Record a dependency on the new type. */
  	tableobj.classId = RelationRelationId;
  	tableobj.objectId = relid;
  	tableobj.objectSubId = 0;
  	typeobj.classId = TypeRelationId;
  	typeobj.objectId = typeid;
  	typeobj.objectSubId = 0;
  	recordDependencyOn(&tableobj, &typeobj, DEPENDENCY_NORMAL);
  
  	/* Update pg_class.reloftype */
  	relationRelation = heap_open(RelationRelationId, RowExclusiveLock);
  	classtuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relid));
  	if (!HeapTupleIsValid(classtuple))
  		elog(ERROR, "cache lookup failed for relation %u", relid);
  	((Form_pg_class) GETSTRUCT(classtuple))->reloftype = typeid;
  	CatalogTupleUpdate(relationRelation, &classtuple->t_self, classtuple);
  
  	InvokeObjectPostAlterHook(RelationRelationId, relid, 0);
  
  	heap_freetuple(classtuple);
  	heap_close(relationRelation, RowExclusiveLock);
  
  	ReleaseSysCache(typetuple);
  
  	return typeobj;
  }
  
  /*
   * ALTER TABLE NOT OF
   *
   * Detach a typed table from its originating type.  Just clear reloftype and
   * remove the dependency.
   */
  static void
  ATExecDropOf(Relation rel, LOCKMODE lockmode)
  {
  	Oid			relid = RelationGetRelid(rel);
  	Relation	relationRelation;
  	HeapTuple	tuple;
  
  	if (!OidIsValid(rel->rd_rel->reloftype))
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is not a typed table",
  						RelationGetRelationName(rel))));
  
  	/*
  	 * We don't bother to check ownership of the type --- ownership of the
  	 * table is presumed enough rights.  No lock required on the type, either.
  	 */
  
  	drop_parent_dependency(relid, TypeRelationId, rel->rd_rel->reloftype,
  						   DEPENDENCY_NORMAL);
  
  	/* Clear pg_class.reloftype */
  	relationRelation = heap_open(RelationRelationId, RowExclusiveLock);
  	tuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relid));
  	if (!HeapTupleIsValid(tuple))
  		elog(ERROR, "cache lookup failed for relation %u", relid);
  	((Form_pg_class) GETSTRUCT(tuple))->reloftype = InvalidOid;
  	CatalogTupleUpdate(relationRelation, &tuple->t_self, tuple);
  
  	InvokeObjectPostAlterHook(RelationRelationId, relid, 0);
  
  	heap_freetuple(tuple);
  	heap_close(relationRelation, RowExclusiveLock);
  }
  
  /*
   * relation_mark_replica_identity: Update a table's replica identity
   *
   * Iff ri_type = REPLICA_IDENTITY_INDEX, indexOid must be the Oid of a suitable
   * index. Otherwise, it should be InvalidOid.
   */
  static void
  relation_mark_replica_identity(Relation rel, char ri_type, Oid indexOid,
  							   bool is_internal)
  {
  	Relation	pg_index;
  	Relation	pg_class;
  	HeapTuple	pg_class_tuple;
  	HeapTuple	pg_index_tuple;
  	Form_pg_class pg_class_form;
  	Form_pg_index pg_index_form;
  
  	ListCell   *index;
  
  	/*
  	 * Check whether relreplident has changed, and update it if so.
  	 */
  	pg_class = heap_open(RelationRelationId, RowExclusiveLock);
  	pg_class_tuple = SearchSysCacheCopy1(RELOID,
  										 ObjectIdGetDatum(RelationGetRelid(rel)));
  	if (!HeapTupleIsValid(pg_class_tuple))
  		elog(ERROR, "cache lookup failed for relation \"%s\"",
  			 RelationGetRelationName(rel));
  	pg_class_form = (Form_pg_class) GETSTRUCT(pg_class_tuple);
  	if (pg_class_form->relreplident != ri_type)
  	{
  		pg_class_form->relreplident = ri_type;
  		CatalogTupleUpdate(pg_class, &pg_class_tuple->t_self, pg_class_tuple);
  	}
  	heap_close(pg_class, RowExclusiveLock);
  	heap_freetuple(pg_class_tuple);
  
  	/*
  	 * Check whether the correct index is marked indisreplident; if so, we're
  	 * done.
  	 */
  	if (OidIsValid(indexOid))
  	{
  		Assert(ri_type == REPLICA_IDENTITY_INDEX);
  
  		pg_index_tuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(indexOid));
  		if (!HeapTupleIsValid(pg_index_tuple))
  			elog(ERROR, "cache lookup failed for index %u", indexOid);
  		pg_index_form = (Form_pg_index) GETSTRUCT(pg_index_tuple);
  
  		if (pg_index_form->indisreplident)
  		{
  			ReleaseSysCache(pg_index_tuple);
  			return;
  		}
  		ReleaseSysCache(pg_index_tuple);
  	}
  
  	/*
  	 * Clear the indisreplident flag from any index that had it previously,
  	 * and set it for any index that should have it now.
  	 */
  	pg_index = heap_open(IndexRelationId, RowExclusiveLock);
  	foreach(index, RelationGetIndexList(rel))
  	{
  		Oid			thisIndexOid = lfirst_oid(index);
  		bool		dirty = false;
  
  		pg_index_tuple = SearchSysCacheCopy1(INDEXRELID,
  											 ObjectIdGetDatum(thisIndexOid));
  		if (!HeapTupleIsValid(pg_index_tuple))
  			elog(ERROR, "cache lookup failed for index %u", thisIndexOid);
  		pg_index_form = (Form_pg_index) GETSTRUCT(pg_index_tuple);
  
  		/*
  		 * Unset the bit if set.  We know it's wrong because we checked this
  		 * earlier.
  		 */
  		if (pg_index_form->indisreplident)
  		{
  			dirty = true;
  			pg_index_form->indisreplident = false;
  		}
  		else if (thisIndexOid == indexOid)
  		{
  			dirty = true;
  			pg_index_form->indisreplident = true;
  		}
  
  		if (dirty)
  		{
  			CatalogTupleUpdate(pg_index, &pg_index_tuple->t_self, pg_index_tuple);
  			InvokeObjectPostAlterHookArg(IndexRelationId, thisIndexOid, 0,
  										 InvalidOid, is_internal);
  		}
  		heap_freetuple(pg_index_tuple);
  	}
  
  	heap_close(pg_index, RowExclusiveLock);
  }
  
  /*
   * ALTER TABLE <name> REPLICA IDENTITY ...
   */
  static void
  ATExecReplicaIdentity(Relation rel, ReplicaIdentityStmt *stmt, LOCKMODE lockmode)
  {
  	Oid			indexOid;
  	Relation	indexRel;
  	int			key;
  
  	if (stmt->identity_type == REPLICA_IDENTITY_DEFAULT)
  	{
  		relation_mark_replica_identity(rel, stmt->identity_type, InvalidOid, true);
  		return;
  	}
  	else if (stmt->identity_type == REPLICA_IDENTITY_FULL)
  	{
  		relation_mark_replica_identity(rel, stmt->identity_type, InvalidOid, true);
  		return;
  	}
  	else if (stmt->identity_type == REPLICA_IDENTITY_NOTHING)
  	{
  		relation_mark_replica_identity(rel, stmt->identity_type, InvalidOid, true);
  		return;
  	}
  	else if (stmt->identity_type == REPLICA_IDENTITY_INDEX)
  	{
  		 /* fallthrough */ ;
  	}
  	else
  		elog(ERROR, "unexpected identity type %u", stmt->identity_type);
  
  
  	/* Check that the index exists */
  	indexOid = get_relname_relid(stmt->name, rel->rd_rel->relnamespace);
  	if (!OidIsValid(indexOid))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_OBJECT),
  				 errmsg("index \"%s\" for table \"%s\" does not exist",
  						stmt->name, RelationGetRelationName(rel))));
  
  	indexRel = index_open(indexOid, ShareLock);
  
  	/* Check that the index is on the relation we're altering. */
  	if (indexRel->rd_index == NULL ||
  		indexRel->rd_index->indrelid != RelationGetRelid(rel))
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is not an index for table \"%s\"",
  						RelationGetRelationName(indexRel),
  						RelationGetRelationName(rel))));
  	/* The AM must support uniqueness, and the index must in fact be unique. */
  	if (!indexRel->rd_amroutine->amcanunique ||
  		!indexRel->rd_index->indisunique)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot use non-unique index \"%s\" as replica identity",
  						RelationGetRelationName(indexRel))));
  	/* Deferred indexes are not guaranteed to be always unique. */
  	if (!indexRel->rd_index->indimmediate)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot use non-immediate index \"%s\" as replica identity",
  						RelationGetRelationName(indexRel))));
  	/* Expression indexes aren't supported. */
  	if (RelationGetIndexExpressions(indexRel) != NIL)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot use expression index \"%s\" as replica identity",
  						RelationGetRelationName(indexRel))));
  	/* Predicate indexes aren't supported. */
  	if (RelationGetIndexPredicate(indexRel) != NIL)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot use partial index \"%s\" as replica identity",
  						RelationGetRelationName(indexRel))));
  	/* And neither are invalid indexes. */
  	if (!IndexIsValid(indexRel->rd_index))
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot use invalid index \"%s\" as replica identity",
  						RelationGetRelationName(indexRel))));
  
  	/* Check index for nullable columns. */
  	for (key = 0; key < IndexRelationGetNumberOfKeyAttributes(indexRel); key++)
  	{
  		int16		attno = indexRel->rd_index->indkey.values[key];
  		Form_pg_attribute attr;
  
  		/* Allow OID column to be indexed; it's certainly not nullable */
  		if (attno == ObjectIdAttributeNumber)
  			continue;
  
  		/*
  		 * Reject any other system columns.  (Going forward, we'll disallow
  		 * indexes containing such columns in the first place, but they might
  		 * exist in older branches.)
  		 */
  		if (attno <= 0)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
  					 errmsg("index \"%s\" cannot be used as replica identity because column %d is a system column",
  							RelationGetRelationName(indexRel), attno)));
  
  		attr = TupleDescAttr(rel->rd_att, attno - 1);
  		if (!attr->attnotnull)
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("index \"%s\" cannot be used as replica identity because column \"%s\" is nullable",
  							RelationGetRelationName(indexRel),
  							NameStr(attr->attname))));
  	}
  
  	/* This index is suitable for use as a replica identity. Mark it. */
  	relation_mark_replica_identity(rel, stmt->identity_type, indexOid, true);
  
  	index_close(indexRel, NoLock);
  }
  
  /*
   * ALTER TABLE ENABLE/DISABLE ROW LEVEL SECURITY
   */
  static void
  ATExecEnableRowSecurity(Relation rel)
  {
  	Relation	pg_class;
  	Oid			relid;
  	HeapTuple	tuple;
  
  	relid = RelationGetRelid(rel);
  
  	pg_class = heap_open(RelationRelationId, RowExclusiveLock);
  
  	tuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relid));
  
  	if (!HeapTupleIsValid(tuple))
  		elog(ERROR, "cache lookup failed for relation %u", relid);
  
  	((Form_pg_class) GETSTRUCT(tuple))->relrowsecurity = true;
  	CatalogTupleUpdate(pg_class, &tuple->t_self, tuple);
  
  	heap_close(pg_class, RowExclusiveLock);
  	heap_freetuple(tuple);
  }
  
  static void
  ATExecDisableRowSecurity(Relation rel)
  {
  	Relation	pg_class;
  	Oid			relid;
  	HeapTuple	tuple;
  
  	relid = RelationGetRelid(rel);
  
  	/* Pull the record for this relation and update it */
  	pg_class = heap_open(RelationRelationId, RowExclusiveLock);
  
  	tuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relid));
  
  	if (!HeapTupleIsValid(tuple))
  		elog(ERROR, "cache lookup failed for relation %u", relid);
  
  	((Form_pg_class) GETSTRUCT(tuple))->relrowsecurity = false;
  	CatalogTupleUpdate(pg_class, &tuple->t_self, tuple);
  
  	heap_close(pg_class, RowExclusiveLock);
  	heap_freetuple(tuple);
  }
  
  /*
   * ALTER TABLE FORCE/NO FORCE ROW LEVEL SECURITY
   */
  static void
  ATExecForceNoForceRowSecurity(Relation rel, bool force_rls)
  {
  	Relation	pg_class;
  	Oid			relid;
  	HeapTuple	tuple;
  
  	relid = RelationGetRelid(rel);
  
  	pg_class = heap_open(RelationRelationId, RowExclusiveLock);
  
  	tuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relid));
  
  	if (!HeapTupleIsValid(tuple))
  		elog(ERROR, "cache lookup failed for relation %u", relid);
  
  	((Form_pg_class) GETSTRUCT(tuple))->relforcerowsecurity = force_rls;
  	CatalogTupleUpdate(pg_class, &tuple->t_self, tuple);
  
  	heap_close(pg_class, RowExclusiveLock);
  	heap_freetuple(tuple);
  }
  
  /*
   * ALTER FOREIGN TABLE <name> OPTIONS (...)
   */
  static void
  ATExecGenericOptions(Relation rel, List *options)
  {
  	Relation	ftrel;
  	ForeignServer *server;
  	ForeignDataWrapper *fdw;
  	HeapTuple	tuple;
  	bool		isnull;
  	Datum		repl_val[Natts_pg_foreign_table];
  	bool		repl_null[Natts_pg_foreign_table];
  	bool		repl_repl[Natts_pg_foreign_table];
  	Datum		datum;
  	Form_pg_foreign_table tableform;
  
  	if (options == NIL)
  		return;
  
  	ftrel = heap_open(ForeignTableRelationId, RowExclusiveLock);
  
  	tuple = SearchSysCacheCopy1(FOREIGNTABLEREL, rel->rd_id);
  	if (!HeapTupleIsValid(tuple))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_OBJECT),
  				 errmsg("foreign table \"%s\" does not exist",
  						RelationGetRelationName(rel))));
  	tableform = (Form_pg_foreign_table) GETSTRUCT(tuple);
  	server = GetForeignServer(tableform->ftserver);
  	fdw = GetForeignDataWrapper(server->fdwid);
  
  	memset(repl_val, 0, sizeof(repl_val));
  	memset(repl_null, false, sizeof(repl_null));
  	memset(repl_repl, false, sizeof(repl_repl));
  
  	/* Extract the current options */
  	datum = SysCacheGetAttr(FOREIGNTABLEREL,
  							tuple,
  							Anum_pg_foreign_table_ftoptions,
  							&isnull);
  	if (isnull)
  		datum = PointerGetDatum(NULL);
  
  	/* Transform the options */
  	datum = transformGenericOptions(ForeignTableRelationId,
  									datum,
  									options,
  									fdw->fdwvalidator);
  
  	if (PointerIsValid(DatumGetPointer(datum)))
  		repl_val[Anum_pg_foreign_table_ftoptions - 1] = datum;
  	else
  		repl_null[Anum_pg_foreign_table_ftoptions - 1] = true;
  
  	repl_repl[Anum_pg_foreign_table_ftoptions - 1] = true;
  
  	/* Everything looks good - update the tuple */
  
  	tuple = heap_modify_tuple(tuple, RelationGetDescr(ftrel),
  							  repl_val, repl_null, repl_repl);
  
  	CatalogTupleUpdate(ftrel, &tuple->t_self, tuple);
  
  	/*
  	 * Invalidate relcache so that all sessions will refresh any cached plans
  	 * that might depend on the old options.
  	 */
  	CacheInvalidateRelcache(rel);
  
  	InvokeObjectPostAlterHook(ForeignTableRelationId,
  							  RelationGetRelid(rel), 0);
  
  	heap_close(ftrel, RowExclusiveLock);
  
  	heap_freetuple(tuple);
  }
  
  /*
   * Preparation phase for SET LOGGED/UNLOGGED
   *
   * This verifies that we're not trying to change a temp table.  Also,
   * existing foreign key constraints are checked to avoid ending up with
   * permanent tables referencing unlogged tables.
   *
   * Return value is false if the operation is a no-op (in which case the
   * checks are skipped), otherwise true.
   */
  static bool
  ATPrepChangePersistence(Relation rel, bool toLogged)
  {
  	Relation	pg_constraint;
  	HeapTuple	tuple;
  	SysScanDesc scan;
  	ScanKeyData skey[1];
  
  	/*
  	 * Disallow changing status for a temp table.  Also verify whether we can
  	 * get away with doing nothing; in such cases we don't need to run the
  	 * checks below, either.
  	 */
  	switch (rel->rd_rel->relpersistence)
  	{
  		case RELPERSISTENCE_TEMP:
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  					 errmsg("cannot change logged status of table \"%s\" because it is temporary",
  							RelationGetRelationName(rel)),
  					 errtable(rel)));
  			break;
  		case RELPERSISTENCE_PERMANENT:
  			if (toLogged)
  				/* nothing to do */
  				return false;
  			break;
  		case RELPERSISTENCE_UNLOGGED:
  			if (!toLogged)
  				/* nothing to do */
  				return false;
  			break;
  	}
  
  	/*
  	 * Check that the table is not part any publication when changing to
  	 * UNLOGGED as UNLOGGED tables can't be published.
  	 */
  	if (!toLogged &&
  		list_length(GetRelationPublications(RelationGetRelid(rel))) > 0)
  		ereport(ERROR,
  				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  				 errmsg("cannot change table \"%s\" to unlogged because it is part of a publication",
  						RelationGetRelationName(rel)),
  				 errdetail("Unlogged relations cannot be replicated.")));
  
  	/*
  	 * Check existing foreign key constraints to preserve the invariant that
  	 * permanent tables cannot reference unlogged ones.  Self-referencing
  	 * foreign keys can safely be ignored.
  	 */
  	pg_constraint = heap_open(ConstraintRelationId, AccessShareLock);
  
  	/*
  	 * Scan conrelid if changing to permanent, else confrelid.  This also
  	 * determines whether a useful index exists.
  	 */
  	ScanKeyInit(&skey[0],
  				toLogged ? Anum_pg_constraint_conrelid :
  				Anum_pg_constraint_confrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(rel)));
  	scan = systable_beginscan(pg_constraint,
  							  toLogged ? ConstraintRelidTypidNameIndexId : InvalidOid,
  							  true, NULL, 1, skey);
  
  	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
  	{
  		Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(tuple);
  
  		if (con->contype == CONSTRAINT_FOREIGN)
  		{
  			Oid			foreignrelid;
  			Relation	foreignrel;
  
  			/* the opposite end of what we used as scankey */
  			foreignrelid = toLogged ? con->confrelid : con->conrelid;
  
  			/* ignore if self-referencing */
  			if (RelationGetRelid(rel) == foreignrelid)
  				continue;
  
  			foreignrel = relation_open(foreignrelid, AccessShareLock);
  
  			if (toLogged)
  			{
  				if (foreignrel->rd_rel->relpersistence != RELPERSISTENCE_PERMANENT)
  					ereport(ERROR,
  							(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  							 errmsg("could not change table \"%s\" to logged because it references unlogged table \"%s\"",
  									RelationGetRelationName(rel),
  									RelationGetRelationName(foreignrel)),
  							 errtableconstraint(rel, NameStr(con->conname))));
  			}
  			else
  			{
  				if (foreignrel->rd_rel->relpersistence == RELPERSISTENCE_PERMANENT)
  					ereport(ERROR,
  							(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
  							 errmsg("could not change table \"%s\" to unlogged because it references logged table \"%s\"",
  									RelationGetRelationName(rel),
  									RelationGetRelationName(foreignrel)),
  							 errtableconstraint(rel, NameStr(con->conname))));
  			}
  
  			relation_close(foreignrel, AccessShareLock);
  		}
  	}
  
  	systable_endscan(scan);
  
  	heap_close(pg_constraint, AccessShareLock);
  
  	return true;
  }
  
  /*
   * Execute ALTER TABLE SET SCHEMA
   */
  ObjectAddress
  AlterTableNamespace(AlterObjectSchemaStmt *stmt, Oid *oldschema)
  {
  	Relation	rel;
  	Oid			relid;
  	Oid			oldNspOid;
  	Oid			nspOid;
  	RangeVar   *newrv;
  	ObjectAddresses *objsMoved;
  	ObjectAddress myself;
  
  	relid = RangeVarGetRelidExtended(stmt->relation, AccessExclusiveLock,
  									 stmt->missing_ok ? RVR_MISSING_OK : 0,
  									 RangeVarCallbackForAlterRelation,
  									 (void *) stmt);
  
  	if (!OidIsValid(relid))
  	{
  		ereport(NOTICE,
  				(errmsg("relation \"%s\" does not exist, skipping",
  						stmt->relation->relname)));
  		return InvalidObjectAddress;
  	}
  
  	rel = relation_open(relid, NoLock);
  
  	oldNspOid = RelationGetNamespace(rel);
  
  	/* If it's an owned sequence, disallow moving it by itself. */
  	if (rel->rd_rel->relkind == RELKIND_SEQUENCE)
  	{
  		Oid			tableId;
  		int32		colId;
  
  		if (sequenceIsOwned(relid, DEPENDENCY_AUTO, &tableId, &colId) ||
  			sequenceIsOwned(relid, DEPENDENCY_INTERNAL, &tableId, &colId))
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("cannot move an owned sequence into another schema"),
  					 errdetail("Sequence \"%s\" is linked to table \"%s\".",
  							   RelationGetRelationName(rel),
  							   get_rel_name(tableId))));
  	}
  
  	/* Get and lock schema OID and check its permissions. */
  	newrv = makeRangeVar(stmt->newschema, RelationGetRelationName(rel), -1);
  	nspOid = RangeVarGetAndCheckCreationNamespace(newrv, NoLock, NULL);
  
  	/* common checks on switching namespaces */
  	CheckSetNamespace(oldNspOid, nspOid);
  
  	objsMoved = new_object_addresses();
  	AlterTableNamespaceInternal(rel, oldNspOid, nspOid, objsMoved);
  	free_object_addresses(objsMoved);
  
  	ObjectAddressSet(myself, RelationRelationId, relid);
  
  	if (oldschema)
  		*oldschema = oldNspOid;
  
  	/* close rel, but keep lock until commit */
  	relation_close(rel, NoLock);
  
  	return myself;
  }
  
  /*
   * The guts of relocating a table or materialized view to another namespace:
   * besides moving the relation itself, its dependent objects are relocated to
   * the new schema.
   */
  void
  AlterTableNamespaceInternal(Relation rel, Oid oldNspOid, Oid nspOid,
  							ObjectAddresses *objsMoved)
  {
  	Relation	classRel;
  
  	Assert(objsMoved != NULL);
  
  	/* OK, modify the pg_class row and pg_depend entry */
  	classRel = heap_open(RelationRelationId, RowExclusiveLock);
  
  	AlterRelationNamespaceInternal(classRel, RelationGetRelid(rel), oldNspOid,
  								   nspOid, true, objsMoved);
  
  	/* Fix the table's row type too */
  	AlterTypeNamespaceInternal(rel->rd_rel->reltype,
  							   nspOid, false, false, objsMoved);
  
  	/* Fix other dependent stuff */
  	if (rel->rd_rel->relkind == RELKIND_RELATION ||
  		rel->rd_rel->relkind == RELKIND_MATVIEW ||
  		rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  	{
  		AlterIndexNamespaces(classRel, rel, oldNspOid, nspOid, objsMoved);
  		AlterSeqNamespaces(classRel, rel, oldNspOid, nspOid,
  						   objsMoved, AccessExclusiveLock);
  		AlterConstraintNamespaces(RelationGetRelid(rel), oldNspOid, nspOid,
  								  false, objsMoved);
  	}
  
  	heap_close(classRel, RowExclusiveLock);
  }
  
  /*
   * The guts of relocating a relation to another namespace: fix the pg_class
   * entry, and the pg_depend entry if any.  Caller must already have
   * opened and write-locked pg_class.
   */
  void
  AlterRelationNamespaceInternal(Relation classRel, Oid relOid,
  							   Oid oldNspOid, Oid newNspOid,
  							   bool hasDependEntry,
  							   ObjectAddresses *objsMoved)
  {
  	HeapTuple	classTup;
  	Form_pg_class classForm;
  	ObjectAddress thisobj;
  	bool		already_done = false;
  
  	classTup = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relOid));
  	if (!HeapTupleIsValid(classTup))
  		elog(ERROR, "cache lookup failed for relation %u", relOid);
  	classForm = (Form_pg_class) GETSTRUCT(classTup);
  
  	Assert(classForm->relnamespace == oldNspOid);
  
  	thisobj.classId = RelationRelationId;
  	thisobj.objectId = relOid;
  	thisobj.objectSubId = 0;
  
  	/*
  	 * If the object has already been moved, don't move it again.  If it's
  	 * already in the right place, don't move it, but still fire the object
  	 * access hook.
  	 */
  	already_done = object_address_present(&thisobj, objsMoved);
  	if (!already_done && oldNspOid != newNspOid)
  	{
  		/* check for duplicate name (more friendly than unique-index failure) */
  		if (get_relname_relid(NameStr(classForm->relname),
  							  newNspOid) != InvalidOid)
  			ereport(ERROR,
  					(errcode(ERRCODE_DUPLICATE_TABLE),
  					 errmsg("relation \"%s\" already exists in schema \"%s\"",
  							NameStr(classForm->relname),
  							get_namespace_name(newNspOid))));
  
  		/* classTup is a copy, so OK to scribble on */
  		classForm->relnamespace = newNspOid;
  
  		CatalogTupleUpdate(classRel, &classTup->t_self, classTup);
  
  		/* Update dependency on schema if caller said so */
  		if (hasDependEntry &&
  			changeDependencyFor(RelationRelationId,
  								relOid,
  								NamespaceRelationId,
  								oldNspOid,
  								newNspOid) != 1)
  			elog(ERROR, "failed to change schema dependency for relation \"%s\"",
  				 NameStr(classForm->relname));
  	}
  	if (!already_done)
  	{
  		add_exact_object_address(&thisobj, objsMoved);
  
  		InvokeObjectPostAlterHook(RelationRelationId, relOid, 0);
  	}
  
  	heap_freetuple(classTup);
  }
  
  /*
   * Move all indexes for the specified relation to another namespace.
   *
   * Note: we assume adequate permission checking was done by the caller,
   * and that the caller has a suitable lock on the owning relation.
   */
  static void
  AlterIndexNamespaces(Relation classRel, Relation rel,
  					 Oid oldNspOid, Oid newNspOid, ObjectAddresses *objsMoved)
  {
  	List	   *indexList;
  	ListCell   *l;
  
  	indexList = RelationGetIndexList(rel);
  
  	foreach(l, indexList)
  	{
  		Oid			indexOid = lfirst_oid(l);
  		ObjectAddress thisobj;
  
  		thisobj.classId = RelationRelationId;
  		thisobj.objectId = indexOid;
  		thisobj.objectSubId = 0;
  
  		/*
  		 * Note: currently, the index will not have its own dependency on the
  		 * namespace, so we don't need to do changeDependencyFor(). There's no
  		 * row type in pg_type, either.
  		 *
  		 * XXX this objsMoved test may be pointless -- surely we have a single
  		 * dependency link from a relation to each index?
  		 */
  		if (!object_address_present(&thisobj, objsMoved))
  		{
  			AlterRelationNamespaceInternal(classRel, indexOid,
  										   oldNspOid, newNspOid,
  										   false, objsMoved);
  			add_exact_object_address(&thisobj, objsMoved);
  		}
  	}
  
  	list_free(indexList);
  }
  
  /*
   * Move all identity and SERIAL-column sequences of the specified relation to another
   * namespace.
   *
   * Note: we assume adequate permission checking was done by the caller,
   * and that the caller has a suitable lock on the owning relation.
   */
  static void
  AlterSeqNamespaces(Relation classRel, Relation rel,
  				   Oid oldNspOid, Oid newNspOid, ObjectAddresses *objsMoved,
  				   LOCKMODE lockmode)
  {
  	Relation	depRel;
  	SysScanDesc scan;
  	ScanKeyData key[2];
  	HeapTuple	tup;
  
  	/*
  	 * SERIAL sequences are those having an auto dependency on one of the
  	 * table's columns (we don't care *which* column, exactly).
  	 */
  	depRel = heap_open(DependRelationId, AccessShareLock);
  
  	ScanKeyInit(&key[0],
  				Anum_pg_depend_refclassid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationRelationId));
  	ScanKeyInit(&key[1],
  				Anum_pg_depend_refobjid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(rel)));
  	/* we leave refobjsubid unspecified */
  
  	scan = systable_beginscan(depRel, DependReferenceIndexId, true,
  							  NULL, 2, key);
  
  	while (HeapTupleIsValid(tup = systable_getnext(scan)))
  	{
  		Form_pg_depend depForm = (Form_pg_depend) GETSTRUCT(tup);
  		Relation	seqRel;
  
  		/* skip dependencies other than auto dependencies on columns */
  		if (depForm->refobjsubid == 0 ||
  			depForm->classid != RelationRelationId ||
  			depForm->objsubid != 0 ||
  			!(depForm->deptype == DEPENDENCY_AUTO || depForm->deptype == DEPENDENCY_INTERNAL))
  			continue;
  
  		/* Use relation_open just in case it's an index */
  		seqRel = relation_open(depForm->objid, lockmode);
  
  		/* skip non-sequence relations */
  		if (RelationGetForm(seqRel)->relkind != RELKIND_SEQUENCE)
  		{
  			/* No need to keep the lock */
  			relation_close(seqRel, lockmode);
  			continue;
  		}
  
  		/* Fix the pg_class and pg_depend entries */
  		AlterRelationNamespaceInternal(classRel, depForm->objid,
  									   oldNspOid, newNspOid,
  									   true, objsMoved);
  
  		/*
  		 * Sequences have entries in pg_type. We need to be careful to move
  		 * them to the new namespace, too.
  		 */
  		AlterTypeNamespaceInternal(RelationGetForm(seqRel)->reltype,
  								   newNspOid, false, false, objsMoved);
  
  		/* Now we can close it.  Keep the lock till end of transaction. */
  		relation_close(seqRel, NoLock);
  	}
  
  	systable_endscan(scan);
  
  	relation_close(depRel, AccessShareLock);
  }
  
  
  /*
   * This code supports
   *	CREATE TEMP TABLE ... ON COMMIT { DROP | PRESERVE ROWS | DELETE ROWS }
   *
   * Because we only support this for TEMP tables, it's sufficient to remember
   * the state in a backend-local data structure.
   */
  
  /*
   * Register a newly-created relation's ON COMMIT action.
   */
  void
  register_on_commit_action(Oid relid, OnCommitAction action)
  {
  	OnCommitItem *oc;
  	MemoryContext oldcxt;
  
  	/*
  	 * We needn't bother registering the relation unless there is an ON COMMIT
  	 * action we need to take.
  	 */
  	if (action == ONCOMMIT_NOOP || action == ONCOMMIT_PRESERVE_ROWS)
  		return;
  
  	oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
  
  	oc = (OnCommitItem *) palloc(sizeof(OnCommitItem));
  	oc->relid = relid;
  	oc->oncommit = action;
  	oc->creating_subid = GetCurrentSubTransactionId();
  	oc->deleting_subid = InvalidSubTransactionId;
  
  	on_commits = lcons(oc, on_commits);
  
  	MemoryContextSwitchTo(oldcxt);
  }
  
  /*
   * Unregister any ON COMMIT action when a relation is deleted.
   *
   * Actually, we only mark the OnCommitItem entry as to be deleted after commit.
   */
  void
  remove_on_commit_action(Oid relid)
  {
  	ListCell   *l;
  
  	foreach(l, on_commits)
  	{
  		OnCommitItem *oc = (OnCommitItem *) lfirst(l);
  
  		if (oc->relid == relid)
  		{
  			oc->deleting_subid = GetCurrentSubTransactionId();
  			break;
  		}
  	}
  }
  
  /*
   * Perform ON COMMIT actions.
   *
   * This is invoked just before actually committing, since it's possible
   * to encounter errors.
   */
  void
  PreCommit_on_commit_actions(void)
  {
  	ListCell   *l;
  	List	   *oids_to_truncate = NIL;
  	List	   *oids_to_drop = NIL;
  
  	foreach(l, on_commits)
  	{
  		OnCommitItem *oc = (OnCommitItem *) lfirst(l);
  
  		/* Ignore entry if already dropped in this xact */
  		if (oc->deleting_subid != InvalidSubTransactionId)
  			continue;
  
  		switch (oc->oncommit)
  		{
  			case ONCOMMIT_NOOP:
  			case ONCOMMIT_PRESERVE_ROWS:
  				/* Do nothing (there shouldn't be such entries, actually) */
  				break;
  			case ONCOMMIT_DELETE_ROWS:
  
  				/*
  				 * If this transaction hasn't accessed any temporary
  				 * relations, we can skip truncating ON COMMIT DELETE ROWS
  				 * tables, as they must still be empty.
  				 */
  				if ((MyXactFlags & XACT_FLAGS_ACCESSEDTEMPREL))
  					oids_to_truncate = lappend_oid(oids_to_truncate, oc->relid);
  				break;
  			case ONCOMMIT_DROP:
  				oids_to_drop = lappend_oid(oids_to_drop, oc->relid);
  				break;
  		}
  	}
  
  	/*
  	 * Truncate relations before dropping so that all dependencies between
  	 * relations are removed after they are worked on.  Doing it like this
  	 * might be a waste as it is possible that a relation being truncated will
  	 * be dropped anyway due to its parent being dropped, but this makes the
  	 * code more robust because of not having to re-check that the relation
  	 * exists at truncation time.
  	 */
  	if (oids_to_truncate != NIL)
  	{
  		heap_truncate(oids_to_truncate);
  		CommandCounterIncrement();	/* XXX needed? */
  	}
  	if (oids_to_drop != NIL)
  	{
  		ObjectAddresses *targetObjects = new_object_addresses();
  		ListCell   *l;
  
  		foreach(l, oids_to_drop)
  		{
  			ObjectAddress object;
  
  			object.classId = RelationRelationId;
  			object.objectId = lfirst_oid(l);
  			object.objectSubId = 0;
  
  			Assert(!object_address_present(&object, targetObjects));
  
  			add_exact_object_address(&object, targetObjects);
  		}
  
  		/*
  		 * Since this is an automatic drop, rather than one directly initiated
  		 * by the user, we pass the PERFORM_DELETION_INTERNAL flag.
  		 */
  		performMultipleDeletions(targetObjects, DROP_CASCADE,
  								 PERFORM_DELETION_INTERNAL | PERFORM_DELETION_QUIETLY);
  
  #ifdef USE_ASSERT_CHECKING
  
  		/*
  		 * Note that table deletion will call remove_on_commit_action, so the
  		 * entry should get marked as deleted.
  		 */
  		foreach(l, on_commits)
  		{
  			OnCommitItem *oc = (OnCommitItem *) lfirst(l);
  
  			if (oc->oncommit != ONCOMMIT_DROP)
  				continue;
  
  			Assert(oc->deleting_subid != InvalidSubTransactionId);
  		}
  #endif
  	}
  }
  
  /*
   * Post-commit or post-abort cleanup for ON COMMIT management.
   *
   * All we do here is remove no-longer-needed OnCommitItem entries.
   *
   * During commit, remove entries that were deleted during this transaction;
   * during abort, remove those created during this transaction.
   */
  void
  AtEOXact_on_commit_actions(bool isCommit)
  {
  	ListCell   *cur_item;
  	ListCell   *prev_item;
  
  	prev_item = NULL;
  	cur_item = list_head(on_commits);
  
  	while (cur_item != NULL)
  	{
  		OnCommitItem *oc = (OnCommitItem *) lfirst(cur_item);
  
  		if (isCommit ? oc->deleting_subid != InvalidSubTransactionId :
  			oc->creating_subid != InvalidSubTransactionId)
  		{
  			/* cur_item must be removed */
  			on_commits = list_delete_cell(on_commits, cur_item, prev_item);
  			pfree(oc);
  			if (prev_item)
  				cur_item = lnext(prev_item);
  			else
  				cur_item = list_head(on_commits);
  		}
  		else
  		{
  			/* cur_item must be preserved */
  			oc->creating_subid = InvalidSubTransactionId;
  			oc->deleting_subid = InvalidSubTransactionId;
  			prev_item = cur_item;
  			cur_item = lnext(prev_item);
  		}
  	}
  }
  
  /*
   * Post-subcommit or post-subabort cleanup for ON COMMIT management.
   *
   * During subabort, we can immediately remove entries created during this
   * subtransaction.  During subcommit, just relabel entries marked during
   * this subtransaction as being the parent's responsibility.
   */
  void
  AtEOSubXact_on_commit_actions(bool isCommit, SubTransactionId mySubid,
  							  SubTransactionId parentSubid)
  {
  	ListCell   *cur_item;
  	ListCell   *prev_item;
  
  	prev_item = NULL;
  	cur_item = list_head(on_commits);
  
  	while (cur_item != NULL)
  	{
  		OnCommitItem *oc = (OnCommitItem *) lfirst(cur_item);
  
  		if (!isCommit && oc->creating_subid == mySubid)
  		{
  			/* cur_item must be removed */
  			on_commits = list_delete_cell(on_commits, cur_item, prev_item);
  			pfree(oc);
  			if (prev_item)
  				cur_item = lnext(prev_item);
  			else
  				cur_item = list_head(on_commits);
  		}
  		else
  		{
  			/* cur_item must be preserved */
  			if (oc->creating_subid == mySubid)
  				oc->creating_subid = parentSubid;
  			if (oc->deleting_subid == mySubid)
  				oc->deleting_subid = isCommit ? parentSubid : InvalidSubTransactionId;
  			prev_item = cur_item;
  			cur_item = lnext(prev_item);
  		}
  	}
  }
  
  /*
   * This is intended as a callback for RangeVarGetRelidExtended().  It allows
   * the relation to be locked only if (1) it's a plain table, materialized
   * view, or TOAST table and (2) the current user is the owner (or the
   * superuser).  This meets the permission-checking needs of CLUSTER, REINDEX
   * TABLE, and REFRESH MATERIALIZED VIEW; we expose it here so that it can be
   * used by all.
   */
  void
  RangeVarCallbackOwnsTable(const RangeVar *relation,
  						  Oid relId, Oid oldRelId, void *arg)
  {
  	char		relkind;
  
  	/* Nothing to do if the relation was not found. */
  	if (!OidIsValid(relId))
  		return;
  
  	/*
  	 * If the relation does exist, check whether it's an index.  But note that
  	 * the relation might have been dropped between the time we did the name
  	 * lookup and now.  In that case, there's nothing to do.
  	 */
  	relkind = get_rel_relkind(relId);
  	if (!relkind)
  		return;
  	if (relkind != RELKIND_RELATION && relkind != RELKIND_TOASTVALUE &&
  		relkind != RELKIND_MATVIEW && relkind != RELKIND_PARTITIONED_TABLE)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is not a table or materialized view", relation->relname)));
  
  	/* Check permissions */
  	if (!pg_class_ownercheck(relId, GetUserId()))
  		aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(get_rel_relkind(relId)), relation->relname);
  }
  
  /*
   * Callback to RangeVarGetRelidExtended(), similar to
   * RangeVarCallbackOwnsTable() but without checks on the type of the relation.
   */
  void
  RangeVarCallbackOwnsRelation(const RangeVar *relation,
  							 Oid relId, Oid oldRelId, void *arg)
  {
  	HeapTuple	tuple;
  
  	/* Nothing to do if the relation was not found. */
  	if (!OidIsValid(relId))
  		return;
  
  	tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relId));
  	if (!HeapTupleIsValid(tuple))	/* should not happen */
  		elog(ERROR, "cache lookup failed for relation %u", relId);
  
  	if (!pg_class_ownercheck(relId, GetUserId()))
  		aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(get_rel_relkind(relId)),
  					   relation->relname);
  
  	if (!allowSystemTableMods &&
  		IsSystemClass(relId, (Form_pg_class) GETSTRUCT(tuple)))
  		ereport(ERROR,
  				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  				 errmsg("permission denied: \"%s\" is a system catalog",
  						relation->relname)));
  
  	ReleaseSysCache(tuple);
  }
  
  /*
   * Common RangeVarGetRelid callback for rename, set schema, and alter table
   * processing.
   */
  static void
  RangeVarCallbackForAlterRelation(const RangeVar *rv, Oid relid, Oid oldrelid,
  								 void *arg)
  {
  	Node	   *stmt = (Node *) arg;
  	ObjectType	reltype;
  	HeapTuple	tuple;
  	Form_pg_class classform;
  	AclResult	aclresult;
  	char		relkind;
  
  	tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
  	if (!HeapTupleIsValid(tuple))
  		return;					/* concurrently dropped */
  	classform = (Form_pg_class) GETSTRUCT(tuple);
  	relkind = classform->relkind;
  
  	/* Must own relation. */
  	if (!pg_class_ownercheck(relid, GetUserId()))
  		aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(get_rel_relkind(relid)), rv->relname);
  
  	/* No system table modifications unless explicitly allowed. */
  	if (!allowSystemTableMods && IsSystemClass(relid, classform))
  		ereport(ERROR,
  				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  				 errmsg("permission denied: \"%s\" is a system catalog",
  						rv->relname)));
  
  	/*
  	 * Extract the specified relation type from the statement parse tree.
  	 *
  	 * Also, for ALTER .. RENAME, check permissions: the user must (still)
  	 * have CREATE rights on the containing namespace.
  	 */
  	if (IsA(stmt, RenameStmt))
  	{
  		aclresult = pg_namespace_aclcheck(classform->relnamespace,
  										  GetUserId(), ACL_CREATE);
  		if (aclresult != ACLCHECK_OK)
  			aclcheck_error(aclresult, OBJECT_SCHEMA,
  						   get_namespace_name(classform->relnamespace));
  		reltype = ((RenameStmt *) stmt)->renameType;
  	}
  	else if (IsA(stmt, AlterObjectSchemaStmt))
  		reltype = ((AlterObjectSchemaStmt *) stmt)->objectType;
  
  	else if (IsA(stmt, AlterTableStmt))
  		reltype = ((AlterTableStmt *) stmt)->relkind;
  	else
  	{
  		elog(ERROR, "unrecognized node type: %d", (int) nodeTag(stmt));
  		reltype = OBJECT_TABLE; /* placate compiler */
  	}
  
  	/*
  	 * For compatibility with prior releases, we allow ALTER TABLE to be used
  	 * with most other types of relations (but not composite types). We allow
  	 * similar flexibility for ALTER INDEX in the case of RENAME, but not
  	 * otherwise.  Otherwise, the user must select the correct form of the
  	 * command for the relation at issue.
  	 */
  	if (reltype == OBJECT_SEQUENCE && relkind != RELKIND_SEQUENCE)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is not a sequence", rv->relname)));
  
  	if (reltype == OBJECT_VIEW && relkind != RELKIND_VIEW)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is not a view", rv->relname)));
  
  	if (reltype == OBJECT_MATVIEW && relkind != RELKIND_MATVIEW)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is not a materialized view", rv->relname)));
  
  	if (reltype == OBJECT_FOREIGN_TABLE && relkind != RELKIND_FOREIGN_TABLE)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is not a foreign table", rv->relname)));
  
  	if (reltype == OBJECT_TYPE && relkind != RELKIND_COMPOSITE_TYPE)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is not a composite type", rv->relname)));
  
  	if (reltype == OBJECT_INDEX && relkind != RELKIND_INDEX &&
  		relkind != RELKIND_PARTITIONED_INDEX
  		&& !IsA(stmt, RenameStmt))
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is not an index", rv->relname)));
  
  	/*
  	 * Don't allow ALTER TABLE on composite types. We want people to use ALTER
  	 * TYPE for that.
  	 */
  	if (reltype != OBJECT_TYPE && relkind == RELKIND_COMPOSITE_TYPE)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is a composite type", rv->relname),
  				 errhint("Use ALTER TYPE instead.")));
  
  	/*
  	 * Don't allow ALTER TABLE .. SET SCHEMA on relations that can't be moved
  	 * to a different schema, such as indexes and TOAST tables.
  	 */
  	if (IsA(stmt, AlterObjectSchemaStmt) &&
  		relkind != RELKIND_RELATION &&
  		relkind != RELKIND_VIEW &&
  		relkind != RELKIND_MATVIEW &&
  		relkind != RELKIND_SEQUENCE &&
  		relkind != RELKIND_FOREIGN_TABLE &&
  		relkind != RELKIND_PARTITIONED_TABLE)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is not a table, view, materialized view, sequence, or foreign table",
  						rv->relname)));
  
  	ReleaseSysCache(tuple);
  }
  
  /*
   * Transform any expressions present in the partition key
   *
   * Returns a transformed PartitionSpec, as well as the strategy code
   */
  static PartitionSpec *
  transformPartitionSpec(Relation rel, PartitionSpec *partspec, char *strategy)
  {
  	PartitionSpec *newspec;
  	ParseState *pstate;
  	RangeTblEntry *rte;
  	ListCell   *l;
  
  	newspec = makeNode(PartitionSpec);
  
  	newspec->strategy = partspec->strategy;
  	newspec->partParams = NIL;
  	newspec->location = partspec->location;
  
  	/* Parse partitioning strategy name */
  	if (pg_strcasecmp(partspec->strategy, "hash") == 0)
  		*strategy = PARTITION_STRATEGY_HASH;
  	else if (pg_strcasecmp(partspec->strategy, "list") == 0)
  		*strategy = PARTITION_STRATEGY_LIST;
  	else if (pg_strcasecmp(partspec->strategy, "range") == 0)
  		*strategy = PARTITION_STRATEGY_RANGE;
  	else
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  				 errmsg("unrecognized partitioning strategy \"%s\"",
  						partspec->strategy)));
  
  	/* Check valid number of columns for strategy */
  	if (*strategy == PARTITION_STRATEGY_LIST &&
  		list_length(partspec->partParams) != 1)
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  				 errmsg("cannot use \"list\" partition strategy with more than one column")));
  
  	/*
  	 * Create a dummy ParseState and insert the target relation as its sole
  	 * rangetable entry.  We need a ParseState for transformExpr.
  	 */
  	pstate = make_parsestate(NULL);
  	rte = addRangeTableEntryForRelation(pstate, rel, NULL, false, true);
  	addRTEtoQuery(pstate, rte, true, true, true);
  
  	/* take care of any partition expressions */
  	foreach(l, partspec->partParams)
  	{
  		PartitionElem *pelem = castNode(PartitionElem, lfirst(l));
  
  		if (pelem->expr)
  		{
  			/* Copy, to avoid scribbling on the input */
  			pelem = copyObject(pelem);
  
  			/* Now do parse transformation of the expression */
  			pelem->expr = transformExpr(pstate, pelem->expr,
  										EXPR_KIND_PARTITION_EXPRESSION);
  
  			/* we have to fix its collations too */
  			assign_expr_collations(pstate, pelem->expr);
  		}
  
  		newspec->partParams = lappend(newspec->partParams, pelem);
  	}
  
  	return newspec;
  }
  
  /*
   * Compute per-partition-column information from a list of PartitionElems.
   * Expressions in the PartitionElems must be parse-analyzed already.
   */
  static void
  ComputePartitionAttrs(Relation rel, List *partParams, AttrNumber *partattrs,
  					  List **partexprs, Oid *partopclass, Oid *partcollation,
  					  char strategy)
  {
  	int			attn;
  	ListCell   *lc;
  	Oid			am_oid;
  
  	attn = 0;
  	foreach(lc, partParams)
  	{
  		PartitionElem *pelem = castNode(PartitionElem, lfirst(lc));
  		Oid			atttype;
  		Oid			attcollation;
  
  		if (pelem->name != NULL)
  		{
  			/* Simple attribute reference */
  			HeapTuple	atttuple;
  			Form_pg_attribute attform;
  
  			atttuple = SearchSysCacheAttName(RelationGetRelid(rel),
  											 pelem->name);
  			if (!HeapTupleIsValid(atttuple))
  				ereport(ERROR,
  						(errcode(ERRCODE_UNDEFINED_COLUMN),
  						 errmsg("column \"%s\" named in partition key does not exist",
  								pelem->name)));
  			attform = (Form_pg_attribute) GETSTRUCT(atttuple);
  
  			if (attform->attnum <= 0)
  				ereport(ERROR,
  						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  						 errmsg("cannot use system column \"%s\" in partition key",
  								pelem->name)));
  
  			partattrs[attn] = attform->attnum;
  			atttype = attform->atttypid;
  			attcollation = attform->attcollation;
  			ReleaseSysCache(atttuple);
  		}
  		else
  		{
  			/* Expression */
  			Node	   *expr = pelem->expr;
  
  			Assert(expr != NULL);
  			atttype = exprType(expr);
  			attcollation = exprCollation(expr);
  
  			/*
  			 * Strip any top-level COLLATE clause.  This ensures that we treat
  			 * "x COLLATE y" and "(x COLLATE y)" alike.
  			 */
  			while (IsA(expr, CollateExpr))
  				expr = (Node *) ((CollateExpr *) expr)->arg;
  
  			if (IsA(expr, Var) &&
  				((Var *) expr)->varattno > 0)
  			{
  				/*
  				 * User wrote "(column)" or "(column COLLATE something)".
  				 * Treat it like simple attribute anyway.
  				 */
  				partattrs[attn] = ((Var *) expr)->varattno;
  			}
  			else
  			{
  				Bitmapset  *expr_attrs = NULL;
  				int			i;
  
  				partattrs[attn] = 0;	/* marks the column as expression */
  				*partexprs = lappend(*partexprs, expr);
  
  				/*
  				 * Try to simplify the expression before checking for
  				 * mutability.  The main practical value of doing it in this
  				 * order is that an inline-able SQL-language function will be
  				 * accepted if its expansion is immutable, whether or not the
  				 * function itself is marked immutable.
  				 *
  				 * Note that expression_planner does not change the passed in
  				 * expression destructively and we have already saved the
  				 * expression to be stored into the catalog above.
  				 */
  				expr = (Node *) expression_planner((Expr *) expr);
  
  				/*
  				 * Partition expression cannot contain mutable functions,
  				 * because a given row must always map to the same partition
  				 * as long as there is no change in the partition boundary
  				 * structure.
  				 */
  				if (contain_mutable_functions(expr))
  					ereport(ERROR,
  							(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  							 errmsg("functions in partition key expression must be marked IMMUTABLE")));
  
  				/*
  				 * transformPartitionSpec() should have already rejected
  				 * subqueries, aggregates, window functions, and SRFs, based
  				 * on the EXPR_KIND_ for partition expressions.
  				 */
  
  				/*
  				 * Cannot have expressions containing whole-row references or
  				 * system column references.
  				 */
  				pull_varattnos(expr, 1, &expr_attrs);
  				if (bms_is_member(0 - FirstLowInvalidHeapAttributeNumber,
  								  expr_attrs))
  					ereport(ERROR,
  							(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  							 errmsg("partition key expressions cannot contain whole-row references")));
  				for (i = FirstLowInvalidHeapAttributeNumber; i < 0; i++)
  				{
  					if (bms_is_member(i - FirstLowInvalidHeapAttributeNumber,
  									  expr_attrs))
  						ereport(ERROR,
  								(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  								 errmsg("partition key expressions cannot contain system column references")));
  				}
  
  				/*
  				 * While it is not exactly *wrong* for a partition expression
  				 * to be a constant, it seems better to reject such keys.
  				 */
  				if (IsA(expr, Const))
  					ereport(ERROR,
  							(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  							 errmsg("cannot use constant expression as partition key")));
  			}
  		}
  
  		/*
  		 * Apply collation override if any
  		 */
  		if (pelem->collation)
  			attcollation = get_collation_oid(pelem->collation, false);
  
  		/*
  		 * Check we have a collation iff it's a collatable type.  The only
  		 * expected failures here are (1) COLLATE applied to a noncollatable
  		 * type, or (2) partition expression had an unresolved collation. But
  		 * we might as well code this to be a complete consistency check.
  		 */
  		if (type_is_collatable(atttype))
  		{
  			if (!OidIsValid(attcollation))
  				ereport(ERROR,
  						(errcode(ERRCODE_INDETERMINATE_COLLATION),
  						 errmsg("could not determine which collation to use for partition expression"),
  						 errhint("Use the COLLATE clause to set the collation explicitly.")));
  		}
  		else
  		{
  			if (OidIsValid(attcollation))
  				ereport(ERROR,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  						 errmsg("collations are not supported by type %s",
  								format_type_be(atttype))));
  		}
  
  		partcollation[attn] = attcollation;
  
  		/*
  		 * Identify the appropriate operator class.  For list and range
  		 * partitioning, we use a btree operator class; hash partitioning uses
  		 * a hash operator class.
  		 */
  		if (strategy == PARTITION_STRATEGY_HASH)
  			am_oid = HASH_AM_OID;
  		else
  			am_oid = IsYugaByteEnabled() ? LSM_AM_OID : BTREE_AM_OID;
  
  		if (!pelem->opclass)
  		{
  			partopclass[attn] = GetDefaultOpClass(atttype, am_oid);
  
  			if (!OidIsValid(partopclass[attn]))
  			{
  				if (strategy == PARTITION_STRATEGY_HASH)
  					ereport(ERROR,
  							(errcode(ERRCODE_UNDEFINED_OBJECT),
  							 errmsg("data type %s has no default hash operator class",
  									format_type_be(atttype)),
  							 errhint("You must specify a hash operator class or define a default hash operator class for the data type.")));
  				else
  					ereport(ERROR,
  							(errcode(ERRCODE_UNDEFINED_OBJECT),
  							 errmsg("data type %s has no default btree operator class",
  									format_type_be(atttype)),
  							 errhint("You must specify a btree operator class or define a default btree operator class for the data type.")));
  
  			}
  		}
  		else
  			partopclass[attn] = ResolveOpClass(pelem->opclass,
  											   atttype,
  											   am_oid == HASH_AM_OID ? "hash" : "btree",
  											   am_oid);
  
  		attn++;
  	}
  }
  
  /*
   * PartConstraintImpliedByRelConstraint
   *		Do scanrel's existing constraints imply the partition constraint?
   *
   * "Existing constraints" include its check constraints and column-level
   * NOT NULL constraints.  partConstraint describes the partition constraint,
   * in implicit-AND form.
   */
  bool
  PartConstraintImpliedByRelConstraint(Relation scanrel,
  									 List *partConstraint)
  {
  	List	   *existConstraint = NIL;
  	TupleConstr *constr = RelationGetDescr(scanrel)->constr;
  	int			num_check,
  				i;
  
  	if (constr && constr->has_not_null)
  	{
  		int			natts = scanrel->rd_att->natts;
  
  		for (i = 1; i <= natts; i++)
  		{
  			Form_pg_attribute att = TupleDescAttr(scanrel->rd_att, i - 1);
  
  			if (att->attnotnull && !att->attisdropped)
  			{
  				NullTest   *ntest = makeNode(NullTest);
  
  				ntest->arg = (Expr *) makeVar(1,
  											  i,
  											  att->atttypid,
  											  att->atttypmod,
  											  att->attcollation,
  											  0);
  				ntest->nulltesttype = IS_NOT_NULL;
  
  				/*
  				 * argisrow=false is correct even for a composite column,
  				 * because attnotnull does not represent a SQL-spec IS NOT
  				 * NULL test in such a case, just IS DISTINCT FROM NULL.
  				 */
  				ntest->argisrow = false;
  				ntest->location = -1;
  				existConstraint = lappend(existConstraint, ntest);
  			}
  		}
  	}
  
  	num_check = (constr != NULL) ? constr->num_check : 0;
  	for (i = 0; i < num_check; i++)
  	{
  		Node	   *cexpr;
  
  		/*
  		 * If this constraint hasn't been fully validated yet, we must ignore
  		 * it here.
  		 */
  		if (!constr->check[i].ccvalid)
  			continue;
  
  		cexpr = stringToNode(constr->check[i].ccbin);
  
  		/*
  		 * Run each expression through const-simplification and
  		 * canonicalization.  It is necessary, because we will be comparing it
  		 * to similarly-processed partition constraint expressions, and may
  		 * fail to detect valid matches without this.
  		 */
  		cexpr = eval_const_expressions(NULL, cexpr);
  		cexpr = (Node *) canonicalize_qual((Expr *) cexpr, true);
  
  		existConstraint = list_concat(existConstraint,
  									  make_ands_implicit((Expr *) cexpr));
  	}
  
  	/*
  	 * Try to make the proof.  Since we are comparing CHECK constraints, we
  	 * need to use weak implication, i.e., we assume existConstraint is
  	 * not-false and try to prove the same for partConstraint.
  	 *
  	 * Note that predicate_implied_by assumes its first argument is known
  	 * immutable.  That should always be true for partition constraints, so we
  	 * don't test it here.
  	 */
  	return predicate_implied_by(partConstraint, existConstraint, true);
  }
  
  /*
   * QueuePartitionConstraintValidation
   *
   * Add an entry to wqueue to have the given partition constraint validated by
   * Phase 3, for the given relation, and all its children.
   *
   * We first verify whether the given constraint is implied by pre-existing
   * relation constraints; if it is, there's no need to scan the table to
   * validate, so don't queue in that case.
   */
  static void
  QueuePartitionConstraintValidation(List **wqueue, Relation scanrel,
  								   List *partConstraint,
  								   bool validate_default)
  {
  	/*
  	 * Based on the table's existing constraints, determine whether or not we
  	 * may skip scanning the table.
  	 */
  	if (PartConstraintImpliedByRelConstraint(scanrel, partConstraint))
  	{
  		if (!validate_default)
  			ereport(INFO,
  					(errmsg("partition constraint for table \"%s\" is implied by existing constraints",
  							RelationGetRelationName(scanrel))));
  		else
  			ereport(INFO,
  					(errmsg("updated partition constraint for default partition \"%s\" is implied by existing constraints",
  							RelationGetRelationName(scanrel))));
  		return;
  	}
  
  	/*
  	 * Constraints proved insufficient. For plain relations, queue a
  	 * validation item now; for partitioned tables, recurse to process each
  	 * partition.
  	 */
  	if (scanrel->rd_rel->relkind == RELKIND_RELATION)
  	{
  		AlteredTableInfo *tab;
  
  		/* Grab a work queue entry. */
  		tab = ATGetQueueEntry(wqueue, scanrel);
  		Assert(tab->partition_constraint == NULL);
  		tab->partition_constraint = (Expr *) linitial(partConstraint);
  		tab->validate_default = validate_default;
  	}
  	else if (scanrel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
  	{
  		PartitionDesc partdesc = RelationGetPartitionDesc(scanrel);
  		int			i;
  
  		for (i = 0; i < partdesc->nparts; i++)
  		{
  			Relation	part_rel;
  			bool		found_whole_row;
  			List	   *thisPartConstraint;
  
  			/*
  			 * This is the minimum lock we need to prevent deadlocks.
  			 */
  			part_rel = heap_open(partdesc->oids[i], AccessExclusiveLock);
  
  			/*
  			 * Adjust the constraint for scanrel so that it matches this
  			 * partition's attribute numbers.
  			 */
  			thisPartConstraint =
  				map_partition_varattnos(partConstraint, 1,
  										part_rel, scanrel, &found_whole_row);
  			/* There can never be a whole-row reference here */
  			if (found_whole_row)
  				elog(ERROR, "unexpected whole-row reference found in partition constraint");
  
  			QueuePartitionConstraintValidation(wqueue, part_rel,
  											   thisPartConstraint,
  											   validate_default);
  			heap_close(part_rel, NoLock);	/* keep lock till commit */
  		}
  	}
  }
  
  /*
   * ALTER TABLE <name> ATTACH PARTITION <partition-name> FOR VALUES
   *
   * Return the address of the newly attached partition.
   */
  static ObjectAddress
  ATExecAttachPartition(List **wqueue, Relation rel, PartitionCmd *cmd)
  {
  	Relation	attachrel,
  				catalog;
  	List	   *attachrel_children;
  	List	   *partConstraint;
  	SysScanDesc scan;
  	ScanKeyData skey;
  	AttrNumber	attno;
  	int			natts;
  	TupleDesc	tupleDesc;
  	ObjectAddress address;
  	const char *trigger_name;
  	bool		found_whole_row;
  	Oid			defaultPartOid;
  	List	   *partBoundConstraint;
  	List	   *cloned;
  	ListCell   *l;
  
  	/*
  	 * We must lock the default partition if one exists, because attaching a
  	 * new partition will change its partition constraint.
  	 */
  	defaultPartOid =
  		get_default_oid_from_partdesc(RelationGetPartitionDesc(rel));
  	if (OidIsValid(defaultPartOid))
  		LockRelationOid(defaultPartOid, AccessExclusiveLock);
  
  	attachrel = heap_openrv(cmd->name, AccessExclusiveLock);
  
  	/*
  	 * XXX I think it'd be a good idea to grab locks on all tables referenced
  	 * by FKs at this point also.
  	 */
  
  	/*
  	 * Must be owner of both parent and source table -- parent was checked by
  	 * ATSimplePermissions call in ATPrepCmd
  	 */
  	ATSimplePermissions(attachrel, ATT_TABLE | ATT_FOREIGN_TABLE);
  
  	/* A partition can only have one parent */
  	if (attachrel->rd_rel->relispartition)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is already a partition",
  						RelationGetRelationName(attachrel))));
  
  	if (OidIsValid(attachrel->rd_rel->reloftype))
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot attach a typed table as partition")));
  
  	/*
  	 * Table being attached should not already be part of inheritance; either
  	 * as a child table...
  	 */
  	catalog = heap_open(InheritsRelationId, AccessShareLock);
  	ScanKeyInit(&skey,
  				Anum_pg_inherits_inhrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(attachrel)));
  	scan = systable_beginscan(catalog, InheritsRelidSeqnoIndexId, true,
  							  NULL, 1, &skey);
  	if (HeapTupleIsValid(systable_getnext(scan)))
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot attach inheritance child as partition")));
  	systable_endscan(scan);
  
  	/* ...or as a parent table (except the case when it is partitioned) */
  	ScanKeyInit(&skey,
  				Anum_pg_inherits_inhparent,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(attachrel)));
  	scan = systable_beginscan(catalog, InheritsParentIndexId, true, NULL,
  							  1, &skey);
  	if (HeapTupleIsValid(systable_getnext(scan)) &&
  		attachrel->rd_rel->relkind == RELKIND_RELATION)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot attach inheritance parent as partition")));
  	systable_endscan(scan);
  	heap_close(catalog, AccessShareLock);
  
  	/*
  	 * Prevent circularity by seeing if rel is a partition of attachrel. (In
  	 * particular, this disallows making a rel a partition of itself.)
  	 *
  	 * We do that by checking if rel is a member of the list of attachrel's
  	 * partitions provided the latter is partitioned at all.  We want to avoid
  	 * having to construct this list again, so we request the strongest lock
  	 * on all partitions.  We need the strongest lock, because we may decide
  	 * to scan them if we find out that the table being attached (or its leaf
  	 * partitions) may contain rows that violate the partition constraint. If
  	 * the table has a constraint that would prevent such rows, which by
  	 * definition is present in all the partitions, we need not scan the
  	 * table, nor its partitions.  But we cannot risk a deadlock by taking a
  	 * weaker lock now and the stronger one only when needed.
  	 */
  	attachrel_children = find_all_inheritors(RelationGetRelid(attachrel),
  											 AccessExclusiveLock, NULL);
  	if (list_member_oid(attachrel_children, RelationGetRelid(rel)))
  		ereport(ERROR,
  				(errcode(ERRCODE_DUPLICATE_TABLE),
  				 errmsg("circular inheritance not allowed"),
  				 errdetail("\"%s\" is already a child of \"%s\".",
  						   RelationGetRelationName(rel),
  						   RelationGetRelationName(attachrel))));
  
  	/* If the parent is permanent, so must be all of its partitions. */
  	if (rel->rd_rel->relpersistence != RELPERSISTENCE_TEMP &&
  		attachrel->rd_rel->relpersistence == RELPERSISTENCE_TEMP)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot attach a temporary relation as partition of permanent relation \"%s\"",
  						RelationGetRelationName(rel))));
  
  	/* Temp parent cannot have a partition that is itself not a temp */
  	if (rel->rd_rel->relpersistence == RELPERSISTENCE_TEMP &&
  		attachrel->rd_rel->relpersistence != RELPERSISTENCE_TEMP)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot attach a permanent relation as partition of temporary relation \"%s\"",
  						RelationGetRelationName(rel))));
  
  	/* If the parent is temp, it must belong to this session */
  	if (rel->rd_rel->relpersistence == RELPERSISTENCE_TEMP &&
  		!rel->rd_islocaltemp)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot attach as partition of temporary relation of another session")));
  
  	/* Ditto for the partition */
  	if (attachrel->rd_rel->relpersistence == RELPERSISTENCE_TEMP &&
  		!attachrel->rd_islocaltemp)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot attach temporary relation of another session as partition")));
  
  	/* If parent has OIDs then child must have OIDs */
  	if (rel->rd_rel->relhasoids && !attachrel->rd_rel->relhasoids)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot attach table \"%s\" without OIDs as partition of"
  						" table \"%s\" with OIDs", RelationGetRelationName(attachrel),
  						RelationGetRelationName(rel))));
  
  	/* OTOH, if parent doesn't have them, do not allow in attachrel either */
  	if (attachrel->rd_rel->relhasoids && !rel->rd_rel->relhasoids)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("cannot attach table \"%s\" with OIDs as partition of table"
  						" \"%s\" without OIDs", RelationGetRelationName(attachrel),
  						RelationGetRelationName(rel))));
  
  	/* Check if there are any columns in attachrel that aren't in the parent */
  	tupleDesc = RelationGetDescr(attachrel);
  	natts = tupleDesc->natts;
  	for (attno = 1; attno <= natts; attno++)
  	{
  		Form_pg_attribute attribute = TupleDescAttr(tupleDesc, attno - 1);
  		char	   *attributeName = NameStr(attribute->attname);
  
  		/* Ignore dropped */
  		if (attribute->attisdropped)
  			continue;
  
  		/* Try to find the column in parent (matching on column name) */
  		if (!SearchSysCacheExists2(ATTNAME,
  								   ObjectIdGetDatum(RelationGetRelid(rel)),
  								   CStringGetDatum(attributeName)))
  			ereport(ERROR,
  					(errcode(ERRCODE_DATATYPE_MISMATCH),
  					 errmsg("table \"%s\" contains column \"%s\" not found in parent \"%s\"",
  							RelationGetRelationName(attachrel), attributeName,
  							RelationGetRelationName(rel)),
  					 errdetail("The new partition may contain only the columns present in parent.")));
  	}
  
  	/*
  	 * If child_rel has row-level triggers with transition tables, we
  	 * currently don't allow it to become a partition.  See also prohibitions
  	 * in ATExecAddInherit() and CreateTrigger().
  	 */
  	trigger_name = FindTriggerIncompatibleWithInheritance(attachrel->trigdesc);
  	if (trigger_name != NULL)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("trigger \"%s\" prevents table \"%s\" from becoming a partition",
  						trigger_name, RelationGetRelationName(attachrel)),
  				 errdetail("ROW triggers with transition tables are not supported on partitions")));
  
  	/*
  	 * Check that the new partition's bound is valid and does not overlap any
  	 * of existing partitions of the parent - note that it does not return on
  	 * error.
  	 */
  	check_new_partition_bound(RelationGetRelationName(attachrel), rel,
  							  cmd->bound);
  
  	/* OK to create inheritance.  Rest of the checks performed there */
  	CreateInheritance(attachrel, rel);
  
  	/* Update the pg_class entry. */
  	StorePartitionBound(attachrel, rel, cmd->bound);
  
  	/* Ensure there exists a correct set of indexes in the partition. */
  	AttachPartitionEnsureIndexes(rel, attachrel);
  
  	/* and triggers */
  	CloneRowTriggersToPartition(rel, attachrel);
  
  	/*
  	 * Clone foreign key constraints, and setup for Phase 3 to verify them.
  	 */
  	cloned = NIL;
  	CloneForeignKeyConstraints(RelationGetRelid(rel),
  							   RelationGetRelid(attachrel), &cloned);
  	foreach(l, cloned)
  	{
  		ClonedConstraint *clonedcon = lfirst(l);
  		NewConstraint *newcon;
  		Relation	clonedrel;
  		AlteredTableInfo *parttab;
  
  		clonedrel = relation_open(clonedcon->relid, NoLock);
  		parttab = ATGetQueueEntry(wqueue, clonedrel);
  
  		newcon = (NewConstraint *) palloc0(sizeof(NewConstraint));
  		newcon->name = clonedcon->constraint->conname;
  		newcon->contype = CONSTR_FOREIGN;
  		newcon->refrelid = clonedcon->refrelid;
  		newcon->refindid = clonedcon->conindid;
  		newcon->conid = clonedcon->conid;
  		newcon->qual = (Node *) clonedcon->constraint;
  
  		parttab->constraints = lappend(parttab->constraints, newcon);
  
  		relation_close(clonedrel, NoLock);
  	}
  
  	/*
  	 * Generate partition constraint from the partition bound specification.
  	 * If the parent itself is a partition, make sure to include its
  	 * constraint as well.
  	 */
  	partBoundConstraint = get_qual_from_partbound(attachrel, rel, cmd->bound);
  	partConstraint = list_concat(partBoundConstraint,
  								 RelationGetPartitionQual(rel));
  
  	/* Skip validation if there are no constraints to validate. */
  	if (partConstraint)
  	{
  		/*
  		 * Run the partition quals through const-simplification similar to
  		 * check constraints.  We skip canonicalize_qual, though, because
  		 * partition quals should be in canonical form already.
  		 */
  		partConstraint =
  			(List *) eval_const_expressions(NULL,
  											(Node *) partConstraint);
  
  		/* XXX this sure looks wrong */
  		partConstraint = list_make1(make_ands_explicit(partConstraint));
  
  		/*
  		 * Adjust the generated constraint to match this partition's attribute
  		 * numbers.
  		 */
  		partConstraint = map_partition_varattnos(partConstraint, 1, attachrel,
  												 rel, &found_whole_row);
  		/* There can never be a whole-row reference here */
  		if (found_whole_row)
  			elog(ERROR,
  				 "unexpected whole-row reference found in partition key");
  
  		/* Validate partition constraints against the table being attached. */
  		QueuePartitionConstraintValidation(wqueue, attachrel, partConstraint,
  										   false);
  	}
  
  	/*
  	 * If we're attaching a partition other than the default partition and a
  	 * default one exists, then that partition's partition constraint changes,
  	 * so add an entry to the work queue to validate it, too.  (We must not do
  	 * this when the partition being attached is the default one; we already
  	 * did it above!)
  	 */
  	if (OidIsValid(defaultPartOid))
  	{
  		Relation	defaultrel;
  		List	   *defPartConstraint;
  
  		Assert(!cmd->bound->is_default);
  
  		/* we already hold a lock on the default partition */
  		defaultrel = heap_open(defaultPartOid, NoLock);
  		defPartConstraint =
  			get_proposed_default_constraint(partBoundConstraint);
  		QueuePartitionConstraintValidation(wqueue, defaultrel,
  										   defPartConstraint, true);
  
  		/* keep our lock until commit. */
  		heap_close(defaultrel, NoLock);
  	}
  
  	ObjectAddressSet(address, RelationRelationId, RelationGetRelid(attachrel));
  
  	/* keep our lock until commit */
  	heap_close(attachrel, NoLock);
  
  	return address;
  }
  
  /*
   * AttachPartitionEnsureIndexes
   *		subroutine for ATExecAttachPartition to create/match indexes
   *
   * Enforce the indexing rule for partitioned tables during ALTER TABLE / ATTACH
   * PARTITION: every partition must have an index attached to each index on the
   * partitioned table.
   */
  static void
  AttachPartitionEnsureIndexes(Relation rel, Relation attachrel)
  {
  	List	   *idxes;
  	List	   *attachRelIdxs;
  	Relation   *attachrelIdxRels;
  	IndexInfo **attachInfos;
  	int			i;
  	ListCell   *cell;
  	MemoryContext cxt;
  	MemoryContext oldcxt;
  
  	cxt = AllocSetContextCreate(GetCurrentMemoryContext(),
  								"AttachPartitionEnsureIndexes",
  								ALLOCSET_DEFAULT_SIZES);
  	oldcxt = MemoryContextSwitchTo(cxt);
  
  	idxes = RelationGetIndexList(rel);
  	attachRelIdxs = RelationGetIndexList(attachrel);
  	attachrelIdxRels = palloc(sizeof(Relation) * list_length(attachRelIdxs));
  	attachInfos = palloc(sizeof(IndexInfo *) * list_length(attachRelIdxs));
  
  	/* Build arrays of all existing indexes and their IndexInfos */
  	i = 0;
  	foreach(cell, attachRelIdxs)
  	{
  		Oid			cldIdxId = lfirst_oid(cell);
  
  		attachrelIdxRels[i] = index_open(cldIdxId, AccessShareLock);
  		attachInfos[i] = BuildIndexInfo(attachrelIdxRels[i]);
  		i++;
  	}
  
  	/*
  	 * For each index on the partitioned table, find a matching one in the
  	 * partition-to-be; if one is not found, create one.
  	 */
  	foreach(cell, idxes)
  	{
  		Oid			idx = lfirst_oid(cell);
  		Relation	idxRel = index_open(idx, AccessShareLock);
  		IndexInfo  *info;
  		AttrNumber *attmap;
  		bool		found = false;
  		Oid			constraintOid;
  
  		/*
  		 * Ignore indexes in the partitioned table other than partitioned
  		 * indexes.
  		 */
  		if (idxRel->rd_rel->relkind != RELKIND_PARTITIONED_INDEX)
  		{
  			index_close(idxRel, AccessShareLock);
  			continue;
  		}
  
  		/* construct an indexinfo to compare existing indexes against */
  		info = BuildIndexInfo(idxRel);
  		attmap = convert_tuples_by_name_map(RelationGetDescr(attachrel),
  											RelationGetDescr(rel),
  											gettext_noop("could not convert row type"));
  		constraintOid = get_relation_idx_constraint_oid(RelationGetRelid(rel), idx);
  
  		/*
  		 * Scan the list of existing indexes in the partition-to-be, and mark
  		 * the first matching, unattached one we find, if any, as partition of
  		 * the parent index.  If we find one, we're done.
  		 */
  		for (i = 0; i < list_length(attachRelIdxs); i++)
  		{
  			Oid			cldIdxId = RelationGetRelid(attachrelIdxRels[i]);
  			Oid			cldConstrOid = InvalidOid;
  
  			/* does this index have a parent?  if so, can't use it */
  			if (attachrelIdxRels[i]->rd_rel->relispartition)
  				continue;
  
  			if (CompareIndexInfo(attachInfos[i], info,
  								 attachrelIdxRels[i]->rd_indcollation,
  								 idxRel->rd_indcollation,
  								 attachrelIdxRels[i]->rd_opfamily,
  								 idxRel->rd_opfamily,
  								 attmap,
  								 RelationGetDescr(rel)->natts))
  			{
  				/*
  				 * If this index is being created in the parent because of a
  				 * constraint, then the child needs to have a constraint also,
  				 * so look for one.  If there is no such constraint, this
  				 * index is no good, so keep looking.
  				 */
  				if (OidIsValid(constraintOid))
  				{
  					cldConstrOid =
  						get_relation_idx_constraint_oid(RelationGetRelid(attachrel),
  														cldIdxId);
  					/* no dice */
  					if (!OidIsValid(cldConstrOid))
  						continue;
  				}
  
  				/* bingo. */
  				IndexSetParentIndex(attachrelIdxRels[i], idx);
  				if (OidIsValid(constraintOid))
  					ConstraintSetParentConstraint(cldConstrOid, constraintOid);
  				update_relispartition(NULL, cldIdxId, true);
  				found = true;
  				break;
  			}
  		}
  
  		/*
  		 * If no suitable index was found in the partition-to-be, create one
  		 * now.
  		 */
  		if (!found)
  		{
  			IndexStmt  *stmt;
  			Oid			constraintOid;
  
  			stmt = generateClonedIndexStmt(NULL, RelationGetRelid(attachrel),
  										   idxRel, attmap,
  										   RelationGetDescr(rel)->natts,
  										   &constraintOid);
  			DefineIndex(RelationGetRelid(attachrel), stmt, InvalidOid,
  						RelationGetRelid(idxRel),
  						constraintOid,
  						true, false, false, false, false);
  		}
  
  		index_close(idxRel, AccessShareLock);
  	}
  
  	/* Clean up. */
  	for (i = 0; i < list_length(attachRelIdxs); i++)
  		index_close(attachrelIdxRels[i], AccessShareLock);
  	MemoryContextSwitchTo(oldcxt);
  	MemoryContextDelete(cxt);
  }
  
  /*
   * CloneRowTriggersToPartition
   *		subroutine for ATExecAttachPartition/DefineRelation to create row
   *		triggers on partitions
   */
  static void
  CloneRowTriggersToPartition(Relation parent, Relation partition)
  {
  	Relation	pg_trigger;
  	ScanKeyData key;
  	SysScanDesc scan;
  	HeapTuple	tuple;
  	MemoryContext oldcxt,
  				perTupCxt;
  
  	ScanKeyInit(&key, Anum_pg_trigger_tgrelid, BTEqualStrategyNumber,
  				F_OIDEQ, ObjectIdGetDatum(RelationGetRelid(parent)));
  	pg_trigger = heap_open(TriggerRelationId, RowExclusiveLock);
  	scan = systable_beginscan(pg_trigger, TriggerRelidNameIndexId,
  							  true, NULL, 1, &key);
  
  	perTupCxt = AllocSetContextCreate(GetCurrentMemoryContext(),
  									  "clone trig", ALLOCSET_SMALL_SIZES);
  	oldcxt = MemoryContextSwitchTo(perTupCxt);
  
  	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
  	{
  		Form_pg_trigger trigForm;
  		CreateTrigStmt *trigStmt;
  		Node	   *qual = NULL;
  		Datum		value;
  		bool		isnull;
  		List	   *cols = NIL;
  
  		trigForm = (Form_pg_trigger) GETSTRUCT(tuple);
  
  		/*
  		 * Ignore statement-level triggers; those are not cloned.
  		 */
  		if (!TRIGGER_FOR_ROW(trigForm->tgtype))
  			continue;
  
  		/* We don't clone internal triggers, either */
  		if (trigForm->tgisinternal)
  			continue;
  
  		/*
  		 * Complain if we find an unexpected trigger type.
  		 */
  		if (!TRIGGER_FOR_AFTER(trigForm->tgtype))
  			elog(ERROR, "unexpected trigger \"%s\" found",
  				 NameStr(trigForm->tgname));
  
  		/*
  		 * If there is a WHEN clause, generate a 'cooked' version of it that's
  		 * appropriate for the partition.
  		 */
  		value = heap_getattr(tuple, Anum_pg_trigger_tgqual,
  							 RelationGetDescr(pg_trigger), &isnull);
  		if (!isnull)
  		{
  			bool		found_whole_row;
  
  			qual = stringToNode(TextDatumGetCString(value));
  			qual = (Node *) map_partition_varattnos((List *) qual, PRS2_OLD_VARNO,
  													partition, parent,
  													&found_whole_row);
  			if (found_whole_row)
  				elog(ERROR, "unexpected whole-row reference found in trigger WHEN clause");
  			qual = (Node *) map_partition_varattnos((List *) qual, PRS2_NEW_VARNO,
  													partition, parent,
  													&found_whole_row);
  			if (found_whole_row)
  				elog(ERROR, "unexpected whole-row reference found in trigger WHEN clause");
  		}
  
  		/*
  		 * If there is a column list, transform it to a list of column names.
  		 * Note we don't need to map this list in any way ...
  		 */
  		if (trigForm->tgattr.dim1 > 0)
  		{
  			int			i;
  
  			for (i = 0; i < trigForm->tgattr.dim1; i++)
  			{
  				Form_pg_attribute col;
  
  				col = TupleDescAttr(parent->rd_att,
  									trigForm->tgattr.values[i] - 1);
  				cols = lappend(cols,
  							   makeString(pstrdup(NameStr(col->attname))));
  			}
  		}
  
  		trigStmt = makeNode(CreateTrigStmt);
  		trigStmt->trigname = NameStr(trigForm->tgname);
  		trigStmt->relation = NULL;
  		trigStmt->funcname = NULL;	/* passed separately */
  		trigStmt->args = NULL;	/* passed separately */
  		trigStmt->row = true;
  		trigStmt->timing = trigForm->tgtype & TRIGGER_TYPE_TIMING_MASK;
  		trigStmt->events = trigForm->tgtype & TRIGGER_TYPE_EVENT_MASK;
  		trigStmt->columns = cols;
  		trigStmt->whenClause = NULL;	/* passed separately */
  		trigStmt->isconstraint = OidIsValid(trigForm->tgconstraint);
  		trigStmt->transitionRels = NIL; /* not supported at present */
  		trigStmt->deferrable = trigForm->tgdeferrable;
  		trigStmt->initdeferred = trigForm->tginitdeferred;
  		trigStmt->constrrel = NULL; /* passed separately */
  
  		CreateTrigger(trigStmt, NULL, RelationGetRelid(partition),
  					  trigForm->tgconstrrelid, InvalidOid, InvalidOid,
  					  trigForm->tgfoid, HeapTupleGetOid(tuple), qual,
  					  false, true);
  
  		MemoryContextReset(perTupCxt);
  	}
  
  	MemoryContextSwitchTo(oldcxt);
  	MemoryContextDelete(perTupCxt);
  
  	systable_endscan(scan);
  	heap_close(pg_trigger, RowExclusiveLock);
  }
  
  /*
   * ALTER TABLE DETACH PARTITION
   *
   * Return the address of the relation that is no longer a partition of rel.
   */
  static ObjectAddress
  ATExecDetachPartition(Relation rel, RangeVar *name)
  {
  	Relation	partRel,
  				classRel;
  	HeapTuple	tuple,
  				newtuple;
  	Datum		new_val[Natts_pg_class];
  	bool		new_null[Natts_pg_class],
  				new_repl[Natts_pg_class];
  	ObjectAddress address;
  	Oid			defaultPartOid;
  	List	   *indexes;
  	List	   *fks;
  	ListCell   *cell;
  
  	/*
  	 * We must lock the default partition, because detaching this partition
  	 * will change its partition constraint.
  	 */
  	defaultPartOid =
  		get_default_oid_from_partdesc(RelationGetPartitionDesc(rel));
  	if (OidIsValid(defaultPartOid))
  		LockRelationOid(defaultPartOid, AccessExclusiveLock);
  
  	partRel = heap_openrv(name, ShareUpdateExclusiveLock);
  
  	/* All inheritance related checks are performed within the function */
  	RemoveInheritance(partRel, rel);
  
  	/* Update pg_class tuple */
  	classRel = heap_open(RelationRelationId, RowExclusiveLock);
  	tuple = SearchSysCacheCopy1(RELOID,
  								ObjectIdGetDatum(RelationGetRelid(partRel)));
  	if (!HeapTupleIsValid(tuple))
  		elog(ERROR, "cache lookup failed for relation %u",
  			 RelationGetRelid(partRel));
  	Assert(((Form_pg_class) GETSTRUCT(tuple))->relispartition);
  
  	/* Clear relpartbound and reset relispartition */
  	memset(new_val, 0, sizeof(new_val));
  	memset(new_null, false, sizeof(new_null));
  	memset(new_repl, false, sizeof(new_repl));
  	new_val[Anum_pg_class_relpartbound - 1] = (Datum) 0;
  	new_null[Anum_pg_class_relpartbound - 1] = true;
  	new_repl[Anum_pg_class_relpartbound - 1] = true;
  	newtuple = heap_modify_tuple(tuple, RelationGetDescr(classRel),
  								 new_val, new_null, new_repl);
  
  	((Form_pg_class) GETSTRUCT(newtuple))->relispartition = false;
  	CatalogTupleUpdate(classRel, &newtuple->t_self, newtuple);
  	heap_freetuple(newtuple);
  
  	if (OidIsValid(defaultPartOid))
  	{
  		/*
  		 * If the relation being detached is the default partition itself,
  		 * remove it from the parent's pg_partitioned_table entry.
  		 *
  		 * If not, we must invalidate default partition's relcache entry, as
  		 * in StorePartitionBound: its partition constraint depends on every
  		 * other partition's partition constraint.
  		 */
  		if (RelationGetRelid(partRel) == defaultPartOid)
  			update_default_partition_oid(RelationGetRelid(rel), InvalidOid);
  		else
  			CacheInvalidateRelcacheByRelid(defaultPartOid);
  	}
  
  	/* detach indexes too */
  	indexes = RelationGetIndexList(partRel);
  	foreach(cell, indexes)
  	{
  		Oid			idxid = lfirst_oid(cell);
  		Relation	idx;
  		Oid			constrOid;
  
  		if (!has_superclass(idxid))
  			continue;
  
  		Assert((IndexGetRelation(get_partition_parent(idxid), false) ==
  				RelationGetRelid(rel)));
  
  		idx = index_open(idxid, AccessExclusiveLock);
  		IndexSetParentIndex(idx, InvalidOid);
  		update_relispartition(classRel, idxid, false);
  
  		/* If there's a constraint associated with the index, detach it too */
  		constrOid = get_relation_idx_constraint_oid(RelationGetRelid(partRel),
  													idxid);
  		if (OidIsValid(constrOid))
  			ConstraintSetParentConstraint(constrOid, InvalidOid);
  
  		index_close(idx, NoLock);
  	}
  	heap_close(classRel, RowExclusiveLock);
  
  	/*
  	 * Detach any foreign keys that are inherited.  This includes creating
  	 * additional action triggers.
  	 */
  	fks = copyObject(RelationGetFKeyList(partRel));
  	foreach(cell, fks)
  	{
  		ForeignKeyCacheInfo *fk = lfirst(cell);
  		HeapTuple	contup;
  		Form_pg_constraint conform;
  		Constraint *fkconstraint;
  
  		contup = SearchSysCache1(CONSTROID, ObjectIdGetDatum(fk->conoid));
  		if (!contup)
  			elog(ERROR, "cache lookup failed for constraint %u", fk->conoid);
  		conform = (Form_pg_constraint) GETSTRUCT(contup);
  
  		/* consider only the inherited foreign keys */
  		if (conform->contype != CONSTRAINT_FOREIGN ||
  			!OidIsValid(conform->conparentid))
  		{
  			ReleaseSysCache(contup);
  			continue;
  		}
  
  		/* unset conparentid and adjust conislocal, coninhcount, etc. */
  		ConstraintSetParentConstraint(fk->conoid, InvalidOid);
  
  		/*
  		 * Make the action triggers on the referenced relation.  When this was
  		 * a partition the action triggers pointed to the parent rel (they
  		 * still do), but now we need separate ones of our own.
  		 */
  		fkconstraint = makeNode(Constraint);
  		fkconstraint->conname = pstrdup(NameStr(conform->conname));
  		fkconstraint->fk_upd_action = conform->confupdtype;
  		fkconstraint->fk_del_action = conform->confdeltype;
  		fkconstraint->deferrable = conform->condeferrable;
  		fkconstraint->initdeferred = conform->condeferred;
  
  		createForeignKeyActionTriggers(partRel, conform->confrelid,
  									   fkconstraint, fk->conoid,
  									   conform->conindid);
  
  		ReleaseSysCache(contup);
  	}
  	list_free_deep(fks);
  
  	/*
  	 * Invalidate the parent's relcache so that the partition is no longer
  	 * included in its partition descriptor.
  	 */
  	CacheInvalidateRelcache(rel);
  
  	ObjectAddressSet(address, RelationRelationId, RelationGetRelid(partRel));
  
  	/* keep our lock until commit */
  	heap_close(partRel, NoLock);
  
  	return address;
  }
  
  /*
   * Before acquiring lock on an index, acquire the same lock on the owning
   * table.
   */
  struct AttachIndexCallbackState
  {
  	Oid			partitionOid;
  	Oid			parentTblOid;
  	bool		lockedParentTbl;
  };
  
  static void
  RangeVarCallbackForAttachIndex(const RangeVar *rv, Oid relOid, Oid oldRelOid,
  							   void *arg)
  {
  	struct AttachIndexCallbackState *state;
  	Form_pg_class classform;
  	HeapTuple	tuple;
  
  	state = (struct AttachIndexCallbackState *) arg;
  
  	if (!state->lockedParentTbl)
  	{
  		LockRelationOid(state->parentTblOid, AccessShareLock);
  		state->lockedParentTbl = true;
  	}
  
  	/*
  	 * If we previously locked some other heap, and the name we're looking up
  	 * no longer refers to an index on that relation, release the now-useless
  	 * lock.  XXX maybe we should do *after* we verify whether the index does
  	 * not actually belong to the same relation ...
  	 */
  	if (relOid != oldRelOid && OidIsValid(state->partitionOid))
  	{
  		UnlockRelationOid(state->partitionOid, AccessShareLock);
  		state->partitionOid = InvalidOid;
  	}
  
  	/* Didn't find a relation, so no need for locking or permission checks. */
  	if (!OidIsValid(relOid))
  		return;
  
  	tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relOid));
  	if (!HeapTupleIsValid(tuple))
  		return;					/* concurrently dropped, so nothing to do */
  	classform = (Form_pg_class) GETSTRUCT(tuple);
  	if (classform->relkind != RELKIND_PARTITIONED_INDEX &&
  		classform->relkind != RELKIND_INDEX)
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  				 errmsg("\"%s\" is not an index", rv->relname)));
  	ReleaseSysCache(tuple);
  
  	/*
  	 * Since we need only examine the heap's tupledesc, an access share lock
  	 * on it (preventing any DDL) is sufficient.
  	 */
  	state->partitionOid = IndexGetRelation(relOid, false);
  	LockRelationOid(state->partitionOid, AccessShareLock);
  }
  
  /*
   * ALTER INDEX i1 ATTACH PARTITION i2
   */
  static ObjectAddress
  ATExecAttachPartitionIdx(List **wqueue, Relation parentIdx, RangeVar *name)
  {
  	Relation	partIdx;
  	Relation	partTbl;
  	Relation	parentTbl;
  	ObjectAddress address;
  	Oid			partIdxId;
  	Oid			currParent;
  	struct AttachIndexCallbackState state;
  
  	/*
  	 * We need to obtain lock on the index 'name' to modify it, but we also
  	 * need to read its owning table's tuple descriptor -- so we need to lock
  	 * both.  To avoid deadlocks, obtain lock on the table before doing so on
  	 * the index.  Furthermore, we need to examine the parent table of the
  	 * partition, so lock that one too.
  	 */
  	state.partitionOid = InvalidOid;
  	state.parentTblOid = parentIdx->rd_index->indrelid;
  	state.lockedParentTbl = false;
  	partIdxId =
  		RangeVarGetRelidExtended(name, AccessExclusiveLock, 0,
  								 RangeVarCallbackForAttachIndex,
  								 (void *) &state);
  	/* Not there? */
  	if (!OidIsValid(partIdxId))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_OBJECT),
  				 errmsg("index \"%s\" does not exist", name->relname)));
  
  	/* no deadlock risk: RangeVarGetRelidExtended already acquired the lock */
  	partIdx = relation_open(partIdxId, AccessExclusiveLock);
  
  	/* we already hold locks on both tables, so this is safe: */
  	parentTbl = relation_open(parentIdx->rd_index->indrelid, AccessShareLock);
  	partTbl = relation_open(partIdx->rd_index->indrelid, NoLock);
  
  	ObjectAddressSet(address, RelationRelationId, RelationGetRelid(partIdx));
  
  	/* Silently do nothing if already in the right state */
  	currParent = partIdx->rd_rel->relispartition ?
  		get_partition_parent(partIdxId) : InvalidOid;
  	if (currParent != RelationGetRelid(parentIdx))
  	{
  		IndexInfo  *childInfo;
  		IndexInfo  *parentInfo;
  		AttrNumber *attmap;
  		bool		found;
  		int			i;
  		PartitionDesc partDesc;
  		Oid			constraintOid,
  					cldConstrId = InvalidOid;
  
  		/*
  		 * If this partition already has an index attached, refuse the
  		 * operation.
  		 */
  		refuseDupeIndexAttach(parentIdx, partIdx, partTbl);
  
  		if (OidIsValid(currParent))
  			ereport(ERROR,
  					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  					 errmsg("cannot attach index \"%s\" as a partition of index \"%s\"",
  							RelationGetRelationName(partIdx),
  							RelationGetRelationName(parentIdx)),
  					 errdetail("Index \"%s\" is already attached to another index.",
  							   RelationGetRelationName(partIdx))));
  
  		/* Make sure it indexes a partition of the other index's table */
  		partDesc = RelationGetPartitionDesc(parentTbl);
  		found = false;
  		for (i = 0; i < partDesc->nparts; i++)
  		{
  			if (partDesc->oids[i] == state.partitionOid)
  			{
  				found = true;
  				break;
  			}
  		}
  		if (!found)
  			ereport(ERROR,
  					(errmsg("cannot attach index \"%s\" as a partition of index \"%s\"",
  							RelationGetRelationName(partIdx),
  							RelationGetRelationName(parentIdx)),
  					 errdetail("Index \"%s\" is not an index on any partition of table \"%s\".",
  							   RelationGetRelationName(partIdx),
  							   RelationGetRelationName(parentTbl))));
  
  		/* Ensure the indexes are compatible */
  		childInfo = BuildIndexInfo(partIdx);
  		parentInfo = BuildIndexInfo(parentIdx);
  		attmap = convert_tuples_by_name_map(RelationGetDescr(partTbl),
  											RelationGetDescr(parentTbl),
  											gettext_noop("could not convert row type"));
  		if (!CompareIndexInfo(childInfo, parentInfo,
  							  partIdx->rd_indcollation,
  							  parentIdx->rd_indcollation,
  							  partIdx->rd_opfamily,
  							  parentIdx->rd_opfamily,
  							  attmap,
  							  RelationGetDescr(partTbl)->natts))
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  					 errmsg("cannot attach index \"%s\" as a partition of index \"%s\"",
  							RelationGetRelationName(partIdx),
  							RelationGetRelationName(parentIdx)),
  					 errdetail("The index definitions do not match.")));
  
  		/*
  		 * If there is a constraint in the parent, make sure there is one in
  		 * the child too.
  		 */
  		constraintOid = get_relation_idx_constraint_oid(RelationGetRelid(parentTbl),
  														RelationGetRelid(parentIdx));
  
  		if (OidIsValid(constraintOid))
  		{
  			cldConstrId = get_relation_idx_constraint_oid(RelationGetRelid(partTbl),
  														  partIdxId);
  			if (!OidIsValid(cldConstrId))
  				ereport(ERROR,
  						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
  						 errmsg("cannot attach index \"%s\" as a partition of index \"%s\"",
  								RelationGetRelationName(partIdx),
  								RelationGetRelationName(parentIdx)),
  						 errdetail("The index \"%s\" belongs to a constraint in table \"%s\" but no constraint exists for index \"%s\".",
  								   RelationGetRelationName(parentIdx),
  								   RelationGetRelationName(parentTbl),
  								   RelationGetRelationName(partIdx))));
  		}
  
  		/* All good -- do it */
  		IndexSetParentIndex(partIdx, RelationGetRelid(parentIdx));
  		if (OidIsValid(constraintOid))
  			ConstraintSetParentConstraint(cldConstrId, constraintOid);
  		update_relispartition(NULL, partIdxId, true);
  
  		pfree(attmap);
  
  		validatePartitionedIndex(parentIdx, parentTbl);
  	}
  
  	relation_close(parentTbl, AccessShareLock);
  	/* keep these locks till commit */
  	relation_close(partTbl, NoLock);
  	relation_close(partIdx, NoLock);
  
  	return address;
  }
  
  /*
   * Verify whether the given partition already contains an index attached
   * to the given partitioned index.  If so, raise an error.
   */
  static void
  refuseDupeIndexAttach(Relation parentIdx, Relation partIdx, Relation partitionTbl)
  {
  	Relation	pg_inherits;
  	ScanKeyData key;
  	HeapTuple	tuple;
  	SysScanDesc scan;
  
  	pg_inherits = heap_open(InheritsRelationId, AccessShareLock);
  	ScanKeyInit(&key, Anum_pg_inherits_inhparent,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(parentIdx)));
  	scan = systable_beginscan(pg_inherits, InheritsParentIndexId, true,
  							  NULL, 1, &key);
  	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
  	{
  		Form_pg_inherits inhForm;
  		Oid			tab;
  
  		inhForm = (Form_pg_inherits) GETSTRUCT(tuple);
  		tab = IndexGetRelation(inhForm->inhrelid, false);
  		if (tab == RelationGetRelid(partitionTbl))
  			ereport(ERROR,
  					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  					 errmsg("cannot attach index \"%s\" as a partition of index \"%s\"",
  							RelationGetRelationName(partIdx),
  							RelationGetRelationName(parentIdx)),
  					 errdetail("Another index is already attached for partition \"%s\".",
  							   RelationGetRelationName(partitionTbl))));
  	}
  
  	systable_endscan(scan);
  	heap_close(pg_inherits, AccessShareLock);
  }
  
  /*
   * Verify whether the set of attached partition indexes to a parent index on
   * a partitioned table is complete.  If it is, mark the parent index valid.
   *
   * This should be called each time a partition index is attached.
   */
  static void
  validatePartitionedIndex(Relation partedIdx, Relation partedTbl)
  {
  	Relation	inheritsRel;
  	SysScanDesc scan;
  	ScanKeyData key;
  	int			tuples = 0;
  	HeapTuple	inhTup;
  	bool		updated = false;
  
  	Assert(partedIdx->rd_rel->relkind == RELKIND_PARTITIONED_INDEX);
  
  	/*
  	 * Scan pg_inherits for this parent index.  Count each valid index we find
  	 * (verifying the pg_index entry for each), and if we reach the total
  	 * amount we expect, we can mark this parent index as valid.
  	 */
  	inheritsRel = heap_open(InheritsRelationId, AccessShareLock);
  	ScanKeyInit(&key, Anum_pg_inherits_inhparent,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(partedIdx)));
  	scan = systable_beginscan(inheritsRel, InheritsParentIndexId, true,
  							  NULL, 1, &key);
  	while ((inhTup = systable_getnext(scan)) != NULL)
  	{
  		Form_pg_inherits inhForm = (Form_pg_inherits) GETSTRUCT(inhTup);
  		HeapTuple	indTup;
  		Form_pg_index indexForm;
  
  		indTup = SearchSysCache1(INDEXRELID,
  								 ObjectIdGetDatum(inhForm->inhrelid));
  		if (!indTup)
  			elog(ERROR, "cache lookup failed for index %u",
  				 inhForm->inhrelid);
  		indexForm = (Form_pg_index) GETSTRUCT(indTup);
  		if (IndexIsValid(indexForm))
  			tuples += 1;
  		ReleaseSysCache(indTup);
  	}
  
  	/* Done with pg_inherits */
  	systable_endscan(scan);
  	heap_close(inheritsRel, AccessShareLock);
  
  	/*
  	 * If we found as many inherited indexes as the partitioned table has
  	 * partitions, we're good; update pg_index to set indisvalid.
  	 */
  	if (tuples == RelationGetPartitionDesc(partedTbl)->nparts)
  	{
  		Relation	idxRel;
  		HeapTuple	newtup;
  
  		idxRel = heap_open(IndexRelationId, RowExclusiveLock);
  
  		newtup = heap_copytuple(partedIdx->rd_indextuple);
  		((Form_pg_index) GETSTRUCT(newtup))->indisvalid = true;
  		updated = true;
  
  		CatalogTupleUpdate(idxRel, &partedIdx->rd_indextuple->t_self, newtup);
  
  		heap_close(idxRel, RowExclusiveLock);
  	}
  
  	/*
  	 * If this index is in turn a partition of a larger index, validating it
  	 * might cause the parent to become valid also.  Try that.
  	 */
  	if (updated && partedIdx->rd_rel->relispartition)
  	{
  		Oid			parentIdxId,
  					parentTblId;
  		Relation	parentIdx,
  					parentTbl;
  
  		/* make sure we see the validation we just did */
  		CommandCounterIncrement();
  
  		parentIdxId = get_partition_parent(RelationGetRelid(partedIdx));
  		parentTblId = get_partition_parent(RelationGetRelid(partedTbl));
  		parentIdx = relation_open(parentIdxId, AccessExclusiveLock);
  		parentTbl = relation_open(parentTblId, AccessExclusiveLock);
  		Assert(!parentIdx->rd_index->indisvalid);
  
  		validatePartitionedIndex(parentIdx, parentTbl);
  
  		relation_close(parentIdx, AccessExclusiveLock);
  		relation_close(parentTbl, AccessExclusiveLock);
  	}
  }
  
  /*
   * Update the relispartition flag of the given relation to the given value.
   *
   * classRel is the pg_class relation, already open and suitably locked.
   * It can be passed as NULL, in which case it's opened and closed locally.
   */
  static void
  update_relispartition(Relation classRel, Oid relationId, bool newval)
  {
  	HeapTuple	tup;
  	HeapTuple	newtup;
  	Form_pg_class classForm;
  	bool		opened = false;
  
  	if (classRel == NULL)
  	{
  		classRel = heap_open(RelationRelationId, RowExclusiveLock);
  		opened = true;
  	}
  
  	tup = SearchSysCache1(RELOID, ObjectIdGetDatum(relationId));
  	newtup = heap_copytuple(tup);
  	classForm = (Form_pg_class) GETSTRUCT(newtup);
  	classForm->relispartition = newval;
  	CatalogTupleUpdate(classRel, &tup->t_self, newtup);
  	heap_freetuple(newtup);
  	ReleaseSysCache(tup);
  
  	if (opened)
  		heap_close(classRel, RowExclusiveLock);
  }
  