text: /*-------------------------------------------------------------------------
   *
   * index.c
   *	  code to create and destroy POSTGRES index relations
   *
   * Portions Copyright (c) 2006-2009, Greenplum inc
   * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   *
   * IDENTIFICATION
   *	  $PostgreSQL: pgsql/src/backend/catalog/index.c,v 1.292.2.3 2009/12/09 21:58:16 tgl Exp $
   *
   *
   * INTERFACE ROUTINES
   *		index_create()			- Create a cataloged index relation
   *		index_drop()			- Removes index relation from catalogs
   *		BuildIndexInfo()		- Prepare to insert index tuples
   *		FormIndexDatum()		- Construct datum vector for one index tuple
   *
   *-------------------------------------------------------------------------
   */
  #include "postgres.h"
  
  #include <unistd.h>
  
  #include "access/genam.h"
  #include "access/heapam.h"
  #include "access/relscan.h"
  #include "access/sysattr.h"
  #include "access/transam.h"
  #include "access/xact.h"
  #include "bootstrap/bootstrap.h"
  #include "catalog/aoblkdir.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/pg_appendonly_fn.h"
  #include "catalog/pg_constraint.h"
  #include "catalog/pg_namespace.h"
  #include "catalog/pg_operator.h"
  #include "catalog/pg_opclass.h"
  #include "catalog/pg_tablespace.h"
  #include "catalog/pg_type.h"
  #include "cdb/cdbpersistentfilesysobj.h"
  #include "catalog/aoblkdir.h"
  #include "commands/tablecmds.h"
  #include "executor/executor.h"
  #include "miscadmin.h"
  #include "optimizer/clauses.h"
  #include "optimizer/var.h"
  #include "parser/parse_expr.h"
  #include "storage/procarray.h"
  #include "storage/smgr.h"
  #include "utils/builtins.h"
  #include "utils/fmgroids.h"
  #include "utils/guc.h"
  #include "utils/inval.h"
  #include "utils/lsyscache.h"
  #include "utils/memutils.h"
  #include "utils/relcache.h"
  #include "utils/syscache.h"
  #include "utils/tuplesort.h"
  #include "utils/tuplesort_mk.h"
  #include "utils/faultinjector.h"
  
  #include "cdb/cdbappendonlyam.h"
  #include "cdb/cdbaocsam.h"
  #include "cdb/cdbvars.h"
  #include "cdb/cdboidsync.h"
  #include "cdb/cdbmirroredfilesysobj.h"
  #include "cdb/cdbpersistentfilesysobj.h"
  
  /* state info for validate_index bulkdelete callback */
  typedef struct
  {
  	void *tuplesort;	/* for sorting the index TIDs */
  	/* statistics (for debug purposes only): */
  	double		htups,
  				itups,
  				tups_inserted;
  } v_i_state;
  
  /* non-export function prototypes */
  static TupleDesc ConstructTupleDescriptor(Relation heapRelation,
  						 IndexInfo *indexInfo,
  						 Oid *classObjectId);
  static void InitializeAttributeOids(Relation indexRelation,
  						int numatts, Oid indexoid);
  static void AppendAttributeTuples(Relation indexRelation, int numatts);
  static void UpdateIndexRelation(Oid indexoid, Oid heapoid,
  					IndexInfo *indexInfo,
  					Oid *classOids,
  					int16 *coloptions,
  					bool primary,
  					bool isvalid);
  static void index_update_stats(Relation rel, bool hasindex, bool isprimary,
  				   Oid reltoastidxid, double reltuples);
  static bool validate_index_callback(ItemPointer itemptr, void *opaque);
  static void validate_index_heapscan(Relation heapRelation,
  						Relation indexRelation,
  						IndexInfo *indexInfo,
  						Snapshot snapshot,
  						v_i_state *state);
  static double IndexBuildHeapScan(Relation heapRelation,
  								 Relation indexRelation,
  								 struct IndexInfo *indexInfo,
  								 bool allow_sync,
  								 EState *estate,
  								 Snapshot snapshot,
  								 TransactionId OldestXmin,
  								 IndexBuildCallback callback,
  								 void *callback_state);
  static double IndexBuildAppendOnlyRowScan(Relation parentRelation,
  										  Relation indexRelation,
  										  struct IndexInfo *indexInfo,
  										  EState *estate,
  										  Snapshot snapshot,
  										  IndexBuildCallback callback,
  										  void *callback_state);
  static double IndexBuildAppendOnlyColScan(Relation parentRelation,
  										  Relation indexRelation,
  										  struct IndexInfo *indexInfo,
  										  EState *estate,
  										  Snapshot snapshot,
  										  IndexBuildCallback callback,
  										  void *callback_state);
  
  
  
  
  /*
   *		ConstructTupleDescriptor
   *
   * Build an index tuple descriptor for a new index
   */
  static TupleDesc
  ConstructTupleDescriptor(Relation heapRelation,
  						 IndexInfo *indexInfo,
  						 Oid *classObjectId)
  {
  	int			numatts = indexInfo->ii_NumIndexAttrs;
  	ListCell   *indexpr_item = list_head(indexInfo->ii_Expressions);
  	TupleDesc	heapTupDesc;
  	TupleDesc	indexTupDesc;
  	int			natts;			/* #atts in heap rel --- for error checks */
  	int			i;
  
  	heapTupDesc = RelationGetDescr(heapRelation);
  	natts = RelationGetForm(heapRelation)->relnatts;
  
  	/*
  	 * allocate the new tuple descriptor
  	 */
  	indexTupDesc = CreateTemplateTupleDesc(numatts, false);
  
  	/*
  	 * For simple index columns, we copy the pg_attribute row from the parent
  	 * relation and modify it as necessary.  For expressions we have to cons
  	 * up a pg_attribute row the hard way.
  	 */
  	for (i = 0; i < numatts; i++)
  	{
  		AttrNumber	atnum = indexInfo->ii_KeyAttrNumbers[i];
  		Form_pg_attribute to = indexTupDesc->attrs[i];
  		HeapTuple	tuple;
  		Form_pg_type typeTup;
  		Oid			keyType;
  
  		if (atnum != 0)
  		{
  			/* Simple index column */
  			Form_pg_attribute from;
  
  			if (atnum < 0)
  			{
  				/*
  				 * here we are indexing on a system attribute (-1...-n)
  				 */
  				from = SystemAttributeDefinition(atnum,
  										   heapRelation->rd_rel->relhasoids);
  			}
  			else
  			{
  				/*
  				 * here we are indexing on a normal attribute (1...n)
  				 */
  				if (atnum > natts)		/* safety check */
  					elog(ERROR, "invalid column number %d", atnum);
  				from = heapTupDesc->attrs[AttrNumberGetAttrOffset(atnum)];
  			}
  
  			/*
  			 * now that we've determined the "from", let's copy the tuple desc
  			 * data...
  			 */
  			memcpy(to, from, ATTRIBUTE_TUPLE_SIZE);
  
  			/*
  			 * Fix the stuff that should not be the same as the underlying
  			 * attr
  			 */
  			to->attnum = i + 1;
  
  			to->attstattarget = -1;
  			to->attcacheoff = -1;
  			to->attnotnull = false;
  			to->atthasdef = false;
  			to->attislocal = true;
  			to->attinhcount = 0;
  		}
  		else
  		{
  			/* Expressional index */
  			Node	   *indexkey;
  
  			MemSet(to, 0, ATTRIBUTE_TUPLE_SIZE);
  
  			if (indexpr_item == NULL)	/* shouldn't happen */
  				elog(ERROR, "too few entries in indexprs list");
  			indexkey = (Node *) lfirst(indexpr_item);
  			indexpr_item = lnext(indexpr_item);
  
  			/*
  			 * Make the attribute's name "pg_expresssion_nnn" (maybe think of
  			 * something better later)
  			 */
  			sprintf(NameStr(to->attname), "pg_expression_%d", i + 1);
  
  			/*
  			 * Lookup the expression type in pg_type for the type length etc.
  			 */
  			keyType = exprType(indexkey);
  
  			tuple = SearchSysCache(TYPEOID,
  								   ObjectIdGetDatum(keyType),
  								   0, 0, 0);
  			if (!HeapTupleIsValid(tuple))
  				elog(ERROR, "cache lookup failed for type %u", keyType);
  			typeTup = (Form_pg_type) GETSTRUCT(tuple);
  
  			/*
  			 * Assign some of the attributes values. Leave the rest as 0.
  			 */
  			to->attnum = i + 1;
  			to->atttypid = keyType;
  			to->attlen = typeTup->typlen;
  			to->attbyval = typeTup->typbyval;
  			to->attstorage = typeTup->typstorage;
  			to->attalign = typeTup->typalign;
  			to->attstattarget = -1;
  			to->attcacheoff = -1;
  			to->atttypmod = -1;
  			to->attislocal = true;
  
  			ReleaseSysCache(tuple);
  		}
  
  		/*
  		 * We do not yet have the correct relation OID for the index, so just
  		 * set it invalid for now.	InitializeAttributeOids() will fix it
  		 * later.
  		 */
  		to->attrelid = InvalidOid;
  
  		/*
  		 * Check the opclass to see if it provides a keytype (overriding the
  		 * attribute type).
  		 */
  		tuple = SearchSysCache(CLAOID,
  							   ObjectIdGetDatum(classObjectId[i]),
  							   0, 0, 0);
  		if (!HeapTupleIsValid(tuple))
  			elog(ERROR, "cache lookup failed for opclass %u",
  				 classObjectId[i]);
  		keyType = ((Form_pg_opclass) GETSTRUCT(tuple))->opckeytype;
  		ReleaseSysCache(tuple);
  
  		if (OidIsValid(keyType) && keyType != to->atttypid)
  		{
  			/* index value and heap value have different types */
  			tuple = SearchSysCache(TYPEOID,
  								   ObjectIdGetDatum(keyType),
  								   0, 0, 0);
  			if (!HeapTupleIsValid(tuple))
  				elog(ERROR, "cache lookup failed for type %u", keyType);
  			typeTup = (Form_pg_type) GETSTRUCT(tuple);
  
  			to->atttypid = keyType;
  			to->atttypmod = -1;
  			to->attlen = typeTup->typlen;
  			to->attbyval = typeTup->typbyval;
  			to->attalign = typeTup->typalign;
  			to->attstorage = typeTup->typstorage;
  
  			ReleaseSysCache(tuple);
  		}
  	}
  
  	return indexTupDesc;
  }
  
  /* ----------------------------------------------------------------
   *		InitializeAttributeOids
   * ----------------------------------------------------------------
   */
  static void
  InitializeAttributeOids(Relation indexRelation,
  						int numatts,
  						Oid indexoid)
  {
  	TupleDesc	tupleDescriptor;
  	int			i;
  
  	tupleDescriptor = RelationGetDescr(indexRelation);
  
  	for (i = 0; i < numatts; i += 1)
  		tupleDescriptor->attrs[i]->attrelid = indexoid;
  }
  
  /* ----------------------------------------------------------------
   *		AppendAttributeTuples
   * ----------------------------------------------------------------
   */
  static void
  AppendAttributeTuples(Relation indexRelation, int numatts)
  {
  	Relation	pg_attribute;
  	CatalogIndexState indstate;
  	TupleDesc	indexTupDesc;
  	HeapTuple	new_tuple;
  	int			i;
  
  	/*
  	 * open the attribute relation and its indexes
  	 */
  	pg_attribute = heap_open(AttributeRelationId, RowExclusiveLock);
  
  	indstate = CatalogOpenIndexes(pg_attribute);
  
  	/*
  	 * insert data from new index's tupdesc into pg_attribute
  	 */
  	indexTupDesc = RelationGetDescr(indexRelation);
  
  	for (i = 0; i < numatts; i++)
  	{
  		/*
  		 * There used to be very grotty code here to set these fields, but I
  		 * think it's unnecessary.  They should be set already.
  		 */
  		Assert(indexTupDesc->attrs[i]->attnum == i + 1);
  		Assert(indexTupDesc->attrs[i]->attcacheoff == -1);
  
  		new_tuple = heap_addheader(Natts_pg_attribute,
  								   false,
  								   ATTRIBUTE_TUPLE_SIZE,
  								   (void *) indexTupDesc->attrs[i]);
  
  		simple_heap_insert(pg_attribute, new_tuple);
  
  		CatalogIndexInsert(indstate, new_tuple);
  
  		heap_freetuple(new_tuple);
  	}
  
  	CatalogCloseIndexes(indstate);
  
  	heap_close(pg_attribute, RowExclusiveLock);
  }
  
  /* ----------------------------------------------------------------
   *		UpdateIndexRelation
   *
   * Construct and insert a new entry in the pg_index catalog
   * ----------------------------------------------------------------
   */
  static void
  UpdateIndexRelation(Oid indexoid,
  					Oid heapoid,
  					IndexInfo *indexInfo,
  					Oid *classOids,
  					int16 *coloptions,
  					bool primary,
  					bool isvalid)
  {
  	int2vector *indkey;
  	oidvector  *indclass;
  	int2vector *indoption;
  	Datum		exprsDatum;
  	Datum		predDatum;
  	Datum		values[Natts_pg_index];
  	bool		nulls[Natts_pg_index];
  	Relation	pg_index;
  	HeapTuple	tuple;
  	int			i;
  
  	/*
  	 * Copy the index key, opclass, and indoption info into arrays (should we
  	 * make the caller pass them like this to start with?)
  	 */
  	indkey = buildint2vector(NULL, indexInfo->ii_NumIndexAttrs);
  	for (i = 0; i < indexInfo->ii_NumIndexAttrs; i++)
  		indkey->values[i] = indexInfo->ii_KeyAttrNumbers[i];
  	indclass = buildoidvector(classOids, indexInfo->ii_NumIndexAttrs);
  	indoption = buildint2vector(coloptions, indexInfo->ii_NumIndexAttrs);
  
  	/*
  	 * Convert the index expressions (if any) to a text datum
  	 */
  	if (indexInfo->ii_Expressions != NIL)
  	{
  		char	   *exprsString;
  
  		exprsString = nodeToString(indexInfo->ii_Expressions);
  		exprsDatum = CStringGetTextDatum(exprsString);
  		pfree(exprsString);
  	}
  	else
  		exprsDatum = (Datum) 0;
  
  	/*
  	 * Convert the index predicate (if any) to a text datum.  Note we convert
  	 * implicit-AND format to normal explicit-AND for storage.
  	 */
  	if (indexInfo->ii_Predicate != NIL)
  	{
  		char	   *predString;
  
  		predString = nodeToString(make_ands_explicit(indexInfo->ii_Predicate));
  		predDatum = CStringGetTextDatum(predString);
  		pfree(predString);
  	}
  	else
  		predDatum = (Datum) 0;
  
  	/*
  	 * open the system catalog index relation
  	 */
  	pg_index = heap_open(IndexRelationId, RowExclusiveLock);
  
  	/*
  	 * Build a pg_index tuple
  	 */
  	MemSet(nulls, false, sizeof(nulls));
  
  	values[Anum_pg_index_indexrelid - 1] = ObjectIdGetDatum(indexoid);
  	values[Anum_pg_index_indrelid - 1] = ObjectIdGetDatum(heapoid);
  	values[Anum_pg_index_indnatts - 1] = Int16GetDatum(indexInfo->ii_NumIndexAttrs);
  	values[Anum_pg_index_indisunique - 1] = BoolGetDatum(indexInfo->ii_Unique);
  	values[Anum_pg_index_indisprimary - 1] = BoolGetDatum(primary);
  	values[Anum_pg_index_indisclustered - 1] = BoolGetDatum(false);
  	values[Anum_pg_index_indisvalid - 1] = BoolGetDatum(isvalid);
  	values[Anum_pg_index_indcheckxmin - 1] = BoolGetDatum(false);
  	/* we set isvalid and isready the same way */
  	values[Anum_pg_index_indisready - 1] = BoolGetDatum(isvalid);
  	values[Anum_pg_index_indkey - 1] = PointerGetDatum(indkey);
  	values[Anum_pg_index_indclass - 1] = PointerGetDatum(indclass);
  	values[Anum_pg_index_indoption - 1] = PointerGetDatum(indoption);
  	values[Anum_pg_index_indexprs - 1] = exprsDatum;
  	if (exprsDatum == (Datum) 0)
  		nulls[Anum_pg_index_indexprs - 1] = true;
  	values[Anum_pg_index_indpred - 1] = predDatum;
  	if (predDatum == (Datum) 0)
  		nulls[Anum_pg_index_indpred - 1] = true;
  
  	tuple = heap_form_tuple(RelationGetDescr(pg_index), values, nulls);
  
  	/*
  	 * insert the tuple into the pg_index catalog
  	 */
  	simple_heap_insert(pg_index, tuple);
  
  	/* update the indexes on pg_index */
  	CatalogUpdateIndexes(pg_index, tuple);
  
  	/*
  	 * close the relation and free the tuple
  	 */
  	heap_close(pg_index, RowExclusiveLock);
  	heap_freetuple(tuple);
  }
  
  
  /*
   * index_create
   *
   * heapRelationId: OID of table to build index on
   * indexRelationName: what it say
   * indexRelationId: normally, pass InvalidOid to let this routine
   *		generate an OID for the index.	During bootstrap this may be
   *		nonzero to specify a preselected OID.
   * indexInfo: same info executor uses to insert into the index
   * accessMethodObjectId: OID of index AM to use
   * tableSpaceId: OID of tablespace to use
   * classObjectId: array of index opclass OIDs, one per index column
   * coloptions: array of per-index-column indoption settings
   * reloptions: AM-specific options
   * isprimary: index is a PRIMARY KEY
   * isconstraint: index is owned by a PRIMARY KEY or UNIQUE constraint
   * allow_system_table_mods: allow table to be a system catalog
   * skip_build: true to skip the index_build() step for the moment; caller
   *		must do it later (typically via reindex_index())
   * concurrent: if true, do not lock the table against writers.	The index
   *		will be marked "invalid" and the caller must take additional steps
   *		to fix it up.
   *
   * Returns OID of the created index.
   */
  Oid
  index_create(Oid heapRelationId,
  			 const char *indexRelationName,
  			 Oid indexRelationId,
  			 struct IndexInfo *indexInfo,
  			 Oid accessMethodObjectId,
  			 Oid tableSpaceId,
  			 Oid *classObjectId,
  			 int16 *coloptions,
  			 Datum reloptions,
  			 bool isprimary,
  			 bool isconstraint,
  			 bool allow_system_table_mods,
  			 bool skip_build,
  			 bool concurrent,
  			 const char *altConName)
  {
  	Relation	pg_class;
  	Relation	gp_relation_node;
  	Relation	heapRelation;
  	Relation	indexRelation;
  	TupleDesc	indexTupDesc;
  	bool		shared_relation;
  	Oid			namespaceId;
  	int			i;
  	LOCKMODE	heap_lockmode;
  
  	pg_class = heap_open(RelationRelationId, RowExclusiveLock);
  
  	if (!IsBootstrapProcessingMode())
  		gp_relation_node = heap_open(GpRelationNodeRelationId, RowExclusiveLock);
  	else
  		gp_relation_node = NULL;
  
  	/*
  	 * Only SELECT ... FOR UPDATE/SHARE are allowed while doing a standard
  	 * index build; but for concurrent builds we allow INSERT/UPDATE/DELETE
  	 * (but not VACUUM).
  	 */
  	heap_lockmode = (concurrent ? ShareUpdateExclusiveLock : ShareLock);
  	heapRelation = heap_open(heapRelationId, heap_lockmode);
  
  
  	/*
  	 * The index will be in the same namespace as its parent table, and is
  	 * shared across databases if and only if the parent is.
  	 */
  	namespaceId = RelationGetNamespace(heapRelation);
  	shared_relation = heapRelation->rd_rel->relisshared;
  
  	/*
  	 * check parameters
  	 */
  	if (indexInfo->ii_NumIndexAttrs < 1)
  		elog(ERROR, "must index at least one column");
  
  	if (!allow_system_table_mods &&
  		IsSystemRelation(heapRelation) &&
  		IsNormalProcessingMode())
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("user-defined indexes on system catalog tables are not supported")));
  
  	/*
  	 * concurrent index build on a system catalog is unsafe because we tend to
  	 * release locks before committing in catalogs
  	 */
  	if (concurrent &&
  		IsSystemRelation(heapRelation))
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("concurrent index creation on system catalog tables is not supported")));
  
  	/*
  	 * We cannot allow indexing a shared relation after initdb (because
  	 * there's no way to make the entry in other databases' pg_class).
  	 */
  	if (shared_relation && !IsBootstrapProcessingMode())
  		ereport(ERROR,
  				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  				 errmsg("shared indexes cannot be created after initdb")));
  
  	/*
  	 * Validate shared/non-shared tablespace (must check this before doing
  	 * GetNewRelFileNode, to prevent Assert therein)
  	 */
  	if (shared_relation)
  	{
  		if (tableSpaceId != GLOBALTABLESPACE_OID)
  			/* elog since this is not a user-facing error */
  			elog(ERROR,
  				 "shared relations must be placed in pg_global tablespace");
  	}
  	else
  	{
  		if (tableSpaceId == GLOBALTABLESPACE_OID)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  					 errmsg("only shared relations can be placed in pg_global tablespace")));
  	}
  
  	if (get_relname_relid(indexRelationName, namespaceId))
  		ereport(ERROR,
  				(errcode(ERRCODE_DUPLICATE_TABLE),
  				 errmsg("relation \"%s\" already exists",
  						indexRelationName)));
  
  	/*
  	 * construct tuple descriptor for index tuples
  	 */
  	indexTupDesc = ConstructTupleDescriptor(heapRelation,
  											indexInfo,
  											classObjectId);
  
  	/*
  	 * Allocate an OID for the index, unless we were told what to use.
  	 *
  	 * The OID will be the relfilenode as well, so make sure it doesn't
  	 * collide with either pg_class OIDs or existing physical files.
  	 *
  	 * (In GPDB, heap_create can choose a different relfilenode, in a QE node,
  	 * if the one we choose is already in use.)
  	 */
  	if (!OidIsValid(indexRelationId))
  	{
  		if (Gp_role == GP_ROLE_EXECUTE || IsBinaryUpgrade)
  			indexRelationId = GetPreassignedOidForRelation(namespaceId, indexRelationName);
  		else
  			indexRelationId = GetNewOid(pg_class);
  	}
  
  	/*
  	 * create the index relation's relcache entry and physical disk file. (If
  	 * we fail further down, it's the smgr's responsibility to remove the disk
  	 * file again.)
  	 */
  	indexRelation = heap_create(indexRelationName,
  								namespaceId,
  								tableSpaceId,
  								indexRelationId,
  								indexTupDesc,
  								accessMethodObjectId,
  								RELKIND_INDEX,
  								RELSTORAGE_HEAP,
  								shared_relation,
  								allow_system_table_mods,
  								/* bufferPoolBulkLoad */ false);
  
  	Assert(indexRelationId == RelationGetRelid(indexRelation));
  
  	/*
  	 * Obtain exclusive lock on it.  Although no other backends can see it
  	 * until we commit, this prevents deadlock-risk complaints from lock
  	 * manager in cases such as CLUSTER.
  	 */
  	LockRelation(indexRelation, AccessExclusiveLock);
  
  	/*
  	 * Fill in fields of the index's pg_class entry that are not set correctly
  	 * by heap_create.
  	 *
  	 * XXX should have a cleaner way to create cataloged indexes
  	 */
  	indexRelation->rd_rel->relowner = heapRelation->rd_rel->relowner;
  	indexRelation->rd_rel->relam = accessMethodObjectId;
  	indexRelation->rd_rel->relkind = RELKIND_INDEX;
  	indexRelation->rd_rel->relhasoids = false;
  
  	/*
  	 * store index's pg_class entry
  	 */
  	InsertPgClassTuple(pg_class, indexRelation,
  					   RelationGetRelid(indexRelation),
  					   reloptions);
  
  	/* done with pg_class */
  	heap_close(pg_class, RowExclusiveLock);
  
  	{							/* MPP-7575: track index creation */
  		bool	 doIt	= true;
  		char	*subtyp = "INDEX";
  
  		/* MPP-7576: don't track internal namespace tables */
  		switch (namespaceId) 
  		{
  			case PG_CATALOG_NAMESPACE:
  				/* MPP-7773: don't track objects in system namespace
  				 * if modifying system tables (eg during upgrade)  
  				 */
  				if (allowSystemTableModsDDL)
  					doIt = false;
  				break;
  
  			case PG_TOAST_NAMESPACE:
  			case PG_BITMAPINDEX_NAMESPACE:
  			case PG_AOSEGMENT_NAMESPACE:
  				doIt = false;
  				break;
  			default:
  				break;
  		}
  
  		if (doIt)
  			doIt = (!(isAnyTempNamespace(namespaceId)));
  
  		/* MPP-6929: metadata tracking */
  		if (doIt)
  			MetaTrackAddObject(RelationRelationId,
  							   RelationGetRelid(indexRelation),
  							   GetUserId(), /* not ownerid */
  							   "CREATE", subtyp
  					);
  	}
  
  	if (gp_relation_node != NULL)
  	{
  		InsertGpRelationNodeTuple(
  							gp_relation_node,
  							indexRelation->rd_id,
  							indexRelation->rd_rel->relname.data,
  							indexRelation->rd_rel->reltablespace,
  							indexRelation->rd_rel->relfilenode,
  							/* segmentFileNum */ 0,
  							/* updateIndex */ true,
  							&indexRelation->rd_segfile0_relationnodeinfo.persistentTid,
  							indexRelation->rd_segfile0_relationnodeinfo.persistentSerialNum);
  	
  		heap_close(gp_relation_node, RowExclusiveLock);
  	}
  
  	/*
  	 * now update the object id's of all the attribute tuple forms in the
  	 * index relation's tuple descriptor
  	 */
  	InitializeAttributeOids(indexRelation,
  							indexInfo->ii_NumIndexAttrs,
  							indexRelationId);
  
  	/*
  	 * append ATTRIBUTE tuples for the index
  	 */
  	AppendAttributeTuples(indexRelation, indexInfo->ii_NumIndexAttrs);
  
  	/* ----------------
  	 *	  update pg_index
  	 *	  (append INDEX tuple)
  	 *
  	 *	  Note that this stows away a representation of "predicate".
  	 *	  (Or, could define a rule to maintain the predicate) --Nels, Feb '92
  	 * ----------------
  	 */
  	UpdateIndexRelation(indexRelationId, heapRelationId, indexInfo,
  						classObjectId, coloptions, isprimary, !concurrent);
  
  	/*
  	 * Register constraint and dependencies for the index.
  	 *
  	 * If the index is from a CONSTRAINT clause, construct a pg_constraint
  	 * entry. The index is then linked to the constraint, which in turn is
  	 * linked to the table.  If it's not a CONSTRAINT, make the dependency
  	 * directly on the table.
  	 *
  	 * We don't need a dependency on the namespace, because there'll be an
  	 * indirect dependency via our parent table.
  	 *
  	 * During bootstrap we can't register any dependencies, and we don't try
  	 * to make a constraint either.
  	 */
  	if (!IsBootstrapProcessingMode())
  	{
  		ObjectAddress myself,
  					referenced;
  
  		myself.classId = RelationRelationId;
  		myself.objectId = indexRelationId;
  		myself.objectSubId = 0;
  
  		if (isconstraint)
  		{
  			char		constraintType;
  			const char *constraintName = indexRelationName;
  			Oid			conOid;
  
  			if ( altConName )
  			{
  				constraintName = altConName;
  			}
  
  			/*
  			 * Let's make sure that the constraint name is unique
  			 * for this relation.
  			 */
  			Assert(constraintName);
  			if (ConstraintNameIsUsed(CONSTRAINT_RELATION,
  									 RelationGetRelid(heapRelation),
  									 RelationGetNamespace(heapRelation),
  									 constraintName))
  				ereport(ERROR,
  						(errcode(ERRCODE_DUPLICATE_OBJECT),
  						 errmsg("constraint \"%s\" for relation \"%s\" already exists",
  								constraintName, RelationGetRelationName(heapRelation))));
  
  			if (isprimary)
  				constraintType = CONSTRAINT_PRIMARY;
  			else if (indexInfo->ii_Unique)
  				constraintType = CONSTRAINT_UNIQUE;
  			else
  			{
  				elog(ERROR, "constraint must be PRIMARY or UNIQUE");
  				constraintType = 0;		/* keep compiler quiet */
  			}
  
  			/* Shouldn't have any expressions */
  			if (indexInfo->ii_Expressions)
  				elog(ERROR, "constraints cannot have index expressions");
  
  			conOid = CreateConstraintEntry(constraintName,
  										   namespaceId,
  										   constraintType,
  										   false,		/* isDeferrable */
  										   false,		/* isDeferred */
  										   heapRelationId,
  										   indexInfo->ii_KeyAttrNumbers,
  										   indexInfo->ii_NumIndexAttrs,
  										   InvalidOid,	/* no domain */
  										   InvalidOid,	/* no foreign key */
  										   NULL,
  										   NULL,
  										   NULL,
  										   NULL,
  										   0,
  										   ' ',
  										   ' ',
  										   ' ',
  										   InvalidOid,	/* no associated index */
  										   NULL,		/* no check constraint */
  										   NULL,
  										   NULL);
  
  			referenced.classId = ConstraintRelationId;
  			referenced.objectId = conOid;
  			referenced.objectSubId = 0;
  
  			recordDependencyOn(&myself, &referenced, DEPENDENCY_INTERNAL);
  		}
  		else
  		{
  			bool		have_simple_col = false;
  
  			/* Create auto dependencies on simply-referenced columns */
  			for (i = 0; i < indexInfo->ii_NumIndexAttrs; i++)
  			{
  				if (indexInfo->ii_KeyAttrNumbers[i] != 0)
  				{
  					referenced.classId = RelationRelationId;
  					referenced.objectId = heapRelationId;
  					referenced.objectSubId = indexInfo->ii_KeyAttrNumbers[i];
  
  					recordDependencyOn(&myself, &referenced, DEPENDENCY_AUTO);
  
  					have_simple_col = true;
  				}
  			}
  
  			/*
  			 * If there are no simply-referenced columns, give the index an
  			 * auto dependency on the whole table.  In most cases, this will
  			 * be redundant, but it might not be if the index expressions and
  			 * predicate contain no Vars or only whole-row Vars.
  			 */
  			if (!have_simple_col)
  			{
  				referenced.classId = RelationRelationId;
  				referenced.objectId = heapRelationId;
  				referenced.objectSubId = 0;
  
  				recordDependencyOn(&myself, &referenced, DEPENDENCY_AUTO);
  			}
  		}
  
  		/* Store dependency on operator classes */
  		for (i = 0; i < indexInfo->ii_NumIndexAttrs; i++)
  		{
  			referenced.classId = OperatorClassRelationId;
  			referenced.objectId = classObjectId[i];
  			referenced.objectSubId = 0;
  
  			recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
  		}
  
  		/* Store dependencies on anything mentioned in index expressions */
  		if (indexInfo->ii_Expressions)
  		{
  			recordDependencyOnSingleRelExpr(&myself,
  										  (Node *) indexInfo->ii_Expressions,
  											heapRelationId,
  											DEPENDENCY_NORMAL,
  											DEPENDENCY_AUTO);
  		}
  
  		/* Store dependencies on anything mentioned in predicate */
  		if (indexInfo->ii_Predicate)
  		{
  			recordDependencyOnSingleRelExpr(&myself,
  											(Node *) indexInfo->ii_Predicate,
  											heapRelationId,
  											DEPENDENCY_NORMAL,
  											DEPENDENCY_AUTO);
  		}
  	}
  
  	/*
  	 * Advance the command counter so that we can see the newly-entered
  	 * catalog tuples for the index.
  	 */
  	CommandCounterIncrement();
  
  	/*
  	 * In bootstrap mode, we have to fill in the index strategy structure with
  	 * information from the catalogs.  If we aren't bootstrapping, then the
  	 * relcache entry has already been rebuilt thanks to sinval update during
  	 * CommandCounterIncrement.
  	 */
  	if (IsBootstrapProcessingMode())
  		RelationInitIndexAccessInfo(indexRelation);
  	else
  		Assert(indexRelation->rd_indexcxt != NULL);
  
  	/*
  	 * If this is bootstrap (initdb) time, then we don't actually fill in the
  	 * index yet.  We'll be creating more indexes and classes later, so we
  	 * delay filling them in until just before we're done with bootstrapping.
  	 * Similarly, if the caller specified skip_build then filling the index is
  	 * delayed till later (ALTER TABLE can save work in some cases with this).
  	 * Otherwise, we call the AM routine that constructs the index.
  	 */
  	if (IsBootstrapProcessingMode())
  	{
  		index_register(heapRelationId, indexRelationId, indexInfo);
  	}
  	else if (skip_build)
  	{
  		/*
  		 * Caller is responsible for filling the index later on.  However,
  		 * we'd better make sure that the heap relation is correctly marked as
  		 * having an index.
  		 */
  		index_update_stats(heapRelation,
  						   true,
  						   isprimary,
  						   InvalidOid,
  						   heapRelation->rd_rel->reltuples);
  		/* Make the above update visible */
  		CommandCounterIncrement();
  	}
  	else
  	{
  		index_build(heapRelation, indexRelation, indexInfo, isprimary, false);
  	}
  
  	/*
  	 * Close the heap and index; but we keep the locks that we acquired above
  	 * until end of transaction unless we're dealing with a child of a partition
  	 * table, in which case the lock on the master is sufficient.
  	 */
  	if (rel_needs_long_lock(RelationGetRelid(heapRelation)))
  	{
  		index_close(indexRelation, NoLock);
  		heap_close(heapRelation, NoLock);
  	}
  	else
  	{
  		index_close(indexRelation, AccessExclusiveLock);
  		heap_close(heapRelation, heap_lockmode);
  	}
  
  	return indexRelationId;
  }
  
  /*
   *		index_drop
   *
   * NOTE: this routine should now only be called through performDeletion(),
   * else associated dependencies won't be cleaned up.
   */
  void
  index_drop(Oid indexId)
  {
  	Oid			heapId;
  	Relation	userHeapRelation;
  	Relation	userIndexRelation;
  	Relation	indexRelation;
  	HeapTuple	tuple;
  	bool		hasexprs;
  	bool		need_long_lock;
  
  	/*
  	 * To drop an index safely, we must grab exclusive lock on its parent
  	 * table; otherwise there could be other backends using the index!
  	 * Exclusive lock on the index alone is insufficient because another
  	 * backend might be in the midst of devising a query plan that will use
  	 * the index.  The parser and planner take care to hold an appropriate
  	 * lock on the parent table while working, but having them hold locks on
  	 * all the indexes too seems overly expensive.	We do grab exclusive lock
  	 * on the index too, just to be safe. Both locks must be held till end of
  	 * transaction, else other backends will still see this index in pg_index.
  	 */
  	heapId = IndexGetRelation(indexId);
  	userHeapRelation = heap_open(heapId, AccessExclusiveLock);
  
  	userIndexRelation = index_open(indexId, AccessExclusiveLock);
  
  
  	if (!userIndexRelation->rd_segfile0_relationnodeinfo.isPresent)
  		RelationFetchSegFile0GpRelationNode(userIndexRelation);
  
  	/*
  	 * There can no longer be anyone *else* touching the index, but we
  	 * might still have open queries using it in our own session.
  	 */
  	CheckTableNotInUse(userIndexRelation, "DROP INDEX");
  
  	/*
  	 * Schedule physical removal of the file
  	 */
  	MirroredFileSysObj_ScheduleDropBufferPoolRel(userIndexRelation);
  
  	DeleteGpRelationNodeTuple(
  					userIndexRelation,
  					/* segmentFileNum */ 0);
  	
  
  	/*
  	 * Close and flush the index's relcache entry, to ensure relcache doesn't
  	 * try to rebuild it while we're deleting catalog entries. We keep the
  	 * lock though.
  	 */
  	need_long_lock = rel_needs_long_lock(RelationGetRelid(userIndexRelation));
  	if (need_long_lock)
  		index_close(userIndexRelation, NoLock);
  	else
  		index_close(userIndexRelation, AccessExclusiveLock);
  
  	RelationForgetRelation(indexId);
  
  	/*
  	 * fix INDEX relation, and check for expressional index
  	 */
  	indexRelation = heap_open(IndexRelationId, RowExclusiveLock);
  
  	tuple = SearchSysCache(INDEXRELID,
  						   ObjectIdGetDatum(indexId),
  						   0, 0, 0);
  	if (!HeapTupleIsValid(tuple))
  		elog(ERROR, "cache lookup failed for index %u", indexId);
  
  	hasexprs = !heap_attisnull(tuple, Anum_pg_index_indexprs);
  
  	simple_heap_delete(indexRelation, &tuple->t_self);
  
  	ReleaseSysCache(tuple);
  	heap_close(indexRelation, RowExclusiveLock);
  
  	/*
  	 * if it has any expression columns, we might have stored statistics about
  	 * them.
  	 */
  	if (hasexprs)
  		RemoveStatistics(indexId, 0);
  
  	/*
  	 * fix ATTRIBUTE relation
  	 */
  	DeleteAttributeTuples(indexId);
  
  	/*
  	 * fix RELATION relation
  	 */
  	DeleteRelationTuple(indexId);
  
  	/* MPP-6929: metadata tracking */
  	MetaTrackDropObject(RelationRelationId, 
  						indexId);
  
  	/*
  	 * We are presently too lazy to attempt to compute the new correct value
  	 * of relhasindex (the next VACUUM will fix it if necessary). So there is
  	 * no need to update the pg_class tuple for the owning relation. But we
  	 * must send out a shared-cache-inval notice on the owning relation to
  	 * ensure other backends update their relcache lists of indexes.
  	 */
  	CacheInvalidateRelcache(userHeapRelation);
  
  	/*
  	 * Close owning rel, but keep lock
  	 */
  	heap_close(userHeapRelation, need_long_lock ? NoLock : AccessExclusiveLock);
  }
  
  /* ----------------------------------------------------------------
   *						index_build support
   * ----------------------------------------------------------------
   */
  
  /* ----------------
   *		BuildIndexInfo
   *			Construct an IndexInfo record for an open index
   *
   * IndexInfo stores the information about the index that's needed by
   * FormIndexDatum, which is used for both index_build() and later insertion
   * of individual index tuples.	Normally we build an IndexInfo for an index
   * just once per command, and then use it for (potentially) many tuples.
   * ----------------
   */
  IndexInfo *
  BuildIndexInfo(Relation index)
  {
  	IndexInfo  *ii = makeNode(IndexInfo);
  	Form_pg_index indexStruct = index->rd_index;
  	int			i;
  	int			numKeys;
  
  	/* check the number of keys, and copy attr numbers into the IndexInfo */
  	numKeys = indexStruct->indnatts;
  	if (numKeys < 1 || numKeys > INDEX_MAX_KEYS)
  		elog(ERROR, "invalid indnatts %d for index %u",
  			 numKeys, RelationGetRelid(index));
  	ii->ii_NumIndexAttrs = numKeys;
  	for (i = 0; i < numKeys; i++)
  		ii->ii_KeyAttrNumbers[i] = indexStruct->indkey.values[i];
  
  	/* fetch any expressions needed for expressional indexes */
  	ii->ii_Expressions = RelationGetIndexExpressions(index);
  	ii->ii_ExpressionsState = NIL;
  
  	/* fetch index predicate if any */
  	ii->ii_Predicate = RelationGetIndexPredicate(index);
  	ii->ii_PredicateState = NIL;
  
  	/* other info */
  	ii->ii_Unique = indexStruct->indisunique;
  	ii->ii_ReadyForInserts = IndexIsReady(indexStruct);
  
  	/* initialize index-build state to default */
  	ii->ii_Concurrent = false;
  	ii->ii_BrokenHotChain = false;
  
  	return ii;
  }
  
  /* ----------------
   *		FormIndexDatum
   *			Construct values[] and isnull[] arrays for a new index tuple.
   *
   *	indexInfo		Info about the index
   *	slot			Heap tuple for which we must prepare an index entry
   *	estate			executor state for evaluating any index expressions
   *	values			Array of index Datums (output area)
   *	isnull			Array of is-null indicators (output area)
   *
   * When there are no index expressions, estate may be NULL.  Otherwise it
   * must be supplied, *and* the ecxt_scantuple slot of its per-tuple expr
   * context must point to the heap tuple passed in.
   *
   * Notice we don't actually call index_form_tuple() here; we just prepare
   * its input arrays values[] and isnull[].	This is because the index AM
   * may wish to alter the data before storage.
   * ----------------
   */
  void
  FormIndexDatum(struct IndexInfo *indexInfo,
  			   TupleTableSlot *slot,
  			   struct EState *estate,
  			   Datum *values,
  			   bool *isnull)
  {
  	ListCell   *indexpr_item;
  	int			i;
  
  	if (indexInfo->ii_Expressions != NIL &&
  		indexInfo->ii_ExpressionsState == NIL)
  	{
  		/* First time through, set up expression evaluation state */
  		indexInfo->ii_ExpressionsState = (List *)
  			ExecPrepareExpr((Expr *) indexInfo->ii_Expressions,
  							estate);
  		/* Check caller has set up context correctly */
  		Assert(GetPerTupleExprContext(estate)->ecxt_scantuple == slot);
  	}
  	indexpr_item = list_head(indexInfo->ii_ExpressionsState);
  
  	for (i = 0; i < indexInfo->ii_NumIndexAttrs; i++)
  	{
  		int			keycol = indexInfo->ii_KeyAttrNumbers[i];
  		Datum		iDatum;
  		bool		isNull;
  
  		if (keycol != 0)
  		{
  			/*
  			 * Plain index column; get the value we need directly from the
  			 * heap tuple.
  			 */
  			iDatum = slot_getattr(slot, keycol, &isNull);
  		}
  		else
  		{
  			/*
  			 * Index expression --- need to evaluate it.
  			 */
  			if (indexpr_item == NULL)
  				elog(ERROR, "wrong number of index expressions");
  			iDatum = ExecEvalExprSwitchContext((ExprState *) lfirst(indexpr_item),
  											   GetPerTupleExprContext(estate),
  											   &isNull,
  											   NULL);
  			indexpr_item = lnext(indexpr_item);
  		}
  		values[i] = iDatum;
  		isnull[i] = isNull;
  	}
  
  	if (indexpr_item != NULL)
  		elog(ERROR, "wrong number of index expressions");
  }
  
  
  /*
   * index_update_stats --- update pg_class entry after CREATE INDEX or REINDEX
   *
   * This routine updates the pg_class row of either an index or its parent
   * relation after CREATE INDEX or REINDEX.	Its rather bizarre API is designed
   * to ensure we can do all the necessary work in just one update.
   *
   * hasindex: set relhasindex to this value
   * isprimary: if true, set relhaspkey true; else no change
   * reltoastidxid: if not InvalidOid, set reltoastidxid to this value;
   *		else no change
   * reltuples: set reltuples to this value
   *
   * relpages is also updated (using RelationGetNumberOfBlocks()).
   *
   * NOTE: an important side-effect of this operation is that an SI invalidation
   * message is sent out to all backends --- including me --- causing relcache
   * entries to be flushed or updated with the new data.	This must happen even
   * if we find that no change is needed in the pg_class row.  When updating
   * a heap entry, this ensures that other backends find out about the new
   * index.  When updating an index, it's important because some index AMs
   * expect a relcache flush to occur after REINDEX.
   */
  static void
  index_update_stats(Relation rel, bool hasindex, bool isprimary,
  				   Oid reltoastidxid, double reltuples)
  {
  	Oid			relid = RelationGetRelid(rel);
  	Relation	pg_class;
  	HeapTuple	tuple;
  	Form_pg_class rd_rel;
  	bool		dirty;
  
  	/*
  	 * We always update the pg_class row using a non-transactional,
  	 * overwrite-in-place update.  There are several reasons for this:
  	 *
  	 * 1. In bootstrap mode, we have no choice --- UPDATE wouldn't work.
  	 *
  	 * 2. We could be reindexing pg_class itself, in which case we can't move
  	 * its pg_class row because CatalogUpdateIndexes might not know about all
  	 * the indexes yet (see reindex_relation).
  	 *
  	 * 3. Because we execute CREATE INDEX with just share lock on the parent
  	 * rel (to allow concurrent index creations), an ordinary update could
  	 * suffer a tuple-concurrently-updated failure against another CREATE
  	 * INDEX committing at about the same time.  We can avoid that by having
  	 * them both do nontransactional updates (we assume they will both be
  	 * trying to change the pg_class row to the same thing, so it doesn't
  	 * matter which goes first).
  	 *
  	 * 4. Even with just a single CREATE INDEX, there's a risk factor because
  	 * someone else might be trying to open the rel while we commit, and this
  	 * creates a race condition as to whether he will see both or neither of
  	 * the pg_class row versions as valid.	Again, a non-transactional update
  	 * avoids the risk.  It is indeterminate which state of the row the other
  	 * process will see, but it doesn't matter (if he's only taking
  	 * AccessShareLock, then it's not critical that he see relhasindex true).
  	 *
  	 * It is safe to use a non-transactional update even though our
  	 * transaction could still fail before committing.	Setting relhasindex
  	 * true is safe even if there are no indexes (VACUUM will eventually fix
  	 * it), and of course the relpages and reltuples counts are correct (or at
  	 * least more so than the old values) regardless.
  	 */
  
  	pg_class = heap_open(RelationRelationId, RowExclusiveLock);
  
  	/*
  	 * Make a copy of the tuple to update.	Normally we use the syscache, but
  	 * we can't rely on that during bootstrap or while reindexing pg_class
  	 * itself.
  	 */
  	if (IsBootstrapProcessingMode() ||
  		ReindexIsProcessingHeap(RelationRelationId))
  	{
  		/* don't assume syscache will work */
  		HeapScanDesc pg_class_scan;
  		ScanKeyData key[1];
  
  		ScanKeyInit(&key[0],
  					ObjectIdAttributeNumber,
  					BTEqualStrategyNumber, F_OIDEQ,
  					ObjectIdGetDatum(relid));
  
  		pg_class_scan = heap_beginscan(pg_class, SnapshotNow, 1, key);
  		tuple = heap_getnext(pg_class_scan, ForwardScanDirection);
  		tuple = heap_copytuple(tuple);
  		heap_endscan(pg_class_scan);
  	}
  	else
  	{
  		/* normal case, use syscache */
  		tuple = SearchSysCacheCopy(RELOID,
  								   ObjectIdGetDatum(relid),
  								   0, 0, 0);
  	}
  
  	if (!HeapTupleIsValid(tuple))
  		elog(ERROR, "could not find tuple for relation %u", relid);
  	rd_rel = (Form_pg_class) GETSTRUCT(tuple);
  
  	/* Apply required updates, if any, to copied tuple */
  
  	dirty = false;
  	if (rd_rel->relhasindex != hasindex)
  	{
  		rd_rel->relhasindex = hasindex;
  		dirty = true;
  	}
  	if (isprimary)
  	{
  		if (!rd_rel->relhaspkey)
  		{
  			rd_rel->relhaspkey = true;
  			dirty = true;
  		}
  	}
  	if (OidIsValid(reltoastidxid))
  	{
  		Assert(rd_rel->relkind == RELKIND_TOASTVALUE);
  		if (rd_rel->reltoastidxid != reltoastidxid)
  		{
  			rd_rel->reltoastidxid = reltoastidxid;
  			dirty = true;
  		}
  	}
  
  	if (Gp_role != GP_ROLE_DISPATCH)
  	{
  		/**
  		 * Do not overwrite relpages, reltuples in QD.
  		 */
  		if (rd_rel->reltuples != (float4) reltuples)
  		{
  			rd_rel->reltuples = (float4) reltuples;
  			dirty = true;
  		}
  
  		BlockNumber relpages = RelationGetNumberOfBlocks(rel);
  
  		if (rd_rel->relpages != (int32) relpages)
  		{
  			rd_rel->relpages = (int32) relpages;
  			dirty = true;
  		}
  	}
  	/*
  	 * If anything changed, write out the tuple
  	 */
  	if (dirty)
  	{
  		heap_inplace_update(pg_class, tuple);
  		/* the above sends a cache inval message */
  	}
  	else
  	{
  		/* no need to change tuple, but force relcache inval anyway */
  		CacheInvalidateRelcacheByTuple(tuple);
  	}
  
  	heap_freetuple(tuple);
  
  	heap_close(pg_class, RowExclusiveLock);
  }
  
  /*
   * setNewRelfilenode		- assign a new relfilenode value to the relation
   *
   * Caller must already hold exclusive lock on the relation.
   *
   * The relation is marked with relfrozenxid=freezeXid (InvalidTransactionId
   * must be passed for indexes)
   *
   * Replaces relfilenode and updates pg_class / gp_relation_node.
   * If the updating relation is gp_relation_node's index, the caller
   * should rebuild the index by index_build().
   */
  void
  setNewRelfilenode(Relation relation, TransactionId freezeXid)
  {
  	Oid			newrelfilenode;
  	RelFileNode newrnode;
  	SMgrRelation srel;
  	Relation	pg_class;
  	Relation	gp_relation_node;
  	HeapTuple	tuple;
  	Form_pg_class rd_rel;
  	bool		isAppendOnly;
  	bool		is_gp_relation_node_index;
  
  	ItemPointerData		persistentTid;
  	int64				persistentSerialNum;
  
  	/* Can't change relfilenode for nailed tables (indexes ok though) */
  	Assert(!relation->rd_isnailed ||
  		   relation->rd_rel->relkind == RELKIND_INDEX);
  	/* Can't change for shared tables or indexes */
  	Assert(!relation->rd_rel->relisshared);
  	/* Indexes must have Invalid frozenxid; other relations must not */
  	Assert((relation->rd_rel->relkind == RELKIND_INDEX &&
  			freezeXid == InvalidTransactionId) ||
  		   TransactionIdIsNormal(freezeXid));
  
  	/* Allocate a new relfilenode */
  	newrelfilenode = GetNewRelFileNode(relation->rd_rel->reltablespace,
  									   relation->rd_rel->relisshared);
  
  	/*
  	 * Find the pg_class tuple for the given relation.	This is not used
  	 * during bootstrap, so okay to use heap_update always.
  	 */
  	pg_class = heap_open(RelationRelationId, RowExclusiveLock);
  	gp_relation_node = heap_open(GpRelationNodeRelationId, RowExclusiveLock);
  
  	tuple = SearchSysCacheCopy(RELOID,
  							   ObjectIdGetDatum(RelationGetRelid(relation)),
  							   0, 0, 0);
  	if (!HeapTupleIsValid(tuple))
  		elog(ERROR, "could not find tuple for relation %u",
  			 RelationGetRelid(relation));
  	rd_rel = (Form_pg_class) GETSTRUCT(tuple);
  
  	/* create another storage file. Is it a little ugly ? */
  	/* NOTE: any conflict in relfilenode value will be caught here */
  	newrnode = relation->rd_node;
  	newrnode.relNode = newrelfilenode;
  
  	/* schedule unlinking old relfilenode */
  	remove_gp_relation_node_and_schedule_drop(relation);
  
  	isAppendOnly = (relation->rd_rel->relstorage == RELSTORAGE_AOROWS || 
  					relation->rd_rel->relstorage == RELSTORAGE_AOCOLS);
  
  	if (!isAppendOnly)
  	{
  		PersistentFileSysRelStorageMgr localRelStorageMgr;
  		PersistentFileSysRelBufpoolKind relBufpoolKind;
  
  		GpPersistentRelationNode_GetRelationInfo(
  											relation->rd_rel->relkind,
  											relation->rd_rel->relstorage,
  											relation->rd_rel->relam,
  											&localRelStorageMgr,
  											&relBufpoolKind);
  		Assert(localRelStorageMgr == PersistentFileSysRelStorageMgr_BufferPool);
  
  		srel = smgropen(newrnode);
  
  		MirroredFileSysObj_TransactionCreateBufferPoolFile(
  											srel,
  											relBufpoolKind,
  											relation->rd_isLocalBuf,
  											NameStr(relation->rd_rel->relname),
  											/* doJustInTimeDirCreate */ true,
  											/* bufferPoolBulkLoad */ false,
  											&persistentTid,
  											&persistentSerialNum);
  		smgrclose(srel);
  	}
  	else
  	{
  		MirroredFileSysObj_TransactionCreateAppendOnlyFile(
  											&newrnode,
  											/* segmentFileNum */ 0,
  											NameStr(relation->rd_rel->relname),
  											/* doJustInTimeDirCreate */ true,
  											&persistentTid,
  											&persistentSerialNum);
  	}
  
  	if (!Persistent_BeforePersistenceWork() &&
  		PersistentStore_IsZeroTid(&persistentTid))
  	{
  		elog(ERROR,
  			 "setNewRelfilenodeCommon has invalid TID (0,0) for relation %u/%u/%u '%s', serial number " INT64_FORMAT,
  			 newrnode.spcNode,
  			 newrnode.dbNode,
  			 newrnode.relNode,
  			 NameStr(relation->rd_rel->relname),
  			 persistentSerialNum);
  	}
  
  	if (Debug_persistent_print)
  		elog(Persistent_DebugPrintLevel(),
  			 "setNewRelfilenodeCommon: NEW '%s', Append-Only '%s', persistent TID %s and serial number " INT64_FORMAT,
  			 relpath(newrnode),
  			 (isAppendOnly ? "true" : "false"),
  			 ItemPointerToString(&persistentTid),
  			 persistentSerialNum);
  
  	/* update the pg_class row */
  	rd_rel->relfilenode = newrelfilenode;
  	rd_rel->relpages = 0;		/* it's empty until further notice */
  	rd_rel->reltuples = 0;
  	rd_rel->relfrozenxid = freezeXid;
  	simple_heap_update(pg_class, &tuple->t_self, tuple);
  	CatalogUpdateIndexes(pg_class, tuple);
  
  	/*
  	 * If the swapping relation is an index of gp_relation_node,
  	 * updating itself is bogus; if gp_relation_node has old indexlist,
  	 * CatalogUpdateIndexes updates old index file, and is crash-unsafe.
  	 * Hence, here we skip it and count on later index_build.
  	 * (Or should we add index_build() call after CCI below in this case?)
  	 */
  	is_gp_relation_node_index = relation->rd_index &&
  								relation->rd_index->indrelid == GpRelationNodeRelationId;
  	InsertGpRelationNodeTuple(
  						gp_relation_node,
  						relation->rd_id,
  						NameStr(relation->rd_rel->relname),
  						relation->rd_rel->reltablespace,
  						newrelfilenode,
  						/* segmentFileNum */ 0,
  						/* updateIndex */ !is_gp_relation_node_index,
  						&persistentTid,
  						persistentSerialNum);
  
  	heap_freetuple(tuple);
  
  	heap_close(pg_class, RowExclusiveLock);
  
  	heap_close(gp_relation_node, RowExclusiveLock);
  
  	/* Make sure the relfilenode change is visible */
  	CommandCounterIncrement();
  
  	/* Mark the rel as having a new relfilenode in current transaction */
  	RelationCacheMarkNewRelfilenode(relation);
  }
  
  
  /*
   * index_build - invoke access-method-specific index build procedure
   *
   * On entry, the index's catalog entries are valid, and its physical disk
   * file has been created but is empty.	We call the AM-specific build
   * procedure to fill in the index contents.  We then update the pg_class
   * entries of the index and heap relation as needed, using statistics
   * returned by ambuild as well as data passed by the caller.
   *
   * isprimary tells whether to mark the index as a primary-key index.
   * isreindex indicates we are recreating a previously-existing index.
   *
   * Note: when reindexing an existing index, isprimary can be false even if
   * the index is a PK; it's already properly marked and need not be re-marked.
   *
   * Note: before Postgres 8.2, the passed-in heap and index Relations
   * were automatically closed by this routine.  This is no longer the case.
   * The caller opened 'em, and the caller should close 'em.
   */
  void
  index_build(Relation heapRelation,
  			Relation indexRelation,
  			IndexInfo *indexInfo,
  			bool isprimary,
  			bool isreindex)
  {
  	RegProcedure procedure;
  	IndexBuildResult *stats;
  	Oid			save_userid;
  	int			save_sec_context;
  	int			save_nestlevel;
  
  	/*
  	 * sanity checks
  	 */
  	Assert(RelationIsValid(indexRelation));
  	Assert(PointerIsValid(indexRelation->rd_am));
  
  	procedure = indexRelation->rd_am->ambuild;
  	Assert(RegProcedureIsValid(procedure));
  
  	/*
  	 * Switch to the table owner's userid, so that any index functions are run
  	 * as that user.  Also lock down security-restricted operations and
  	 * arrange to make GUC variable changes local to this command.
  	 */
  	GetUserIdAndSecContext(&save_userid, &save_sec_context);
  	SetUserIdAndSecContext(heapRelation->rd_rel->relowner,
  						   save_sec_context | SECURITY_RESTRICTED_OPERATION);
  	save_nestlevel = NewGUCNestLevel();
  
  	/*
  	 * Call the access method's build procedure
  	 */
  	stats = (IndexBuildResult *)
  		DatumGetPointer(OidFunctionCall3(procedure,
  										 PointerGetDatum(heapRelation),
  										 PointerGetDatum(indexRelation),
  										 PointerGetDatum(indexInfo)));
  	Assert(PointerIsValid(stats));
  
  	/* Roll back any GUC changes executed by index functions */
  	AtEOXact_GUC(false, save_nestlevel);
  
  	/* Restore userid and security context */
  	SetUserIdAndSecContext(save_userid, save_sec_context);
  
  	/*
  	 * If we found any potentially broken HOT chains, mark the index as not
  	 * being usable until the current transaction is below the event horizon.
  	 * See src/backend/access/heap/README.HOT for discussion.
  	 *
  	 * However, when reindexing an existing index, we should do nothing here.
  	 * Any HOT chains that are broken with respect to the index must predate
  	 * the index's original creation, so there is no need to change the
  	 * index's usability horizon.  Moreover, we *must not* try to change
  	 * the index's pg_index entry while reindexing pg_index itself, and this
  	 * optimization nicely prevents that.
  	 *
  	 * We also need not set indcheckxmin during a concurrent index build,
  	 * because we won't set indisvalid true until all transactions that care
  	 * about the broken HOT chains are gone.
  	 *
  	 * Therefore, this code path can only be taken during non-concurrent
  	 * CREATE INDEX.  Thus the fact that heap_update will set the pg_index
  	 * tuple's xmin doesn't matter, because that tuple was created in the
  	 * current transaction anyway.	That also means we don't need to worry
  	 * about any concurrent readers of the tuple; no other transaction can see
  	 * it yet.
  	 */
  	if (indexInfo->ii_BrokenHotChain && !isreindex &&
  		!indexInfo->ii_Concurrent)
  	{
  		Oid			indexId = RelationGetRelid(indexRelation);
  		Relation	pg_index;
  		HeapTuple	indexTuple;
  		Form_pg_index indexForm;
  
  		pg_index = heap_open(IndexRelationId, RowExclusiveLock);
  
  		indexTuple = SearchSysCacheCopy(INDEXRELID,
  										ObjectIdGetDatum(indexId),
  										0, 0, 0);
  		if (!HeapTupleIsValid(indexTuple))
  			elog(ERROR, "cache lookup failed for index %u", indexId);
  		indexForm = (Form_pg_index) GETSTRUCT(indexTuple);
  
  		/* If it's a new index, indcheckxmin shouldn't be set ... */
  		Assert(!indexForm->indcheckxmin);
  
  		indexForm->indcheckxmin = true;
  		simple_heap_update(pg_index, &indexTuple->t_self, indexTuple);
  		CatalogUpdateIndexes(pg_index, indexTuple);
  
  		heap_freetuple(indexTuple);
  		heap_close(pg_index, RowExclusiveLock);
  	}
  
  	/*
  	 * Update heap and index pg_class rows
  	 */
  	index_update_stats(heapRelation,
  					   true,
  					   isprimary,
  					   (heapRelation->rd_rel->relkind == RELKIND_TOASTVALUE) ?
  					   RelationGetRelid(indexRelation) : InvalidOid,
  					   stats->heap_tuples);
  
  	index_update_stats(indexRelation,
  					   false,
  					   false,
  					   InvalidOid,
  					   stats->index_tuples);
  
  	/* Make the updated versions visible */
  	CommandCounterIncrement();
  }
  
  
  /*
   * IndexBuildScan - scan the heap, or the append-only row, or the append-only
   * column relation to find tuples to be indexed.
   *
   * This is called back from an access-method-specific index build procedure
   * after the AM has done whatever setup it needs.  The parent relation
   * is scanned to find tuples that should be entered into the index.  Each
   * such tuple is passed to the AM's callback routine, which does the right
   * things to add it to the new index.  After we return, the AM's index
   * build procedure does whatever cleanup is needed; in particular, it should
   * close the heap and index relations.
   *
   * The total count of heap tuples is returned.	This is for updating pg_class
   * statistics.	(It's annoying not to be able to do that here, but we can't
   * do it until after the relation is closed.)  Note that the index AM itself
   * must keep track of the number of index tuples; we don't do so here because
   * the AM might reject some of the tuples for its own reasons, such as being
   * unable to store NULLs.
   *
   * A side effect is to set indexInfo->ii_BrokenHotChain to true if we detect
   * any potentially broken HOT chains.  Currently, we set this if there are
   * any RECENTLY_DEAD or DELETE_IN_PROGRESS entries in a HOT chain, without
   * trying very hard to detect whether they're really incompatible with the
   * chain tip.
   */
  double
  IndexBuildScan(Relation parentRelation,
  			   Relation indexRelation,
  			   struct IndexInfo *indexInfo,
  			   bool allow_sync,
  			   IndexBuildCallback callback,
  			   void *callback_state)
  {
  	double		reltuples;
  	TupleTableSlot *slot;
  	EState	   *estate;
  	ExprContext *econtext;
  	Snapshot	snapshot;
  	TransactionId OldestXmin;
  
  	/*
  	 * sanity checks
  	 */
  	Assert(OidIsValid(indexRelation->rd_rel->relam));
  
  	/*
  	 * Need an EState for evaluation of index expressions and partial-index
  	 * predicates.	Also a slot to hold the current tuple.
  	 */
  	estate = CreateExecutorState();
  	econtext = GetPerTupleExprContext(estate);
  	slot = MakeSingleTupleTableSlot(RelationGetDescr(parentRelation));
  
  	/* Arrange for econtext's scan tuple to be the tuple under test */
  	econtext->ecxt_scantuple = slot;
  
  	/*
  	 * Prepare for scan of the base relation.  In a normal index build, we use
  	 * SnapshotAny because we must retrieve all tuples and do our own time
  	 * qual checks (because we have to index RECENTLY_DEAD tuples). In a
  	 * concurrent build, we take a regular MVCC snapshot and index whatever's
  	 * live according to that.	During bootstrap we just use SnapshotNow.
  	 *
  	 * If the relation is an append-only table, we use a regular MVCC snapshot
  	 * and index what is actually in the table.
  	 */
  	if (IsBootstrapProcessingMode())
  	{
  		snapshot = SnapshotNow;
  		OldestXmin = InvalidTransactionId;		/* not used */
  	}
  	else if (indexInfo->ii_Concurrent ||
  			 RelationIsAoRows(parentRelation) ||
  			 RelationIsAoCols(parentRelation))
  	{
  		snapshot = CopySnapshot(GetTransactionSnapshot());
  		OldestXmin = InvalidTransactionId;		/* not used */
  	}
  	else
  	{
  		snapshot = SnapshotAny;
  		/* okay to ignore lazy VACUUMs here */
  		OldestXmin = GetOldestXmin(parentRelation->rd_rel->relisshared, true);
  	}
  
  	if (RelationIsHeap(parentRelation))
  		reltuples = IndexBuildHeapScan(parentRelation,
  									   indexRelation,
  									   indexInfo,
  									   allow_sync,
  									   estate,
  									   snapshot,
  									   OldestXmin,
  									   callback,
  									   callback_state);
  	else if (RelationIsAoRows(parentRelation))
  		reltuples = IndexBuildAppendOnlyRowScan(parentRelation,
  												indexRelation,
  												indexInfo,
  												estate,
  												snapshot,
  												callback,
  												callback_state);
  	else if (RelationIsAoCols(parentRelation))
  		reltuples = IndexBuildAppendOnlyColScan(parentRelation,
  												indexRelation,
  												indexInfo,
  												estate,
  												snapshot,
  												callback,
  												callback_state);
  	else
  	{
  		reltuples = 0; /* keep compiler quiet */
  		elog(ERROR, "unrecognized relation storage type: %c",
  			 parentRelation->rd_rel->relstorage);
  	}
  
  	ExecDropSingleTupleTableSlot(slot);
  	FreeExecutorState(estate);
  
  	/* These may have been pointing to the now-gone estate */
  	indexInfo->ii_ExpressionsState = NIL;
  	indexInfo->ii_PredicateState = NIL;
  
  	return reltuples;
  }
  
  
  /*
   * IndexBuildHeapScan - scan the heap relation to find tuples to be indexed
   *
   * This is called back from an access-method-specific index build procedure
   * after the AM has done whatever setup it needs.  The parent heap relation
   * is scanned to find tuples that should be entered into the index.  Each
   * such tuple is passed to the AM's callback routine, which does the right
   * things to add it to the new index.  After we return, the AM's index
   * build procedure does whatever cleanup is needed; in particular, it should
   * close the heap and index relations.
   *
   * The total count of heap tuples is returned.	This is for updating pg_class
   * statistics.	(It's annoying not to be able to do that here, but we can't
   * do it until after the relation is closed.)  Note that the index AM itself
   * must keep track of the number of index tuples; we don't do so here because
   * the AM might reject some of the tuples for its own reasons, such as being
   * unable to store NULLs.
   */
  static double
  IndexBuildHeapScan(Relation heapRelation,
  				   Relation indexRelation,
  				   struct IndexInfo *indexInfo,
  				   bool allow_sync,
  				   EState *estate,
  				   Snapshot snapshot,
  				   TransactionId OldestXmin,
  				   IndexBuildCallback callback,
  				   void *callback_state)
  {
  	MIRROREDLOCK_BUFMGR_DECLARE;
  
  	HeapScanDesc scan;
  	HeapTuple	heapTuple;
  	Datum		values[INDEX_MAX_KEYS];
  	bool		isnull[INDEX_MAX_KEYS];
  	double		reltuples;
  	List	   *predicate = NIL;
  	ExprContext *econtext;
  	TupleTableSlot *slot;
  	BlockNumber root_blkno = InvalidBlockNumber;
  	OffsetNumber root_offsets[MaxHeapTuplesPerPage];
  
  	Assert(estate->es_per_tuple_exprcontext != NULL);
  	econtext = estate->es_per_tuple_exprcontext;
  	slot = econtext->ecxt_scantuple;
  
  	/* Set up execution state for predicate, if any. */
  	predicate = (List *)
  		ExecPrepareExpr((Expr *) indexInfo->ii_Predicate,
  						estate);
  
  	scan = heap_beginscan_strat(heapRelation,	/* relation */
  								snapshot,		/* snapshot */
  								0,				/* number of keys */
  								NULL,			/* scan key */
  								true,			/* buffer access strategy OK */
  								allow_sync);	/* syncscan OK? */
  
  	reltuples = 0;
  
  	/*
  	 * Scan all tuples in the base relation.
  	 */
  	while ((heapTuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
  	{
  		bool		tupleIsAlive;
  
  		CHECK_FOR_INTERRUPTS();
  
  		/*
  		 * When dealing with a HOT-chain of updated tuples, we want to index
  		 * the values of the live tuple (if any), but index it under the TID
  		 * of the chain's root tuple.  This approach is necessary to preserve
  		 * the HOT-chain structure in the heap. So we need to be able to find
  		 * the root item offset for every tuple that's in a HOT-chain.  When
  		 * first reaching a new page of the relation, call
  		 * heap_get_root_tuples() to build a map of root item offsets on the
  		 * page.
  		 *
  		 * It might look unsafe to use this information across buffer
  		 * lock/unlock.  However, we hold ShareLock on the table so no
  		 * ordinary insert/update/delete should occur; and we hold pin on the
  		 * buffer continuously while visiting the page, so no pruning
  		 * operation can occur either.
  		 *
  		 * Also, although our opinions about tuple liveness could change while
  		 * we scan the page (due to concurrent transaction commits/aborts),
  		 * the chain root locations won't, so this info doesn't need to be
  		 * rebuilt after waiting for another transaction.
  		 *
  		 * Note the implied assumption that there is no more than one live
  		 * tuple per HOT-chain --- else we could create more than one index
  		 * entry pointing to the same root tuple.
  		 */
  		if (scan->rs_cblock != root_blkno)
  		{
  			Page		page = BufferGetPage(scan->rs_cbuf);
  
  			// -------- MirroredLock ----------
  			MIRROREDLOCK_BUFMGR_LOCK;
  
  			LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
  			heap_get_root_tuples(page, root_offsets);
  			LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
  
  			MIRROREDLOCK_BUFMGR_UNLOCK;
  			// -------- MirroredLock ----------
  
  			root_blkno = scan->rs_cblock;
  		}
  
  		if (snapshot == SnapshotAny)
  		{
  			/* do our own time qual check */
  			bool		indexIt;
  
  	recheck:
  
  			/*
  			 * We could possibly get away with not locking the buffer here,
  			 * since caller should hold ShareLock on the relation, but let's
  			 * be conservative about it.  (This remark is still correct even
  			 * with HOT-pruning: our pin on the buffer prevents pruning.)
  			 */
  
  			// -------- MirroredLock ----------
  			MIRROREDLOCK_BUFMGR_LOCK;
  			
  			LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
  
  			switch (HeapTupleSatisfiesVacuum(heapRelation, heapTuple->t_data, OldestXmin,
  											 scan->rs_cbuf))
  			{
  				case HEAPTUPLE_DEAD:
  					/* Definitely dead, we can ignore it */
  					indexIt = false;
  					tupleIsAlive = false;
  					break;
  				case HEAPTUPLE_LIVE:
  					/* Normal case, index and unique-check it */
  					indexIt = true;
  					tupleIsAlive = true;
  					break;
  				case HEAPTUPLE_RECENTLY_DEAD:
  
  					/*
  					 * If tuple is recently deleted then we must index it
  					 * anyway to preserve MVCC semantics.  (Pre-existing
  					 * transactions could try to use the index after we finish
  					 * building it, and may need to see such tuples.)
  					 *
  					 * However, if it was HOT-updated then we must only index
  					 * the live tuple at the end of the HOT-chain.	Since this
  					 * breaks semantics for pre-existing snapshots, mark the
  					 * index as unusable for them.
  					 */
  					if (HeapTupleIsHotUpdated(heapTuple))
  					{
  						indexIt = false;
  						/* mark the index as unsafe for old snapshots */
  						indexInfo->ii_BrokenHotChain = true;
  					}
  					else
  						indexIt = true;
  					/* In any case, exclude the tuple from unique-checking */
  					tupleIsAlive = false;
  					break;
  				case HEAPTUPLE_INSERT_IN_PROGRESS:
  
  					/*
  					 * Since caller should hold ShareLock or better, we should
  					 * not see any tuples inserted by open transactions ---
  					 * unless it's our own transaction. (Consider INSERT
  					 * followed by CREATE INDEX within a transaction.)	An
  					 * exception occurs when reindexing a system catalog,
  					 * because we often release lock on system catalogs before
  					 * committing.	In that case we wait for the inserting
  					 * transaction to finish and check again.  (We could do
  					 * that on user tables too, but since the case is not
  					 * expected it seems better to throw an error.)
  					 */
  					if (!TransactionIdIsCurrentTransactionId(
  								  HeapTupleHeaderGetXmin(heapTuple->t_data)))
  					{
  						if (!IsSystemRelation(heapRelation))
  							elog(ERROR, "concurrent insert in progress");
  						else
  						{
  							/*
  							 * Must drop the lock on the buffer before we wait
  							 */
  							TransactionId xwait = HeapTupleHeaderGetXmin(heapTuple->t_data);
  
  							LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
  							XactLockTableWait(xwait);
  							goto recheck;
  						}
  					}
  
  					/*
  					 * We must index such tuples, since if the index build
  					 * commits then they're good.
  					 */
  					indexIt = true;
  					tupleIsAlive = true;
  					break;
  				case HEAPTUPLE_DELETE_IN_PROGRESS:
  
  					/*
  					 * As with INSERT_IN_PROGRESS case, this is unexpected
  					 * unless it's our own deletion or a system catalog.
  					 */
  					Assert(!(heapTuple->t_data->t_infomask & HEAP_XMAX_IS_MULTI));
  					if (!TransactionIdIsCurrentTransactionId(
  								  HeapTupleHeaderGetXmax(heapTuple->t_data)))
  					{
  						if (!IsSystemRelation(heapRelation))
  							elog(ERROR, "concurrent delete in progress");
  						else
  						{
  							/*
  							 * Must drop the lock on the buffer before we wait
  							 */
  							TransactionId xwait = HeapTupleHeaderGetXmax(heapTuple->t_data);
  
  							LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
  							XactLockTableWait(xwait);
  							goto recheck;
  						}
  
  						/*
  						 * Otherwise index it but don't check for uniqueness,
  						 * the same as a RECENTLY_DEAD tuple.  (We can't
  						 * actually get here, but keep compiler quiet.)
  						 */
  						indexIt = true;
  					}
  					else if (HeapTupleIsHotUpdated(heapTuple))
  					{
  						/*
  						 * It's a HOT-updated tuple deleted by our own xact.
  						 * We can assume the deletion will commit (else the
  						 * index contents don't matter), so treat the same
  						 * as RECENTLY_DEAD HOT-updated tuples.
  						 */
  						indexIt = false;
  						/* mark the index as unsafe for old snapshots */
  						indexInfo->ii_BrokenHotChain = true;
  					}
  					else
  					{
  						/*
  						 * It's a regular tuple deleted by our own xact.
  						 * Index it but don't check for uniqueness, the same
  						 * as a RECENTLY_DEAD tuple.
  						 */
  						indexIt = true;
  					}
  					/* In any case, exclude the tuple from unique-checking */
  					tupleIsAlive = false;
  					break;
  				default:
  					elog(ERROR, "unexpected HeapTupleSatisfiesVacuum result");
  					indexIt = tupleIsAlive = false;		/* keep compiler quiet */
  					break;
  			}
  
  			LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
  
  			MIRROREDLOCK_BUFMGR_UNLOCK;
  			// -------- MirroredLock ----------
  
  			if (!indexIt)
  				continue;
  		}
  		else
  		{
  			/* heap_getnext did the time qual check */
  			tupleIsAlive = true;
  		}
  
  		reltuples += 1;
  
  		MemoryContextReset(econtext->ecxt_per_tuple_memory);
  
  		/* Set up for predicate or expression evaluation */
  		ExecStoreGenericTuple(heapTuple, slot, false);
  
  		/*
  		 * In a partial index, discard tuples that don't satisfy the
  		 * predicate.
  		 */
  		if (predicate != NIL)
  		{
  			if (!ExecQual(predicate, econtext, false))
  				continue;
  		}
  
  		/*
  		 * For the current heap tuple, extract all the attributes we use in
  		 * this index, and note which are null.  This also performs evaluation
  		 * of any expressions needed.
  		 */
  		FormIndexDatum(indexInfo,
  					   slot,
  					   estate,
  					   values,
  					   isnull);
  
  		/*
  		 * You'd think we should go ahead and build the index tuple here, but
  		 * some index AMs want to do further processing on the data first.	So
  		 * pass the values[] and isnull[] arrays, instead.
  		 */
  
  		if (HeapTupleIsHeapOnly(heapTuple))
  		{
  			/*
  			 * For a heap-only tuple, pretend its TID is that of the root. See
  			 * src/backend/access/heap/README.HOT for discussion.
  			 */
  			HeapTupleData rootTuple;
  			OffsetNumber offnum;
  
  			rootTuple = *heapTuple;
  			offnum = ItemPointerGetOffsetNumber(&heapTuple->t_self);
  
  			Assert(OffsetNumberIsValid(root_offsets[offnum - 1]));
  
  			ItemPointerSetOffsetNumber(&rootTuple.t_self,
  									   root_offsets[offnum - 1]);
  
  			/* Call the AM's callback routine to process the tuple */
  			callback(indexRelation, &rootTuple.t_self, values, isnull, tupleIsAlive,
  					 callback_state);
  		}
  		else
  		{
  			/* Call the AM's callback routine to process the tuple */
  			callback(indexRelation, &heapTuple->t_self, values, isnull, tupleIsAlive,
  					 callback_state);
  		}
  	}
  
  	heap_endscan(scan);
  
  	return reltuples;
  }
  
  /*
   * IndexBuildAppendOnlyRowScan - scan the Append-Only Row relation to find
   * tuples to be indexed.
   *
   * If the block directory of the append-only relation does not exist, it is
   * created here.
   */
  static double
  IndexBuildAppendOnlyRowScan(Relation parentRelation,
  							Relation indexRelation,
  							struct IndexInfo *indexInfo,
  							EState *estate,
  							Snapshot snapshot,
  							IndexBuildCallback callback,
  							void *callback_state)
  {
  	List *predicate = NIL;
  	ExprContext *econtext;
  	struct AppendOnlyScanDescData *aoscan;
  	TupleTableSlot *slot;
  	double reltuples = 0;
  	Datum		values[INDEX_MAX_KEYS];
  	bool		isnull[INDEX_MAX_KEYS];
  	AppendOnlyBlockDirectory *blockDirectory = NULL;
  	
  	Assert(estate->es_per_tuple_exprcontext != NULL);
  	econtext = estate->es_per_tuple_exprcontext;
  	slot = econtext->ecxt_scantuple;
  
  	/* Set up execution state for predicate, if any */
  	predicate = (List *)
  		ExecPrepareExpr((Expr *)indexInfo->ii_Predicate, estate);
  	
  	aoscan = appendonly_beginscan(parentRelation,
  								  snapshot,
  								  snapshot,
  								  0,
  								  NULL);
  
  	if (!OidIsValid(parentRelation->rd_appendonly->blkdirrelid) ||
  		!OidIsValid(parentRelation->rd_appendonly->blkdiridxid))
  	{
  		if (indexInfo->ii_Concurrent)
  			ereport(ERROR,
  					(errcode(ERRCODE_GP_COMMAND_ERROR),
  					 errmsg("Cannot create index concurrently. Create an index non-concurrently "
  					        "before creating an index concurrently in an appendonly table.")));
  
  		AlterTableCreateAoBlkdirTable(RelationGetRelid(parentRelation), false);
  
  		aoscan->blockDirectory =
  			(AppendOnlyBlockDirectory *)palloc0(sizeof(AppendOnlyBlockDirectory));
  		blockDirectory = aoscan->blockDirectory;
  	}
  	
  	while (appendonly_getnext(aoscan, ForwardScanDirection, slot) != NULL)
  	{
  		CHECK_FOR_INTERRUPTS();
  
  		reltuples++;
  
  		MemoryContextReset(econtext->ecxt_per_tuple_memory);
  		
  		if (predicate != NIL)
  		{
  			if (!ExecQual(predicate, econtext, false))
  				continue;
  		}
  		
  		/*
  		 * For the current heap tuple, extract all the attributes we use in
  		 * this index, and note which are null.  This also performs evaluation
  		 * of any expressions needed.
  		 */
  		FormIndexDatum(indexInfo,
  					   slot,
  					   estate,
  					   values,
  					   isnull);
  
  		/*
  		 * You'd think we should go ahead and build the index tuple here, but
  		 * some index AMs want to do further processing on the data first.	So
  		 * pass the values[] and isnull[] arrays, instead.
  		 */
  		Assert(ItemPointerIsValid(slot_get_ctid(slot)));
  		
  		/* Call the AM's callback routine to process the tuple */
  		callback(indexRelation, slot_get_ctid(slot),
  				 values, isnull, true, callback_state);
  	}
  	
  	appendonly_endscan(aoscan);
  	
  	if (blockDirectory != NULL)
  		pfree(blockDirectory);
  	
  	return reltuples;
  }
  
  /*
   * IndexBuildAppendOnlyColScan - scan the appendonly columnar relation to
   * find tuples to be indexed.
   *
   * If the block directory of the append-only relation does not exist, it is
   * created here.
   */
  static double
  IndexBuildAppendOnlyColScan(Relation parentRelation,
  							Relation indexRelation,
  							struct IndexInfo *indexInfo,
  							EState *estate,
  							Snapshot snapshot,
  							IndexBuildCallback callback,
  							void *callback_state)
  {
  	List *predicate = NIL;
  	ExprContext *econtext;
  	struct AOCSScanDescData *aocsscan;
  	TupleTableSlot *slot;
  	double reltuples = 0;
  	bool *proj;
  	int attno;
  	Datum		values[INDEX_MAX_KEYS];
  	bool		isnull[INDEX_MAX_KEYS];
  	Oid blkdirrelid = InvalidOid;
  	Oid blkdiridxid = InvalidOid;
  	AppendOnlyBlockDirectory *blockDirectory = NULL;
  
  	Assert(estate->es_per_tuple_exprcontext != NULL);
  	econtext = estate->es_per_tuple_exprcontext;
  	slot = econtext->ecxt_scantuple;
  
  	/* Set up execution state for predicate, if any */
  	predicate = (List *)
  		ExecPrepareExpr((Expr *)indexInfo->ii_Predicate, estate);
  
  	/*
  	 * Mark columns that need to be scanned for the index creation. Normally,
  	 * only index key columns need to be scanned. We create the block
  	 * directory as part of the index creation process, if one doesn't
  	 * exist. In that case, all columns need to be scanned.
  	 */
  	Assert(parentRelation->rd_att != NULL);
  	proj = palloc0(parentRelation->rd_att->natts * sizeof(bool));
  
  	GetAppendOnlyEntryAuxOids(RelationGetRelid(parentRelation), SnapshotNow,
  							  NULL,
  							  &blkdirrelid, &blkdiridxid,
  							  NULL, NULL);
  
  	if (OidIsValid(blkdirrelid) && OidIsValid(blkdiridxid))
  	{
  		for (attno = 0; attno < indexInfo->ii_NumIndexAttrs; attno++)
  		{
  			Assert(indexInfo->ii_KeyAttrNumbers[attno] <= parentRelation->rd_att->natts);
  			/* Skip expression */
  			if (indexInfo->ii_KeyAttrNumbers[attno] > 0)
  				proj[indexInfo->ii_KeyAttrNumbers[attno] - 1] = true;
  		}
  
  		GetNeededColumnsForScan((Node *)indexInfo->ii_Expressions,
  								proj,
  								parentRelation->rd_att->natts);
  	}
  	
  	else
  	{
  		for (attno = 0; attno < parentRelation->rd_att->natts; attno++)
  			proj[attno] = true;
  	}
  	
  	aocsscan = aocs_beginscan(parentRelation, snapshot, snapshot, NULL /* relationTupleDesc */, proj);
  
  	if (!OidIsValid(blkdirrelid) || !OidIsValid(blkdiridxid))
  	{
  		if (indexInfo->ii_Concurrent)
  			ereport(ERROR,
  					(errcode(ERRCODE_GP_COMMAND_ERROR),
  					 errmsg("Cannot create index concurrently. Create an index non-concurrently "
  					        "before creating an index concurrently in an appendonly table.")));
  
  		AlterTableCreateAoBlkdirTable(RelationGetRelid(parentRelation), false);
  
  		aocsscan->blockDirectory =
  			(AppendOnlyBlockDirectory *)palloc0(sizeof(AppendOnlyBlockDirectory));
  		blockDirectory = aocsscan->blockDirectory;
  	}
  		
  
  	while (true)
  	{
  		CHECK_FOR_INTERRUPTS();
  		
  		aocs_getnext(aocsscan, ForwardScanDirection, slot);
  		if (TupIsNull(slot))
  			break;
  
  		reltuples++;
  		
  		MemoryContextReset(econtext->ecxt_per_tuple_memory);
  		
  		if (predicate != NIL)
  		{
  			if (!ExecQual(predicate, econtext, false))
  				continue;
  		}
  
  		/*
  		 * For the current heap tuple, extract all the attributes we use in
  		 * this index, and note which are null.  This also performs evaluation
  		 * of any expressions needed.
  		 */
  		FormIndexDatum(indexInfo,
  					   slot,
  					   estate,
  					   values,
  					   isnull);
  
  		Assert(ItemPointerIsValid(slot_get_ctid(slot)));
  
  		callback(indexRelation, slot_get_ctid(slot),
  				 values, isnull, true, callback_state);
  		
  	}
  
  	pfree(proj);
  	
  	aocs_endscan(aocsscan);
  
  	if (blockDirectory != NULL)
  		pfree(blockDirectory);
  
  	return reltuples;
  }
  
  /*
   * validate_index - support code for concurrent index builds
   *
   * We do a concurrent index build by first inserting the catalog entry for the
   * index via index_create(), marking it not indisready and not indisvalid.
   * Then we commit our transaction and start a new one, then we wait for all
   * transactions that could have been modifying the table to terminate.	Now
   * we know that any subsequently-started transactions will see the index and
   * honor its constraints on HOT updates; so while existing HOT-chains might
   * be broken with respect to the index, no currently live tuple will have an
   * incompatible HOT update done to it.	We now build the index normally via
   * index_build(), while holding a weak lock that allows concurrent
   * insert/update/delete.  Also, we index only tuples that are valid
   * as of the start of the scan (see IndexBuildHeapScan), whereas a normal
   * build takes care to include recently-dead tuples.  This is OK because
   * we won't mark the index valid until all transactions that might be able
   * to see those tuples are gone.  The reason for doing that is to avoid
   * bogus unique-index failures due to concurrent UPDATEs (we might see
   * different versions of the same row as being valid when we pass over them,
   * if we used HeapTupleSatisfiesVacuum).  This leaves us with an index that
   * does not contain any tuples added to the table while we built the index.
   *
   * Next, we mark the index "indisready" (but still not "indisvalid") and
   * commit the second transaction and start a third.  Again we wait for all
   * transactions that could have been modifying the table to terminate.	Now
   * we know that any subsequently-started transactions will see the index and
   * insert their new tuples into it.  We then take a new reference snapshot
   * which is passed to validate_index().  Any tuples that are valid according
   * to this snap, but are not in the index, must be added to the index.
   * (Any tuples committed live after the snap will be inserted into the
   * index by their originating transaction.	Any tuples committed dead before
   * the snap need not be indexed, because we will wait out all transactions
   * that might care about them before we mark the index valid.)
   *
   * validate_index() works by first gathering all the TIDs currently in the
   * index, using a bulkdelete callback that just stores the TIDs and doesn't
   * ever say "delete it".  (This should be faster than a plain indexscan;
   * also, not all index AMs support full-index indexscan.)  Then we sort the
   * TIDs, and finally scan the table doing a "merge join" against the TID list
   * to see which tuples are missing from the index.	Thus we will ensure that
   * all tuples valid according to the reference snapshot are in the index.
   *
   * Building a unique index this way is tricky: we might try to insert a
   * tuple that is already dead or is in process of being deleted, and we
   * mustn't have a uniqueness failure against an updated version of the same
   * row.  We could try to check the tuple to see if it's already dead and tell
   * index_insert() not to do the uniqueness check, but that still leaves us
   * with a race condition against an in-progress update.  To handle that,
   * we expect the index AM to recheck liveness of the to-be-inserted tuple
   * before it declares a uniqueness error.
   *
   * After completing validate_index(), we wait until all transactions that
   * were alive at the time of the reference snapshot are gone; this is
   * necessary to be sure there are none left with a serializable snapshot
   * older than the reference (and hence possibly able to see tuples we did
   * not index).	Then we mark the index "indisvalid" and commit.  Subsequent
   * transactions will be able to use it for queries.
   *
   * Doing two full table scans is a brute-force strategy.  We could try to be
   * cleverer, eg storing new tuples in a special area of the table (perhaps
   * making the table append-only by setting use_fsm).  However that would
   * add yet more locking issues.
   */
  void
  validate_index(Oid heapId, Oid indexId, Snapshot snapshot)
  {
  	Relation	heapRelation,
  				indexRelation;
  	IndexInfo  *indexInfo;
  	IndexVacuumInfo ivinfo;
  	v_i_state	state;
  	Oid			save_userid;
  	int			save_sec_context;
  	int			save_nestlevel;
  
  	/* Open and lock the parent heap relation */
  	heapRelation = heap_open(heapId, ShareUpdateExclusiveLock);
  	/* And the target index relation */
  	indexRelation = index_open(indexId, RowExclusiveLock);
  
  	/*
  	 * Fetch info needed for index_insert.	(You might think this should be
  	 * passed in from DefineIndex, but its copy is long gone due to having
  	 * been built in a previous transaction.)
  	 */
  	indexInfo = BuildIndexInfo(indexRelation);
  
  	/* mark build is concurrent just for consistency */
  	indexInfo->ii_Concurrent = true;
  
  	/*
  	 * Switch to the table owner's userid, so that any index functions are run
  	 * as that user.  Also lock down security-restricted operations and
  	 * arrange to make GUC variable changes local to this command.
  	 */
  	GetUserIdAndSecContext(&save_userid, &save_sec_context);
  	SetUserIdAndSecContext(heapRelation->rd_rel->relowner,
  						   save_sec_context | SECURITY_RESTRICTED_OPERATION);
  	save_nestlevel = NewGUCNestLevel();
  
  	/*
  	 * Scan the index and gather up all the TIDs into a tuplesort object.
  	 */
  	ivinfo.index = indexRelation;
  	ivinfo.vacuum_full = false;
  	ivinfo.message_level = DEBUG2;
  	ivinfo.num_heap_tuples = -1;
  	ivinfo.strategy = NULL;
  	state.tuplesort = NULL;
  
  	if(gp_enable_mk_sort)
  		state.tuplesort = tuplesort_begin_datum_mk(NULL,
  												   TIDOID,
  												   TIDLessOperator, false,
  												   maintenance_work_mem,
  												   false);
  	else
  		state.tuplesort = tuplesort_begin_datum(TIDOID,
  												TIDLessOperator, false,
  												maintenance_work_mem,
  												false);
  	state.htups = state.itups = state.tups_inserted = 0;
  
  	(void) index_bulk_delete(&ivinfo, NULL,
  							 validate_index_callback, (void *) &state);
  
  	/* Execute the sort */
  	if(gp_enable_mk_sort)
  	{
  		tuplesort_performsort_mk((Tuplesortstate_mk *)state.tuplesort);
  	}
  	else
  	{
  		tuplesort_performsort((Tuplesortstate *) state.tuplesort);
  	}
  
  	/*
  	 * Now scan the heap and "merge" it with the index
  	 */
  	validate_index_heapscan(heapRelation,
  							indexRelation,
  							indexInfo,
  							snapshot,
  							&state);
  
  	/* Done with tuplesort object */
  	if(gp_enable_mk_sort)
  	{
  		tuplesort_end_mk((Tuplesortstate_mk *)state.tuplesort);
  	}
  	else
  	{
  		tuplesort_end((Tuplesortstate *) state.tuplesort);
  	}
  
  	elog(DEBUG2,
  		 "validate_index found %.0f heap tuples, %.0f index tuples; inserted %.0f missing tuples",
  		 state.htups, state.itups, state.tups_inserted);
  
  	/* Roll back any GUC changes executed by index functions */
  	AtEOXact_GUC(false, save_nestlevel);
  
  	/* Restore userid and security context */
  	SetUserIdAndSecContext(save_userid, save_sec_context);
  
  	/* Close rels, but keep locks */
  	index_close(indexRelation, NoLock);
  	heap_close(heapRelation, NoLock);
  }
  
  /*
   * validate_index_callback - bulkdelete callback to collect the index TIDs
   */
  static bool
  validate_index_callback(ItemPointer itemptr, void *opaque)
  {
  	v_i_state  *state = (v_i_state *) opaque;
  
  	if(gp_enable_mk_sort)
  		tuplesort_putdatum_mk((Tuplesortstate_mk *) state->tuplesort, PointerGetDatum(itemptr), false);
  	else
  		tuplesort_putdatum((Tuplesortstate *) state->tuplesort, PointerGetDatum(itemptr), false);
  
  	state->itups += 1;
  	return false;				/* never actually delete anything */
  }
  
  /*
   * validate_index_heapscan - second table scan for concurrent index build
   *
   * This has much code in common with IndexBuildHeapScan, but it's enough
   * different that it seems cleaner to have two routines not one.
   */
  static void
  validate_index_heapscan(Relation heapRelation,
  						Relation indexRelation,
  						IndexInfo *indexInfo,
  						Snapshot snapshot,
  						v_i_state *state)
  {
  	MIRROREDLOCK_BUFMGR_DECLARE;
  
  	HeapScanDesc scan;
  	HeapTuple	heapTuple;
  	Datum		values[INDEX_MAX_KEYS];
  	bool		isnull[INDEX_MAX_KEYS];
  	List	   *predicate;
  	TupleTableSlot *slot;
  	EState	   *estate;
  	ExprContext *econtext;
  	BlockNumber root_blkno = InvalidBlockNumber;
  	OffsetNumber root_offsets[MaxHeapTuplesPerPage];
  	bool		in_index[MaxHeapTuplesPerPage];
  
  	/* state variables for the merge */
  	ItemPointer indexcursor = NULL;
  	bool		tuplesort_empty = false;
  
  	/*
  	 * sanity checks
  	 */
  	Assert(OidIsValid(indexRelation->rd_rel->relam));
  
  	/*
  	 * Need an EState for evaluation of index expressions and partial-index
  	 * predicates.	Also a slot to hold the current tuple.
  	 */
  	estate = CreateExecutorState();
  	econtext = GetPerTupleExprContext(estate);
  	slot = MakeSingleTupleTableSlot(RelationGetDescr(heapRelation));
  
  	/* Arrange for econtext's scan tuple to be the tuple under test */
  	econtext->ecxt_scantuple = slot;
  
  	/* Set up execution state for predicate, if any. */
  	predicate = (List *)
  		ExecPrepareExpr((Expr *) indexInfo->ii_Predicate,
  						estate);
  
  	/*
  	 * Prepare for scan of the base relation.  We need just those tuples
  	 * satisfying the passed-in reference snapshot.  We must disable syncscan
  	 * here, because it's critical that we read from block zero forward to
  	 * match the sorted TIDs.
  	 */
  	scan = heap_beginscan_strat(heapRelation,	/* relation */
  								snapshot,		/* snapshot */
  								0,				/* number of keys */
  								NULL,			/* scan key */
  								true,			/* buffer access strategy OK */
  								false);			/* syncscan not OK */
  
  	/*
  	 * Scan all tuples matching the snapshot.
  	 */
  	while ((heapTuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
  	{
  		ItemPointer heapcursor = &heapTuple->t_self;
  		ItemPointerData rootTuple;
  		OffsetNumber root_offnum;
  
  		CHECK_FOR_INTERRUPTS();
  
  		state->htups += 1;
  
  		/*
  		 * As commented in IndexBuildHeapScan, we should index heap-only
  		 * tuples under the TIDs of their root tuples; so when we advance onto
  		 * a new heap page, build a map of root item offsets on the page.
  		 *
  		 * This complicates merging against the tuplesort output: we will
  		 * visit the live tuples in order by their offsets, but the root
  		 * offsets that we need to compare against the index contents might be
  		 * ordered differently.  So we might have to "look back" within the
  		 * tuplesort output, but only within the current page.	We handle that
  		 * by keeping a bool array in_index[] showing all the
  		 * already-passed-over tuplesort output TIDs of the current page. We
  		 * clear that array here, when advancing onto a new heap page.
  		 */
  		if (scan->rs_cblock != root_blkno)
  		{
  			Page		page = BufferGetPage(scan->rs_cbuf);
  
  			// -------- MirroredLock ----------
  			MIRROREDLOCK_BUFMGR_LOCK;
  
  			LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
  			heap_get_root_tuples(page, root_offsets);
  			LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
  
  			MIRROREDLOCK_BUFMGR_UNLOCK;
  			// -------- MirroredLock ----------
  
  			memset(in_index, 0, sizeof(in_index));
  
  			root_blkno = scan->rs_cblock;
  		}
  
  		/* Convert actual tuple TID to root TID */
  		rootTuple = *heapcursor;
  		root_offnum = ItemPointerGetOffsetNumber(heapcursor);
  
  		if (HeapTupleIsHeapOnly(heapTuple))
  		{
  			root_offnum = root_offsets[root_offnum - 1];
  			Assert(OffsetNumberIsValid(root_offnum));
  			ItemPointerSetOffsetNumber(&rootTuple, root_offnum);
  		}
  
  		/*
  		 * "merge" by skipping through the index tuples until we find or pass
  		 * the current root tuple.
  		 */
  		while (!tuplesort_empty &&
  			   (!indexcursor ||
  				ItemPointerCompare(indexcursor, &rootTuple) < 0))
  		{
  			Datum		ts_val;
  			bool		ts_isnull;
  
  			if (indexcursor)
  			{
  				/*
  				 * Remember index items seen earlier on the current heap page
  				 */
  				if (ItemPointerGetBlockNumber(indexcursor) == root_blkno)
  					in_index[ItemPointerGetOffsetNumber(indexcursor) - 1] = true;
  				pfree(indexcursor);
  			}
  
  			if (gp_enable_mk_sort)
  				tuplesort_empty = !tuplesort_getdatum_mk((Tuplesortstate_mk *) state->tuplesort,
  						true, &ts_val, &ts_isnull);
  			else
  				tuplesort_empty = !tuplesort_getdatum((Tuplesortstate *) state->tuplesort,
  						true, &ts_val, &ts_isnull);
  			Assert(tuplesort_empty || !ts_isnull);
  			indexcursor = (ItemPointer) DatumGetPointer(ts_val);
  		}
  
  		/*
  		 * If the tuplesort has overshot *and* we didn't see a match earlier,
  		 * then this tuple is missing from the index, so insert it.
  		 */
  		if ((tuplesort_empty ||
  			 ItemPointerCompare(indexcursor, &rootTuple) > 0) &&
  			!in_index[root_offnum - 1])
  		{
  			MemoryContextReset(econtext->ecxt_per_tuple_memory);
  
  			/* Set up for predicate or expression evaluation */
  			ExecStoreGenericTuple(heapTuple, slot, false);
  
  			/*
  			 * In a partial index, discard tuples that don't satisfy the
  			 * predicate.
  			 */
  			if (predicate != NIL)
  			{
  				if (!ExecQual(predicate, econtext, false))
  					continue;
  			}
  
  			/*
  			 * For the current heap tuple, extract all the attributes we use
  			 * in this index, and note which are null.	This also performs
  			 * evaluation of any expressions needed.
  			 */
  			FormIndexDatum(indexInfo,
  						   slot,
  						   estate,
  						   values,
  						   isnull);
  
  			/*
  			 * You'd think we should go ahead and build the index tuple here,
  			 * but some index AMs want to do further processing on the data
  			 * first. So pass the values[] and isnull[] arrays, instead.
  			 */
  
  			/*
  			 * If the tuple is already committed dead, you might think we
  			 * could suppress uniqueness checking, but this is no longer true
  			 * in the presence of HOT, because the insert is actually a proxy
  			 * for a uniqueness check on the whole HOT-chain.  That is, the
  			 * tuple we have here could be dead because it was already
  			 * HOT-updated, and if so the updating transaction will not have
  			 * thought it should insert index entries.	The index AM will
  			 * check the whole HOT-chain and correctly detect a conflict if
  			 * there is one.
  			 */
  
  			index_insert(indexRelation,
  						 values,
  						 isnull,
  						 &rootTuple,
  						 heapRelation,
  						 indexInfo->ii_Unique);
  
  			state->tups_inserted += 1;
  		}
  	}
  
  	heap_endscan(scan);
  
  	ExecDropSingleTupleTableSlot(slot);
  
  	FreeExecutorState(estate);
  
  	/* These may have been pointing to the now-gone estate */
  	indexInfo->ii_ExpressionsState = NIL;
  	indexInfo->ii_PredicateState = NIL;
  }
  
  
  /*
   * index_set_state_flags - adjust pg_index state flags
   *
   * This is used during CREATE INDEX CONCURRENTLY to adjust the pg_index
   * flags that denote the index's state.  We must use an in-place update of
   * the pg_index tuple, because we do not have exclusive lock on the parent
   * table and so other sessions might concurrently be doing SnapshotNow scans
   * of pg_index to identify the table's indexes.  A transactional update would
   * risk somebody not seeing the index at all.  Because the update is not
   * transactional and will not roll back on error, this must only be used as
   * the last step in a transaction that has not made any transactional catalog
   * updates!
   *
   * Note that heap_inplace_update does send a cache inval message for the
   * tuple, so other sessions will hear about the update as soon as we commit.
   */
  void
  index_set_state_flags(Oid indexId, IndexStateFlagsAction action)
  {
  	Relation	pg_index;
  	HeapTuple	indexTuple;
  	Form_pg_index indexForm;
  
  	/* Assert that current xact hasn't done any transactional updates */
  	Assert(GetTopTransactionIdIfAny() == InvalidTransactionId);
  
  	/* Open pg_index and fetch a writable copy of the index's tuple */
  	pg_index = heap_open(IndexRelationId, RowExclusiveLock);
  
  	indexTuple = SearchSysCacheCopy(INDEXRELID,
  									ObjectIdGetDatum(indexId),
  									0, 0, 0);
  	if (!HeapTupleIsValid(indexTuple))
  		elog(ERROR, "cache lookup failed for index %u", indexId);
  	indexForm = (Form_pg_index) GETSTRUCT(indexTuple);
  
  	/* Perform the requested state change on the copy */
  	switch (action)
  	{
  		case INDEX_CREATE_SET_READY:
  			/* Set indisready during a CREATE INDEX CONCURRENTLY sequence */
  			Assert(!indexForm->indisready);
  			Assert(!indexForm->indisvalid);
  			indexForm->indisready = true;
  			break;
  		case INDEX_CREATE_SET_VALID:
  			/* Set indisvalid during a CREATE INDEX CONCURRENTLY sequence */
  			Assert(indexForm->indisready);
  			Assert(!indexForm->indisvalid);
  			indexForm->indisvalid = true;
  			break;
  	}
  
  	/* ... and write it back in-place */
  	heap_inplace_update(pg_index, indexTuple);
  
  	heap_close(pg_index, RowExclusiveLock);
  }
  
  
  /*
   * IndexGetRelation: given an index's relation OID, get the OID of the
   * relation it is an index on.	Uses the system cache.
   */
  Oid
  IndexGetRelation(Oid indexId)
  {
  	HeapTuple	tuple;
  	Form_pg_index index;
  	Oid			result;
  
  	tuple = SearchSysCache(INDEXRELID,
  						   ObjectIdGetDatum(indexId),
  						   0, 0, 0);
  	if (!HeapTupleIsValid(tuple))
  		elog(ERROR, "cache lookup failed for index %u", indexId);
  	index = (Form_pg_index) GETSTRUCT(tuple);
  	Assert(index->indexrelid == indexId);
  
  	result = index->indrelid;
  	ReleaseSysCache(tuple);
  	return result;
  }
  
  /*
   * reindex_index - This routine is used to recreate a single index
   */
  void
  reindex_index(Oid indexId)
  {
  	Relation	iRel,
  				heapRelation,
  				pg_index;
  	Oid			heapId;
  	bool		inplace;
  	HeapTuple	indexTuple;
  	Form_pg_index indexForm;
  	Oid			namespaceId;
  
  	Assert(OidIsValid(indexId));
  
  	/*
  	 * Open and lock the parent heap relation.	ShareLock is sufficient since
  	 * we only need to be sure no schema or data changes are going on.
  	 */
  	heapId = IndexGetRelation(indexId);
  	heapRelation = heap_open(heapId, ShareLock);
  
  	namespaceId = RelationGetNamespace(heapRelation);
  
  	/*
  	 * Open the target index relation and get an exclusive lock on it, to
  	 * ensure that no one else is touching this particular index.
  	 */
  	iRel = index_open(indexId, AccessExclusiveLock);
  
  	/*
  	 * Don't allow reindex on temp tables of other backends ... their local
  	 * buffer manager is not going to cope.
  	 */
  	if (isOtherTempNamespace(RelationGetNamespace(iRel)))
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("cannot reindex temporary tables of other sessions")));
  
  	/*
  	 * Also check for active uses of the index in the current transaction;
  	 * we don't want to reindex underneath an open indexscan.
  	 */
  	CheckTableNotInUse(iRel, "REINDEX INDEX");
  
  	/*
  	 * If it's a shared index, we must do inplace processing (because we have
  	 * no way to update relfilenode in other databases).  Otherwise we can do
  	 * it the normal transaction-safe way.
  	 *
  	 * Since inplace processing isn't crash-safe, we only allow it in a
  	 * standalone backend.	(In the REINDEX TABLE and REINDEX DATABASE cases,
  	 * the caller should have detected this.)
  	 *
  	 * MPP: If we are in a standalone backend always perform reindex operations
  	 * in place.  In postgres this only applies to shared relations, for 
  	 * Greenplum we apply it to all tables as a means of enabling upgrade to
  	 * filerep: it is required to reindex gp_relation_node in place before it
  	 * is possible to populate the gp_persistent tables.
  	 */
  	inplace = iRel->rd_rel->relisshared || !IsUnderPostmaster;
  
  	if (inplace && IsUnderPostmaster)
  		ereport(ERROR,
  				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  				 errmsg("shared index \"%s\" can only be reindexed in stand-alone mode",
  						RelationGetRelationName(iRel))));
  
  	PG_TRY();
  	{
  		IndexInfo  *indexInfo;
  
  		/* Suppress use of the target index while rebuilding it */
  		SetReindexProcessing(heapId, indexId);
  
  		/* Fetch info needed for index_build */
  		indexInfo = BuildIndexInfo(iRel);
  
  		if (inplace)
  		{
  			/* Truncate the actual file (and discard buffers) */
  
  			RelationTruncate(
  						iRel, 
  						0,
  						/* markPersistentAsPhysicallyTruncated */ true);
  		}
  		else
  		{
  			/*
  			 * We'll build a new physical relation for the index.
  			 */
  			setNewRelfilenode(iRel, InvalidTransactionId);
  		}
  
  		/* Initialize the index and rebuild */
  		/* Note: we do not need to re-establish pkey setting */
  		index_build(heapRelation, iRel, indexInfo, false, true);
  	}
  	PG_CATCH();
  	{
  		/* Make sure flag gets cleared on error exit */
  		ResetReindexProcessing();
  		PG_RE_THROW();
  	}
  	PG_END_TRY();
  	ResetReindexProcessing();
  
  	/*
  	 * If the index is marked invalid or not ready (ie, it's from a failed
  	 * CREATE INDEX CONCURRENTLY), we can now mark it valid.  This allows
  	 * REINDEX to be used to clean up in such cases.
  	 *
  	 * Note that it is important to not update the pg_index entry if we don't
  	 * have to, because updating it will move the index's usability horizon
  	 * (recorded as the tuple's xmin value) if indcheckxmin is true.  We don't
  	 * really want REINDEX to move the usability horizon forward ever, but we
  	 * have no choice if we are to fix indisvalid or indisready.  Of course,
  	 * clearing indcheckxmin eliminates the issue, so we're happy to do that
  	 * if we can.  Another reason for caution here is that while reindexing
  	 * pg_index itself, we must not try to update it.  We assume that
  	 * pg_index's indexes will always have these flags in their clean state.
  	 */
  	pg_index = heap_open(IndexRelationId, RowExclusiveLock);
  
  	indexTuple = SearchSysCacheCopy(INDEXRELID,
  									ObjectIdGetDatum(indexId),
  									0, 0, 0);
  	if (!HeapTupleIsValid(indexTuple))
  		elog(ERROR, "cache lookup failed for index %u", indexId);
  	indexForm = (Form_pg_index) GETSTRUCT(indexTuple);
  
  	if (!indexForm->indisvalid || !indexForm->indisready)
  	{
  		indexForm->indisvalid = true;
  		indexForm->indisready = true;
  		simple_heap_update(pg_index, &indexTuple->t_self, indexTuple);
  		CatalogUpdateIndexes(pg_index, indexTuple);
  
  		/*
  		 * Invalidate the relcache for the table, so that after we commit
  		 * all sessions will refresh the table's index list.  This ensures
  		 * that if anyone misses seeing the pg_index row during this
  		 * update, they'll refresh their list before attempting any update
  		 * on the table.
  		 */
  		CacheInvalidateRelcache(heapRelation);
  	}
  	heap_close(pg_index, RowExclusiveLock);
  
  	{
  		bool	 doIt	= true;
  		char	*subtyp = "REINDEX";
  
  		/* MPP-7576: don't track internal namespace tables */
  		switch (namespaceId) 
  		{
  			case PG_CATALOG_NAMESPACE:
  				/* MPP-7773: don't track objects in system namespace
  				 * if modifying system tables (eg during upgrade)  
  				 */
  				if (allowSystemTableModsDDL)
  					doIt = false;
  				break;
  
  			case PG_TOAST_NAMESPACE:
  			case PG_BITMAPINDEX_NAMESPACE:
  			case PG_AOSEGMENT_NAMESPACE:
  				doIt = false;
  				break;
  			default:
  				break;
  		}
  
  		if (doIt)
  			doIt = (!(isAnyTempNamespace(namespaceId)));
  
  		/* MPP-6929: metadata tracking */
  		/* MPP-7587: treat as a VACUUM operation, since the index is
  		 * rebuilt */
  		if (doIt)
  			MetaTrackUpdObject(RelationRelationId,
  							   indexId,
  							   GetUserId(), /* not ownerid */
  							   "VACUUM", subtyp
  					);
  	}
  
  	/* Close rels, but keep locks */
  	index_close(iRel, NoLock);
  	heap_close(heapRelation, NoLock);
  }
  
  /*
   * reindex_relation - This routine is used to recreate all indexes
   * of a relation (and optionally its toast relation too, if any).
   *
   * Returns true if any indexes were rebuilt.  Note that a
   * CommandCounterIncrement will occur after each index rebuild.
   *
   * In GPDB, if 'toast_too' is true, we also reindex auxiliary AO heap
   * tables: AO segments, AO block directory, and AO visibilitymap.
   */
  bool
  reindex_relation(Oid relid, bool toast_too)
  {
  	Relation	rel;
  	Oid			toast_relid;
  	Oid			aoseg_relid = InvalidOid;
  	Oid         aoblkdir_relid = InvalidOid;
  	Oid         aovisimap_relid = InvalidOid;
  	bool		is_pg_class;
  	bool		result;
  	List	   *indexIds,
  			   *doneIndexes;
  	ListCell   *indexId;
  	bool relIsAO = false;
  
  	/*
  	 * Open and lock the relation.	ShareLock is sufficient since we only need
  	 * to prevent schema and data changes in it.
  	 */
  	rel = heap_open(relid, ShareLock);
  
  	relIsAO = (RelationIsAoRows(rel) || RelationIsAoCols(rel));
  
  	toast_relid = rel->rd_rel->reltoastrelid;
  
  	/*
  	 * Get the list of index OIDs for this relation.  (We trust to the
  	 * relcache to get this with a sequential scan if ignoring system
  	 * indexes.)
  	 */
  	indexIds = RelationGetIndexList(rel);
  
  	/*
  	 * reindex_index will attempt to update the pg_class rows for the relation
  	 * and index.  If we are processing pg_class itself, we want to make sure
  	 * that the updates do not try to insert index entries into indexes we
  	 * have not processed yet.	(When we are trying to recover from corrupted
  	 * indexes, that could easily cause a crash.) We can accomplish this
  	 * because CatalogUpdateIndexes will use the relcache's index list to know
  	 * which indexes to update. We just force the index list to be only the
  	 * stuff we've processed.
  	 *
  	 * It is okay to not insert entries into the indexes we have not processed
  	 * yet because all of this is transaction-safe.  If we fail partway
  	 * through, the updated rows are dead and it doesn't matter whether they
  	 * have index entries.	Also, a new pg_class index will be created with an
  	 * entry for its own pg_class row because we do setNewRelfilenode() before
  	 * we do index_build().
  	 *
  	 * Note that we also clear pg_class's rd_oidindex until the loop is done,
  	 * so that that index can't be accessed either.  This means we cannot
  	 * safely generate new relation OIDs while in the loop; shouldn't be a
  	 * problem.
  	 */
  	is_pg_class = (RelationGetRelid(rel) == RelationRelationId);
  
  	/* Ensure rd_indexattr is valid; see comments for RelationSetIndexList */
  	if (is_pg_class)
  		(void) RelationGetIndexAttrBitmap(rel);
  
  	/* Reindex all the indexes. */
  	doneIndexes = NIL;
  	foreach(indexId, indexIds)
  	{
  		Oid			indexOid = lfirst_oid(indexId);
  
  		if (is_pg_class)
  			RelationSetIndexList(rel, doneIndexes, InvalidOid);
  
  		reindex_index(indexOid);
  
  		CommandCounterIncrement();
  
  		if (is_pg_class)
  			doneIndexes = lappend_oid(doneIndexes, indexOid);
  	}
  
  	if (is_pg_class)
  		RelationSetIndexList(rel, indexIds, ClassOidIndexId);
  
  	/*
  	 * Close rel, but continue to hold the lock.
  	 */
  	heap_close(rel, NoLock);
  
  	result = (indexIds != NIL);
  
  	SIMPLE_FAULT_INJECTOR(ReindexRelation);
  
  	/*
  	 * If the relation has a secondary toast rel, reindex that too while we
  	 * still hold the lock on the master table.
  	 */
  	if (toast_too && OidIsValid(toast_relid))
  		result |= reindex_relation(toast_relid, false);
  
  	/* Obtain the aoseg_relid and aoblkdir_relid if the relation is an AO table. */
  	if (toast_too && relIsAO)
  		GetAppendOnlyEntryAuxOids(relid, SnapshotNow,
  								  &aoseg_relid,
  								  &aoblkdir_relid, NULL,
  								  &aovisimap_relid, NULL);
  
  	/*
  	 * If an AO rel has a secondary segment list rel, reindex that too while we
  	 * still hold the lock on the master table.
  	 */
  	if (toast_too && OidIsValid(aoseg_relid))
  		result |= reindex_relation(aoseg_relid, false);
  
  	/*
  	 * If an AO rel has a secondary block directory rel, reindex that too while we
  	 * still hold the lock on the master table.
  	 */
  	if (toast_too && OidIsValid(aoblkdir_relid))
  		result |= reindex_relation(aoblkdir_relid, false);
  	
  	/*
  	 * If an AO rel has a secondary visibility map rel, reindex that too while we
  	 * still hold the lock on the master table.
  	 */
  	if (toast_too && OidIsValid(aovisimap_relid))
  		result |= reindex_relation(aovisimap_relid, false);
  
  	return result;
  }
  