text: /*-------------------------------------------------------------------------
   *
   * tablecmds.c
   *	  Commands for creating and altering table structures and settings
   *
   * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   *
   * IDENTIFICATION
   *	  src/backend/commands/tablecmds.c
   *
   *-------------------------------------------------------------------------
   */
  #include "postgres.h"
  
  #include "access/genam.h"
  #include "access/heapam.h"
  #include "access/multixact.h"
  #include "access/reloptions.h"
  #include "access/relscan.h"
  #include "access/sysattr.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/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_inherits_fn.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/pg_type_fn.h"
  #include "catalog/storage.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/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 "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 "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/relcache.h"
  #include "utils/ruleutils.h"
  #include "utils/snapmgr.h"
  #include "utils/syscache.h"
  #include "utils/tqual.h"
  #include "utils/typcache.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 */
  	/* 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 */
  	List	   *qualstate;		/* Execution state for CHECK */
  } 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.")},
  	{'\0', 0, NULL, NULL, NULL, NULL}
  };
  
  struct DropRelationCallbackState
  {
  	char		relkind;
  	Oid			heapOid;
  	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
  
  static void truncate_check_rel(Relation rel);
  static List *MergeAttributes(List *schema, List *supers, char relpersistence,
  				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);
  static void StoreCatalogInheritance1(Oid relationId, Oid parentOid,
  						 int16 seqNumber, Relation inhRelation);
  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 createForeignKeyTriggers(Relation rel, Oid refRelOid,
  						 Constraint *fkconstraint,
  						 Oid constraintOid, Oid indexOid);
  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);
  static void ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation 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 ObjectAddress ATExecDropNotNull(Relation rel, const char *colName, LOCKMODE lockmode);
  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 void ATPrepSetStatistics(Relation rel, const char *colName,
  					Node *newValue, LOCKMODE lockmode);
  static ObjectAddress ATExecSetStatistics(Relation rel, const char *colName,
  					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 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(AlteredTableInfo *tab, Relation rel,
  						  Constraint *fkconstraint, LOCKMODE lockmode);
  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, 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,
  					char *tablespacename, LOCKMODE lockmode);
  static void ATExecSetTableSpace(Oid tableOid, Oid newTableSpace, LOCKMODE lockmode);
  static void ATExecSetRelOptions(Relation rel, List *defList,
  					AlterTableType operation,
  					LOCKMODE lockmode);
  static void ATExecEnableDisableTrigger(Relation rel, char *trigname,
  					   char fires_when, bool skip_system, LOCKMODE lockmode);
  static void ATExecEnableDisableRule(Relation rel, 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);
  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);
  
  
  /* ----------------------------------------------------------------
   *		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.
   *
   * 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)
  {
  	char		relname[NAMEDATALEN];
  	Oid			namespaceId;
  	List	   *schema = stmt->tableElts;
  	Oid			relationId;
  	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;
  
  	/*
  	 * 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")));
  
  	/*
  	 * 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, ACL_KIND_TABLESPACE,
  						   get_tablespace_name(tablespaceId));
  	}
  
  	/* In all cases disallow placing user relations in pg_global */
  	if (tablespaceId == GLOBALTABLESPACE_OID)
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  				 errmsg("only shared relations can be placed in pg_global tablespace")));
  
  	/* Identify user ID that will own the table */
  	if (!OidIsValid(ownerId))
  		ownerId = 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.
  	 */
  	schema = MergeAttributes(schema, stmt->inhRelations,
  							 stmt->relation->relpersistence,
  							 &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(schema);
  
  	/*
  	 * Notice that we allow OIDs here only for plain 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));
  	descriptor->tdhasoid = (localHasOids || parentOidCount > 0);
  
  	/*
  	 * 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, schema)
  	{
  		ColumnDef  *colDef = lfirst(listptr);
  
  		attnum++;
  
  		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;
  			rawDefaults = lappend(rawDefaults, rawEnt);
  			descriptor->attrs[attnum - 1]->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);
  			descriptor->attrs[attnum - 1]->atthasdef = true;
  		}
  	}
  
  	/*
  	 * 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,
  										  InvalidOid,
  										  InvalidOid,
  										  ofTypeId,
  										  ownerId,
  										  descriptor,
  										  list_concat(cookedDefaults,
  													  old_constraints),
  										  relkind,
  										  stmt->relation->relpersistence,
  										  false,
  										  false,
  										  localHasOids,
  										  parentOidCount,
  										  stmt->oncommit,
  										  reloptions,
  										  true,
  										  allowSystemTableMods,
  										  false,
  										  typaddress);
  
  	/* Store inheritance information for new rel. */
  	StoreCatalogInheritance(relationId, inheritOids);
  
  	/*
  	 * We must bump the command counter to make the newly-created relation
  	 * tuple visible for opening.
  	 */
  	CommandCounterIncrement();
  
  	/*
  	 * 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);
  
  	/*
  	 * 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);
  
  	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.concurrent = drop->concurrent;
  		relOid = RangeVarGetRelidExtended(rel, lockmode, true,
  										  false,
  										  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.
   */
  static void
  RangeVarCallbackForDropRelation(const RangeVar *rel, Oid relOid, Oid oldRelOid,
  								void *arg)
  {
  	HeapTuple	tuple;
  	struct DropRelationCallbackState *state;
  	char		relkind;
  	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;
  	}
  
  	/* 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)
  		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, ACL_KIND_CLASS,
  					   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 && relOid != oldRelOid)
  	{
  		state->heapOid = IndexGetRelation(relOid, true);
  		if (OidIsValid(state->heapOid))
  			LockRelationOid(state->heapOid, heap_lockmode);
  	}
  }
  
  /*
   * 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	   *seq_relids = NIL;
  	EState	   *estate;
  	ResultRelInfo *resultRelInfos;
  	ResultRelInfo *resultRelInfo;
  	SubTransactionId mySubid;
  	ListCell   *cell;
  
  	/*
  	 * Open, exclusive-lock, and check all the explicitly-specified relations
  	 */
  	foreach(cell, stmt->relations)
  	{
  		RangeVar   *rv = lfirst(cell);
  		Relation	rel;
  		bool		recurse = interpretInhOption(rv->inhOpt);
  		Oid			myrelid;
  
  		rel = heap_openrv(rv, AccessExclusiveLock);
  		myrelid = RelationGetRelid(rel);
  		/* don't throw error for "TRUNCATE foo, foo" */
  		if (list_member_oid(relids, myrelid))
  		{
  			heap_close(rel, AccessExclusiveLock);
  			continue;
  		}
  		truncate_check_rel(rel);
  		rels = lappend(rels, rel);
  		relids = lappend_oid(relids, myrelid);
  
  		if (recurse)
  		{
  			ListCell   *child;
  			List	   *children;
  
  			children = find_all_inheritors(myrelid, AccessExclusiveLock, 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);
  				truncate_check_rel(rel);
  				rels = lappend(rels, rel);
  				relids = lappend_oid(relids, childrelid);
  			}
  		}
  	}
  
  	/*
  	 * 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.
  	 */
  	if (stmt->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);
  			}
  		}
  	}
  
  	/*
  	 * 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 (stmt->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 (stmt->restart_seqs)
  	{
  		foreach(cell, rels)
  		{
  			Relation	rel = (Relation) lfirst(cell);
  			List	   *seqlist = getOwnedSequences(RelationGetRelid(rel));
  			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, ACL_KIND_CLASS,
  								   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 */
  						  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);
  
  		/*
  		 * 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 (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);
  			toast_relid = rel->rd_rel->reltoastrelid;
  
  			/*
  			 * The same for the toast table, if any.
  			 */
  			if (OidIsValid(toast_relid))
  			{
  				rel = relation_open(toast_relid, AccessExclusiveLock);
  				RelationSetNewRelfilenode(rel, rel->rd_rel->relpersistence,
  										  RecentXmin, minmulti);
  				if (rel->rd_rel->relpersistence == RELPERSISTENCE_UNLOGGED)
  					heap_create_init_fork(rel);
  				heap_close(rel, 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);
  	}
  
  	/*
  	 * 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);
  
  	/* And close the rels (can't do this while EState still holds refs) */
  	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 */
  	if (rel->rd_rel->relkind != RELKIND_RELATION)
  		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, ACL_KIND_CLASS,
  					   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.
   *
   * 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,
  				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 */
  
  	/*
  	 * 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 any 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 (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.
  			 */
  			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;
  		}
  	}
  
  	/*
  	 * 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.
  		 */
  		relation = heap_openrv(parent, ShareUpdateExclusiveLock);
  
  		if (relation->rd_rel->relkind != RELKIND_RELATION &&
  			relation->rd_rel->relkind != RELKIND_FOREIGN_TABLE)
  			ereport(ERROR,
  					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  					 errmsg("inherited relation \"%s\" is not a table or foreign table",
  							parent->relname)));
  		/* 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("cannot inherit from 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("cannot inherit from 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, ACL_KIND_CLASS,
  						   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 = tupleDesc->attrs[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",
  									   TypeNameToString(def->typeName),
  									   format_type_be(attribute->atttypid))));
  				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,
  										   &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 ShareUpdateExclusiveLock 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.
  	 */
  	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;
  
  				/*
  				 * 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",
  									   TypeNameToString(def->typeName),
  									   TypeNameToString(newdef->typeName))));
  				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))));
  
  				/* 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)));
  	}
  
  	/*
  	 * 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)
  {
  	Relation	relation;
  	int16		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);
  		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,
  						 int16 seqNumber, Relation inhRelation)
  {
  	TupleDesc	desc = RelationGetDescr(inhRelation);
  	Datum		values[Natts_pg_inherits];
  	bool		nulls[Natts_pg_inherits];
  	ObjectAddress childobject,
  				parentobject;
  	HeapTuple	tuple;
  
  	/*
  	 * Make the pg_inherits entry
  	 */
  	values[Anum_pg_inherits_inhrelid - 1] = ObjectIdGetDatum(relationId);
  	values[Anum_pg_inherits_inhparent - 1] = ObjectIdGetDatum(parentOid);
  	values[Anum_pg_inherits_inhseqno - 1] = Int16GetDatum(seqNumber);
  
  	memset(nulls, 0, sizeof(nulls));
  
  	tuple = heap_form_tuple(desc, values, nulls);
  
  	simple_heap_insert(inhRelation, tuple);
  
  	CatalogUpdateIndexes(inhRelation, tuple);
  
  	heap_freetuple(tuple);
  
  	/*
  	 * 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, DEPENDENCY_NORMAL);
  
  	/*
  	 * 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;
  		simple_heap_update(relationRelation, &tuple->t_self, tuple);
  
  		/* keep the catalog indexes up to date */
  		CatalogUpdateIndexes(relationRelation, 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_FOREIGN_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, ACL_KIND_CLASS,
  					   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);
  
  	simple_heap_update(attrelation, &atttup->t_self, atttup);
  
  	/* keep system catalog indexes current */
  	CatalogUpdateIndexes(attrelation, 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, false,
  									 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 */
  						   interpretInhOption(stmt->relation->inhOpt),	/* recursive? */
  						   false,		/* recursing? */
  						   0,	/* expected inhcount */
  						   stmt->behavior);
  
  	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)
  		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(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, false,
  										 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 ? interpretInhOption(stmt->relation->inhOpt) : false,	/* 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;
  
  	/*
  	 * 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, false,
  									 RangeVarCallbackForAlterRelation,
  									 (void *) stmt);
  
  	if (!OidIsValid(relid))
  	{
  		ereport(NOTICE,
  				(errmsg("relation \"%s\" does not exist, skipping",
  						stmt->relation->relname)));
  		return InvalidObjectAddress;
  	}
  
  	/* Do the work */
  	RenameRelationInternal(relid, stmt->newname, false);
  
  	ObjectAddressSet(address, RelationRelationId, relid);
  
  	return address;
  }
  
  /*
   *		RenameRelationInternal - change the name of a relation
   *
   *		XXX - When renaming sequences, we don't bother to modify the
   *			  sequence name that is stored within the sequence itself
   *			  (this would cause problems with MVCC). In the future,
   *			  the sequence name should probably be removed from the
   *			  sequence, AFAIK there's no need for it to be there.
   */
  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);
  
  	simple_heap_update(relrelation, &reltup->t_self, reltup);
  
  	/* keep the system catalog indexes current */
  	CatalogUpdateIndexes(relrelation, 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)
  	{
  		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 &&
  		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, false,
  									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, interpretInhOption(stmt->relation->inhOpt),
  				 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 optimisation.
  				 */
  			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:
  				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 */
  				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;
  
  			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 */
  	ATRewriteCatalogs(&wqueue, lockmode);
  
  	/* Phase 3: scan/rewrite tables as needed */
  	ATRewriteTables(parsetree, &wqueue, lockmode);
  }
  
  /*
   * 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_DropNotNull:	/* ALTER COLUMN DROP NOT NULL */
  			ATSimplePermissions(rel, ATT_TABLE | ATT_FOREIGN_TABLE);
  			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);
  			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->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);
  			/* 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;
  		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)
  {
  	int			pass;
  	ListCell   *ltab;
  
  	/*
  	 * 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++)
  	{
  		/* 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, (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);
  		}
  	}
  
  	/* Check to see if a toast table must be added. */
  	foreach(ltab, *wqueue)
  	{
  		AlteredTableInfo *tab = (AlteredTableInfo *) lfirst(ltab);
  
  		if (tab->relkind == RELKIND_RELATION ||
  			tab->relkind == RELKIND_MATVIEW)
  			AlterTableCreateToastTable(tab->relid, (Datum) 0, lockmode);
  	}
  }
  
  /*
   * ATExecCmd: dispatch a subcommand to appropriate execution routine
   */
  static void
  ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
  		  AlterTableCmd *cmd, LOCKMODE lockmode)
  {
  	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, false, 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_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->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, rel, (IndexStmt *) cmd->def, false,
  									 lockmode);
  			break;
  		case AT_ReAddIndex:		/* ADD INDEX */
  			address = ATExecAddIndex(tab, 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,
  									false, true, lockmode);
  			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 */
  
  			/*
  			 * Nothing to do here; Phase 3 does the work
  			 */
  			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;
  		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. */
  		if (tab->relkind == RELKIND_FOREIGN_TABLE)
  			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)
  				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;
  
  	/*
  	 * 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 = (List *)
  					ExecPrepareExpr((Expr *) con->qual, estate);
  				break;
  			case CONSTR_FOREIGN:
  				/* Nothing to do here */
  				break;
  			default:
  				elog(ERROR, "unrecognized constraint type: %d",
  					 (int) con->contype);
  		}
  	}
  
  	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++)
  		{
  			if (newTupDesc->attrs[i]->attnotnull &&
  				!newTupDesc->attrs[i]->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 (newTupDesc->attrs[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.
  				 */
  				ExecStoreTuple(tuple, oldslot, InvalidBuffer, 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],
  														  NULL);
  				}
  
  				/*
  				 * 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 */
  			ExecStoreTuple(tuple, newslot, InvalidBuffer, false);
  			econtext->ecxt_scantuple = newslot;
  
  			foreach(l, notnull_attrs)
  			{
  				int			attn = lfirst_int(l);
  
  				if (heap_attisnull(tuple, attn + 1))
  					ereport(ERROR,
  							(errcode(ERRCODE_NOT_NULL_VIOLATION),
  							 errmsg("column \"%s\" contains null values",
  								  NameStr(newTupDesc->attrs[attn]->attname)),
  							 errtablecol(oldrel, attn + 1)));
  			}
  
  			foreach(l, tab->constraints)
  			{
  				NewConstraint *con = lfirst(l);
  
  				switch (con->contype)
  				{
  					case CONSTR_CHECK:
  						if (!ExecQual(con->qualstate, econtext, true))
  							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);
  				}
  			}
  
  			/* 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 = CreateTupleDescCopy(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:
  			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_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, ACL_KIND_CLASS,
  					   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))
  	{
  		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 a composite type is being used as a column in some
   * other table (possibly nested several levels deep in composite types!).
   * Eventually, we'd like to propagate the check or rewrite operation
   * into other such tables, but for now, just error out if we find any.
   *
   * Caller should provide either a table name or a type name (not both) to
   * report in the error message, if any.
   *
   * 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;
  	Oid			arrayOid;
  
  	/*
  	 * We scan pg_depend to find those things that depend on the rowtype. (We
  	 * assume we can ignore refobjsubid for a rowtype.)
  	 */
  	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;
  
  		/* Ignore dependees that aren't user columns of relations */
  		/* (we assume system columns are never of rowtypes) */
  		if (pg_depend->classid != RelationRelationId ||
  			pg_depend->objsubid <= 0)
  			continue;
  
  		rel = relation_open(pg_depend->objid, AccessShareLock);
  		att = rel->rd_att->attrs[pg_depend->objsubid - 1];
  
  		if (rel->rd_rel->relkind == RELKIND_RELATION ||
  			rel->rd_rel->relkind == RELKIND_MATVIEW)
  		{
  			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);
  
  	/*
  	 * If there's an array type for the rowtype, must check for uses of it,
  	 * too.
  	 */
  	arrayOid = get_array_type(typeOid);
  	if (OidIsValid(arrayOid))
  		find_composite_type_dependencies(arrayOid, origRelation, origTypeName);
  }
  
  
  /*
   * 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.
   */
  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);
  
  	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++;
  			simple_heap_update(attrdesc, &tuple->t_self, tuple);
  			CatalogUpdateIndexes(attrdesc, 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;
  
  	/* 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.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);
  
  	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;
  
  	simple_heap_update(pgclass, &reltup->t_self, reltup);
  
  	/* keep catalog indexes current */
  	CatalogUpdateIndexes(pgclass, 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);
  
  		/*
  		 * 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);
  
  		/* Make the additional catalog changes visible */
  		CommandCounterIncrement();
  	}
  
  	/*
  	 * 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)
  	{
  		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);
  			tab->rewrite |= AT_REWRITE_DEFAULT_VAL;
  		}
  
  		/*
  		 * If the new column is NOT NULL, 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 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)));
  
  	/*
  	 * 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->indnatts; 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);
  
  	/*
  	 * Okay, actually perform the catalog change ... if needed
  	 */
  	if (((Form_pg_attribute) GETSTRUCT(tuple))->attnotnull)
  	{
  		((Form_pg_attribute) GETSTRUCT(tuple))->attnotnull = FALSE;
  
  		simple_heap_update(attr_rel, &tuple->t_self, tuple);
  
  		/* keep the system catalog indexes current */
  		CatalogUpdateIndexes(attr_rel, 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
   *
   * 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;
  
  		simple_heap_update(attr_rel, &tuple->t_self, tuple);
  
  		/* keep the system catalog indexes current */
  		CatalogUpdateIndexes(attr_rel, 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)));
  
  	/*
  	 * 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;
  
  		/*
  		 * 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);
  	}
  
  	ObjectAddressSubSet(address, RelationRelationId,
  						RelationGetRelid(rel), attnum);
  	return address;
  }
  
  /*
   * ALTER TABLE ALTER COLUMN SET STATISTICS
   */
  static void
  ATPrepSetStatistics(Relation rel, const char *colName, 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_FOREIGN_TABLE)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is not a table, materialized view, index, or foreign table",
  						RelationGetRelationName(rel))));
  
  	/* Permissions checks */
  	if (!pg_class_ownercheck(RelationGetRelid(rel), GetUserId()))
  		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
  					   RelationGetRelationName(rel));
  }
  
  /*
   * Return value is the address of the modified column
   */
  static ObjectAddress
  ATExecSetStatistics(Relation rel, const char *colName, 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);
  
  	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)));
  
  	attrtuple->attstattarget = newtarget;
  
  	simple_heap_update(attrelation, &tuple->t_self, tuple);
  
  	/* keep system catalog indexes current */
  	CatalogUpdateIndexes(attrelation, 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) */
  	Assert(IsA(options, List));
  	datum = SysCacheGetAttr(ATTNAME, tuple, Anum_pg_attribute_attoptions,
  							&isnull);
  	newOptions = transformRelOptions(isnull ? (Datum) 0 : datum,
  									 (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. */
  	simple_heap_update(attrelation, &newtuple->t_self, newtuple);
  	CatalogUpdateIndexes(attrelation, 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))));
  
  	simple_heap_update(attrelation, &tuple->t_self, tuple);
  
  	/* keep system catalog indexes current */
  	CatalogUpdateIndexes(attrelation, 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;
  
  	/* 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)));
  
  	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;
  
  		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--;
  
  					simple_heap_update(attr_rel, &tuple->t_self, tuple);
  
  					/* keep the system catalog indexes current */
  					CatalogUpdateIndexes(attr_rel, 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;
  
  				simple_heap_update(attr_rel, &tuple->t_self, tuple);
  
  				/* keep the system catalog indexes current */
  				CatalogUpdateIndexes(attr_rel, 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;
  		simple_heap_update(class_rel, &tuple->t_self, tuple);
  
  		/* Keep the catalog indexes up to date */
  		CatalogUpdateIndexes(class_rel, 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;
  }
  
  /*
   * 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.
   */
  static ObjectAddress
  ATExecAddIndex(AlteredTableInfo *tab, Relation 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;
  
  	address = DefineIndex(RelationGetRelid(rel),
  						  stmt,
  						  InvalidOid,	/* no predefined OID */
  						  true, /* is_alter_table */
  						  check_rights,
  						  skip_build,
  						  quiet);
  
  	/*
  	 * 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;
  
  	Assert(IsA(stmt, IndexStmt));
  	Assert(OidIsValid(index_oid));
  	Assert(stmt->isconstraint);
  
  	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);
  
  	/* 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 */
  	address = index_constraint_create(rel,
  									  index_oid,
  									  indexInfo,
  									  constraintName,
  									  constraintType,
  									  stmt->deferrable,
  									  stmt->initdeferred,
  									  stmt->primary,
  									  true,		/* update pg_index */
  									  true,		/* remove old dependencies */
  									  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),
  										 RelationGetNamespace(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(tab, rel, newConstraint,
  												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.
   *
   * When re-adding a previously existing constraint (during ALTER COLUMN TYPE),
   * we don't need to recurse here, because recursion will be carried out at a
   * higher level; the constraint name issue doesn't apply because the names
   * have already been assigned and are just being re-used.  We need a separate
   * "is_readd" flag for that; just setting recurse=false would result in an
   * error if there are child tables.
   */
  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,		/* allow_merge */
  										!recursing,		/* is_local */
  										is_readd);		/* is_internal */
  
  	/* 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;
  			/* ExecQual wants implicit-AND format */
  			newcon->qual = (Node *) make_ands_implicit((Expr *) 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.
  	 * Likewise, in a re-add operation, we don't need to recurse (that will be
  	 * handled at higher levels).
  	 */
  	if (constr->is_no_inherit || is_readd)
  		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
  	 * contraint 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(AlteredTableInfo *tab, Relation rel,
  						  Constraint *fkconstraint, 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];
  	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_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);
  	checkFkeyPermissions(rel, fkattnum, numfks);
  
  	/*
  	 * 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)
  			elog(ERROR, "only b-tree 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;
  
  			/*
  			 * 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 = tab->oldDesc->attrs[fkattnum[i] - 1]->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;
  	}
  
  	/*
  	 * Record the FK constraint in pg_constraint.
  	 */
  	constrOid = CreateConstraintEntry(fkconstraint->conname,
  									  RelationGetNamespace(rel),
  									  CONSTRAINT_FOREIGN,
  									  fkconstraint->deferrable,
  									  fkconstraint->initdeferred,
  									  fkconstraint->initially_valid,
  									  RelationGetRelid(rel),
  									  fkattnum,
  									  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 */
  									  true,		/* isnoinherit */
  									  false);	/* is_internal */
  	ObjectAddressSet(address, ConstraintRelationId, constrOid);
  
  	/*
  	 * Create the triggers that will enforce the constraint.
  	 */
  	createForeignKeyTriggers(rel, RelationGetRelid(pkrel), fkconstraint,
  							 constrOid, indexOid);
  
  	/*
  	 * 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);
  	}
  
  	/*
  	 * Close pk table, but keep lock until we've committed.
  	 */
  	heap_close(pkrel, NoLock);
  
  	return address;
  }
  
  /*
   * 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 key;
  	HeapTuple	contuple;
  	Form_pg_constraint currcon = NULL;
  	bool		found = false;
  	ObjectAddress address;
  
  	Assert(IsA(cmd->def, Constraint));
  	cmdcon = (Constraint *) cmd->def;
  
  	conrel = heap_open(ConstraintRelationId, RowExclusiveLock);
  
  	/*
  	 * Find and check the target constraint
  	 */
  	ScanKeyInit(&key,
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(rel)));
  	scan = systable_beginscan(conrel, ConstraintRelidIndexId,
  							  true, NULL, 1, &key);
  
  	while (HeapTupleIsValid(contuple = systable_getnext(scan)))
  	{
  		currcon = (Form_pg_constraint) GETSTRUCT(contuple);
  		if (strcmp(NameStr(currcon->conname), cmdcon->conname) == 0)
  		{
  			found = true;
  			break;
  		}
  	}
  
  	if (!found)
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_OBJECT),
  				 errmsg("constraint \"%s\" of relation \"%s\" does not exist",
  						cmdcon->conname, RelationGetRelationName(rel))));
  
  	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;
  		simple_heap_update(conrel, &copyTuple->t_self, copyTuple);
  		CatalogUpdateIndexes(conrel, 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 copy_tg;
  
  			copyTuple = heap_copytuple(tgtuple);
  			copy_tg = (Form_pg_trigger) GETSTRUCT(copyTuple);
  
  			/* Remember OIDs of other relation(s) involved in FK constraint */
  			if (copy_tg->tgrelid != RelationGetRelid(rel))
  				otherrelids = list_append_unique_oid(otherrelids,
  													 copy_tg->tgrelid);
  
  			copy_tg->tgdeferrable = cmdcon->deferrable;
  			copy_tg->tginitdeferred = cmdcon->initdeferred;
  			simple_heap_update(tgrel, &copyTuple->t_self, copyTuple);
  			CatalogUpdateIndexes(tgrel, 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 key;
  	HeapTuple	tuple;
  	Form_pg_constraint con = NULL;
  	bool		found = false;
  	ObjectAddress address;
  
  	conrel = heap_open(ConstraintRelationId, RowExclusiveLock);
  
  	/*
  	 * Find and check the target constraint
  	 */
  	ScanKeyInit(&key,
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(rel)));
  	scan = systable_beginscan(conrel, ConstraintRelidIndexId,
  							  true, NULL, 1, &key);
  
  	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
  	{
  		con = (Form_pg_constraint) GETSTRUCT(tuple);
  		if (strcmp(NameStr(con->conname), constrName) == 0)
  		{
  			found = true;
  			break;
  		}
  	}
  
  	if (!found)
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_OBJECT),
  				 errmsg("constraint \"%s\" of relation \"%s\" does not exist",
  						constrName, RelationGetRelationName(rel))));
  
  	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);
  
  			/*
  			 * Foreign keys do not inherit, so we purposely ignore the
  			 * recursion bit here
  			 */
  		}
  		else if (con->contype == CONSTRAINT_CHECK)
  		{
  			List	   *children = NIL;
  			ListCell   *child;
  
  			/*
  			 * If we're recursing, the parent has already done this, so skip
  			 * it.
  			 */
  			if (!recursing)
  				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; else the addition would put them out of step.
  				 */
  				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;
  		simple_heap_update(conrel, &copyTuple->t_self, copyTuple);
  		CatalogUpdateIndexes(conrel, 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->indnatts; 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->indnatts == numattrs &&
  			indexStruct->indisunique &&
  			IndexIsValid(indexStruct) &&
  			heap_attisnull(indexTuple, Anum_pg_index_indpred) &&
  			heap_attisnull(indexTuple, Anum_pg_index_indexprs))
  		{
  			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 for ADD FOREIGN KEY */
  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, ACL_KIND_CLASS,
  						   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;
  	List	   *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 */
  	if (rel->rd_rel->relkind == RELKIND_FOREIGN_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 = (List *)
  		ExecPrepareExpr((Expr *) make_ands_implicit(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)
  	{
  		ExecStoreTuple(tuple, slot, InvalidBuffer, false);
  
  		if (!ExecQual(exprstate, econtext, true))
  			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 tgargs or tgqual */
  
  	/*
  	 * 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)
  	{
  		FunctionCallInfoData fcinfo;
  		TriggerData trigdata;
  
  		/*
  		 * Make a call to the trigger function
  		 *
  		 * No parameters are passed, but we do set a context
  		 */
  		MemSet(&fcinfo, 0, sizeof(fcinfo));
  
  		/*
  		 * 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->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, true);
  
  	/* Make changes-so-far visible */
  	CommandCounterIncrement();
  }
  
  /*
   * Create the triggers that implement an FK constraint.
   */
  static void
  createForeignKeyTriggers(Relation rel, Oid refRelOid, Constraint *fkconstraint,
  						 Oid constraintOid, Oid indexOid)
  {
  	Oid			myRelOid;
  	CreateTrigStmt *fk_trigger;
  
  	myRelOid = RelationGetRelid(rel);
  
  	/* Make changes-so-far visible */
  	CommandCounterIncrement();
  
  	/*
  	 * 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->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, myRelOid, constraintOid,
  						 indexOid, true);
  
  	/* 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->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, myRelOid, constraintOid,
  						 indexOid, true);
  
  	/* Make changes-so-far visible */
  	CommandCounterIncrement();
  
  	/*
  	 * Build and execute CREATE CONSTRAINT TRIGGER statements for the CHECK
  	 * action for both INSERTs and UPDATEs on the referencing table.
  	 */
  	CreateFKCheckTrigger(myRelOid, refRelOid, fkconstraint, constraintOid,
  						 indexOid, true);
  	CreateFKCheckTrigger(myRelOid, refRelOid, fkconstraint, constraintOid,
  						 indexOid, false);
  }
  
  /*
   * 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 key;
  	HeapTuple	tuple;
  	bool		found = false;
  	bool		is_no_inherit_constraint = false;
  
  	/* 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(&key,
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(rel)));
  	scan = systable_beginscan(conrel, ConstraintRelidIndexId,
  							  true, NULL, 1, &key);
  
  	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
  	{
  		ObjectAddress conobj;
  
  		con = (Form_pg_constraint) GETSTRUCT(tuple);
  
  		if (strcmp(NameStr(con->conname), constrName) != 0)
  			continue;
  
  		/* 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;
  
  		/*
  		 * Perform the actual constraint deletion
  		 */
  		conobj.classId = ConstraintRelationId;
  		conobj.objectId = HeapTupleGetOid(tuple);
  		conobj.objectSubId = 0;
  
  		performDeletion(&conobj, behavior, 0);
  
  		found = true;
  
  		/* constraint found and dropped -- no need to keep looping */
  		break;
  	}
  
  	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;
  		}
  	}
  
  	/*
  	 * 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;
  
  	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(&key,
  					Anum_pg_constraint_conrelid,
  					BTEqualStrategyNumber, F_OIDEQ,
  					ObjectIdGetDatum(childrelid));
  		scan = systable_beginscan(conrel, ConstraintRelidIndexId,
  								  true, NULL, 1, &key);
  
  		/* scan for matching tuple - there should only be one */
  		while (HeapTupleIsValid(tuple = systable_getnext(scan)))
  		{
  			con = (Form_pg_constraint) GETSTRUCT(tuple);
  
  			/* Right now only CHECK constraints can be inherited */
  			if (con->contype != CONSTRAINT_CHECK)
  				continue;
  
  			if (strcmp(NameStr(con->conname), constrName) == 0)
  				break;
  		}
  
  		if (!HeapTupleIsValid(tuple))
  			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);
  
  		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--;
  				simple_heap_update(conrel, &copy_tuple->t_self, copy_tuple);
  				CatalogUpdateIndexes(conrel, 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;
  
  			simple_heap_update(conrel, &copy_tuple->t_self, copy_tuple);
  			CatalogUpdateIndexes(conrel, 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;
  
  	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)));
  
  	/* 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)
  	{
  		/*
  		 * 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);
  
  	/*
  	 * The recursion case is handled by ATSimpleRecursion.  However, 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)
  		ATSimpleRecursion(wqueue, rel, cmd, recurse, lockmode);
  	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 if the old type is binary coercible to the new type, or if the
   * new type is an unconstrained domain over the old type.  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
  			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;
  	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;
  
  	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;
  
  	/* Check for multiple ALTER TYPE on same column --- can't cope */
  	if (attTup->atttypid != tab->oldDesc->attrs[attnum - 1]->atttypid ||
  		attTup->atttypmod != tab->oldDesc->attrs[attnum - 1]->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)
  					{
  						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_string(foundObject.objectId);
  
  					/*
  					 * Put NORMAL dependencies at the front of the list and
  					 * AUTO dependencies at the back.  This makes sure that
  					 * foreign-key constraints depending on this column will
  					 * be dropped before unique or primary-key constraints of
  					 * the column; which we must have because the FK
  					 * constraints depend on the indexes belonging to the
  					 * unique constraints.
  					 */
  					if (foundDep->deptype == DEPENDENCY_NORMAL)
  					{
  						tab->changedConstraintOids =
  							lcons_oid(foundObject.objectId,
  									  tab->changedConstraintOids);
  						tab->changedConstraintDefs =
  							lcons(defstring,
  								  tab->changedConstraintDefs);
  					}
  					else
  					{
  						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_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_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_TBLSPACE:
  			case OCLASS_FDW:
  			case OCLASS_FOREIGN_SERVER:
  			case OCLASS_USER_MAPPING:
  			case OCLASS_DEFACL:
  			case OCLASS_EXTENSION:
  
  				/*
  				 * 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;
  
  			default:
  				elog(ERROR, "unrecognized object class: %u",
  					 foundObject.classId);
  		}
  	}
  
  	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");
  
  		simple_heap_delete(depRel, &depTup->t_self);
  	}
  
  	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.)
  	 */
  	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);
  
  	simple_heap_update(attrelation, &heapTup->t_self, heapTup);
  
  	/* keep system catalog indexes current */
  	CatalogUpdateIndexes(attrelation, 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);
  	}
  
  	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);
  
  	simple_heap_update(attrel, &newtuple->t_self, newtuple);
  	CatalogUpdateIndexes(attrel, 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;
  	ListCell   *def_item;
  	ListCell   *oid_item;
  
  	/*
  	 * 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 dropping.  It's safe because the parser won't actually look
  	 * at the catalogs to detect the existing entry.
  	 *
  	 * 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);
  		Oid			relid;
  		Oid			confrelid;
  
  		get_constraint_relation_oids(oldId, &relid, &confrelid);
  		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);
  	}
  
  	/*
  	 * Now we can drop the existing constraints and indexes --- constraints
  	 * first, since some of them might depend on the indexes.  In fact, we
  	 * have to delete FOREIGN KEY constraints before UNIQUE constraints, but
  	 * we already ordered the constraint list to ensure that would happen. It
  	 * should be okay to use DROP_RESTRICT here, since nothing else should be
  	 * depending on these objects.
  	 */
  	foreach(oid_item, tab->changedConstraintOids)
  	{
  		obj.classId = ConstraintRelationId;
  		obj.objectId = lfirst_oid(oid_item);
  		obj.objectSubId = 0;
  		performDeletion(&obj, DROP_RESTRICT, PERFORM_DELETION_INTERNAL);
  	}
  
  	foreach(oid_item, tab->changedIndexOids)
  	{
  		obj.classId = RelationRelationId;
  		obj.objectId = lfirst_oid(oid_item);
  		obj.objectSubId = 0;
  		performDeletion(&obj, DROP_RESTRICT, PERFORM_DELETION_INTERNAL);
  	}
  
  	/*
  	 * 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)
  	{
  		Node	   *stmt = (Node *) lfirst(list_item);
  
  		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 = (AlterTableCmd *) lfirst(lcmd);
  
  				if (cmd->subtype == AT_AddIndex)
  				{
  					IndexStmt  *indstmt;
  					Oid			indoid;
  
  					Assert(IsA(cmd->def, IndexStmt));
  
  					indstmt = (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, indstmt->idxname);
  				}
  				else if (cmd->subtype == AT_AddConstraint)
  				{
  					Constraint *con;
  
  					Assert(IsA(cmd->def, Constraint));
  
  					con = (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, con->conname);
  				}
  				else
  					elog(ERROR, "unexpected statement type: %d",
  						 (int) cmd->subtype);
  			}
  		}
  		else
  			elog(ERROR, "unexpected statement type: %d",
  				 (int) nodeTag(stm));
  	}
  
  	relation_close(rel, NoLock);
  }
  
  /*
   * Subroutine for ATPostAlterTypeParse() to recreate a comment entry for
   * a constraint that is being re-added.
   */
  static void
  RebuildConstraintComment(AlteredTableInfo *tab, int pass, Oid objid,
  						 Relation rel, 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 node CommentStmt */
  	cmd = makeNode(CommentStmt);
  	cmd->objtype = OBJECT_TABCONSTRAINT;
  	cmd->objname = list_make3(
  				   makeString(get_namespace_name(RelationGetNamespace(rel))),
  							  makeString(RelationGetRelationName(rel)),
  							  makeString(conname));
  	cmd->objargs = NIL;
  	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:
  			/* 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_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, &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;
  			/* FALL THRU */
  		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, ACL_KIND_CLASS,
  								   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, ACL_KIND_NAMESPACE,
  								   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);
  
  		simple_heap_update(class_rel, &newtuple->t_self, newtuple);
  		CatalogUpdateIndexes(class_rel, 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_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)
  			AlterTypeOwnerInternal(tuple_class->reltype, newOwnerId,
  							 tuple_class->relkind == RELKIND_COMPOSITE_TYPE);
  
  		/*
  		 * 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_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 (tuple_class->relkind == RELKIND_RELATION ||
  			tuple_class->relkind == RELKIND_MATVIEW)
  		{
  			/* 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);
  
  		simple_heap_update(attRelation, &newtuple->t_self, newtuple);
  		CatalogUpdateIndexes(attRelation, 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)
  			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, 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, ACL_KIND_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:
  			(void) heap_reloptions(rel->rd_rel->relkind, newOptions, true);
  			break;
  		case RELKIND_VIEW:
  			(void) view_reloptions(newOptions, true);
  			break;
  		case RELKIND_INDEX:
  			(void) index_reloptions(rel->rd_am->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 (pg_strcasecmp(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);
  
  	simple_heap_update(pgclass, &newtuple->t_self, newtuple);
  
  	CatalogUpdateIndexes(pgclass, 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);
  
  		simple_heap_update(pgclass, &newtuple->t_self, newtuple);
  
  		CatalogUpdateIndexes(pgclass, 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);
  			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;
  	simple_heap_update(pg_class, &tuple->t_self, tuple);
  	CatalogUpdateIndexes(pg_class, 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);
  }
  
  /*
   * 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, ACL_KIND_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) ||
  			(stmt->objtype == OBJECT_INDEX &&
  			 relForm->relkind != RELKIND_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, ACL_KIND_CLASS,
  						   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)
  {
  	char	   *buf;
  	Page		page;
  	bool		use_wal;
  	BlockNumber nblocks;
  	BlockNumber blkno;
  
  	/*
  	 * palloc the buffer so that it's MAXALIGN'd.  If it were just a local
  	 * char[] array, the compiler might align it on any byte boundary, which
  	 * can seriously hurt transfer speed to and from the kernel; not to
  	 * mention possibly making log_newpage's accesses to the page header fail.
  	 */
  	buf = (char *) palloc(BLCKSZ);
  	page = (Page) buf;
  
  	/*
  	 * 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;
  
  	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);
  
  		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, true);
  	}
  
  	pfree(buf);
  
  	/*
  	 * 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)
  		smgrimmedsync(dst, forkNum);
  }
  
  /*
   * ALTER TABLE ENABLE/DISABLE TRIGGER
   *
   * We just pass this off to trigger.c.
   */
  static void
  ATExecEnableDisableTrigger(Relation rel, char *trigname,
  						char fires_when, bool skip_system, LOCKMODE lockmode)
  {
  	EnableDisableTrigger(rel, trigname, fires_when, skip_system);
  }
  
  /*
   * ALTER TABLE ENABLE/DISABLE RULE
   *
   * We just pass this off to rewriteDefine.c.
   */
  static void
  ATExecEnableDisableRule(Relation rel, char *trigname,
  						char fires_when, LOCKMODE lockmode)
  {
  	EnableDisableRule(rel, trigname, 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")));
  }
  
  /*
   * Return the address of the new parent relation.
   */
  static ObjectAddress
  ATExecAddInherit(Relation child_rel, RangeVar *parent, LOCKMODE lockmode)
  {
  	Relation	parent_rel,
  				catalogRelation;
  	SysScanDesc scan;
  	ScanKeyData key;
  	HeapTuple	inheritsTuple;
  	int32		inhseqno;
  	List	   *children;
  	ObjectAddress address;
  
  	/*
  	 * 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")));
  
  	/*
  	 * 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.
  	 * (Note: get RowExclusiveLock because we will write pg_inherits below.)
  	 *
  	 * Note: we do not reject the case where the child already inherits from
  	 * the parent indirectly; CREATE TABLE doesn't reject comparable cases.
  	 */
  	catalogRelation = heap_open(InheritsRelationId, RowExclusiveLock);
  	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);
  
  	/*
  	 * 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))));
  
  	/* 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);
  
  	ObjectAddressSet(address, RelationRelationId,
  					 RelationGetRelid(parent_rel));
  
  	/* Now we're done with pg_inherits */
  	heap_close(catalogRelation, RowExclusiveLock);
  
  	/* keep our lock on the parent relation until commit */
  	heap_close(parent_rel, NoLock);
  
  	return address;
  }
  
  /*
   * 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 ATExecAddInherit
   *
   * 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;
  
  	attrrel = heap_open(AttributeRelationId, RowExclusiveLock);
  
  	tupleDesc = RelationGetDescr(parent_rel);
  	parent_natts = tupleDesc->natts;
  
  	for (parent_attno = 1; parent_attno <= parent_natts; parent_attno++)
  	{
  		Form_pg_attribute attribute = tupleDesc->attrs[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++;
  			simple_heap_update(attrrel, &tuple->t_self, tuple);
  			CatalogUpdateIndexes(attrrel, tuple);
  			heap_freetuple(tuple);
  		}
  		else
  		{
  			ereport(ERROR,
  					(errcode(ERRCODE_DATATYPE_MISMATCH),
  					 errmsg("child table is missing column \"%s\"",
  							attributeName)));
  		}
  	}
  
  	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 ATExecAddInherit
   *
   * 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;
  
  	catalog_relation = heap_open(ConstraintRelationId, RowExclusiveLock);
  	tuple_desc = RelationGetDescr(catalog_relation);
  
  	/* 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, ConstraintRelidIndexId,
  									 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, ConstraintRelidIndexId,
  										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 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))));
  
  			/*
  			 * 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++;
  			simple_heap_update(catalog_relation, &child_copy->t_self, child_copy);
  			CatalogUpdateIndexes(catalog_relation, 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
   *
   * 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.
   *
   * Return value is the address of the relation that is no longer parent.
   */
  static ObjectAddress
  ATExecDropInherit(Relation rel, RangeVar *parent, LOCKMODE lockmode)
  {
  	Relation	parent_rel;
  	Oid			parent_oid;
  	Relation	catalogRelation;
  	SysScanDesc scan;
  	ScanKeyData key[3];
  	HeapTuple	inheritsTuple,
  				attributeTuple,
  				constraintTuple;
  	List	   *connames;
  	bool		found = false;
  	ObjectAddress address;
  
  	/*
  	 * 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.
  	 */
  
  	/*
  	 * Find and destroy the pg_inherits entry linking the two, or error out if
  	 * there is none.
  	 */
  	catalogRelation = heap_open(InheritsRelationId, RowExclusiveLock);
  	ScanKeyInit(&key[0],
  				Anum_pg_inherits_inhrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(rel)));
  	scan = systable_beginscan(catalogRelation, InheritsRelidSeqnoIndexId,
  							  true, NULL, 1, key);
  
  	while (HeapTupleIsValid(inheritsTuple = systable_getnext(scan)))
  	{
  		Oid			inhparent;
  
  		inhparent = ((Form_pg_inherits) GETSTRUCT(inheritsTuple))->inhparent;
  		if (inhparent == RelationGetRelid(parent_rel))
  		{
  			simple_heap_delete(catalogRelation, &inheritsTuple->t_self);
  			found = true;
  			break;
  		}
  	}
  
  	systable_endscan(scan);
  	heap_close(catalogRelation, RowExclusiveLock);
  
  	if (!found)
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_TABLE),
  				 errmsg("relation \"%s\" is not a parent of relation \"%s\"",
  						RelationGetRelationName(parent_rel),
  						RelationGetRelationName(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(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;
  
  			simple_heap_update(catalogRelation, &copyTuple->t_self, copyTuple);
  			CatalogUpdateIndexes(catalogRelation, 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, ConstraintRelidIndexId,
  							  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(rel)));
  	scan = systable_beginscan(catalogRelation, ConstraintRelidIndexId,
  							  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(rel), NameStr(copy_con->conname));
  
  			copy_con->coninhcount--;
  			if (copy_con->coninhcount == 0)
  				copy_con->conislocal = true;
  
  			simple_heap_update(catalogRelation, &copyTuple->t_self, copyTuple);
  			CatalogUpdateIndexes(catalogRelation, copyTuple);
  			heap_freetuple(copyTuple);
  		}
  	}
  
  	parent_oid = RelationGetRelid(parent_rel);
  
  	systable_endscan(scan);
  	heap_close(catalogRelation, RowExclusiveLock);
  
  	drop_parent_dependency(RelationGetRelid(rel),
  						   RelationRelationId,
  						   RelationGetRelid(parent_rel));
  
  	/*
  	 * 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(rel), 0,
  								 RelationGetRelid(parent_rel), false);
  
  	/* keep our lock on the parent relation until commit */
  	heap_close(parent_rel, NoLock);
  
  	ObjectAddressSet(address, RelationRelationId, parent_oid);
  
  	return address;
  }
  
  /*
   * 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)
  {
  	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 == DEPENDENCY_NORMAL)
  			simple_heap_delete(catalogRelation, &depTuple->t_self);
  	}
  
  	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 = typeTupleDesc->attrs[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 = tableTupleDesc->attrs[table_attno++ - 1];
  		} 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 = tableTupleDesc->attrs[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);
  
  	/* 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;
  	simple_heap_update(relationRelation, &classtuple->t_self, classtuple);
  	CatalogUpdateIndexes(relationRelation, 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);
  
  	/* 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;
  	simple_heap_update(relationRelation, &tuple->t_self, tuple);
  	CatalogUpdateIndexes(relationRelation, 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;
  		simple_heap_update(pg_class, &pg_class_tuple->t_self, pg_class_tuple);
  		CatalogUpdateIndexes(pg_class, 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)
  		{
  			simple_heap_update(pg_index, &pg_index_tuple->t_self, pg_index_tuple);
  			CatalogUpdateIndexes(pg_index, 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_am->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 < indexRel->rd_index->indnatts; key++)
  	{
  		int16		attno = indexRel->rd_index->indkey.values[key];
  		Form_pg_attribute attr;
  
  		/* Of the system columns, only oid is indexable. */
  		if (attno <= 0 && attno != ObjectIdAttributeNumber)
  			elog(ERROR, "internal column %u in unique index \"%s\"",
  				 attno, RelationGetRelationName(indexRel));
  
  		attr = rel->rd_att->attrs[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;
  	simple_heap_update(pg_class, &tuple->t_self, tuple);
  
  	/* keep catalog indexes current */
  	CatalogUpdateIndexes(pg_class, 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;
  	simple_heap_update(pg_class, &tuple->t_self, tuple);
  
  	/* keep catalog indexes current */
  	CatalogUpdateIndexes(pg_class, 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;
  	simple_heap_update(pg_class, &tuple->t_self, tuple);
  
  	/* keep catalog indexes current */
  	CatalogUpdateIndexes(pg_class, 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);
  
  	simple_heap_update(ftrel, &tuple->t_self, tuple);
  	CatalogUpdateIndexes(ftrel, tuple);
  
  	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 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 ? ConstraintRelidIndexId : 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, false,
  									 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, &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, RelationRelationId, relid);
  
  	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)
  	{
  		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;
  
  	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;
  
  	/*
  	 * Do nothing when there's nothing to do.
  	 */
  	if (!object_address_present(&thisobj, objsMoved))
  	{
  		/* 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;
  
  		simple_heap_update(classRel, &classTup->t_self, classTup);
  		CatalogUpdateIndexes(classRel, 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));
  
  		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 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)
  			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;
  
  	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 (MyXactAccessedTempRel)
  					oids_to_truncate = lappend_oid(oids_to_truncate, oc->relid);
  				break;
  			case ONCOMMIT_DROP:
  				{
  					ObjectAddress object;
  
  					object.classId = RelationRelationId;
  					object.objectId = oc->relid;
  					object.objectSubId = 0;
  
  					/*
  					 * Since this is an automatic drop, rather than one
  					 * directly initiated by the user, we pass the
  					 * PERFORM_DELETION_INTERNAL flag.
  					 */
  					performDeletion(&object,
  									DROP_CASCADE, PERFORM_DELETION_INTERNAL);
  
  					/*
  					 * Note that table deletion will call
  					 * remove_on_commit_action, so the entry should get marked
  					 * as deleted.
  					 */
  					Assert(oc->deleting_subid != InvalidSubTransactionId);
  					break;
  				}
  		}
  	}
  	if (oids_to_truncate != NIL)
  	{
  		heap_truncate(oids_to_truncate);
  		CommandCounterIncrement();		/* XXX needed? */
  	}
  }
  
  /*
   * 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)
  		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, ACL_KIND_CLASS, 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, ACL_KIND_CLASS,
  					   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, ACL_KIND_CLASS, 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, ACL_KIND_NAMESPACE,
  						   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
  	{
  		reltype = OBJECT_TABLE; /* placate compiler */
  		elog(ERROR, "unrecognized node type: %d", (int) nodeTag(stmt));
  	}
  
  	/*
  	 * 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
  		&& !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)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
  				 errmsg("\"%s\" is not a table, view, materialized view, sequence, or foreign table",
  						rv->relname)));
  
  	ReleaseSysCache(tuple);
  }
  