relcache.c

/*-------------------------------------------------------------------------
 *
 * relcache.c
 *	  POSTGRES relation descriptor cache code
 *
 * Portions Copyright (c) 2005-2009, 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/utils/cache/relcache.c,v 1.266.2.10 2010/09/02 03:17:06 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
/*
 * INTERFACE ROUTINES
 *		RelationCacheInitialize			- initialize relcache (to empty)
 *		RelationCacheInitializePhase2	- initialize shared-catalog entries
 *		RelationCacheInitializePhase3	- finish initializing relcache
 *		RelationIdGetRelation			- get a reldesc by relation id
 *		RelationClose					- close an open relation
 *
 * NOTES
 *		The following code contains many undocumented hacks.  Please be
 *		careful....
 */
#include "postgres.h"

#include <sys/file.h>
#include <fcntl.h>
#include <unistd.h>

#include "access/genam.h"
#include "access/heapam.h"
#include "access/reloptions.h"
#include "access/sysattr.h"
#include "access/xact.h"
#include "catalog/catalog.h"
#include "catalog/index.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/pg_amop.h"
#include "catalog/pg_amproc.h"
#include "catalog/pg_attrdef.h"
#include "catalog/pg_authid.h"
#include "catalog/pg_auth_members.h"
#include "catalog/pg_constraint.h"
#include "catalog/pg_database.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_opclass.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_rewrite.h"
#include "catalog/pg_tablespace.h"
#include "catalog/pg_trigger.h"
#include "catalog/pg_type.h"
#include "commands/trigger.h"
#include "miscadmin.h"
#include "optimizer/clauses.h"
#include "optimizer/planmain.h"
#include "optimizer/prep.h"
#include "optimizer/var.h"
#include "rewrite/rewriteDefine.h"
#include "storage/fd.h"
#include "storage/smgr.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/inval.h"
#include "utils/memutils.h"
#include "utils/relcache.h"
#include "utils/relationnode.h"
#include "utils/resowner.h"
#include "utils/syscache.h"

#include "catalog/gp_policy.h"         /* GpPolicy */
#include "cdb/cdbtm.h"
#include "cdb/cdbvars.h"        /* Gp_role */
#include "cdb/cdbmirroredflatfile.h"
#include "cdb/cdbpersistentfilesysobj.h"
#include "cdb/cdbsreh.h"


/*
 * name of relcache init file, used to speed up backend startup
 */
#define RELCACHE_INIT_FILENAME	"pg_internal.init"

#define RELCACHE_INIT_FILEMAGIC		0x773264	/* version ID value */

/*
 *		hardcoded tuple descriptors.  see include/catalog/pg_attribute.h
 */
static const FormData_pg_attribute Desc_pg_class[Natts_pg_class] = {Schema_pg_class};
static const FormData_pg_attribute Desc_pg_attribute[Natts_pg_attribute] = {Schema_pg_attribute};
static const FormData_pg_attribute Desc_pg_proc[Natts_pg_proc] = {Schema_pg_proc};
static const FormData_pg_attribute Desc_pg_type[Natts_pg_type] = {Schema_pg_type};
static const FormData_pg_attribute Desc_pg_index[Natts_pg_index] = {Schema_pg_index};

static const FormData_pg_attribute Desc_pg_database[Natts_pg_database] = {Schema_pg_database};
static const FormData_pg_attribute Desc_pg_authid[Natts_pg_authid] = {Schema_pg_authid};
static const FormData_pg_attribute Desc_pg_auth_members[Natts_pg_auth_members] = {Schema_pg_auth_members};

/*
 *		Hash tables that index the relation cache
 *
 *		We used to index the cache by both name and OID, but now there
 *		is only an index by OID.
 */
typedef struct relidcacheent
{
	Oid			reloid;
	Relation	reldesc;
} RelIdCacheEnt;

static HTAB *RelationIdCache;

/*
 * This flag is false until we have prepared the critical relcache entries
 * that are needed to do indexscans on the tables read by relcache building.
 */
bool		criticalRelcachesBuilt = false;

/*
 * This flag is false until we have prepared the critical relcache entries
 * for shared catalogs (which are the tables needed for login).
 */
bool		criticalSharedRelcachesBuilt = false;

/*
 * This counter counts relcache inval events received since backend startup
 * (but only for rels that are actually in cache).	Presently, we use it only
 * to detect whether data about to be written by write_relcache_init_file()
 * might already be obsolete.
 */
static long relcacheInvalsReceived = 0L;

/*
 * This list remembers the OIDs of the non-shared relations cached in the
 * database's local relcache init file.  Note that there is no corresponding
 * list for the shared relcache init file, for reasons explained in the
 * comments for RelationCacheInitFileRemove.
 */
static List *initFileRelationIds = NIL;

/*
 * This flag lets us optimize away work in AtEO(Sub)Xact_RelationCache().
 */
static bool need_eoxact_work = false;


/*
 *		macros to manipulate the lookup hashtables
 */
#define RelationCacheInsert(RELATION)	\
do { \
	RelIdCacheEnt *idhentry; bool found; \
	idhentry = (RelIdCacheEnt*)hash_search(RelationIdCache, \
										   (void *) &(RELATION->rd_id), \
										   HASH_ENTER, &found); \
	/* used to give notice if found -- now just keep quiet */ \
	idhentry->reldesc = RELATION; \
} while(0)

#define RelationIdCacheLookup(ID, RELATION) \
do { \
	RelIdCacheEnt *hentry; \
	hentry = (RelIdCacheEnt*)hash_search(RelationIdCache, \
										 (void *) &(ID), \
										 HASH_FIND, NULL); \
	if (hentry) \
		RELATION = hentry->reldesc; \
	else \
		RELATION = NULL; \
} while(0)

#define RelationCacheDelete(RELATION) \
do { \
	RelIdCacheEnt *idhentry; \
	idhentry = (RelIdCacheEnt*)hash_search(RelationIdCache, \
										   (void *) &(RELATION->rd_id), \
										   HASH_REMOVE, NULL); \
	if (idhentry == NULL) \
		elog(WARNING, "trying to delete a rd_id reldesc that does not exist"); \
} while(0)


/*
 * Special cache for opclass-related information
 *
 * Note: only default operators and support procs get cached, ie, those with
 * lefttype = righttype = opcintype.
 */
typedef struct opclasscacheent
{
	Oid			opclassoid;		/* lookup key: OID of opclass */
	bool		valid;			/* set TRUE after successful fill-in */
	StrategyNumber numStrats;	/* max # of strategies (from pg_am) */
	StrategyNumber numSupport;	/* max # of support procs (from pg_am) */
	Oid			opcfamily;		/* OID of opclass's family */
	Oid			opcintype;		/* OID of opclass's declared input type */
	Oid		   *operatorOids;	/* strategy operators' OIDs */
	RegProcedure *supportProcs; /* support procs */
} OpClassCacheEnt;

static HTAB *OpClassCache = NULL;


/* non-export function prototypes */

static void RelationDestroyRelation(Relation relation);
static void RelationClearRelation(Relation relation, bool rebuild);

static void RelationReloadIndexInfo(Relation relation);
static void RelationFlushRelation(Relation relation);
static bool load_relcache_init_file(bool shared);
static void write_relcache_init_file(bool shared);
static void write_item(const void *data, Size len, FILE *fp);

static void formrdesc(const char *relationName, Oid relationReltype,
		  bool isshared, bool hasoids,
		  int natts, const FormData_pg_attribute *att);

static HeapTuple ScanPgRelation(Oid targetRelId, bool indexOK, Relation *pg_class_relation);
static Relation AllocateRelationDesc(Form_pg_class relp);
static void RelationParseRelOptions(Relation relation, HeapTuple tuple);
static void RelationBuildTupleDesc(Relation relation);
static Relation RelationBuildDesc(Oid targetRelId, bool insertIt);
static void RelationInitPhysicalAddr(Relation relation);
static void RelationInitAppendOnlyInfo(Relation relation);
static void load_critical_index(Oid indexoid, Oid heapoid);
static TupleDesc GetPgClassDescriptor(void);
static TupleDesc GetPgIndexDescriptor(void);
static void AttrDefaultFetch(Relation relation);
static void CheckConstraintFetch(Relation relation);
static List *insert_ordered_oid(List *list, Oid datum);
static OpClassCacheEnt *LookupOpclassInfo(Oid operatorClassOid,
				  StrategyNumber numStrats,
				  StrategyNumber numSupport);
static void RelationCacheInitFileRemoveInDir(const char *tblspcpath);
static void unlink_initfile(const char *initfilename);


/*
 *		ScanPgRelation
 *
 *		This is used by RelationBuildDesc to find a pg_class
 *		tuple matching targetRelId.  The caller must hold at least
 *		AccessShareLock on the target relid to prevent concurrent-update
 *		scenarios --- else our SnapshotNow scan might fail to find any
 *		version that it thinks is live.
 *
 *		NB: the returned tuple has been copied into palloc'd storage
 *		and must eventually be freed with heap_freetuple.
 */
static HeapTuple
ScanPgRelation(Oid targetRelId, bool indexOK, Relation *pg_class_relation)
{
	HeapTuple	pg_class_tuple;
	Relation	pg_class_desc;
	SysScanDesc pg_class_scan;
	ScanKeyData key[1];

	/*
	 * If something goes wrong during backend startup, we might find ourselves
	 * trying to read pg_class before we've selected a database.  That ain't
	 * gonna work, so bail out with a useful error message.  If this happens,
	 * it probably means a relcache entry that needs to be nailed isn't.
	 */
	if (!OidIsValid(MyDatabaseId))
		elog(FATAL, "cannot read pg_class without having selected a database");

	/*
	 * form a scan key
	 */
	ScanKeyInit(&key[0],
				ObjectIdAttributeNumber,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(targetRelId));

	/*
	 * Open pg_class and fetch a tuple.  Force heap scan if we haven't yet
	 * built the critical relcache entries (this includes initdb and startup
	 * without a pg_internal.init file).  The caller can also force a heap
	 * scan by setting indexOK == false.
	 */
	pg_class_desc = heap_open(RelationRelationId, AccessShareLock);
	pg_class_scan = systable_beginscan(pg_class_desc, ClassOidIndexId,
									   indexOK && criticalRelcachesBuilt,
									   SnapshotNow,
									   1, key);

	pg_class_tuple = systable_getnext(pg_class_scan);

	/*
	 * Must copy tuple before releasing buffer.
	 */
	if (HeapTupleIsValid(pg_class_tuple))
		pg_class_tuple = heap_copytuple(pg_class_tuple);

	/* all done */
	systable_endscan(pg_class_scan);
	if (pg_class_relation == NULL)
		heap_close(pg_class_desc, AccessShareLock);
	else
		*pg_class_relation = pg_class_desc;

	return pg_class_tuple;
}

void
GpRelationNodeBeginScan(
	Snapshot	snapshot,
	Relation 	gp_relation_node,
	Oid		relationId,
	Oid 		tablespaceOid,
	Oid 		relfilenode,
	GpRelationNodeScan 	*gpRelationNodeScan)
{
	Assert (relfilenode != 0);

	MemSet(gpRelationNodeScan, 0, sizeof(GpRelationNodeScan));

	/*
	 * form a scan key
	 */
	ScanKeyInit(&gpRelationNodeScan->scankey[0],
				Anum_gp_relation_node_tablespace_oid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(tablespaceOid));

	ScanKeyInit(&gpRelationNodeScan->scankey[1],
				Anum_gp_relation_node_relfilenode_oid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(relfilenode));

	/*
	 * Open gp_relation_node and fetch a tuple.  Force heap scan if we haven't yet
	 * built the critical relcache entries (this includes initdb and startup
	 * without a pg_internal.init file).  The caller can also force a heap
	 * scan by setting indexOK == false.
	 */
	gpRelationNodeScan->scan = \
		systable_beginscan(gp_relation_node, GpRelationNodeOidIndexId,
						   /* indexOK */ true,
						   snapshot,
						   /* nKeys */ 2,
						   gpRelationNodeScan->scankey);

	gpRelationNodeScan->gp_relation_node = gp_relation_node;
	gpRelationNodeScan->relationId = relationId;
	gpRelationNodeScan->tablespaceOid = tablespaceOid;
	gpRelationNodeScan->relfilenode = relfilenode;
}

HeapTuple
GpRelationNodeGetNext(
	GpRelationNodeScan 	*gpRelationNodeScan,
	int32				*segmentFileNum,
	ItemPointer			persistentTid,
	int64				*persistentSerialNum)
{
	HeapTuple tuple;
	
	bool			nulls[Natts_gp_relation_node];
	Datum			values[Natts_gp_relation_node];
	
	Oid actualRelationNode;
	
	int64 createMirrorDataLossTrackingSessionNum;

	tuple = systable_getnext((SysScanDesc)gpRelationNodeScan->scan);

	/*
	 * if no such tuple exists, return NULL
	 */
	if (!HeapTupleIsValid(tuple))
	{
		MemSet(persistentTid, 0, sizeof(ItemPointerData));
		*persistentSerialNum = 0;
		return tuple;
	}
	
	heap_deform_tuple(tuple, RelationGetDescr(gpRelationNodeScan->gp_relation_node), values, nulls);
		
	GpRelationNode_GetValues(
						values,
						&actualRelationNode,
						segmentFileNum,
						&createMirrorDataLossTrackingSessionNum,
						persistentTid,
						persistentSerialNum);
	if (actualRelationNode != gpRelationNodeScan->relfilenode)
		elog(FATAL, "Index on gp_relation_node broken."
			   "Mismatch in node tuple for gp_relation_node for relation %u, tablespace %u, relfilenode %u, relation node %u",
			 gpRelationNodeScan->relationId,
			 gpRelationNodeScan->tablespaceOid,
			 gpRelationNodeScan->relfilenode,
			 actualRelationNode);

	return tuple;
}


void
GpRelationNodeEndScan(
	GpRelationNodeScan 	*gpRelationNodeScan)
{
	/* all done */
	systable_endscan((SysScanDesc)gpRelationNodeScan->scan);
}

static HeapTuple
ScanGpRelationNodeTuple(
	Relation 	gp_relation_node,
	Oid 		tablespaceOid,
	Oid 		relfilenode,
	int32		segmentFileNum)
{
	HeapTuple	tuple;
	SysScanDesc scan;
	ScanKeyData key[3];

	Assert (tablespaceOid != MyDatabaseTableSpace);
	Assert (relfilenode != 0);

	/*
	 * form a scan key
	 */
	ScanKeyInit(&key[0],
				Anum_gp_relation_node_tablespace_oid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(tablespaceOid));
	ScanKeyInit(&key[1],
				Anum_gp_relation_node_relfilenode_oid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(relfilenode));
	ScanKeyInit(&key[2],
				Anum_gp_relation_node_segment_file_num,
				BTEqualStrategyNumber, F_INT4EQ,
				Int32GetDatum(segmentFileNum));

	/*
	 * Open gp_relation_node and fetch a tuple.  Force heap scan if we haven't yet
	 * built the critical relcache entries (this includes initdb and startup
	 * without a pg_internal.init file).  The caller can also force a heap
	 * scan by setting indexOK == false.
	 */
	scan = systable_beginscan(gp_relation_node, GpRelationNodeOidIndexId,
									   /* indexOK */ true,
									   SnapshotNow,
									   3, key);

	tuple = systable_getnext(scan);

	/*
	 * Must copy tuple before releasing buffer.
	 */
	if (HeapTupleIsValid(tuple))
		tuple = heap_copytuple(tuple);

	/* all done */
	systable_endscan(scan);

	return tuple;
}

HeapTuple
FetchGpRelationNodeTuple(
	Relation 		gp_relation_node,
	Oid 			tablespaceOid,
	Oid 			relfilenode,
	int32			segmentFileNum,
	ItemPointer		persistentTid,
	int64			*persistentSerialNum)
{
	HeapTuple tuple;
	
	bool			nulls[Natts_gp_relation_node];
	Datum			values[Natts_gp_relation_node];
	
	Oid actualRelationNode;
	int32 actualSegmentFileNum;

	int64 createMirrorDataLossTrackingSessionNum;

	/*
	 * gp_relation_node stores tablespaceOId in pg_class fashion, hence need
	 * to fetch the similar way.
	 */
	Assert (tablespaceOid != MyDatabaseTableSpace);
	Assert (relfilenode != 0);
	
	tuple = ScanGpRelationNodeTuple(
					gp_relation_node,
					tablespaceOid,
					relfilenode,
					segmentFileNum);
	
	/*
	 * if no such tuple exists, return NULL
	 */
	if (!HeapTupleIsValid(tuple))
	{
		MemSet(persistentTid, 0, sizeof(ItemPointerData));
		*persistentSerialNum = 0;
		return tuple;
	}
	
	heap_deform_tuple(tuple, RelationGetDescr(gp_relation_node), values, nulls);
		
	GpRelationNode_GetValues(
						values,
						&actualRelationNode,
						&actualSegmentFileNum,
						&createMirrorDataLossTrackingSessionNum,
						persistentTid,
						persistentSerialNum);
	
	if (actualRelationNode != relfilenode)
	{
		elog(ERROR, "Index on gp_relation_node broken."
			   "Mismatch in node tuple for gp_relation_node intended relfilenode %u, fetched relfilenode %u",
			 relfilenode,
			 actualRelationNode);
	}

	return tuple;
}

/*
 * Deletes the gp relation node entry for the
 * given segment file.
 */ 
void
DeleteGpRelationNodeTuple(
	Relation 	relation,
	int32		segmentFileNum)
{
	Relation	gp_relation_node;
	HeapTuple	tuple;
	ItemPointerData     persistentTid;
	int64               persistentSerialNum;

	gp_relation_node = heap_open(GpRelationNodeRelationId, RowExclusiveLock);

	tuple = FetchGpRelationNodeTuple(gp_relation_node,
									 relation->rd_rel->reltablespace,
									 relation->rd_rel->relfilenode,
									 segmentFileNum,
									 &persistentTid,
									 &persistentSerialNum);

	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "could not find node tuple for relation %u, tablespace %u, relation file node %u, segment file #%d",
			 RelationGetRelid(relation),
			 relation->rd_rel->reltablespace,
			 relation->rd_rel->relfilenode,
			 segmentFileNum);

	/* delete the relation tuple from gp_relation_node, and finish up */
	simple_heap_delete(gp_relation_node, &tuple->t_self);
	heap_freetuple(tuple);

	heap_close(gp_relation_node, RowExclusiveLock);
}

bool
ReadGpRelationNode(
	Oid 			tablespaceOid,
	Oid 			relfilenode,
	int32			segmentFileNum,
	ItemPointer		persistentTid,
	int64			*persistentSerialNum)
{
	Relation gp_relation_node;
	HeapTuple tuple;
	bool found;

	MemSet(persistentTid, 0, sizeof(ItemPointerData));
	*persistentSerialNum = 0;

	gp_relation_node = heap_open(GpRelationNodeRelationId, AccessShareLock);

	tuple = FetchGpRelationNodeTuple(
						gp_relation_node,
						tablespaceOid,
						relfilenode,
						segmentFileNum,
						persistentTid,
						persistentSerialNum);

	/*
	 * if no such tuple exists, return NULL
	 */
	if (!HeapTupleIsValid(tuple))
	{
		found = false;
	}
	else
	{
		if (Debug_persistent_print)
		{
			TupleVisibilitySummary tupleVisibilitySummary;
			char *tupleVisibilitySummaryString;
			
			GetTupleVisibilitySummary(
									tuple,
									&tupleVisibilitySummary);
			tupleVisibilitySummaryString = GetTupleVisibilitySummaryString(&tupleVisibilitySummary);
			
			elog(Persistent_DebugPrintLevel(), 
				 "ReadGpRelationNode: For tablespace %u relfilenode %u, segment file #%d found persistent serial number " INT64_FORMAT ", TID %s (gp_relation_node tuple visibility: %s)",
				 tablespaceOid,
				 relfilenode,
				 segmentFileNum,
				 *persistentSerialNum,
				 ItemPointerToString(persistentTid),
				 tupleVisibilitySummaryString);
			pfree(tupleVisibilitySummaryString);
		}

		found = true;
		heap_freetuple(tuple);
	}

	heap_close(gp_relation_node, AccessShareLock);

	return found;
}

void
RelationFetchSegFile0GpRelationNode(
	Relation relation)
{
	if (!relation->rd_segfile0_relationnodeinfo.isPresent)
	{
		if (Persistent_BeforePersistenceWork() || InRecovery)
		{
			MemSet(&relation->rd_segfile0_relationnodeinfo.persistentTid, 0, sizeof(ItemPointerData));
			relation->rd_segfile0_relationnodeinfo.persistentSerialNum = 0;
		
			relation->rd_segfile0_relationnodeinfo.isPresent = true;
			relation->rd_segfile0_relationnodeinfo.tidAllowedToBeZero = true;
			
			return; // The initdb process will load the persistent table once we out of bootstrap mode.
		}

		if (!ReadGpRelationNode(
				relation->rd_rel->reltablespace,
				relation->rd_rel->relfilenode,
				/* segmentFileNum */ 0,
				&relation->rd_segfile0_relationnodeinfo.persistentTid,
				&relation->rd_segfile0_relationnodeinfo.persistentSerialNum))
		{
			elog(ERROR, "Did not find gp_relation_node entry for relation name %s, relation id %u, tablespaceOid %u, relfilenode %u",
				 relation->rd_rel->relname.data,
				 relation->rd_id,
				 relation->rd_rel->reltablespace,
				 relation->rd_rel->relfilenode);
		}

		Assert(!Persistent_BeforePersistenceWork());
		if (PersistentStore_IsZeroTid(&relation->rd_segfile0_relationnodeinfo.persistentTid))
		{	
			elog(ERROR, 
				 "RelationFetchSegFile0GpRelationNode has invalid TID (0,0) into relation %u/%u/%u '%s', serial number " INT64_FORMAT,
				 relation->rd_node.spcNode,
				 relation->rd_node.dbNode,
				 relation->rd_node.relNode,
				 NameStr(relation->rd_rel->relname),
				 relation->rd_segfile0_relationnodeinfo.persistentSerialNum);
		}

		relation->rd_segfile0_relationnodeinfo.isPresent = true;
		
	}
	else if (gp_validate_pt_info_relcache &&
		     !(relation->rd_index &&
			   relation->rd_index->indrelid == GpRelationNodeRelationId))
	{
		/*
		 * bypass the check for gp_relation_node_index because
		 * ReadGpRelationNode() uses the same index to probe relfile node.
		 */

		ItemPointerData persistentTid;
		int64			persistentSerialNum;

		if (!ReadGpRelationNode(
				relation->rd_rel->reltablespace,
				relation->rd_rel->relfilenode,
				/* segmentFileNum */ 0,
				&persistentTid,
				&persistentSerialNum))
		{
			elog(ERROR,
				 "did not find gp_relation_node entry for relation name %s, "
				 "relation id %u, tablespace %u, relfilenode %u",
				 relation->rd_rel->relname.data,
				 relation->rd_id,
				 relation->rd_rel->reltablespace,
				 relation->rd_rel->relfilenode);
		}

		if (ItemPointerCompare(&persistentTid,
							   &relation->rd_segfile0_relationnodeinfo.persistentTid) ||
			(persistentSerialNum != relation->rd_segfile0_relationnodeinfo.persistentSerialNum))
		{
			ereport(ERROR,
					(errmsg("invalid persistent TID and/or serial number in "
							"relcache entry"),
					 errdetail("relation name %s, relation id %u, relfilenode %u "
							   "contains invalid persistent TID %s and/or serial "
							   "number " INT64_FORMAT ".  Expected TID is %s and "
							   "serial number " INT64_FORMAT,
							   relation->rd_rel->relname.data, relation->rd_id,
							   relation->rd_node.relNode,
							   ItemPointerToString(
								   &relation->rd_segfile0_relationnodeinfo.persistentTid),
							   relation->rd_segfile0_relationnodeinfo.persistentSerialNum,
							   ItemPointerToString2(&persistentTid),
							   persistentSerialNum)));
		}
	}

}

// UNDONE: Temporary
void
RelationFetchGpRelationNodeForXLog_Index(
	Relation relation)
{
	static int countInThisBackend = 0;
	static int deep = 0;
	
	deep++;

	countInThisBackend++;

	if (deep >= 2)
	{
		int saveDeep;

		if (Debug_gp_relation_node_fetch_wait_for_debugging)
		{
			/* Code for investigating MPP-16395, will be removed as part of the fix */
			elog(WARNING, "RelationFetchGpRelationNodeForXLog_Index [%d] for non-heap %u/%u/%u (deep %d) -- waiting for debug attach...",
				 countInThisBackend,
				 relation->rd_node.spcNode,
				 relation->rd_node.dbNode,
				 relation->rd_node.relNode,
				 deep);

			for (int i=0; i < 24 * 60; i++)
			{
				pg_usleep(60000000L); /* 60 sec */
			}
		}

		/*
		 * Reset counter in case the user continues to use the session.
		 */
		saveDeep = deep;
		deep = 0;

		elog(ERROR, "RelationFetchGpRelationNodeForXLog_Index [%d] for non-heap %u/%u/%u (deep %d)",
			 countInThisBackend,
			 relation->rd_node.spcNode,
			 relation->rd_node.dbNode,
			 relation->rd_node.relNode,
			 saveDeep);
	}

	RelationFetchSegFile0GpRelationNode(relation);

	deep--;
}

/*
 *		AllocateRelationDesc
 *
 *		This is used to allocate memory for a new relation descriptor
 *		and initialize the rd_rel field from the given pg_class tuple.
 */
static Relation
AllocateRelationDesc(Form_pg_class relp)
{
	Relation	relation;
	MemoryContext oldcxt;
	Form_pg_class relationForm;

	/* Relcache entries must live in CacheMemoryContext */
	oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

	/*
	 * allocate and zero space for new relation descriptor
	 */
	relation = (Relation) palloc0(sizeof(RelationData));

	/*
	 * clear fields of reldesc that should initialize to something non-zero
	 */
	relation->rd_targblock = InvalidBlockNumber;

	/* make sure relation is marked as having no open file yet */
	relation->rd_smgr = NULL;

	/*
	 * Copy the relation tuple form
	 *
	 * We only allocate space for the fixed fields, ie, CLASS_TUPLE_SIZE. The
	 * variable-length fields (relacl, reloptions) are NOT stored in the
	 * relcache --- there'd be little point in it, since we don't copy the
	 * tuple's nulls bitmap and hence wouldn't know if the values are valid.
	 * Bottom line is that relacl *cannot* be retrieved from the relcache. Get
	 * it from the syscache if you need it.  The same goes for the original
	 * form of reloptions (however, we do store the parsed form of reloptions
	 * in rd_options).
	 */
	relationForm = (Form_pg_class) palloc(CLASS_TUPLE_SIZE);

	memcpy(relationForm, relp, CLASS_TUPLE_SIZE);

	/* initialize relation tuple form */
	relation->rd_rel = relationForm;

	/*
	 * This part MUST be remain as a fetch on demand, otherwise you end up
	 * needing it to open pg_class and then relation_open does infinite recursion...
	 */
	relation->rd_segfile0_relationnodeinfo.isPresent = false;
	relation->rd_segfile0_relationnodeinfo.tidAllowedToBeZero = false;

	/* and allocate attribute tuple form storage */
	relation->rd_att = CreateTemplateTupleDesc(relationForm->relnatts,
											   relationForm->relhasoids);
	/* which we mark as a reference-counted tupdesc */
	relation->rd_att->tdrefcount = 1;

	MemoryContextSwitchTo(oldcxt);

	return relation;
}

/*
 * RelationParseRelOptions
 *		Convert pg_class.reloptions into pre-parsed rd_options
 *
 * tuple is the real pg_class tuple (not rd_rel!) for relation
 *
 * Note: rd_rel and (if an index) rd_am must be valid already
 */
static void
RelationParseRelOptions(Relation relation, HeapTuple tuple)
{
	Datum		datum;
	bool		isnull;
	bytea	   *options;

	relation->rd_options = NULL;

	/* Fall out if relkind should not have options */
	switch (relation->rd_rel->relkind)
	{
		case RELKIND_RELATION:
		case RELKIND_TOASTVALUE:
		case RELKIND_AOSEGMENTS:
		case RELKIND_AOBLOCKDIR:
		case RELKIND_AOVISIMAP:
		case RELKIND_INDEX:
			break;
		default:
			return;
	}

	/*
	 * Fetch reloptions from tuple; have to use a hardwired descriptor because
	 * we might not have any other for pg_class yet (consider executing this
	 * code for pg_class itself)
	 */
	datum = fastgetattr(tuple,
						Anum_pg_class_reloptions,
						GetPgClassDescriptor(),
						&isnull);
	if (isnull)
		return;

	/* Parse into appropriate format; don't error out here */
	switch (relation->rd_rel->relkind)
	{
		case RELKIND_RELATION:
		case RELKIND_TOASTVALUE:
		case RELKIND_AOSEGMENTS:
		case RELKIND_AOBLOCKDIR:
		case RELKIND_AOVISIMAP:
		case RELKIND_UNCATALOGED:
			options = heap_reloptions(relation->rd_rel->relkind, datum,
									  false);
			break;
		case RELKIND_INDEX:
			options = index_reloptions(relation->rd_am->amoptions, datum,
									   false);
			break;
		default:
			Assert(false);		/* can't get here */
			options = NULL;		/* keep compiler quiet */
			break;
	}

	/*
	 * Copy parsed data into CacheMemoryContext.  To guard against the
	 * possibility of leaks in the reloptions code, we want to do the actual
	 * parsing in the caller's memory context and copy the results into
	 * CacheMemoryContext after the fact.
	 */
	if (options)
	{
		relation->rd_options = MemoryContextAlloc(CacheMemoryContext,
												  VARSIZE(options));
		memcpy(relation->rd_options, options, VARSIZE(options));
		pfree(options);
	}
}

/*
 *		RelationBuildTupleDesc
 *
 *		Form the relation's tuple descriptor from information in
 *		the pg_attribute, pg_attrdef & pg_constraint system catalogs.
 */
static void
RelationBuildTupleDesc(Relation relation)
{
	HeapTuple	pg_attribute_tuple;
	Relation	pg_attribute_desc;
	SysScanDesc pg_attribute_scan;
	ScanKeyData skey[2];
	int			need;
	TupleConstr *constr;
	AttrDefault *attrdef = NULL;
	int			ndef = 0;

	/* copy some fields from pg_class row to rd_att */
	relation->rd_att->tdtypeid = relation->rd_rel->reltype;
	relation->rd_att->tdtypmod = -1;	/* unnecessary, but... */
	relation->rd_att->tdhasoid = relation->rd_rel->relhasoids;

	constr = (TupleConstr *) MemoryContextAlloc(CacheMemoryContext,
												sizeof(TupleConstr));
	constr->has_not_null = false;

	/*
	 * Form a scan key that selects only user attributes (attnum > 0).
	 * (Eliminating system attribute rows at the index level is lots faster
	 * than fetching them.)
	 */
	ScanKeyInit(&skey[0],
				Anum_pg_attribute_attrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(relation)));
	ScanKeyInit(&skey[1],
				Anum_pg_attribute_attnum,
				BTGreaterStrategyNumber, F_INT2GT,
				Int16GetDatum(0));

	/*
	 * Open pg_attribute and begin a scan.	Force heap scan if we haven't yet
	 * built the critical relcache entries (this includes initdb and startup
	 * without a pg_internal.init file).
	 */
	pg_attribute_desc = heap_open(AttributeRelationId, AccessShareLock);
	pg_attribute_scan = systable_beginscan(pg_attribute_desc,
										   AttributeRelidNumIndexId,
										   criticalRelcachesBuilt,
										   SnapshotNow,
										   2, skey);

	/*
	 * add attribute data to relation->rd_att
	 */
	need = relation->rd_rel->relnatts;

	while (HeapTupleIsValid(pg_attribute_tuple = systable_getnext(pg_attribute_scan)))
	{
		Form_pg_attribute attp;

		attp = (Form_pg_attribute) GETSTRUCT(pg_attribute_tuple);

		if (attp->attnum <= 0 ||
			attp->attnum > relation->rd_rel->relnatts)
			elog(ERROR, "invalid attribute number %d for %s",
				 attp->attnum, RelationGetRelationName(relation));

		memcpy(relation->rd_att->attrs[attp->attnum - 1],
			   attp,
			   ATTRIBUTE_FIXED_PART_SIZE);

		/* Update constraint/default info */
		if (attp->attnotnull)
			constr->has_not_null = true;

		if (attp->atthasdef)
		{
			if (attrdef == NULL)
				attrdef = (AttrDefault *)
					MemoryContextAllocZero(CacheMemoryContext,
										   relation->rd_rel->relnatts *
										   sizeof(AttrDefault));
			attrdef[ndef].adnum = attp->attnum;
			attrdef[ndef].adbin = NULL;
			ndef++;
		}
		need--;
		if (need == 0)
			break;
	}

	/*
	 * end the scan and close the attribute relation
	 */
	systable_endscan(pg_attribute_scan);
	heap_close(pg_attribute_desc, AccessShareLock);

	if (need != 0)
		elog(ERROR, "catalog is missing %d attribute(s) for relid %u",
			 need, RelationGetRelid(relation));

	/*
	 * The attcacheoff values we read from pg_attribute should all be -1
	 * ("unknown").  Verify this if assert checking is on.	They will be
	 * computed when and if needed during tuple access.
	 */
#ifdef USE_ASSERT_CHECKING
	{
		int			i;

		for (i = 0; i < relation->rd_rel->relnatts; i++)
			Assert(relation->rd_att->attrs[i]->attcacheoff == -1);
	}
#endif

	/*
	 * However, we can easily set the attcacheoff value for the first
	 * attribute: it must be zero.	This eliminates the need for special cases
	 * for attnum=1 that used to exist in fastgetattr() and index_getattr().
	 */
	if (relation->rd_rel->relnatts > 0)
		relation->rd_att->attrs[0]->attcacheoff = 0;

	/*
	 * Set up constraint/default info
	 */
	if (constr->has_not_null || ndef > 0 || relation->rd_rel->relchecks)
	{
		relation->rd_att->constr = constr;

		if (ndef > 0)			/* DEFAULTs */
		{
			if (ndef < relation->rd_rel->relnatts)
				constr->defval = (AttrDefault *)
					repalloc(attrdef, ndef * sizeof(AttrDefault));
			else
				constr->defval = attrdef;
			constr->num_defval = ndef;
			AttrDefaultFetch(relation);
		}
		else
			constr->num_defval = 0;

		if (relation->rd_rel->relchecks > 0)	/* CHECKs */
		{
			constr->num_check = relation->rd_rel->relchecks;
			constr->check = (ConstrCheck *)
				MemoryContextAllocZero(CacheMemoryContext,
									constr->num_check * sizeof(ConstrCheck));
			CheckConstraintFetch(relation);
		}
		else
			constr->num_check = 0;
	}
	else
	{
		pfree(constr);
		relation->rd_att->constr = NULL;
	}
}

/*
 *		RelationBuildRuleLock
 *
 *		Form the relation's rewrite rules from information in
 *		the pg_rewrite system catalog.
 *
 * Note: The rule parsetrees are potentially very complex node structures.
 * To allow these trees to be freed when the relcache entry is flushed,
 * we make a private memory context to hold the RuleLock information for
 * each relcache entry that has associated rules.  The context is used
 * just for rule info, not for any other subsidiary data of the relcache
 * entry, because that keeps the update logic in RelationClearRelation()
 * manageable.	The other subsidiary data structures are simple enough
 * to be easy to free explicitly, anyway.
 */
static void
RelationBuildRuleLock(Relation relation)
{
	MemoryContext rulescxt;
	MemoryContext oldcxt;
	HeapTuple	rewrite_tuple;
	Relation	rewrite_desc;
	TupleDesc	rewrite_tupdesc;
	SysScanDesc rewrite_scan;
	ScanKeyData key;
	RuleLock   *rulelock;
	int			numlocks;
	RewriteRule **rules;
	int			maxlocks;

	/*
	 * Make the private context.  Parameters are set on the assumption that
	 * it'll probably not contain much data.
	 */
	rulescxt = AllocSetContextCreate(CacheMemoryContext,
									 RelationGetRelationName(relation),
									 ALLOCSET_SMALL_MINSIZE,
									 ALLOCSET_SMALL_INITSIZE,
									 ALLOCSET_SMALL_MAXSIZE);
	relation->rd_rulescxt = rulescxt;

	/*
	 * allocate an array to hold the rewrite rules (the array is extended if
	 * necessary)
	 */
	maxlocks = 4;
	rules = (RewriteRule **)
		MemoryContextAlloc(rulescxt, sizeof(RewriteRule *) * maxlocks);
	numlocks = 0;

	/*
	 * form a scan key
	 */
	ScanKeyInit(&key,
				Anum_pg_rewrite_ev_class,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(relation)));

	/*
	 * open pg_rewrite and begin a scan
	 *
	 * Note: since we scan the rules using RewriteRelRulenameIndexId, we will
	 * be reading the rules in name order, except possibly during
	 * emergency-recovery operations (ie, IgnoreSystemIndexes). This in turn
	 * ensures that rules will be fired in name order.
	 */
	rewrite_desc = heap_open(RewriteRelationId, AccessShareLock);
	rewrite_tupdesc = RelationGetDescr(rewrite_desc);

	rewrite_scan = systable_beginscan(rewrite_desc,
									  RewriteRelRulenameIndexId,
									  true, SnapshotNow,
									  1, &key);

	while (HeapTupleIsValid(rewrite_tuple = systable_getnext(rewrite_scan)))
	{
		Form_pg_rewrite rewrite_form = (Form_pg_rewrite) GETSTRUCT(rewrite_tuple);
		bool		isnull;
		Datum		rule_datum;
		char	   *rule_str;
		RewriteRule *rule;

		rule = (RewriteRule *) MemoryContextAlloc(rulescxt,
												  sizeof(RewriteRule));

		rule->ruleId = HeapTupleGetOid(rewrite_tuple);

		rule->event = rewrite_form->ev_type - '0';
		rule->attrno = rewrite_form->ev_attr;
		rule->enabled = rewrite_form->ev_enabled;
		rule->isInstead = rewrite_form->is_instead;

		/*
		 * Must use heap_getattr to fetch ev_action and ev_qual.  Also, the
		 * rule strings are often large enough to be toasted.  To avoid
		 * leaking memory in the caller's context, do the detoasting here so
		 * we can free the detoasted version.
		 */
		rule_datum = heap_getattr(rewrite_tuple,
								  Anum_pg_rewrite_ev_action,
								  rewrite_tupdesc,
								  &isnull);
		Assert(!isnull);
		rule_str = TextDatumGetCString(rule_datum);
		oldcxt = MemoryContextSwitchTo(rulescxt);
		rule->actions = (List *) stringToNode(rule_str);
		MemoryContextSwitchTo(oldcxt);
		pfree(rule_str);

		rule_datum = heap_getattr(rewrite_tuple,
								  Anum_pg_rewrite_ev_qual,
								  rewrite_tupdesc,
								  &isnull);
		Assert(!isnull);
		rule_str = TextDatumGetCString(rule_datum);
		oldcxt = MemoryContextSwitchTo(rulescxt);
		rule->qual = (Node *) stringToNode(rule_str);
		MemoryContextSwitchTo(oldcxt);
		pfree(rule_str);

		/*
		 * We want the rule's table references to be checked as though by the
		 * table owner, not the user referencing the rule.	Therefore, scan
		 * through the rule's actions and set the checkAsUser field on all
		 * rtable entries.	We have to look at the qual as well, in case it
		 * contains sublinks.
		 *
		 * The reason for doing this when the rule is loaded, rather than when
		 * it is stored, is that otherwise ALTER TABLE OWNER would have to
		 * grovel through stored rules to update checkAsUser fields. Scanning
		 * the rule tree during load is relatively cheap (compared to
		 * constructing it in the first place), so we do it here.
		 */
		setRuleCheckAsUser((Node *) rule->actions, relation->rd_rel->relowner);
		setRuleCheckAsUser(rule->qual, relation->rd_rel->relowner);

		if (numlocks >= maxlocks)
		{
			maxlocks *= 2;
			rules = (RewriteRule **)
				repalloc(rules, sizeof(RewriteRule *) * maxlocks);
		}
		rules[numlocks++] = rule;
	}

	/*
	 * end the scan and close the attribute relation
	 */
	systable_endscan(rewrite_scan);
	heap_close(rewrite_desc, AccessShareLock);

	/*
	 * form a RuleLock and insert into relation
	 */
	rulelock = (RuleLock *) MemoryContextAlloc(rulescxt, sizeof(RuleLock));
	rulelock->numLocks = numlocks;
	rulelock->rules = rules;

	relation->rd_rules = rulelock;
}

/*
 *		equalRuleLocks
 *
 *		Determine whether two RuleLocks are equivalent
 *
 *		Probably this should be in the rules code someplace...
 */
static bool
equalRuleLocks(RuleLock *rlock1, RuleLock *rlock2)
{
	int			i;

	/*
	 * As of 7.3 we assume the rule ordering is repeatable, because
	 * RelationBuildRuleLock should read 'em in a consistent order.  So just
	 * compare corresponding slots.
	 */
	if (rlock1 != NULL)
	{
		if (rlock2 == NULL)
			return false;
		if (rlock1->numLocks != rlock2->numLocks)
			return false;
		for (i = 0; i < rlock1->numLocks; i++)
		{
			RewriteRule *rule1 = rlock1->rules[i];
			RewriteRule *rule2 = rlock2->rules[i];

			if (rule1->ruleId != rule2->ruleId)
				return false;
			if (rule1->event != rule2->event)
				return false;
			if (rule1->attrno != rule2->attrno)
				return false;
			if (rule1->enabled != rule2->enabled)
				return false;
			if (rule1->isInstead != rule2->isInstead)
				return false;
			if (!equal(rule1->qual, rule2->qual))
				return false;
			if (!equal(rule1->actions, rule2->actions))
				return false;
		}
	}
	else if (rlock2 != NULL)
		return false;
	return true;
}


/*
 *		RelationBuildDesc
 *
 *		Build a relation descriptor.  The caller must hold at least
 *		AccessShareLock on the target relid.
 *
 *		The new descriptor is inserted into the hash table if insertIt is true.
 *
 *		Returns NULL if no pg_class row could be found for the given relid
 *		(suggesting we are trying to access a just-deleted relation).
 *		Any other error is reported via elog.
 */
static Relation
RelationBuildDesc(Oid targetRelId, bool insertIt)
{
	Relation	relation;
	Oid			relid;
	Relation    pg_class_relation;
	HeapTuple	pg_class_tuple;
	Form_pg_class relp;

	/*
	 * find the tuple in pg_class corresponding to the given relation id
	 */
	pg_class_tuple = ScanPgRelation(targetRelId, true, &pg_class_relation);

	/*
	 * if no such tuple exists, return NULL
	 */
	if (!HeapTupleIsValid(pg_class_tuple))
		return NULL;

	/*
	 * get information from the pg_class_tuple
	 */
	relid = HeapTupleGetOid(pg_class_tuple);
	relp = (Form_pg_class) GETSTRUCT(pg_class_tuple);
	heap_close(pg_class_relation, AccessShareLock);

	/*
	 * allocate storage for the relation descriptor, and copy pg_class_tuple
	 * to relation->rd_rel and new fields into relation->rd_newfields.
	 */
	relation = AllocateRelationDesc(relp);

	/*
	 * initialize the relation's relation id (relation->rd_id)
	 */
	RelationGetRelid(relation) = relid;

	/*
	 * normal relations are not nailed into the cache; nor can a pre-existing
	 * relation be new.  It could be temp though.  (Actually, it could be new
	 * too, but it's okay to forget that fact if forced to flush the entry.)
	 */
	relation->rd_refcnt = 0;
	relation->rd_isnailed = false;
	relation->rd_createSubid = InvalidSubTransactionId;
	relation->rd_newRelfilenodeSubid = InvalidSubTransactionId;
	relation->rd_istemp = isTempOrToastNamespace(relation->rd_rel->relnamespace);
	relation->rd_issyscat = (strncmp(relation->rd_rel->relname.data, "pg_", 3) == 0);

	/*
	 * CDB: On QEs, temp relations must use shared buffer cache so data
	 * will be visible to all segmates.  On QD, sequence objects must
	 * use shared buffer cache so data will be visible to sequence server.
	 */
	if (relation->rd_istemp &&
		relation->rd_rel->relkind != RELKIND_SEQUENCE &&
		Gp_role != GP_ROLE_EXECUTE)
		relation->rd_isLocalBuf = true;
	else
		relation->rd_isLocalBuf = false;

	/*
	 * initialize the tuple descriptor (relation->rd_att).
	 */
	RelationBuildTupleDesc(relation);

	/*
	 * Fetch rules and triggers that affect this relation
	 */
	if (relation->rd_rel->relhasrules)
		RelationBuildRuleLock(relation);
	else
	{
		relation->rd_rules = NULL;
		relation->rd_rulescxt = NULL;
	}

	if (relation->rd_rel->reltriggers > 0)
		RelationBuildTriggers(relation);
	else
		relation->trigdesc = NULL;

	/*
	 * if it's an index, initialize index-related information
	 */
	if (OidIsValid(relation->rd_rel->relam))
		RelationInitIndexAccessInfo(relation);

	/*
	 * if it's an append-only table, get information from pg_appendonly
	 */
	if (relation->rd_rel->relstorage == RELSTORAGE_AOROWS ||
		relation->rd_rel->relstorage == RELSTORAGE_AOCOLS)
	{
		RelationInitAppendOnlyInfo(relation);
	}

	/* extract reloptions if any */
	RelationParseRelOptions(relation, pg_class_tuple);

	/*
	 * initialize the relation lock manager information
	 */
	RelationInitLockInfo(relation);		/* see lmgr.c */

	/*
	 * initialize physical addressing information for the relation
	 */
	RelationInitPhysicalAddr(relation);

	/* make sure relation is marked as having no open file yet */
	relation->rd_smgr = NULL;

    /*
     * initialize Greenplum Database partitioning info
     */
    if (relation->rd_rel->relkind == RELKIND_RELATION &&
        !IsSystemRelation(relation))
        relation->rd_cdbpolicy = GpPolicyFetch(CacheMemoryContext, targetRelId);

    relation->rd_cdbDefaultStatsWarningIssued = false;

	/*
	 * now we can free the memory allocated for pg_class_tuple
	 */
	heap_freetuple(pg_class_tuple);

	/*
	 * Insert newly created relation into relcache hash table, if requested.
	 */
	if (insertIt)
		RelationCacheInsert(relation);

	/* It's fully valid */
	relation->rd_isvalid = true;

	return relation;
}

/*
 * Initialize the physical addressing info (RelFileNode) for a relcache entry
 */
static void
RelationInitPhysicalAddr(Relation relation)
{
	if (relation->rd_rel->reltablespace)
		relation->rd_node.spcNode = relation->rd_rel->reltablespace;
	else
		relation->rd_node.spcNode = MyDatabaseTableSpace;
	if (relation->rd_rel->relisshared)
		relation->rd_node.dbNode = InvalidOid;
	else
		relation->rd_node.dbNode = MyDatabaseId;
	relation->rd_node.relNode = relation->rd_rel->relfilenode;
}

/*
 * Initialize index-access-method support data for an index relation
 */
void
RelationInitIndexAccessInfo(Relation relation)
{
	HeapTuple	tuple;
	Form_pg_am	aform;
	Datum		indclassDatum;
	Datum		indoptionDatum;
	bool		isnull;
	oidvector  *indclass;
	int2vector *indoption;
	MemoryContext indexcxt;
	MemoryContext oldcontext;
	int			natts;
	uint16		amstrategies;
	uint16		amsupport;

	/*
	 * Make a copy of the pg_index entry for the index.  Since pg_index
	 * contains variable-length and possibly-null fields, we have to do this
	 * honestly rather than just treating it as a Form_pg_index struct.
	 */
	tuple = SearchSysCache(INDEXRELID,
						   ObjectIdGetDatum(RelationGetRelid(relation)),
						   0, 0, 0);
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "cache lookup failed for index %u",
			 RelationGetRelid(relation));
	oldcontext = MemoryContextSwitchTo(CacheMemoryContext);
	relation->rd_indextuple = heap_copytuple(tuple);
	relation->rd_index = (Form_pg_index) GETSTRUCT(relation->rd_indextuple);
	MemoryContextSwitchTo(oldcontext);
	ReleaseSysCache(tuple);

	/*
	 * Make a copy of the pg_am entry for the index's access method
	 */
	tuple = SearchSysCache(AMOID,
						   ObjectIdGetDatum(relation->rd_rel->relam),
						   0, 0, 0);
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "cache lookup failed for access method %u",
			 relation->rd_rel->relam);
	aform = (Form_pg_am) MemoryContextAlloc(CacheMemoryContext, sizeof *aform);
	memcpy(aform, GETSTRUCT(tuple), sizeof *aform);
	ReleaseSysCache(tuple);
	relation->rd_am = aform;

	natts = relation->rd_rel->relnatts;
	if (natts != relation->rd_index->indnatts)
		elog(ERROR, "relnatts disagrees with indnatts for index %u",
			 RelationGetRelid(relation));
	amstrategies = aform->amstrategies;
	amsupport = aform->amsupport;

	/*
	 * Make the private context to hold index access info.	The reason we need
	 * a context, and not just a couple of pallocs, is so that we won't leak
	 * any subsidiary info attached to fmgr lookup records.
	 *
	 * Context parameters are set on the assumption that it'll probably not
	 * contain much data.
	 */
	indexcxt = AllocSetContextCreate(CacheMemoryContext,
									 RelationGetRelationName(relation),
									 ALLOCSET_SMALL_MINSIZE,
									 ALLOCSET_SMALL_INITSIZE,
									 ALLOCSET_SMALL_MAXSIZE);
	relation->rd_indexcxt = indexcxt;

	/*
	 * Allocate arrays to hold data
	 */
	relation->rd_aminfo = (RelationAmInfo *)
		MemoryContextAllocZero(indexcxt, sizeof(RelationAmInfo));

	relation->rd_opfamily = (Oid *)
		MemoryContextAllocZero(indexcxt, natts * sizeof(Oid));
	relation->rd_opcintype = (Oid *)
		MemoryContextAllocZero(indexcxt, natts * sizeof(Oid));

	if (amstrategies > 0)
		relation->rd_operator = (Oid *)
			MemoryContextAllocZero(indexcxt,
								   natts * amstrategies * sizeof(Oid));
	else
		relation->rd_operator = NULL;

	if (amsupport > 0)
	{
		int			nsupport = natts * amsupport;

		relation->rd_support = (RegProcedure *)
			MemoryContextAllocZero(indexcxt, nsupport * sizeof(RegProcedure));
		relation->rd_supportinfo = (FmgrInfo *)
			MemoryContextAllocZero(indexcxt, nsupport * sizeof(FmgrInfo));
	}
	else
	{
		relation->rd_support = NULL;
		relation->rd_supportinfo = NULL;
	}

	relation->rd_indoption = (int16 *)
		MemoryContextAllocZero(indexcxt, natts * sizeof(int16));

	/*
	 * indclass cannot be referenced directly through the C struct, because it
	 * comes after the variable-width indkey field.  Must extract the datum
	 * the hard way...
	 */
	indclassDatum = fastgetattr(relation->rd_indextuple,
								Anum_pg_index_indclass,
								GetPgIndexDescriptor(),
								&isnull);
	Assert(!isnull);
	indclass = (oidvector *) DatumGetPointer(indclassDatum);

	/*
	 * Fill the operator and support procedure OID arrays, as well as the info
	 * about opfamilies and opclass input types.  (aminfo and supportinfo are
	 * left as zeroes, and are filled on-the-fly when used)
	 */
	IndexSupportInitialize(indclass,
						   relation->rd_operator, relation->rd_support,
						   relation->rd_opfamily, relation->rd_opcintype,
						   amstrategies, amsupport, natts);

	/*
	 * Similarly extract indoption and copy it to the cache entry
	 */
	indoptionDatum = fastgetattr(relation->rd_indextuple,
								 Anum_pg_index_indoption,
								 GetPgIndexDescriptor(),
								 &isnull);
	Assert(!isnull);
	indoption = (int2vector *) DatumGetPointer(indoptionDatum);
	memcpy(relation->rd_indoption, indoption->values, natts * sizeof(int16));

	/*
	 * expressions and predicate cache will be filled later
	 */
	relation->rd_indexprs = NIL;
	relation->rd_indpred = NIL;
	relation->rd_amcache = NULL;
}

/*
 * IndexSupportInitialize
 *		Initializes an index's cached opclass information,
 *		given the index's pg_index.indclass entry.
 *
 * Data is returned into *indexOperator, *indexSupport, *opFamily, and
 * *opcInType, which are arrays allocated by the caller.
 *
 * The caller also passes maxStrategyNumber, maxSupportNumber, and
 * maxAttributeNumber, since these indicate the size of the arrays
 * it has allocated --- but in practice these numbers must always match
 * those obtainable from the system catalog entries for the index and
 * access method.
 */
void
IndexSupportInitialize(oidvector *indclass,
					   Oid *indexOperator,
					   RegProcedure *indexSupport,
					   Oid *opFamily,
					   Oid *opcInType,
					   StrategyNumber maxStrategyNumber,
					   StrategyNumber maxSupportNumber,
					   AttrNumber maxAttributeNumber)
{
	int			attIndex;

	for (attIndex = 0; attIndex < maxAttributeNumber; attIndex++)
	{
		OpClassCacheEnt *opcentry;

		if (!OidIsValid(indclass->values[attIndex]))
			elog(ERROR, "bogus pg_index tuple");

		/* look up the info for this opclass, using a cache */
		opcentry = LookupOpclassInfo(indclass->values[attIndex],
									 maxStrategyNumber,
									 maxSupportNumber);

		/* copy cached data into relcache entry */
		opFamily[attIndex] = opcentry->opcfamily;
		opcInType[attIndex] = opcentry->opcintype;
		if (maxStrategyNumber > 0)
			memcpy(&indexOperator[attIndex * maxStrategyNumber],
				   opcentry->operatorOids,
				   maxStrategyNumber * sizeof(Oid));
		if (maxSupportNumber > 0)
			memcpy(&indexSupport[attIndex * maxSupportNumber],
				   opcentry->supportProcs,
				   maxSupportNumber * sizeof(RegProcedure));
	}
}

/*
 * LookupOpclassInfo
 *
 * This routine maintains a per-opclass cache of the information needed
 * by IndexSupportInitialize().  This is more efficient than relying on
 * the catalog cache, because we can load all the info about a particular
 * opclass in a single indexscan of pg_amproc or pg_amop.
 *
 * The information from pg_am about expected range of strategy and support
 * numbers is passed in, rather than being looked up, mainly because the
 * caller will have it already.
 *
 * Note there is no provision for flushing the cache.  This is OK at the
 * moment because there is no way to ALTER any interesting properties of an
 * existing opclass --- all you can do is drop it, which will result in
 * a useless but harmless dead entry in the cache.  To support altering
 * opclass membership (not the same as opfamily membership!), we'd need to
 * be able to flush this cache as well as the contents of relcache entries
 * for indexes.
 */
static OpClassCacheEnt *
LookupOpclassInfo(Oid operatorClassOid,
				  StrategyNumber numStrats,
				  StrategyNumber numSupport)
{
	OpClassCacheEnt *opcentry;
	bool		found;
	Relation	rel;
	SysScanDesc scan;
	ScanKeyData skey[3];
	HeapTuple	htup;
	bool		indexOK;

	if (OpClassCache == NULL)
	{
		/* First time through: initialize the opclass cache */
		HASHCTL		ctl;

		if (!CacheMemoryContext)
			CreateCacheMemoryContext();

		MemSet(&ctl, 0, sizeof(ctl));
		ctl.keysize = sizeof(Oid);
		ctl.entrysize = sizeof(OpClassCacheEnt);
		ctl.hash = oid_hash;
		OpClassCache = hash_create("Operator class cache", 64,
								   &ctl, HASH_ELEM | HASH_FUNCTION);
	}

	opcentry = (OpClassCacheEnt *) hash_search(OpClassCache,
											   (void *) &operatorClassOid,
											   HASH_ENTER, &found);

	if (!found)
	{
		/* Need to allocate memory for new entry */
		opcentry->valid = false;	/* until known OK */
		opcentry->numStrats = numStrats;
		opcentry->numSupport = numSupport;

		if (numStrats > 0)
			opcentry->operatorOids = (Oid *)
				MemoryContextAllocZero(CacheMemoryContext,
									   numStrats * sizeof(Oid));
		else
			opcentry->operatorOids = NULL;

		if (numSupport > 0)
			opcentry->supportProcs = (RegProcedure *)
				MemoryContextAllocZero(CacheMemoryContext,
									   numSupport * sizeof(RegProcedure));
		else
			opcentry->supportProcs = NULL;
	}
	else
	{
		Assert(numStrats == opcentry->numStrats);
		Assert(numSupport == opcentry->numSupport);
	}

	/*
	 * When testing for cache-flush hazards, we intentionally disable the
	 * operator class cache and force reloading of the info on each call.
	 * This is helpful because we want to test the case where a cache flush
	 * occurs while we are loading the info, and it's very hard to provoke
	 * that if this happens only once per opclass per backend.
	 */
#if defined(CLOBBER_CACHE_ALWAYS)
	opcentry->valid = false;
#endif

	if (opcentry->valid)
		return opcentry;

	/*
	 * Need to fill in new entry.
	 *
	 * To avoid infinite recursion during startup, force heap scans if we're
	 * looking up info for the opclasses used by the indexes we would like to
	 * reference here.
	 */
	indexOK = criticalRelcachesBuilt ||
		(operatorClassOid != OID_BTREE_OPS_OID &&
		 operatorClassOid != INT2_BTREE_OPS_OID);

	/*
	 * We have to fetch the pg_opclass row to determine its opfamily and
	 * opcintype, which are needed to look up the operators and functions.
	 * It'd be convenient to use the syscache here, but that probably doesn't
	 * work while bootstrapping.
	 */
	ScanKeyInit(&skey[0],
				ObjectIdAttributeNumber,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(operatorClassOid));
	rel = heap_open(OperatorClassRelationId, AccessShareLock);
	scan = systable_beginscan(rel, OpclassOidIndexId, indexOK,
							  SnapshotNow, 1, skey);

	if (HeapTupleIsValid(htup = systable_getnext(scan)))
	{
		Form_pg_opclass opclassform = (Form_pg_opclass) GETSTRUCT(htup);

		opcentry->opcfamily = opclassform->opcfamily;
		opcentry->opcintype = opclassform->opcintype;
	}
	else
		elog(ERROR, "could not find tuple for opclass %u", operatorClassOid);

	systable_endscan(scan);
	heap_close(rel, AccessShareLock);


	/*
	 * Scan pg_amop to obtain operators for the opclass.  We only fetch the
	 * default ones (those with lefttype = righttype = opcintype).
	 */
	if (numStrats > 0)
	{
		ScanKeyInit(&skey[0],
					Anum_pg_amop_amopfamily,
					BTEqualStrategyNumber, F_OIDEQ,
					ObjectIdGetDatum(opcentry->opcfamily));
		ScanKeyInit(&skey[1],
					Anum_pg_amop_amoplefttype,
					BTEqualStrategyNumber, F_OIDEQ,
					ObjectIdGetDatum(opcentry->opcintype));
		ScanKeyInit(&skey[2],
					Anum_pg_amop_amoprighttype,
					BTEqualStrategyNumber, F_OIDEQ,
					ObjectIdGetDatum(opcentry->opcintype));
		rel = heap_open(AccessMethodOperatorRelationId, AccessShareLock);
		scan = systable_beginscan(rel, AccessMethodStrategyIndexId, indexOK,
								  SnapshotNow, 3, skey);

		while (HeapTupleIsValid(htup = systable_getnext(scan)))
		{
			Form_pg_amop amopform = (Form_pg_amop) GETSTRUCT(htup);

			if (amopform->amopstrategy <= 0 ||
				(StrategyNumber) amopform->amopstrategy > numStrats)
				elog(ERROR, "invalid amopstrategy number %d for opclass %u",
					 amopform->amopstrategy, operatorClassOid);
			opcentry->operatorOids[amopform->amopstrategy - 1] =
				amopform->amopopr;
		}

		systable_endscan(scan);
		heap_close(rel, AccessShareLock);
	}

	/*
	 * Scan pg_amproc to obtain support procs for the opclass.	We only fetch
	 * the default ones (those with lefttype = righttype = opcintype).
	 */
	if (numSupport > 0)
	{
		ScanKeyInit(&skey[0],
					Anum_pg_amproc_amprocfamily,
					BTEqualStrategyNumber, F_OIDEQ,
					ObjectIdGetDatum(opcentry->opcfamily));
		ScanKeyInit(&skey[1],
					Anum_pg_amproc_amproclefttype,
					BTEqualStrategyNumber, F_OIDEQ,
					ObjectIdGetDatum(opcentry->opcintype));
		ScanKeyInit(&skey[2],
					Anum_pg_amproc_amprocrighttype,
					BTEqualStrategyNumber, F_OIDEQ,
					ObjectIdGetDatum(opcentry->opcintype));
		rel = heap_open(AccessMethodProcedureRelationId, AccessShareLock);
		scan = systable_beginscan(rel, AccessMethodProcedureIndexId, indexOK,
								  SnapshotNow, 3, skey);

		while (HeapTupleIsValid(htup = systable_getnext(scan)))
		{
			Form_pg_amproc amprocform = (Form_pg_amproc) GETSTRUCT(htup);

			if (amprocform->amprocnum <= 0 ||
				(StrategyNumber) amprocform->amprocnum > numSupport)
				elog(ERROR, "invalid amproc number %d for opclass %u",
					 amprocform->amprocnum, operatorClassOid);

			opcentry->supportProcs[amprocform->amprocnum - 1] =
				amprocform->amproc;
		}

		systable_endscan(scan);
		heap_close(rel, AccessShareLock);
	}

	opcentry->valid = true;
	return opcentry;
}


/*
 *		formrdesc
 *
 *		This is a special cut-down version of RelationBuildDesc(),
 *		used while initializing the relcache.
 *		The relation descriptor is built just from the supplied parameters,
 *		without actually looking at any system table entries.  We cheat
 *		quite a lot since we only need to work for a few basic system
 *		catalogs.
 *
 * formrdesc is currently used for: pg_database, pg_authid, pg_auth_members,
 * pg_class, pg_attribute, pg_proc, and pg_type
 * (see RelationCacheInitializePhase2/3).
 *
 * Note that these catalogs can't have constraints (except attnotnull),
 * default values, rules, or triggers, since we don't cope with any of that.
 * (Well, actually, this only matters for properties that need to be valid
 * during bootstrap or before RelationCacheInitializePhase3 runs, and none of
 * these properties matter then...)
 *
 * NOTE: we assume we are already switched into CacheMemoryContext.
 */
static void
formrdesc(const char *relationName, Oid relationReltype,
		  bool isshared, bool hasoids,
		  int natts, const FormData_pg_attribute *attrs)
{
	Relation	relation;
	int			i;
	bool		has_not_null;

	/*
	 * allocate new relation desc, clear all fields of reldesc
	 */
	relation = (Relation) palloc0(sizeof(RelationData));
	relation->rd_targblock = InvalidBlockNumber;

	/* make sure relation is marked as having no open file yet */
	relation->rd_smgr = NULL;

	/*
	 * initialize reference count: 1 because it is nailed in cache
	 */
	relation->rd_refcnt = 1;

	/*
	 * all entries built with this routine are nailed-in-cache; none are for
	 * new or temp relations.
	 */
	relation->rd_isnailed = true;
	relation->rd_createSubid = InvalidSubTransactionId;
	relation->rd_newRelfilenodeSubid = InvalidSubTransactionId;
	relation->rd_istemp = false;
	relation->rd_issyscat = (strncmp(relationName, "pg_", 3) == 0);	/* GP */
    relation->rd_isLocalBuf = false;    /*CDB*/

	/*
	 * initialize relation tuple form
	 *
	 * The data we insert here is pretty incomplete/bogus, but it'll serve to
	 * get us launched.  RelationCacheInitializePhase2() will read the real
	 * data from pg_class and replace what we've done here.  Note in particular
	 * that relowner is left as zero; this cues RelationCacheInitializePhase2
	 * that the real data isn't there yet.
	 */
	relation->rd_rel = (Form_pg_class) palloc0(CLASS_TUPLE_SIZE);

	namestrcpy(&relation->rd_rel->relname, relationName);
	relation->rd_rel->relnamespace = PG_CATALOG_NAMESPACE;
	relation->rd_rel->reltype = relationReltype;

	/*
	 * It's important to distinguish between shared and non-shared relations,
	 * even at bootstrap time, to make sure we know where they are stored.
	 */
	relation->rd_rel->relisshared = isshared;
	if (isshared)
		relation->rd_rel->reltablespace = GLOBALTABLESPACE_OID;

	relation->rd_rel->relpages = 0;
	relation->rd_rel->reltuples = 0;
	relation->rd_rel->relkind = RELKIND_RELATION;
	relation->rd_rel->relstorage = RELSTORAGE_HEAP;
	relation->rd_rel->relhasoids = hasoids;
	relation->rd_rel->relnatts = (int16) natts;

	/*
	 * Physical file-system information.
	 */
	relation->rd_segfile0_relationnodeinfo.isPresent = false;
	relation->rd_segfile0_relationnodeinfo.tidAllowedToBeZero = false;
	
	/*
	 * initialize attribute tuple form
	 *
	 * Unlike the case with the relation tuple, this data had better be right
	 * because it will never be replaced.  The input values must be correctly
	 * defined by macros in src/include/catalog/ headers.
	 */
	relation->rd_att = CreateTemplateTupleDesc(natts, hasoids);
	relation->rd_att->tdrefcount = 1;	/* mark as refcounted */

	relation->rd_att->tdtypeid = relationReltype;
	relation->rd_att->tdtypmod = -1;	/* unnecessary, but... */

	/*
	 * initialize tuple desc info
	 */
	has_not_null = false;
	for (i = 0; i < natts; i++)
	{
		memcpy(relation->rd_att->attrs[i],
			   &attrs[i],
			   ATTRIBUTE_FIXED_PART_SIZE);
		has_not_null |= attrs[i].attnotnull;
		/* make sure attcacheoff is valid */
		relation->rd_att->attrs[i]->attcacheoff = -1;
	}

	/* initialize first attribute's attcacheoff, cf RelationBuildTupleDesc */
	relation->rd_att->attrs[0]->attcacheoff = 0;

	/* mark not-null status */
	if (has_not_null)
	{
		TupleConstr *constr = (TupleConstr *) palloc0(sizeof(TupleConstr));

		constr->has_not_null = true;
		relation->rd_att->constr = constr;
	}

	/*
	 * initialize relation id from info in att array (my, this is ugly)
	 */
	RelationGetRelid(relation) = relation->rd_att->attrs[0]->attrelid;
	relation->rd_rel->relfilenode = RelationGetRelid(relation);

	/*
	 * initialize the relation lock manager information
	 */
	RelationInitLockInfo(relation);		/* see lmgr.c */

	/*
	 * initialize physical addressing information for the relation
	 */
	RelationInitPhysicalAddr(relation);

	/*
	 * initialize the rel-has-index flag, using hardwired knowledge
	 */
	if (IsBootstrapProcessingMode())
	{
		/* In bootstrap mode, we have no indexes */
		relation->rd_rel->relhasindex = false;
	}
	else
	{
		/* Otherwise, all the rels formrdesc is used for have indexes */
		relation->rd_rel->relhasindex = true;
	}

	/*
	 * add new reldesc to relcache
	 */
	RelationCacheInsert(relation);

	/* It's fully valid */
	relation->rd_isvalid = true;
}


static void
RelationInitAppendOnlyInfo(Relation relation)
{
	Relation	pg_appendonly_rel;
	HeapTuple	tuple;
	MemoryContext oldcontext;
	SysScanDesc scan;
	ScanKeyData skey;

	/*
	 * Check the pg_appendonly relation to be certain the ao table
	 * is there.
	 */
	pg_appendonly_rel = heap_open(AppendOnlyRelationId, AccessShareLock);

	ScanKeyInit(&skey,
				Anum_pg_appendonly_relid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(relation)));
	/* FIXME: isn't there a mode in relcache code to *not* use an index? Should
	 * we do something here to obey it?
	 */
	scan = systable_beginscan(pg_appendonly_rel, AppendOnlyRelidIndexId, true,
							  SnapshotNow, 1, &skey);

	tuple = systable_getnext(scan);
	if (!tuple)
		elog(ERROR, "could not find pg_appendonly tuple for relation \"%s\"",
			 RelationGetRelationName(relation));

	/*
	 * Make a copy of the pg_appendonly entry for the table.
	 */
	oldcontext = MemoryContextSwitchTo(CacheMemoryContext);
	relation->rd_aotuple = heap_copytuple(tuple);
	relation->rd_appendonly = (Form_pg_appendonly) GETSTRUCT(relation->rd_aotuple);
	MemoryContextSwitchTo(oldcontext);
	systable_endscan(scan);
	heap_close(pg_appendonly_rel, AccessShareLock);

}


/* ----------------------------------------------------------------
 *				 Relation Descriptor Lookup Interface
 * ----------------------------------------------------------------
 */

/*
 *		RelationIdGetRelation
 *
 *		Lookup a reldesc by OID; make one if not already in cache.
 *
 *		Returns NULL if no pg_class row could be found for the given relid
 *		(suggesting we are trying to access a just-deleted relation).
 *		Any other error is reported via elog.
 *
 *		NB: caller should already have at least AccessShareLock on the
 *		relation ID, else there are nasty race conditions.
 *
 *		NB: relation ref count is incremented, or set to 1 if new entry.
 *		Caller should eventually decrement count.  (Usually,
 *		that happens by calling RelationClose().)
 */
Relation
RelationIdGetRelation(Oid relationId)
{
	Relation	rd;

	/*
	 * first try to find reldesc in the cache
	 */
	RelationIdCacheLookup(relationId, rd);

	if (RelationIsValid(rd))
	{
		RelationIncrementReferenceCount(rd);
		/* revalidate cache entry if necessary */
		if (!rd->rd_isvalid)
		{
			/*
			 * Indexes only have a limited number of possible schema changes,
			 * and we don't want to use the full-blown procedure because it's
			 * a headache for indexes that reload itself depends on.
			 */
			if (rd->rd_rel->relkind == RELKIND_INDEX)
				RelationReloadIndexInfo(rd);
			else
				RelationClearRelation(rd, true);
		}
		return rd;
	}

	/*
	 * no reldesc in the cache, so have RelationBuildDesc() build one and add
	 * it.
	 */
	rd = RelationBuildDesc(relationId, true);
	if (RelationIsValid(rd))
		RelationIncrementReferenceCount(rd);

	return rd;
}

/* ----------------------------------------------------------------
 *				cache invalidation support routines
 * ----------------------------------------------------------------
 */

/*
 * RelationIncrementReferenceCount
 *		Increments relation reference count.
 *
 * Note: bootstrap mode has its own weird ideas about relation refcount
 * behavior; we ought to fix it someday, but for now, just disable
 * reference count ownership tracking in bootstrap mode.
 */
void
RelationIncrementReferenceCount(Relation rel)
{
	ResourceOwnerEnlargeRelationRefs(CurrentResourceOwner);
	rel->rd_refcnt += 1;
	if (!IsBootstrapProcessingMode())
		ResourceOwnerRememberRelationRef(CurrentResourceOwner, rel);
}

/*
 * RelationDecrementReferenceCount
 *		Decrements relation reference count.
 */
void
RelationDecrementReferenceCount(Relation rel)
{
	if (rel->rd_refcnt <= 0)
	{
		elog(ERROR,
			 "Relation decrement reference count found relation %u/%u/%u with bad count (reference count %d)",
			 rel->rd_node.spcNode,
			 rel->rd_node.dbNode,
			 rel->rd_node.relNode,
			 rel->rd_refcnt);
	}
	
	rel->rd_refcnt -= 1;
	if (!IsBootstrapProcessingMode())
		ResourceOwnerForgetRelationRef(CurrentResourceOwner, rel);
}

/*
 * RelationClose - close an open relation
 *
 *	Actually, we just decrement the refcount.
 *
 *	NOTE: if compiled with -DRELCACHE_FORCE_RELEASE then relcache entries
 *	will be freed as soon as their refcount goes to zero.  In combination
 *	with aset.c's CLOBBER_FREED_MEMORY option, this provides a good test
 *	to catch references to already-released relcache entries.  It slows
 *	things down quite a bit, however.
 */
void
RelationClose(Relation relation)
{
	/* Note: no locking manipulations needed */
	RelationDecrementReferenceCount(relation);

#ifdef RELCACHE_FORCE_RELEASE
	if (RelationHasReferenceCountZero(relation) &&
		relation->rd_createSubid == InvalidSubTransactionId &&
		relation->rd_newRelfilenodeSubid == InvalidSubTransactionId)
		RelationClearRelation(relation, false);
#endif
}

/*
 * RelationReloadIndexInfo - reload minimal information for an open index
 *
 *	This function is used only for indexes.  A relcache inval on an index
 *	can mean that its pg_class or pg_index row changed.  There are only
 *	very limited changes that are allowed to an existing index's schema,
 *	so we can update the relcache entry without a complete rebuild; which
 *	is fortunate because we can't rebuild an index entry that is "nailed"
 *	and/or in active use.  We support full replacement of the pg_class row,
 *	as well as updates of a few simple fields of the pg_index row.
 *
 *	We can't necessarily reread the catalog rows right away; we might be
 *	in a failed transaction when we receive the SI notification.  If so,
 *	RelationClearRelation just marks the entry as invalid by setting
 *	rd_isvalid to false.  This routine is called to fix the entry when it
 *	is next needed.
 *
 *	We assume that at the time we are called, we have at least AccessShareLock
 *	on the target index.  (Note: in the calls from RelationClearRelation,
 *	this is legitimate because we know the rel has positive refcount.)
 *
 *	If the target index is an index on pg_class or pg_index, we'd better have
 *	previously gotten at least AccessShareLock on its underlying catalog,
 *	else we are at risk of deadlock against someone trying to exclusive-lock
 *	the heap and index in that order.  This is ensured in current usage by
 *	only applying this to indexes being opened or having positive refcount.
 */
static void
RelationReloadIndexInfo(Relation relation)
{
	bool		indexOK;
	HeapTuple	pg_class_tuple;
	Form_pg_class relp;

	/* Should be called only for invalidated indexes */
	Assert(relation->rd_rel->relkind == RELKIND_INDEX &&
		   !relation->rd_isvalid);
	/* Should be closed at smgr level */
	Assert(relation->rd_smgr == NULL);

	/* Make sure targblock is reset in case rel was truncated */
	relation->rd_targblock = InvalidBlockNumber;
	/* Must free any AM cached data, too */
	if (relation->rd_amcache)
		pfree(relation->rd_amcache);
	relation->rd_amcache = NULL;

	/*
	 * If it's a shared index, we might be called before backend startup has
	 * finished selecting a database, in which case we have no way to read
	 * pg_class yet.  However, a shared index can never have any significant
	 * schema updates, so it's okay to ignore the invalidation signal.  Just
	 * mark it valid and return without doing anything more.
	 */
	if (relation->rd_rel->relisshared && !criticalRelcachesBuilt)
	{
		relation->rd_isvalid = true;
		return;
	}

	/*
	 * Read the pg_class row
	 *
	 * Don't try to use an indexscan of pg_class_oid_index to reload the info
	 * for pg_class_oid_index ...
	 */
	indexOK = (RelationGetRelid(relation) != ClassOidIndexId);
	pg_class_tuple = ScanPgRelation(RelationGetRelid(relation), indexOK, NULL);
	if (!HeapTupleIsValid(pg_class_tuple))
		elog(ERROR, "could not find pg_class tuple for index %u",
			 RelationGetRelid(relation));
	relp = (Form_pg_class) GETSTRUCT(pg_class_tuple);
	memcpy(relation->rd_rel, relp, CLASS_TUPLE_SIZE);
	/* Reload reloptions in case they changed */
	if (relation->rd_options)
		pfree(relation->rd_options);
	RelationParseRelOptions(relation, pg_class_tuple);
	/* done with pg_class tuple */
	heap_freetuple(pg_class_tuple);
	/* We must recalculate physical address in case it changed */
	RelationInitPhysicalAddr(relation);

	/* Forget gp_relation_node information -- it may have changed. */
	MemSet(&relation->rd_segfile0_relationnodeinfo, 0, sizeof(RelationNodeInfo));

	/*
	 * For a non-system index, there are fields of the pg_index row that are
	 * allowed to change, so re-read that row and update the relcache entry.
	 * Most of the info derived from pg_index (such as support function lookup
	 * info) cannot change, and indeed the whole point of this routine is to
	 * update the relcache entry without clobbering that data; so wholesale
	 * replacement is not appropriate.
	 */
	if (!IsSystemRelation(relation))
	{
		HeapTuple	tuple;
		Form_pg_index index;

		tuple = SearchSysCache(INDEXRELID,
							   ObjectIdGetDatum(RelationGetRelid(relation)),
							   0, 0, 0);
		if (!HeapTupleIsValid(tuple))
			elog(ERROR, "cache lookup failed for index %u",
				 RelationGetRelid(relation));
		index = (Form_pg_index) GETSTRUCT(tuple);

		/*
		 * Basically, let's just copy all the bool fields.  There are one or
		 * two of these that can't actually change in the current code, but
		 * it's not worth it to track exactly which ones they are.  None of
		 * the array fields are allowed to change, though.
		 */
		relation->rd_index->indisunique = index->indisunique;
		relation->rd_index->indisprimary = index->indisprimary;
		relation->rd_index->indisclustered = index->indisclustered;
		relation->rd_index->indisvalid = index->indisvalid;
		relation->rd_index->indcheckxmin = index->indcheckxmin;
		relation->rd_index->indisready = index->indisready;

		/* Copy xmin too, as that is needed to make sense of indcheckxmin */
		HeapTupleHeaderSetXmin(relation->rd_indextuple->t_data,
							   HeapTupleHeaderGetXmin(tuple->t_data));

		ReleaseSysCache(tuple);
	}

	/* Okay, now it's valid again */
	relation->rd_isvalid = true;
}

/*
 * RelationDestroyRelation
 *
 *	Physically delete a relation cache entry and all subsidiary data.
 *	Caller must already have unhooked the entry from the hash table.
 */
static void
RelationDestroyRelation(Relation relation)
{
	Assert(RelationHasReferenceCountZero(relation));

	/*
	 * Make sure smgr and lower levels close the relation's files, if they
	 * weren't closed already.  (This was probably done by caller, but let's
	 * just be real sure.)
	 */
	RelationCloseSmgr(relation);

	/*
	 * Free all the subsidiary data structures of the relcache entry,
	 * then the entry itself.
	 */
	if (relation->rd_rel)
		pfree(relation->rd_rel);
	/* can't use DecrTupleDescRefCount here */
	Assert(relation->rd_att->tdrefcount > 0);
	if (--relation->rd_att->tdrefcount == 0)
		FreeTupleDesc(relation->rd_att);
	list_free(relation->rd_indexlist);
	bms_free(relation->rd_indexattr);
	FreeTriggerDesc(relation->trigdesc);
	if (relation->rd_options)
		pfree(relation->rd_options);
	if (relation->rd_indextuple)
		pfree(relation->rd_indextuple);
	if (relation->rd_aotuple)
		pfree(relation->rd_aotuple);
	if (relation->rd_am)
		pfree(relation->rd_am);
	if (relation->rd_indexcxt)
		MemoryContextDelete(relation->rd_indexcxt);
	if (relation->rd_rulescxt)
		MemoryContextDelete(relation->rd_rulescxt);
	if (relation->rd_cdbpolicy)
		pfree(relation->rd_cdbpolicy);

	pfree(relation);
}

/*
 * RelationClearRelation
 *
 *	 Physically blow away a relation cache entry, or reset it and rebuild
 *	 it from scratch (that is, from catalog entries).  The latter path is
 *	 used when we are notified of a change to an open relation (one with
 *	 refcount > 0).
 *
 *	 NB: when rebuilding, we'd better hold some lock on the relation,
 *	 else the catalog data we need to read could be changing under us.
 *	 Also, a rel to be rebuilt had better have refcnt > 0.  This is because
 *	 an sinval reset could happen while we're accessing the catalogs, and
 *	 the rel would get blown away underneath us by RelationCacheInvalidate
 *	 if it has zero refcnt.
 *
 *	 The "rebuild" parameter is redundant in current usage because it has
 *	 to match the relation's refcnt status, but we keep it as a crosscheck
 *	 that we're doing what the caller expects.
 */
static void
RelationClearRelation(Relation relation, bool rebuild)
{
	/*
	 * As per notes above, a rel to be rebuilt MUST have refcnt > 0; while
	 * of course it would be a bad idea to blow away one with nonzero refcnt.
	 */
	Assert(rebuild ?
		   !RelationHasReferenceCountZero(relation) :
		   RelationHasReferenceCountZero(relation));

	/*
	 * Make sure smgr and lower levels close the relation's files, if they
	 * weren't closed already.  If the relation is not getting deleted, the
	 * next smgr access should reopen the files automatically.	This ensures
	 * that the low-level file access state is updated after, say, a vacuum
	 * truncation.
	 */
	RelationCloseSmgr(relation);

	/*
	 * Never, never ever blow away a nailed-in system relation, because we'd
	 * be unable to recover.  However, we must reset rd_targblock, in case we
	 * got called because of a relation cache flush that was triggered by
	 * VACUUM.  Likewise reset the fsm and vm size info.
	 *
	 * If it's a nailed index, then we need to re-read the pg_class row to see
	 * if its relfilenode changed.	We can't necessarily do that here, because
	 * we might be in a failed transaction.  We assume it's okay to do it if
	 * there are open references to the relcache entry (cf notes for
	 * AtEOXact_RelationCache).  Otherwise just mark the entry as possibly
	 * invalid, and it'll be fixed when next opened.
	 */
	if (relation->rd_isnailed)
	{
		relation->rd_targblock = InvalidBlockNumber;
		if (relation->rd_rel->relkind == RELKIND_INDEX)
		{
			relation->rd_isvalid = false;		/* needs to be revalidated */
			if (relation->rd_refcnt > 1)
				RelationReloadIndexInfo(relation);
		}
		return;
	}

	/*
	 * Even non-system indexes should not be blown away if they are open and
	 * have valid index support information.  This avoids problems with active
	 * use of the index support information.  As with nailed indexes, we
	 * re-read the pg_class row to handle possible physical relocation of the
	 * index, and we check for pg_index updates too.
	 */
	if (relation->rd_rel->relkind == RELKIND_INDEX &&
		relation->rd_refcnt > 0 &&
		relation->rd_indexcxt != NULL)
	{
		relation->rd_isvalid = false;	/* needs to be revalidated */
		RelationReloadIndexInfo(relation);
		return;
	}

	/* Mark it invalid until we've finished rebuild */
	relation->rd_isvalid = false;

	/*
	 * If we're really done with the relcache entry, blow it away. But if
	 * someone is still using it, reconstruct the whole deal without moving
	 * the physical RelationData record (so that the someone's pointer is
	 * still valid).
	 */
	if (!rebuild)
	{
		/* Remove it from the hash table */
		RelationCacheDelete(relation);

		/* And release storage */
		RelationDestroyRelation(relation);
	}
	else
	{
		/*
		 * Our strategy for rebuilding an open relcache entry is to build
		 * a new entry from scratch, swap its contents with the old entry,
		 * and finally delete the new entry (along with any infrastructure
		 * swapped over from the old entry).  This is to avoid trouble in case
		 * an error causes us to lose control partway through.  The old entry
		 * will still be marked !rd_isvalid, so we'll try to rebuild it again
		 * on next access.  Meanwhile it's not any less valid than it was
		 * before, so any code that might expect to continue accessing it
		 * isn't hurt by the rebuild failure.  (Consider for example a
		 * subtransaction that ALTERs a table and then gets cancelled partway
		 * through the cache entry rebuild.  The outer transaction should
		 * still see the not-modified cache entry as valid.)  The worst
		 * consequence of an error is leaking the necessarily-unreferenced
		 * new entry, and this shouldn't happen often enough for that to be
		 * a big problem.
		 *
		 * When rebuilding an open relcache entry, we must preserve ref count
		 * and rd_createSubid/rd_newRelfilenodeSubid state.  Also attempt to
		 * preserve the pg_class entry (rd_rel), tupledesc, and rewrite-rule
		 * substructures in place, because various places assume that these
		 * structures won't move while they are working with an open relcache
		 * entry.  (Note: the refcount mechanism for tupledescs might someday
		 * allow us to remove this hack for the tupledesc.)
 		 *
 		 * Note that this process does not touch CurrentResourceOwner; which
 		 * is good because whatever ref counts the entry may have do not
 		 * necessarily belong to that resource owner.
 		 */
		Relation	newrel;
 		Oid			save_relid = RelationGetRelid(relation);
		bool		keep_tupdesc;
		bool		keep_rules;
		bool		keep_pt_info;

		/* Build temporary entry, but don't link it into hashtable */
		newrel = RelationBuildDesc(save_relid, false);
		if (newrel == NULL)
 		{
 			/* Should only get here if relation was deleted */
			RelationCacheDelete(relation);
			RelationDestroyRelation(relation);
 			elog(ERROR, "relation %u deleted while still in use", save_relid);
 		}
 
		keep_tupdesc = equalTupleDescs(relation->rd_att, newrel->rd_att, true);
		keep_rules = equalRuleLocks(relation->rd_rules, newrel->rd_rules);
		keep_pt_info = (relation->rd_rel->relfilenode ==
						newrel->rd_rel->relfilenode);

		/*
		 * Perform swapping of the relcache entry contents.  Within this
		 * process the old entry is momentarily invalid, so there *must*
		 * be no possibility of CHECK_FOR_INTERRUPTS within this sequence.
		 * Do it in all-in-line code for safety.
		 *
		 * Since the vast majority of fields should be swapped, our method
		 * is to swap the whole structures and then re-swap those few fields
		 * we didn't want swapped.
		 */
#define SWAPFIELD(fldtype, fldname) \
		do { \
			fldtype _tmp = newrel->fldname; \
			newrel->fldname = relation->fldname; \
			relation->fldname = _tmp; \
		} while (0)

		/* swap all Relation struct fields */
 		{
			RelationData tmpstruct;

			memcpy(&tmpstruct, newrel, sizeof(RelationData));
			memcpy(newrel, relation, sizeof(RelationData));
			memcpy(relation, &tmpstruct, sizeof(RelationData));
		}

		/* rd_smgr must not be swapped, due to back-links from smgr level */
		SWAPFIELD(SMgrRelation, rd_smgr);
		/* rd_refcnt must be preserved */
		SWAPFIELD(int, rd_refcnt);
		/* isnailed shouldn't change */
		Assert(newrel->rd_isnailed == relation->rd_isnailed);
		/* creation sub-XIDs must be preserved */
		SWAPFIELD(SubTransactionId, rd_createSubid);
		SWAPFIELD(SubTransactionId, rd_newRelfilenodeSubid);
		/* un-swap rd_rel pointers, swap contents instead */
		SWAPFIELD(Form_pg_class, rd_rel);
		/* ... but actually, we don't have to update newrel->rd_rel */
		memcpy(relation->rd_rel, newrel->rd_rel, CLASS_TUPLE_SIZE);
		/* preserve old tupledesc and rules if no logical change */
		if (keep_tupdesc)
			SWAPFIELD(TupleDesc, rd_att);
		if (keep_rules)
 		{
			SWAPFIELD(RuleLock *, rd_rules);
			SWAPFIELD(MemoryContext, rd_rulescxt);
 		}
		/* pgstat_info must be preserved */
		SWAPFIELD(struct PgStat_TableStatus *, pgstat_info);

		/* preserve persistent table information for the relation  */
		if (keep_pt_info)
			SWAPFIELD(struct RelationNodeInfo, rd_segfile0_relationnodeinfo);

#undef SWAPFIELD

		/* And now we can throw away the temporary entry */
		RelationDestroyRelation(newrel);
	}
}

/*
 * RelationFlushRelation
 *
 *	 Rebuild the relation if it is open (refcount > 0), else blow it away.
 */
static void
RelationFlushRelation(Relation relation)
{
	if (relation->rd_createSubid != InvalidSubTransactionId ||
		relation->rd_newRelfilenodeSubid != InvalidSubTransactionId)
	{
		/*
		 * New relcache entries are always rebuilt, not flushed; else we'd
		 * forget the "new" status of the relation, which is a useful
		 * optimization to have.  Ditto for the new-relfilenode status.
		 *
		 * The rel could have zero refcnt here, so temporarily increment
		 * the refcnt to ensure it's safe to rebuild it.  We can assume that
		 * the current transaction has some lock on the rel already.
		 */
		RelationIncrementReferenceCount(relation);
		RelationClearRelation(relation, true);
		RelationDecrementReferenceCount(relation);
	}
	else
	{
		/*
		 * Pre-existing rels can be dropped from the relcache if not open.
		 */
		bool	rebuild = !RelationHasReferenceCountZero(relation);

		RelationClearRelation(relation, rebuild);
	}
}

/*
 * RelationForgetRelation - unconditionally remove a relcache entry
 *
 *		   External interface for destroying a relcache entry when we
 *		   drop the relation.
 */
void
RelationForgetRelation(Oid rid)
{
	Relation	relation;

	RelationIdCacheLookup(rid, relation);

	if (!PointerIsValid(relation))
		return;					/* not in cache, nothing to do */

	if (!RelationHasReferenceCountZero(relation))
		elog(ERROR, "relation %u is still open", rid);

	/* Unconditionally destroy the relcache entry */
	RelationClearRelation(relation, false);
}

/*
 *		RelationCacheInvalidateEntry
 *
 *		This routine is invoked for SI cache flush messages.
 *
 * Any relcache entry matching the relid must be flushed.  (Note: caller has
 * already determined that the relid belongs to our database or is a shared
 * relation.)
 *
 * We used to skip local relations, on the grounds that they could
 * not be targets of cross-backend SI update messages; but it seems
 * safer to process them, so that our *own* SI update messages will
 * have the same effects during CommandCounterIncrement for both
 * local and nonlocal relations.
 */
void
RelationCacheInvalidateEntry(Oid relationId)
{
	Relation	relation;

	RelationIdCacheLookup(relationId, relation);

	if (PointerIsValid(relation))
	{
		relcacheInvalsReceived++;
		RelationFlushRelation(relation);
	}
}

/*
 * RelationCacheInvalidate
 *	 Blow away cached relation descriptors that have zero reference counts,
 *	 and rebuild those with positive reference counts.	Also reset the smgr
 *	 relation cache.
 *
 *	 This is currently used only to recover from SI message buffer overflow,
 *	 so we do not touch new-in-transaction relations; they cannot be targets
 *	 of cross-backend SI updates (and our own updates now go through a
 *	 separate linked list that isn't limited by the SI message buffer size).
 *	 Likewise, we need not discard new-relfilenode-in-transaction hints,
 *	 since any invalidation of those would be a local event.
 *
 *	 We do this in two phases: the first pass deletes deletable items, and
 *	 the second one rebuilds the rebuildable items.  This is essential for
 *	 safety, because hash_seq_search only copes with concurrent deletion of
 *	 the element it is currently visiting.	If a second SI overflow were to
 *	 occur while we are walking the table, resulting in recursive entry to
 *	 this routine, we could crash because the inner invocation blows away
 *	 the entry next to be visited by the outer scan.  But this way is OK,
 *	 because (a) during the first pass we won't process any more SI messages,
 *	 so hash_seq_search will complete safely; (b) during the second pass we
 *	 only hold onto pointers to nondeletable entries.
 *
 *	 The two-phase approach also makes it easy to ensure that we process
 *	 nailed-in-cache indexes before other nondeletable items, and that we
 *	 process pg_class_oid_index first of all.  In scenarios where a nailed
 *	 index has been given a new relfilenode, we have to detect that update
 *	 before the nailed index is used in reloading any other relcache entry.
 */
void
RelationCacheInvalidate(void)
{
	HASH_SEQ_STATUS status;
	RelIdCacheEnt *idhentry;
	Relation	relation;
	List	   *rebuildFirstList = NIL;
	List	   *rebuildList = NIL;
	ListCell   *l;

	/* Phase 1 */
	hash_seq_init(&status, RelationIdCache);

	while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
	{
		relation = idhentry->reldesc;

		/* Must close all smgr references to avoid leaving dangling ptrs */
		RelationCloseSmgr(relation);

		/* Ignore new relations, since they are never SI targets */
		if (relation->rd_createSubid != InvalidSubTransactionId)
			continue;

		relcacheInvalsReceived++;

		if (RelationHasReferenceCountZero(relation))
		{
			/* Delete this entry immediately */
			Assert(!relation->rd_isnailed);
			RelationClearRelation(relation, false);
		}
		else
		{
			/*
			 * Add this entry to list of stuff to rebuild in second pass.
			 * pg_class_oid_index goes on the front of rebuildFirstList, other
			 * nailed indexes on the back, and everything else into
			 * rebuildList (in no particular order).
			 */
			if (relation->rd_isnailed &&
				relation->rd_rel->relkind == RELKIND_INDEX)
			{
				if (RelationGetRelid(relation) == ClassOidIndexId)
					rebuildFirstList = lcons(relation, rebuildFirstList);
				else
					rebuildFirstList = lappend(rebuildFirstList, relation);
			}
			else
				rebuildList = lcons(relation, rebuildList);
		}
	}

	/*
	 * Now zap any remaining smgr cache entries.  This must happen before we
	 * start to rebuild entries, since that may involve catalog fetches which
	 * will re-open catalog files.
	 */
	smgrcloseall();

	/* Phase 2: rebuild the items found to need rebuild in phase 1 */
	foreach(l, rebuildFirstList)
	{
		relation = (Relation) lfirst(l);
		RelationClearRelation(relation, true);
	}
	list_free(rebuildFirstList);
	foreach(l, rebuildList)
	{
		relation = (Relation) lfirst(l);
		RelationClearRelation(relation, true);
	}
	list_free(rebuildList);
}

/*
 * AtEOXact_RelationCache
 *
 *	Clean up the relcache at main-transaction commit or abort.
 *
 * Note: this must be called *before* processing invalidation messages.
 * In the case of abort, we don't want to try to rebuild any invalidated
 * cache entries (since we can't safely do database accesses).  Therefore
 * we must reset refcnts before handling pending invalidations.
 *
 * As of PostgreSQL 8.1, relcache refcnts should get released by the
 * ResourceOwner mechanism.  This routine just does a debugging
 * cross-check that no pins remain.  However, we also need to do special
 * cleanup when the current transaction created any relations or made use
 * of forced index lists.
 */
void
AtEOXact_RelationCache(bool isCommit)
{
	HASH_SEQ_STATUS status;
	RelIdCacheEnt *idhentry;

	/*
	 * To speed up transaction exit, we want to avoid scanning the relcache
	 * unless there is actually something for this routine to do.  Other than
	 * the debug-only Assert checks, most transactions don't create any work
	 * for us to do here, so we keep a static flag that gets set if there is
	 * anything to do.	(Currently, this means either a relation is created in
	 * the current xact, or one is given a new relfilenode, or an index list
	 * is forced.)  For simplicity, the flag remains set till end of top-level
	 * transaction, even though we could clear it at subtransaction end in
	 * some cases.
	 *
	 * MPP-3333: READERS need to *always* scan, otherwise they will not be able
	 * to maintain a coherent view of the storage layer.
	 */
	if (!need_eoxact_work
		&& DistributedTransactionContext != DTX_CONTEXT_QE_READER
#ifdef USE_ASSERT_CHECKING
		&& !assert_enabled
#endif
		)
		return;

	hash_seq_init(&status, RelationIdCache);

	while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
	{
		Relation	relation = idhentry->reldesc;

		/*
		 * The relcache entry's ref count should be back to its normal
		 * not-in-a-transaction state: 0 unless it's nailed in cache.
		 *
		 * In bootstrap mode, this is NOT true, so don't check it --- the
		 * bootstrap code expects relations to stay open across start/commit
		 * transaction calls.  (That seems bogus, but it's not worth fixing.)
		 */
#ifdef USE_ASSERT_CHECKING
		if (!IsBootstrapProcessingMode())
		{
			int			expected_refcnt;

			expected_refcnt = relation->rd_isnailed ? 1 : 0;
			Assert(relation->rd_refcnt == expected_refcnt);
		}
#endif

		/*
		 * QE-readers aren't properly enrolled in transactions, they
		 * just get the snapshot which corresponds -- so here, where
		 * we are maintaining their relcache, we want to just clean
		 * up (almost as if we had aborted). (MPP-3338)
		 */
		if (DistributedTransactionContext == DTX_CONTEXT_QE_ENTRY_DB_SINGLETON ||
			DistributedTransactionContext == DTX_CONTEXT_QE_READER)
		{
			RelationClearRelation(relation, relation->rd_isnailed ? true : false);
			continue;
		}

		/*
		 * Is it a relation created in the current transaction?
		 *
		 * During commit, reset the flag to zero, since we are now out of the
		 * creating transaction.  During abort, simply delete the relcache
		 * entry --- it isn't interesting any longer.  (NOTE: if we have
		 * forgotten the new-ness of a new relation due to a forced cache
		 * flush, the entry will get deleted anyway by shared-cache-inval
		 * processing of the aborted pg_class insertion.)
		 */
		if (relation->rd_createSubid != InvalidSubTransactionId)
		{
			if (isCommit)
				relation->rd_createSubid = InvalidSubTransactionId;
			else
			{
				/*
				 * In abort, delete the error log file before forgetting
				 * this relation.
				 */
				ErrorLogDelete(MyDatabaseId, RelationGetRelid(relation));
				RelationClearRelation(relation, false);
				continue;
			}
		}

		/*
		 * Likewise, reset the hint about the relfilenode being new.
		 */
		relation->rd_newRelfilenodeSubid = InvalidSubTransactionId;

		/*
		 * Flush any temporary index list.
		 */
		if (relation->rd_indexvalid == 2)
		{
			list_free(relation->rd_indexlist);
			relation->rd_indexlist = NIL;
			relation->rd_oidindex = InvalidOid;
			relation->rd_indexvalid = 0;
		}
	}

	/* Once done with the transaction, we can reset need_eoxact_work */
	need_eoxact_work = false;
}

/*
 * AtEOSubXact_RelationCache
 *
 *	Clean up the relcache at sub-transaction commit or abort.
 *
 * Note: this must be called *before* processing invalidation messages.
 */
void
AtEOSubXact_RelationCache(bool isCommit, SubTransactionId mySubid,
						  SubTransactionId parentSubid)
{
	HASH_SEQ_STATUS status;
	RelIdCacheEnt *idhentry;

	/*
	 * Skip the relcache scan if nothing to do --- see notes for
	 * AtEOXact_RelationCache.
	 */
	if (!need_eoxact_work &&
		DistributedTransactionContext != DTX_CONTEXT_QE_READER)
		return;

	hash_seq_init(&status, RelationIdCache);

	while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
	{
		Relation	relation = idhentry->reldesc;

		/*
		 * As opposed to AtEOXact_RelationCache, subtransactions
		 * in readers are only caused by internal commands, and
		 * there shouldn't be interaction with global transactions,
		 * (reader gangs commit their transaction independently)
		 * we must not clear the relcache here.
		 */

		/*
		 * Is it a relation created in the current subtransaction?
		 *
		 * During subcommit, mark it as belonging to the parent, instead.
		 * During subabort, simply delete the relcache entry.
		 */
		if (relation->rd_createSubid == mySubid)
		{
			if (isCommit)
				relation->rd_createSubid = parentSubid;
			else if (RelationHasReferenceCountZero(relation))
			{
				/*
				 * In abort, delete the error log file before forgetting
				 * this relation.
				 */
				ErrorLogDelete(MyDatabaseId, RelationGetRelid(relation));

				RelationClearRelation(relation, false);
				continue;
			}
			else
			{
				/*
				 * Hmm, somewhere there's a (leaked?) reference to the
				 * relation.  We daren't remove the entry for fear of
				 * dereferencing a dangling pointer later.  Bleat, and mark it
				 * as not belonging to the current transaction.  Hopefully
				 * it'll get cleaned up eventually.  This must be just a
				 * WARNING to avoid error-during-error-recovery loops.
				 */
				relation->rd_createSubid = InvalidSubTransactionId;
				elog(WARNING, "cannot remove relcache entry for \"%s\" because it has nonzero refcount",
					 RelationGetRelationName(relation));
			}
		}

		/*
		 * Likewise, update or drop any new-relfilenode-in-subtransaction
		 * hint.
		 */
		if (relation->rd_newRelfilenodeSubid == mySubid)
		{
			if (isCommit)
				relation->rd_newRelfilenodeSubid = parentSubid;
			else
				relation->rd_newRelfilenodeSubid = InvalidSubTransactionId;
		}

		/*
		 * Flush any temporary index list.
		 */
		if (relation->rd_indexvalid == 2)
		{
			list_free(relation->rd_indexlist);
			relation->rd_indexlist = NIL;
			relation->rd_oidindex = InvalidOid;
			relation->rd_indexvalid = 0;
		}
	}
}

/*
 * RelationCacheMarkNewRelfilenode
 *
 *	Mark the rel as having been given a new relfilenode in the current
 *	(sub) transaction.	This is a hint that can be used to optimize
 *	later operations on the rel in the same transaction.
 */
void
RelationCacheMarkNewRelfilenode(Relation rel)
{
	/* Mark it... */
	rel->rd_newRelfilenodeSubid = GetCurrentSubTransactionId();
	/* ... and now we have eoxact cleanup work to do */
	need_eoxact_work = true;
}


/*
 *		RelationBuildLocalRelation
 *			Build a relcache entry for an about-to-be-created relation,
 *			and enter it into the relcache.
 */
Relation
RelationBuildLocalRelation(const char *relname,
						   Oid relnamespace,
						   TupleDesc tupDesc,
						   Oid relid,
						   Oid reltablespace,
			               char relkind,            /*CDB*/
						   bool shared_relation)
{
	Relation	rel;
	MemoryContext oldcxt;
	int			natts = tupDesc->natts;
	int			i;
	bool		has_not_null;
	bool		nailit;
	Oid			relfilenode;

	AssertArg(natts >= 0);

	/*
	 * check for creation of a rel that must be nailed in cache.
	 *
	 * XXX this list had better match the relations specially handled in
	 * RelationCacheInitializePhase2/3.
	 */
	switch (relid)
	{
		case DatabaseRelationId:
		case AuthIdRelationId:
		case AuthMemRelationId:
		case RelationRelationId:
		case AttributeRelationId:
		case ProcedureRelationId:
		case TypeRelationId:
			nailit = true;
			break;
		default:
			nailit = false;
			break;
	}

	/*
	 * check that hardwired list of shared rels matches what's in the
	 * bootstrap .bki file.  If you get a failure here during initdb, you
	 * probably need to fix IsSharedRelation() to match whatever you've done
	 * to the set of shared relations.
	 */
	if (shared_relation != IsSharedRelation(relid))
		elog(ERROR, "shared_relation flag for \"%s\" does not match IsSharedRelation(%u)",
			 relname, relid);

	/*
	 * switch to the cache context to create the relcache entry.
	 */
	if (!CacheMemoryContext)
		CreateCacheMemoryContext();

	oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

	/*
	 * allocate a new relation descriptor and fill in basic state fields.
	 */
	rel = (Relation) palloc0(sizeof(RelationData));

	rel->rd_targblock = InvalidBlockNumber;

	/* make sure relation is marked as having no open file yet */
	rel->rd_smgr = NULL;

	/* mark it nailed if appropriate */
	rel->rd_isnailed = nailit;

	rel->rd_refcnt = nailit ? 1 : 0;

	/* it's being created in this transaction */
	rel->rd_createSubid = GetCurrentSubTransactionId();
	rel->rd_newRelfilenodeSubid = InvalidSubTransactionId;

	/* must flag that we have rels created in this transaction */
	need_eoxact_work = true;

	/* is it a temporary relation? */
	rel->rd_istemp = isTempOrToastNamespace(relnamespace);

	/* is it a system catalog? */
	rel->rd_issyscat = (strncmp(relname, "pg_", 3) == 0);

	/*
	 * CDB: On QEs, temp relations must use shared buffer cache so data
	 * will be visible to all segmates.  On QD, sequence objects must
	 * use shared buffer cache so data will be visible to sequence server.
	 */
	if (rel->rd_istemp &&
		relkind != RELKIND_SEQUENCE &&
		Gp_role != GP_ROLE_EXECUTE)
		rel->rd_isLocalBuf = true;
	else
		rel->rd_isLocalBuf = false;

	/*
	 * create a new tuple descriptor from the one passed in.  We do this
	 * partly to copy it into the cache context, and partly because the new
	 * relation can't have any defaults or constraints yet; they have to be
	 * added in later steps, because they require additions to multiple system
	 * catalogs.  We can copy attnotnull constraints here, however.
	 */
	rel->rd_att = CreateTupleDescCopy(tupDesc);
	rel->rd_att->tdrefcount = 1;	/* mark as refcounted */
	has_not_null = false;
	for (i = 0; i < natts; i++)
	{
		rel->rd_att->attrs[i]->attnotnull = tupDesc->attrs[i]->attnotnull;
		has_not_null |= tupDesc->attrs[i]->attnotnull;
	}

	if (has_not_null)
	{
		TupleConstr *constr = (TupleConstr *) palloc0(sizeof(TupleConstr));

		constr->has_not_null = true;
		rel->rd_att->constr = constr;
	}

	/*
	 * initialize relation tuple form (caller may add/override data later)
	 */
	rel->rd_rel = (Form_pg_class) palloc0(CLASS_TUPLE_SIZE);

	namestrcpy(&rel->rd_rel->relname, relname);
	rel->rd_rel->relnamespace = relnamespace;

	rel->rd_rel->relkind = RELKIND_UNCATALOGED;
	rel->rd_rel->relstorage = RELSTORAGE_HEAP;
	rel->rd_rel->relhasoids = rel->rd_att->tdhasoid;
	rel->rd_rel->relnatts = natts;
	rel->rd_rel->reltype = InvalidOid;
	/* needed when bootstrapping: */
	rel->rd_rel->relowner = BOOTSTRAP_SUPERUSERID;

	/*
	 * Create zeroed-out gp_relation_node data.  It will be filled in when the
	 * disk file is created.
	 */
	rel->rd_segfile0_relationnodeinfo.isPresent = false;
	rel->rd_segfile0_relationnodeinfo.tidAllowedToBeZero = false;

	/*
	 * Insert relation physical and logical identifiers (OIDs) into the right
	 * places.
	 *
	 * In PostgreSQL, the physical ID (relfilenode) is initially the same
	 * as the logical ID (OID). In GPDB, the table's logical OID is allocated
	 * in the master, and might already be in use as a relfilenode of an
	 * existing relation in a segment.
	 */
	rel->rd_rel->relisshared = shared_relation;

	RelationGetRelid(rel) = relid;

	for (i = 0; i < natts; i++)
		rel->rd_att->attrs[i]->attrelid = relid;

	if (Gp_role != GP_ROLE_EXECUTE ||
		CheckNewRelFileNodeIsOk(relid, reltablespace, shared_relation))
	{
		relfilenode = relid;
	}
	else
	{
		/* FIXME: should we pass pg_class here? */
		relfilenode = GetNewRelFileNode(reltablespace, shared_relation, NULL);
	}
	rel->rd_rel->relfilenode = relfilenode;

	rel->rd_rel->reltablespace = reltablespace;

	RelationInitLockInfo(rel);	/* see lmgr.c */

	RelationInitPhysicalAddr(rel);

	/*
	 * Okay to insert into the relcache hash tables.
	 */
	RelationCacheInsert(rel);

	/*
	 * done building relcache entry.
	 */
	MemoryContextSwitchTo(oldcxt);

	/* It's fully valid */
	rel->rd_isvalid = true;

	/*
	 * Caller expects us to pin the returned entry.
	 */
	RelationIncrementReferenceCount(rel);

	return rel;
}

/*
 *		RelationCacheInitialize
 *
 *		This initializes the relation descriptor cache.  At the time
 *		that this is invoked, we can't do database access yet (mainly
 *		because the transaction subsystem is not up); all we are doing
 *		is making an empty cache hashtable.  This must be done before
 *		starting the initialization transaction, because otherwise
 *		AtEOXact_RelationCache would crash if that transaction aborts
 *		before we can get the relcache set up.
 */

#define INITRELCACHESIZE		400

void
RelationCacheInitialize(void)
{
	MemoryContext oldcxt;
	HASHCTL		ctl;

	/*
	 * make sure cache memory context exists
	 */
	if (!CacheMemoryContext)
		CreateCacheMemoryContext();

    /*
	 * switch to cache memory context
	 */
	oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

	/*
	 * create hashtable that indexes the relcache
	 */
	MemSet(&ctl, 0, sizeof(ctl));
	ctl.keysize = sizeof(Oid);
	ctl.entrysize = sizeof(RelIdCacheEnt);
	ctl.hash = oid_hash;
	RelationIdCache = hash_create("Relcache by OID", INITRELCACHESIZE,
								  &ctl, HASH_ELEM | HASH_FUNCTION);

	MemoryContextSwitchTo(oldcxt);
}

/*
 *		RelationCacheInitializePhase2
 *
 *		This is called to prepare for access to shared catalogs during startup.
 *		We must at least set up nailed reldescs for pg_database, pg_authid,
 *		and pg_auth_members.  Ideally we'd like to have reldescs for their
 *		indexes, too.  We attempt to load this information from the shared
 *		relcache init file.  If that's missing or broken, just make phony
 *		entries for the catalogs themselves.  RelationCacheInitializePhase3
 *		will clean up as needed.
 */
void
RelationCacheInitializePhase2(void)
{
	MemoryContext oldcxt;

	/*
	 * In bootstrap mode, the shared catalogs aren't there yet anyway, so do
	 * nothing.
	 */
	if (IsBootstrapProcessingMode())
		return;

	/*
	 * switch to cache memory context
	 */
	oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

	/*
	 * Try to load the shared relcache cache file.	If unsuccessful, bootstrap
	 * the cache with pre-made descriptors for the critical shared catalogs.
	 */
	if (!load_relcache_init_file(true))
	{
		formrdesc("pg_database", PG_DATABASE_RELTYPE_OID, true,
				  true, Natts_pg_database, Desc_pg_database);
		formrdesc("pg_authid", PG_AUTHID_RELTYPE_OID, true,
				  true, Natts_pg_authid, Desc_pg_authid);
		formrdesc("pg_auth_members", PG_AUTH_MEMBERS_RELTYPE_OID, true,
				  false, Natts_pg_auth_members, Desc_pg_auth_members);

#define NUM_CRITICAL_SHARED_RELS	3	/* fix if you change list above */
	}

	MemoryContextSwitchTo(oldcxt);
}

/*
 *		RelationCacheInitializePhase3
 *
 *		This is called as soon as the catcache and transaction system
 *		are functional and we have determined MyDatabaseId.  At this point
 *		we can actually read data from the database's system catalogs.
 *		We first try to read pre-computed relcache entries from the local
 *		relcache init file.  If that's missing or broken, make phony entries
 *		for the minimum set of nailed-in-cache relations.  Then (unless
 *		bootstrapping) make sure we have entries for the critical system
 *		indexes.  Once we've done all this, we have enough infrastructure to
 *		open any system catalog or use any catcache.  The last step is to
 *		rewrite the cache files if needed.
 */
void
RelationCacheInitializePhase3(void)
{
	HASH_SEQ_STATUS status;
	RelIdCacheEnt *idhentry;
	MemoryContext oldcxt;
	bool		needNewCacheFile = !criticalSharedRelcachesBuilt;

	/*
	 * switch to cache memory context
	 */
	oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

	/*
	 * Try to load the local relcache cache file.  If unsuccessful, bootstrap
	 * the cache with pre-made descriptors for the critical "nailed-in" system
	 * catalogs.
	 */
	if (IsBootstrapProcessingMode() ||
		!load_relcache_init_file(false))
	{
		needNewCacheFile = true;

		formrdesc("pg_class", PG_CLASS_RELTYPE_OID, false,
				  true, Natts_pg_class, Desc_pg_class);
		formrdesc("pg_attribute", PG_ATTRIBUTE_RELTYPE_OID, false,
				  false, Natts_pg_attribute, Desc_pg_attribute);
		formrdesc("pg_proc", PG_PROC_RELTYPE_OID, false,
				  true, Natts_pg_proc, Desc_pg_proc);
		formrdesc("pg_type", PG_TYPE_RELTYPE_OID, false,
				  true, Natts_pg_type, Desc_pg_type);

#define NUM_CRITICAL_LOCAL_RELS 4		/* fix if you change list above */
	}

	MemoryContextSwitchTo(oldcxt);

	/* In bootstrap mode, the faked-up formrdesc info is all we'll have */
	if (IsBootstrapProcessingMode())
		return;

	/*
	 * If we didn't get the critical system indexes loaded into relcache, do
	 * so now.	These are critical because the catcache and/or opclass cache
	 * depend on them for fetches done during relcache load.  Thus, we have an
	 * infinite-recursion problem.	We can break the recursion by doing
	 * heapscans instead of indexscans at certain key spots. To avoid hobbling
	 * performance, we only want to do that until we have the critical indexes
	 * loaded into relcache.  Thus, the flag criticalRelcachesBuilt is used to
	 * decide whether to do heapscan or indexscan at the key spots, and we set
	 * it true after we've loaded the critical indexes.
	 *
	 * The critical indexes are marked as "nailed in cache", partly to make it
	 * easy for load_relcache_init_file to count them, but mainly because we
	 * cannot flush and rebuild them once we've set criticalRelcachesBuilt to
	 * true.  (NOTE: perhaps it would be possible to reload them by
	 * temporarily setting criticalRelcachesBuilt to false again.  For now,
	 * though, we just nail 'em in.)
	 *
	 * RewriteRelRulenameIndexId and TriggerRelidNameIndexId are not critical
	 * in the same way as the others, because the critical catalogs don't
	 * (currently) have any rules or triggers, and so these indexes can be
	 * rebuilt without inducing recursion.	However they are used during
	 * relcache load when a rel does have rules or triggers, so we choose to
	 * nail them for performance reasons.
	 */
	if (!criticalRelcachesBuilt)
	{
		load_critical_index(ClassOidIndexId,
							RelationRelationId);
		load_critical_index(AttributeRelidNumIndexId,
							AttributeRelationId);
		load_critical_index(IndexRelidIndexId,
							IndexRelationId);
		load_critical_index(AccessMethodStrategyIndexId,
							AccessMethodOperatorRelationId);
		load_critical_index(OpclassOidIndexId,
							OperatorClassRelationId);
		load_critical_index(AccessMethodProcedureIndexId,
							AccessMethodProcedureRelationId);
		load_critical_index(OperatorOidIndexId,
							OperatorRelationId);
		load_critical_index(RewriteRelRulenameIndexId,
							RewriteRelationId);
		load_critical_index(TriggerRelidNameIndexId,
							TriggerRelationId);

#define NUM_CRITICAL_LOCAL_INDEXES	9	/* fix if you change list above */

		criticalRelcachesBuilt = true;
	}

	/*
	 * Process critical shared indexes too.
	 *
	 * DatabaseNameIndexId isn't critical for relcache loading, but rather for
	 * initial lookup of MyDatabaseId, without which we'll never find any
	 * non-shared catalogs at all.	Autovacuum calls InitPostgres with a
	 * database OID, so it instead depends on DatabaseOidIndexId.  We also
	 * need to nail up some indexes on pg_authid and pg_auth_members for use
	 * during client authentication.
	 */
	if (!criticalSharedRelcachesBuilt)
	{
		load_critical_index(DatabaseNameIndexId,
							DatabaseRelationId);
		load_critical_index(DatabaseOidIndexId,
							DatabaseRelationId);
		load_critical_index(AuthIdRolnameIndexId,
							AuthIdRelationId);
		load_critical_index(AuthIdOidIndexId,
							AuthIdRelationId);
		load_critical_index(AuthMemMemRoleIndexId,
							AuthMemRelationId);

#define NUM_CRITICAL_SHARED_INDEXES 5	/* fix if you change list above */

		criticalSharedRelcachesBuilt = true;
	}

	/*
	 * Now, scan all the relcache entries and update anything that might be
	 * wrong in the results from formrdesc or the relcache cache file. If we
	 * faked up relcache entries using formrdesc, then read the real pg_class
	 * rows and replace the fake entries with them. Also, if any of the
	 * relcache entries have rules or triggers, load that info the hard way
	 * since it isn't recorded in the cache file.
	 *
	 * Whenever we access the catalogs to read data, there is a possibility
	 * of a shared-inval cache flush causing relcache entries to be removed.
	 * Since hash_seq_search only guarantees to still work after the *current*
	 * entry is removed, it's unsafe to continue the hashtable scan afterward.
	 * We handle this by restarting the scan from scratch after each access.
	 * This is theoretically O(N^2), but the number of entries that actually
	 * need to be fixed is small enough that it doesn't matter.
	 */
	hash_seq_init(&status, RelationIdCache);

	while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
	{
		Relation	relation = idhentry->reldesc;
		bool		restart = false;

		/*
		 * Make sure *this* entry doesn't get flushed while we work with it.
		 */
		RelationIncrementReferenceCount(relation);

		/*
		 * If it's a faked-up entry, read the real pg_class tuple.
		 */
		if (relation->rd_rel->relowner == InvalidOid)
		{
			HeapTuple	htup;
			Form_pg_class relp;

			htup = SearchSysCache(RELOID,
							   ObjectIdGetDatum(RelationGetRelid(relation)),
								  0, 0, 0);
			if (!HeapTupleIsValid(htup))
				elog(FATAL, "cache lookup failed for relation %u",
					 RelationGetRelid(relation));
			relp = (Form_pg_class) GETSTRUCT(htup);

			/*
			 * Copy tuple to relation->rd_rel. (See notes in
			 * AllocateRelationDesc())
			 */
			memcpy((char *) relation->rd_rel, (char *) relp, CLASS_TUPLE_SIZE);

			/* Update rd_options while we have the tuple */
			if (relation->rd_options)
				pfree(relation->rd_options);
			RelationParseRelOptions(relation, htup);

			/*
			 * Check the values in rd_att were set up correctly.  (We cannot
			 * just copy them over now: formrdesc must have set up the
			 * rd_att data correctly to start with, because it may already
			 * have been copied into one or more catcache entries.)
			 */
			Assert(relation->rd_att->tdtypeid == relp->reltype);
			Assert(relation->rd_att->tdtypmod == -1);
			Assert(relation->rd_att->tdhasoid == relp->relhasoids);

			ReleaseSysCache(htup);

			/* relowner had better be OK now, else we'll loop forever */
			if (relation->rd_rel->relowner == InvalidOid)
				elog(ERROR, "invalid relowner in pg_class entry for \"%s\"",
					 RelationGetRelationName(relation));

			restart = true;
		}

		/*
		 * Fix data that isn't saved in relcache cache file.
		 *
		 * relhasrules or relhastriggers could possibly be wrong or out of
		 * date.  If we don't actually find any rules or triggers, clear the
		 * local copy of the flag so that we don't get into an infinite loop
		 * here.  We don't make any attempt to fix the pg_class entry, though.
		 */
		if (relation->rd_rel->relhasrules && relation->rd_rules == NULL)
		{
			RelationBuildRuleLock(relation);
			if (relation->rd_rules == NULL)
				relation->rd_rel->relhasrules = false;
			restart = true;
		}
		if (relation->rd_rel->reltriggers > 0 && relation->trigdesc == NULL)
		{
			RelationBuildTriggers(relation);
			if (relation->trigdesc == NULL)
				relation->rd_rel->reltriggers = 0;
			restart = true;
		}

		/* Release hold on the relation */
		RelationDecrementReferenceCount(relation);

		/* Now, restart the hashtable scan if needed */
		if (restart)
		{
			hash_seq_term(&status);
			hash_seq_init(&status, RelationIdCache);
		}
	}

	/*
	 * Lastly, write out new relcache cache files if needed.  We don't bother
	 * to distinguish cases where only one of the two needs an update.
	 */
	if (needNewCacheFile)
	{
		/*
		 * Force all the catcaches to finish initializing and thereby open the
		 * catalogs and indexes they use.  This will preload the relcache with
		 * entries for all the most important system catalogs and indexes, so
		 * that the init files will be most useful for future backends.
		 */
		InitCatalogCachePhase2();

		/* reset initFileRelationIds list; we'll fill it during write */
		initFileRelationIds = NIL;

		/* now write the files */
		write_relcache_init_file(true);
		write_relcache_init_file(false);
	}
}

/*
 * Load one critical system index into the relcache
 *
 * indexoid is the OID of the target index, heapoid is the OID of the catalog
 * it belongs to.
 */
static void
load_critical_index(Oid indexoid, Oid heapoid)
{
	Relation	ird;

	/*
	 * We must lock the underlying catalog before locking the index to avoid
	 * deadlock, since RelationBuildDesc might well need to read the catalog,
	 * and if anyone else is exclusive-locking this catalog and index they'll
	 * be doing it in that order.
	 */
	LockRelationOid(heapoid, AccessShareLock);
	LockRelationOid(indexoid, AccessShareLock);
	ird = RelationBuildDesc(indexoid, true);
	if (ird == NULL)
		elog(PANIC, "could not open critical system index %u", indexoid);
	ird->rd_isnailed = true;
	ird->rd_refcnt = 1;
	UnlockRelationOid(indexoid, AccessShareLock);
	UnlockRelationOid(heapoid, AccessShareLock);
}

/*
 * GetPgClassDescriptor -- get a predefined tuple descriptor for pg_class
 * GetPgIndexDescriptor -- get a predefined tuple descriptor for pg_index
 *
 * We need this kluge because we have to be able to access non-fixed-width
 * fields of pg_class and pg_index before we have the standard catalog caches
 * available.  We use predefined data that's set up in just the same way as
 * the bootstrapped reldescs used by formrdesc().  The resulting tupdesc is
 * not 100% kosher: it does not have the correct rowtype OID in tdtypeid, nor
 * does it have a TupleConstr field.  But it's good enough for the purpose of
 * extracting fields.
 */
static TupleDesc
BuildHardcodedDescriptor(int natts, const FormData_pg_attribute *attrs,
						 bool hasoids)
{
	TupleDesc	result;
	MemoryContext oldcxt;
	int			i;

	oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

	result = CreateTemplateTupleDesc(natts, hasoids);
	result->tdtypeid = RECORDOID;		/* not right, but we don't care */
	result->tdtypmod = -1;

	for (i = 0; i < natts; i++)
	{
		memcpy(result->attrs[i], &attrs[i], ATTRIBUTE_FIXED_PART_SIZE);
		/* make sure attcacheoff is valid */
		result->attrs[i]->attcacheoff = -1;
	}

	/* initialize first attribute's attcacheoff, cf RelationBuildTupleDesc */
	result->attrs[0]->attcacheoff = 0;

	/* Note: we don't bother to set up a TupleConstr entry */

	MemoryContextSwitchTo(oldcxt);

	return result;
}

static TupleDesc
GetPgClassDescriptor(void)
{
	static TupleDesc pgclassdesc = NULL;

	/* Already done? */
	if (pgclassdesc == NULL)
		pgclassdesc = BuildHardcodedDescriptor(Natts_pg_class,
											   Desc_pg_class,
											   true);

	return pgclassdesc;
}

static TupleDesc
GetPgIndexDescriptor(void)
{
	static TupleDesc pgindexdesc = NULL;

	/* Already done? */
	if (pgindexdesc == NULL)
		pgindexdesc = BuildHardcodedDescriptor(Natts_pg_index,
											   Desc_pg_index,
											   false);

	return pgindexdesc;
}

/*
 * Load any default attribute value definitions for the relation.
 */
static void
AttrDefaultFetch(Relation relation)
{
	AttrDefault *attrdef = relation->rd_att->constr->defval;
	int			ndef = relation->rd_att->constr->num_defval;
	Relation	adrel;
	SysScanDesc adscan;
	ScanKeyData skey;
	HeapTuple	htup;
	Datum		val;
	bool		isnull;
	int			found;
	int			i;

	ScanKeyInit(&skey,
				Anum_pg_attrdef_adrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(relation)));

	adrel = heap_open(AttrDefaultRelationId, AccessShareLock);
	adscan = systable_beginscan(adrel, AttrDefaultIndexId, true,
								SnapshotNow, 1, &skey);
	found = 0;

	while (HeapTupleIsValid(htup = systable_getnext(adscan)))
	{
		Form_pg_attrdef adform = (Form_pg_attrdef) GETSTRUCT(htup);

		for (i = 0; i < ndef; i++)
		{
			if (adform->adnum != attrdef[i].adnum)
				continue;
			if (attrdef[i].adbin != NULL)
				elog(WARNING, "multiple attrdef records found for attr %s of rel %s",
				NameStr(relation->rd_att->attrs[adform->adnum - 1]->attname),
					 RelationGetRelationName(relation));
			else
				found++;

			val = fastgetattr(htup,
							  Anum_pg_attrdef_adbin,
							  adrel->rd_att, &isnull);
			if (isnull)
				elog(WARNING, "null adbin for attr %s of rel %s",
				NameStr(relation->rd_att->attrs[adform->adnum - 1]->attname),
					 RelationGetRelationName(relation));
			else
				attrdef[i].adbin = MemoryContextStrdup(CacheMemoryContext,
												   TextDatumGetCString(val));
			break;
		}

		if (i >= ndef)
			elog(WARNING, "unexpected attrdef record found for attr %d of rel %s",
				 adform->adnum, RelationGetRelationName(relation));
	}

	systable_endscan(adscan);
	heap_close(adrel, AccessShareLock);

	if (found != ndef)
		elog(WARNING, "%d attrdef record(s) missing for rel %s",
			 ndef - found, RelationGetRelationName(relation));
}

/*
 * Load any check constraints for the relation.
 */
static void
CheckConstraintFetch(Relation relation)
{
	ConstrCheck *check = relation->rd_att->constr->check;
	int			ncheck = relation->rd_att->constr->num_check;
	Relation	conrel;
	SysScanDesc conscan;
	ScanKeyData skey[1];
	HeapTuple	htup;
	Datum		val;
	bool		isnull;
	int			found = 0;

	ScanKeyInit(&skey[0],
				Anum_pg_constraint_conrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(relation)));

	conrel = heap_open(ConstraintRelationId, AccessShareLock);
	conscan = systable_beginscan(conrel, ConstraintRelidIndexId, true,
								 SnapshotNow, 1, skey);

	while (HeapTupleIsValid(htup = systable_getnext(conscan)))
	{
		Form_pg_constraint conform = (Form_pg_constraint) GETSTRUCT(htup);

		/* We want check constraints only */
		if (conform->contype != CONSTRAINT_CHECK)
			continue;

		if (found >= ncheck)
			elog(ERROR,
			     "pg_class reports %d constraint record(s) for rel %s, but found extra in pg_constraint",
			     ncheck, RelationGetRelationName(relation));

		check[found].ccname = MemoryContextStrdup(CacheMemoryContext,
												  NameStr(conform->conname));

		/* Grab and test conbin is actually set */
		val = fastgetattr(htup,
						  Anum_pg_constraint_conbin,
						  conrel->rd_att, &isnull);
		if (isnull)
			elog(ERROR, "null conbin for rel %s",
				 RelationGetRelationName(relation));

		check[found].ccbin = MemoryContextStrdup(CacheMemoryContext,
												 TextDatumGetCString(val));
		found++;
	}

	systable_endscan(conscan);
	heap_close(conrel, AccessShareLock);

	if (found != ncheck)
		elog(ERROR,
		     "found %d in pg_constraint, but pg_class reports %d constraint record(s) for rel %s",
		     found, ncheck, RelationGetRelationName(relation));
}


/*
 * RelationGetPartitioningKey -- get GpPolicy struct for distributed relation
 *
 * Returns a copy of the relation's GpPolicy object, palloc'd in
 * the caller's context.  Caller should pfree() it.  If NULL is
 * returned, relation should be accessed locally.
 */
GpPolicy*
RelationGetPartitioningKey(Relation relation)
{
    return GpPolicyCopy(CurrentMemoryContext, relation->rd_cdbpolicy);
}                                       /* RelationGetPartitioningKey */


/*
 * RelationGetIndexList -- get a list of OIDs of indexes on this relation
 *
 * The index list is created only if someone requests it.  We scan pg_index
 * to find relevant indexes, and add the list to the relcache entry so that
 * we won't have to compute it again.  Note that shared cache inval of a
 * relcache entry will delete the old list and set rd_indexvalid to 0,
 * so that we must recompute the index list on next request.  This handles
 * creation or deletion of an index.
 *
 * The returned list is guaranteed to be sorted in order by OID.  This is
 * needed by the executor, since for index types that we obtain exclusive
 * locks on when updating the index, all backends must lock the indexes in
 * the same order or we will get deadlocks (see ExecOpenIndices()).  Any
 * consistent ordering would do, but ordering by OID is easy.
 *
 * Since shared cache inval causes the relcache's copy of the list to go away,
 * we return a copy of the list palloc'd in the caller's context.  The caller
 * may list_free() the returned list after scanning it. This is necessary
 * since the caller will typically be doing syscache lookups on the relevant
 * indexes, and syscache lookup could cause SI messages to be processed!
 *
 * We also update rd_oidindex, which this module treats as effectively part
 * of the index list.  rd_oidindex is valid when rd_indexvalid isn't zero;
 * it is the pg_class OID of a unique index on OID when the relation has one,
 * and InvalidOid if there is no such index.
 */
List *
RelationGetIndexList(Relation relation)
{
	Relation	indrel;
	SysScanDesc indscan;
	ScanKeyData skey;
	HeapTuple	htup;
	List	   *result;
	Oid			oidIndex;
	MemoryContext oldcxt;

	/* Quick exit if we already computed the list. */
	if (relation->rd_indexvalid != 0)
		return list_copy(relation->rd_indexlist);

	/*
	 * We build the list we intend to return (in the caller's context) while
	 * doing the scan.	After successfully completing the scan, we copy that
	 * list into the relcache entry.  This avoids cache-context memory leakage
	 * if we get some sort of error partway through.
	 */
	result = NIL;
	oidIndex = InvalidOid;

	/* Prepare to scan pg_index for entries having indrelid = this rel. */
	ScanKeyInit(&skey,
				Anum_pg_index_indrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(relation)));

	indrel = heap_open(IndexRelationId, AccessShareLock);
	indscan = systable_beginscan(indrel, IndexIndrelidIndexId, true,
								 SnapshotNow, 1, &skey);

	while (HeapTupleIsValid(htup = systable_getnext(indscan)))
	{
		Form_pg_index index = (Form_pg_index) GETSTRUCT(htup);

		/* Add index's OID to result list in the proper order */
		result = insert_ordered_oid(result, index->indexrelid);

		/* Check to see if it is a unique, non-partial btree index on OID */
		if (IndexIsValid(index) &&
			index->indnatts == 1 &&
			index->indisunique &&
			index->indkey.values[0] == ObjectIdAttributeNumber &&
			index->indclass.values[0] == OID_BTREE_OPS_OID &&
			heap_attisnull(htup, Anum_pg_index_indpred))
			oidIndex = index->indexrelid;
	}

	systable_endscan(indscan);
	heap_close(indrel, AccessShareLock);

	/* Now save a copy of the completed list in the relcache entry. */
	oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
	relation->rd_indexlist = list_copy(result);
	relation->rd_oidindex = oidIndex;
	relation->rd_indexvalid = 1;
	MemoryContextSwitchTo(oldcxt);

	return result;
}

/*
 * insert_ordered_oid
 *		Insert a new Oid into a sorted list of Oids, preserving ordering
 *
 * Building the ordered list this way is O(N^2), but with a pretty small
 * constant, so for the number of entries we expect it will probably be
 * faster than trying to apply qsort().  Most tables don't have very many
 * indexes...
 */
static List *
insert_ordered_oid(List *list, Oid datum)
{
	ListCell   *prev;

	/* Does the datum belong at the front? */
	if (list == NIL || datum < linitial_oid(list))
		return lcons_oid(datum, list);
	/* No, so find the entry it belongs after */
	prev = list_head(list);
	for (;;)
	{
		ListCell   *curr = lnext(prev);

		if (curr == NULL || datum < lfirst_oid(curr))
			break;				/* it belongs after 'prev', before 'curr' */

		prev = curr;
	}
	/* Insert datum into list after 'prev' */
	lappend_cell_oid(list, prev, datum);
	return list;
}

/*
 * RelationSetIndexList -- externally force the index list contents
 *
 * This is used to temporarily override what we think the set of valid
 * indexes is (including the presence or absence of an OID index).
 * The forcing will be valid only until transaction commit or abort.
 *
 * This should only be applied to nailed relations, because in a non-nailed
 * relation the hacked index list could be lost at any time due to SI
 * messages.  In practice it is only used on pg_class (see REINDEX).
 *
 * It is up to the caller to make sure the given list is correctly ordered.
 *
 * We deliberately do not change rd_indexattr here: even when operating
 * with a temporary partial index list, HOT-update decisions must be made
 * correctly with respect to the full index set.  It is up to the caller
 * to ensure that a correct rd_indexattr set has been cached before first
 * calling RelationSetIndexList; else a subsequent inquiry might cause a
 * wrong rd_indexattr set to get computed and cached.
 */
void
RelationSetIndexList(Relation relation, List *indexIds, Oid oidIndex)
{
	MemoryContext oldcxt;

	Assert(relation->rd_isnailed);
	/* Copy the list into the cache context (could fail for lack of mem) */
	oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
	indexIds = list_copy(indexIds);
	MemoryContextSwitchTo(oldcxt);
	/* Okay to replace old list */
	list_free(relation->rd_indexlist);
	relation->rd_indexlist = indexIds;
	relation->rd_oidindex = oidIndex;
	relation->rd_indexvalid = 2;	/* mark list as forced */
	/* must flag that we have a forced index list */
	need_eoxact_work = true;
}

/*
 * RelationGetOidIndex -- get the pg_class OID of the relation's OID index
 *
 * Returns InvalidOid if there is no such index.
 */
Oid
RelationGetOidIndex(Relation relation)
{
	List	   *ilist;

	/*
	 * If relation doesn't have OIDs at all, caller is probably confused. (We
	 * could just silently return InvalidOid, but it seems better to throw an
	 * assertion.)
	 */
	Assert(relation->rd_rel->relhasoids);

	if (relation->rd_indexvalid == 0)
	{
		/* RelationGetIndexList does the heavy lifting. */
		ilist = RelationGetIndexList(relation);
		list_free(ilist);
		Assert(relation->rd_indexvalid != 0);
	}

	return relation->rd_oidindex;
}

/*
 * RelationGetIndexExpressions -- get the index expressions for an index
 *
 * We cache the result of transforming pg_index.indexprs into a node tree.
 * If the rel is not an index or has no expressional columns, we return NIL.
 * Otherwise, the returned tree is copied into the caller's memory context.
 * (We don't want to return a pointer to the relcache copy, since it could
 * disappear due to relcache invalidation.)
 */
List *
RelationGetIndexExpressions(Relation relation)
{
	List	   *result;
	Datum		exprsDatum;
	bool		isnull;
	char	   *exprsString;
	MemoryContext oldcxt;

	/* Quick exit if we already computed the result. */
	if (relation->rd_indexprs)
		return (List *) copyObject(relation->rd_indexprs);

	/* Quick exit if there is nothing to do. */
	if (relation->rd_indextuple == NULL ||
		heap_attisnull(relation->rd_indextuple, Anum_pg_index_indexprs))
		return NIL;

	/*
	 * We build the tree we intend to return in the caller's context. After
	 * successfully completing the work, we copy it into the relcache entry.
	 * This avoids problems if we get some sort of error partway through.
	 */
	exprsDatum = heap_getattr(relation->rd_indextuple,
							  Anum_pg_index_indexprs,
							  GetPgIndexDescriptor(),
							  &isnull);
	Assert(!isnull);
	exprsString = TextDatumGetCString(exprsDatum);
	result = (List *) stringToNode(exprsString);
	pfree(exprsString);

	/*
	 * Run the expressions through eval_const_expressions. This is not just an
	 * optimization, but is necessary, because the planner will be comparing
	 * them to similarly-processed qual clauses, and may fail to detect valid
	 * matches without this.  We don't bother with canonicalize_qual, however.
	 */
	result = (List *) eval_const_expressions(NULL, (Node *) result);

	/*
	 * Also mark any coercion format fields as "don't care", so that the
	 * planner can match to both explicit and implicit coercions.
	 */
	set_coercionform_dontcare((Node *) result);

	/* May as well fix opfuncids too */
	fix_opfuncids((Node *) result);

	/* Now save a copy of the completed tree in the relcache entry. */
	oldcxt = MemoryContextSwitchTo(relation->rd_indexcxt);
	relation->rd_indexprs = (List *) copyObject(result);
	MemoryContextSwitchTo(oldcxt);

	return result;
}

/*
 * RelationGetIndexPredicate -- get the index predicate for an index
 *
 * We cache the result of transforming pg_index.indpred into an implicit-AND
 * node tree (suitable for ExecQual).
 * If the rel is not an index or has no predicate, we return NIL.
 * Otherwise, the returned tree is copied into the caller's memory context.
 * (We don't want to return a pointer to the relcache copy, since it could
 * disappear due to relcache invalidation.)
 */
List *
RelationGetIndexPredicate(Relation relation)
{
	List	   *result;
	Datum		predDatum;
	bool		isnull;
	char	   *predString;
	MemoryContext oldcxt;

	/* Quick exit if we already computed the result. */
	if (relation->rd_indpred)
		return (List *) copyObject(relation->rd_indpred);

	/* Quick exit if there is nothing to do. */
	if (relation->rd_indextuple == NULL ||
		heap_attisnull(relation->rd_indextuple, Anum_pg_index_indpred))
		return NIL;

	/*
	 * We build the tree we intend to return in the caller's context. After
	 * successfully completing the work, we copy it into the relcache entry.
	 * This avoids problems if we get some sort of error partway through.
	 */
	predDatum = heap_getattr(relation->rd_indextuple,
							 Anum_pg_index_indpred,
							 GetPgIndexDescriptor(),
							 &isnull);
	Assert(!isnull);
	predString = TextDatumGetCString(predDatum);
	result = (List *) stringToNode(predString);
	pfree(predString);

	/*
	 * Run the expression through const-simplification and canonicalization.
	 * This is not just an optimization, but is necessary, because the planner
	 * will be comparing it to similarly-processed qual clauses, and may fail
	 * to detect valid matches without this.  This must match the processing
	 * done to qual clauses in preprocess_expression()!  (We can skip the
	 * stuff involving subqueries, however, since we don't allow any in index
	 * predicates.)
	 */
	result = (List *) eval_const_expressions(NULL, (Node *) result);

	result = (List *) canonicalize_qual((Expr *) result);

	/*
	 * Also mark any coercion format fields as "don't care", so that the
	 * planner can match to both explicit and implicit coercions.
	 */
	set_coercionform_dontcare((Node *) result);

	/* Also convert to implicit-AND format */
	result = make_ands_implicit((Expr *) result);

	/* May as well fix opfuncids too */
	fix_opfuncids((Node *) result);

	/* Now save a copy of the completed tree in the relcache entry. */
	oldcxt = MemoryContextSwitchTo(relation->rd_indexcxt);
	relation->rd_indpred = (List *) copyObject(result);
	MemoryContextSwitchTo(oldcxt);

	return result;
}

/*
 * RelationGetIndexAttrBitmap -- get a bitmap of index attribute numbers
 *
 * The result has a bit set for each attribute used anywhere in the index
 * definitions of all the indexes on this relation.  (This includes not only
 * simple index keys, but attributes used in expressions and partial-index
 * predicates.)
 *
 * Attribute numbers are offset by FirstLowInvalidHeapAttributeNumber so that
 * we can include system attributes (e.g., OID) in the bitmap representation.
 *
 * Caller had better hold at least RowExclusiveLock on the target relation
 * to ensure that it has a stable set of indexes.  This also makes it safe
 * (deadlock-free) for us to take locks on the relation's indexes.
 *
 * The returned result is palloc'd in the caller's memory context and should
 * be bms_free'd when not needed anymore.
 */
Bitmapset *
RelationGetIndexAttrBitmap(Relation relation)
{
	Bitmapset  *indexattrs;
	List	   *indexoidlist;
	ListCell   *l;
	MemoryContext oldcxt;

	/* Quick exit if we already computed the result. */
	if (relation->rd_indexattr != NULL)
		return bms_copy(relation->rd_indexattr);

	/* Fast path if definitely no indexes */
	if (!RelationGetForm(relation)->relhasindex)
		return NULL;

	/*
	 * Get cached list of index OIDs
	 */
	indexoidlist = RelationGetIndexList(relation);

	/* Fall out if no indexes (but relhasindex was set) */
	if (indexoidlist == NIL)
		return NULL;

	/*
	 * For each index, add referenced attributes to indexattrs.
	 *
	 * Note: we consider all indexes returned by RelationGetIndexList, even if
	 * they are not indisready or indisvalid.  This is important because an
	 * index for which CREATE INDEX CONCURRENTLY has just started must be
	 * included in HOT-safety decisions (see README.HOT).
	 */
	indexattrs = NULL;
	foreach(l, indexoidlist)
	{
		Oid			indexOid = lfirst_oid(l);
		Relation	indexDesc;
		IndexInfo  *indexInfo;
		int			i;

		indexDesc = index_open(indexOid, AccessShareLock);

		/* Extract index key information from the index's pg_index row */
		indexInfo = BuildIndexInfo(indexDesc);

		/* Collect simple attribute references */
		for (i = 0; i < indexInfo->ii_NumIndexAttrs; i++)
		{
			int			attrnum = indexInfo->ii_KeyAttrNumbers[i];

			if (attrnum != 0)
				indexattrs = bms_add_member(indexattrs,
							   attrnum - FirstLowInvalidHeapAttributeNumber);
		}

		/* Collect all attributes used in expressions, too */
		pull_varattnos((Node *) indexInfo->ii_Expressions, &indexattrs);

		/* Collect all attributes in the index predicate, too */
		pull_varattnos((Node *) indexInfo->ii_Predicate, &indexattrs);

		index_close(indexDesc, AccessShareLock);
	}

	list_free(indexoidlist);

	/* Now save a copy of the bitmap in the relcache entry. */
	oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
	relation->rd_indexattr = bms_copy(indexattrs);
	MemoryContextSwitchTo(oldcxt);

	/* We return our original working copy for caller to play with */
	return indexattrs;
}


/*
 *	load_relcache_init_file, write_relcache_init_file
 *
 *		In late 1992, we started regularly having databases with more than
 *		a thousand classes in them.  With this number of classes, it became
 *		critical to do indexed lookups on the system catalogs.
 *
 *		Bootstrapping these lookups is very hard.  We want to be able to
 *		use an index on pg_attribute, for example, but in order to do so,
 *		we must have read pg_attribute for the attributes in the index,
 *		which implies that we need to use the index.
 *
 *		In order to get around the problem, we do the following:
 *
 *		   +  When the database system is initialized (at initdb time), we
 *			  don't use indexes.  We do sequential scans.
 *
 *		   +  When the backend is started up in normal mode, we load an image
 *			  of the appropriate relation descriptors, in internal format,
 *			  from an initialization file in the data/base/... directory.
 *
 *		   +  If the initialization file isn't there, then we create the
 *			  relation descriptors using sequential scans and write 'em to
 *			  the initialization file for use by subsequent backends.
 *
 *		We could dispense with the initialization files and just build the
 *		critical reldescs the hard way on every backend startup, but that
 *		slows down backend startup noticeably.
 *
 *		We can in fact go further, and save more relcache entries than
 *		just the ones that are absolutely critical; this allows us to speed
 *		up backend startup by not having to build such entries the hard way.
 *		Presently, all the catalog and index entries that are referred to
 *		by catcaches are stored in the initialization files.
 *
 *		The same mechanism that detects when catcache and relcache entries
 *		need to be invalidated (due to catalog updates) also arranges to
 *		unlink the initialization files when the contents may be out of date.
 *		The files will then be rebuilt during the next backend startup.
 */

/*
 * load_relcache_init_file -- attempt to load cache from the init file
 *
 * If successful, return TRUE and set criticalRelcachesBuilt to true.
 * If not successful, return FALSE.
 *
 * NOTE: we assume we are already switched into CacheMemoryContext.
 */
static bool
load_relcache_init_file(bool shared)
{
	FILE	   *fp;
	char		initfilename[MAXPGPATH];
	Relation   *rels;
	int			relno,
				num_rels,
				max_rels,
				nailed_rels,
				nailed_indexes,
				magic;
	int			i;

	if (shared)
		snprintf(initfilename, sizeof(initfilename), "global/%s",
				 RELCACHE_INIT_FILENAME);
	else
		snprintf(initfilename, sizeof(initfilename), "%s/%s",
				 DatabasePath, RELCACHE_INIT_FILENAME);

	fp = AllocateFile(initfilename, PG_BINARY_R);
	if (fp == NULL)
		return false;

	/*
	 * Read the index relcache entries from the file.  Note we will not enter
	 * any of them into the cache if the read fails partway through; this
	 * helps to guard against broken init files.
	 */
	max_rels = 100;
	rels = (Relation *) palloc(max_rels * sizeof(Relation));
	num_rels = 0;
	nailed_rels = nailed_indexes = 0;
	initFileRelationIds = NIL;

	/* check for correct magic number (compatible version) */
	if (fread(&magic, 1, sizeof(magic), fp) != sizeof(magic))
		goto read_failed;
	if (magic != RELCACHE_INIT_FILEMAGIC)
		goto read_failed;

	for (relno = 0;; relno++)
	{
		Size		len;
		size_t		nread;
		Relation	rel;
		Form_pg_class relform;
		bool		has_not_null;

		/* first read the relation descriptor length */
		if ((nread = fread(&len, 1, sizeof(len), fp)) != sizeof(len))
		{
			if (nread == 0)
				break;			/* end of file */
			goto read_failed;
		}

		/* safety check for incompatible relcache layout */
		if (len != sizeof(RelationData))
			goto read_failed;

		/* allocate another relcache header */
		if (num_rels >= max_rels)
		{
			max_rels *= 2;
			rels = (Relation *) repalloc(rels, max_rels * sizeof(Relation));
		}

		rel = rels[num_rels++] = (Relation) palloc(len);

		/* then, read the Relation structure */
		if ((nread = fread(rel, 1, len, fp)) != len)
			goto read_failed;

		/* next read the relation tuple form */
		if ((nread = fread(&len, 1, sizeof(len), fp)) != sizeof(len))
			goto read_failed;

		relform = (Form_pg_class) palloc(len);
		if ((nread = fread(relform, 1, len, fp)) != len)
			goto read_failed;

		rel->rd_rel = relform;

		/* initialize attribute tuple forms */
		rel->rd_att = CreateTemplateTupleDesc(relform->relnatts,
											  relform->relhasoids);
		rel->rd_att->tdrefcount = 1;	/* mark as refcounted */

		rel->rd_att->tdtypeid = relform->reltype;
		rel->rd_att->tdtypmod = -1;		/* unnecessary, but... */

		/* next read all the attribute tuple form data entries */
		has_not_null = false;
		for (i = 0; i < relform->relnatts; i++)
		{
			if ((nread = fread(&len, 1, sizeof(len), fp)) != sizeof(len))
				goto read_failed;
			if (len != ATTRIBUTE_FIXED_PART_SIZE)
				goto read_failed;
			if ((nread = fread(rel->rd_att->attrs[i], 1, len, fp)) != len)
				goto read_failed;

			has_not_null |= rel->rd_att->attrs[i]->attnotnull;
		}

		/* next read the access method specific field */
		if ((nread = fread(&len, 1, sizeof(len), fp)) != sizeof(len))
			goto read_failed;
		if (len > 0)
		{
			rel->rd_options = palloc(len);
			if ((nread = fread(rel->rd_options, 1, len, fp)) != len)
				goto read_failed;
			if (len != VARSIZE(rel->rd_options))
				goto read_failed;		/* sanity check */
		}
		else
		{
			rel->rd_options = NULL;
		}

		/* mark not-null status */
		if (has_not_null)
		{
			TupleConstr *constr = (TupleConstr *) palloc0(sizeof(TupleConstr));

			constr->has_not_null = true;
			rel->rd_att->constr = constr;
		}

		/* If it's an index, there's more to do */
		if (rel->rd_rel->relkind == RELKIND_INDEX)
		{
			Form_pg_am	am;
			MemoryContext indexcxt;
			Oid		   *opfamily;
			Oid		   *opcintype;
			Oid		   *operator;
			RegProcedure *support;
			int			nsupport;
			int16	   *indoption;

			/* Count nailed indexes to ensure we have 'em all */
			if (rel->rd_isnailed)
				nailed_indexes++;

			/* next, read the pg_index tuple */
			if ((nread = fread(&len, 1, sizeof(len), fp)) != sizeof(len))
				goto read_failed;

			rel->rd_indextuple = (HeapTuple) palloc(len);
			if ((nread = fread(rel->rd_indextuple, 1, len, fp)) != len)
				goto read_failed;

			/* Fix up internal pointers in the tuple -- see heap_copytuple */
			rel->rd_indextuple->t_data = (HeapTupleHeader) ((char *) rel->rd_indextuple + HEAPTUPLESIZE);
			rel->rd_index = (Form_pg_index) GETSTRUCT(rel->rd_indextuple);

			/* next, read the access method tuple form */
			if ((nread = fread(&len, 1, sizeof(len), fp)) != sizeof(len))
				goto read_failed;

			am = (Form_pg_am) palloc(len);
			if ((nread = fread(am, 1, len, fp)) != len)
				goto read_failed;
			rel->rd_am = am;

			/*
			 * prepare index info context --- parameters should match
			 * RelationInitIndexAccessInfo
			 */
			indexcxt = AllocSetContextCreate(CacheMemoryContext,
											 RelationGetRelationName(rel),
											 ALLOCSET_SMALL_MINSIZE,
											 ALLOCSET_SMALL_INITSIZE,
											 ALLOCSET_SMALL_MAXSIZE);
			rel->rd_indexcxt = indexcxt;

			/* next, read the vector of opfamily OIDs */
			if ((nread = fread(&len, 1, sizeof(len), fp)) != sizeof(len))
				goto read_failed;

			opfamily = (Oid *) MemoryContextAlloc(indexcxt, len);
			if ((nread = fread(opfamily, 1, len, fp)) != len)
				goto read_failed;

			rel->rd_opfamily = opfamily;

			/* next, read the vector of opcintype OIDs */
			if ((nread = fread(&len, 1, sizeof(len), fp)) != sizeof(len))
				goto read_failed;

			opcintype = (Oid *) MemoryContextAlloc(indexcxt, len);
			if ((nread = fread(opcintype, 1, len, fp)) != len)
				goto read_failed;

			rel->rd_opcintype = opcintype;

			/* next, read the vector of operator OIDs */
			if ((nread = fread(&len, 1, sizeof(len), fp)) != sizeof(len))
				goto read_failed;

			operator = (Oid *) MemoryContextAlloc(indexcxt, len);
			if ((nread = fread(operator, 1, len, fp)) != len)
				goto read_failed;

			rel->rd_operator = operator;

			/* next, read the vector of support procedures */
			if ((nread = fread(&len, 1, sizeof(len), fp)) != sizeof(len))
				goto read_failed;
			support = (RegProcedure *) MemoryContextAlloc(indexcxt, len);
			if ((nread = fread(support, 1, len, fp)) != len)
				goto read_failed;

			rel->rd_support = support;

			/* finally, read the vector of indoption values */
			if ((nread = fread(&len, 1, sizeof(len), fp)) != sizeof(len))
				goto read_failed;

			indoption = (int16 *) MemoryContextAlloc(indexcxt, len);
			if ((nread = fread(indoption, 1, len, fp)) != len)
				goto read_failed;

			rel->rd_indoption = indoption;

			/* set up zeroed fmgr-info vectors */
			rel->rd_aminfo = (RelationAmInfo *)
				MemoryContextAllocZero(indexcxt, sizeof(RelationAmInfo));
			nsupport = relform->relnatts * am->amsupport;
			rel->rd_supportinfo = (FmgrInfo *)
				MemoryContextAllocZero(indexcxt, nsupport * sizeof(FmgrInfo));
		}
		else
		{
			/* Count nailed rels to ensure we have 'em all */
			if (rel->rd_isnailed)
				nailed_rels++;

			Assert(rel->rd_index == NULL);
			Assert(rel->rd_indextuple == NULL);
			Assert(rel->rd_am == NULL);
			Assert(rel->rd_indexcxt == NULL);
			Assert(rel->rd_aminfo == NULL);
			Assert(rel->rd_opfamily == NULL);
			Assert(rel->rd_opcintype == NULL);
			Assert(rel->rd_operator == NULL);
			Assert(rel->rd_support == NULL);
			Assert(rel->rd_supportinfo == NULL);
			Assert(rel->rd_indoption == NULL);
		}

		/*
		 * Rules and triggers are not saved (mainly because the internal
		 * format is complex and subject to change).  They must be rebuilt if
		 * needed by RelationCacheInitializePhase3.  This is not expected to
		 * be a big performance hit since few system catalogs have such. Ditto
		 * for index expressions and predicates.
		 */
		rel->rd_rules = NULL;
		rel->rd_rulescxt = NULL;
		rel->trigdesc = NULL;
		rel->rd_indexprs = NIL;
		rel->rd_indpred = NIL;

		/*
		 * Reset transient-state fields in the relcache entry
		 */
		rel->rd_smgr = NULL;
		rel->rd_targblock = InvalidBlockNumber;
		if (rel->rd_isnailed)
			rel->rd_refcnt = 1;
		else
			rel->rd_refcnt = 0;
		rel->rd_indexvalid = 0;
		rel->rd_indexlist = NIL;
		rel->rd_indexattr = NULL;
		rel->rd_oidindex = InvalidOid;
		rel->rd_createSubid = InvalidSubTransactionId;
		rel->rd_newRelfilenodeSubid = InvalidSubTransactionId;
		rel->rd_amcache = NULL;
		MemSet(&rel->pgstat_info, 0, sizeof(rel->pgstat_info));
        rel->rd_cdbpolicy = NULL;
        rel->rd_cdbDefaultStatsWarningIssued = false;

		/*
		 * Recompute lock and physical addressing info.  This is needed in
		 * case the pg_internal.init file was copied from some other database
		 * by CREATE DATABASE.
		 */
		RelationInitLockInfo(rel);
		RelationInitPhysicalAddr(rel);
	}

	/*
	 * We reached the end of the init file without apparent problem. Did we
	 * get the right number of nailed items?  (This is a useful crosscheck in
	 * case the set of critical rels or indexes changes.)
	 */
	if (shared)
	{
		if (nailed_rels != NUM_CRITICAL_SHARED_RELS ||
			nailed_indexes != NUM_CRITICAL_SHARED_INDEXES)
			goto read_failed;
	}
	else
	{
		if (nailed_rels != NUM_CRITICAL_LOCAL_RELS ||
			nailed_indexes != NUM_CRITICAL_LOCAL_INDEXES)
			goto read_failed;
	}


	/*
	 * OK, all appears well.
	 *
	 * Now insert all the new relcache entries into the cache.
	 */
	for (relno = 0; relno < num_rels; relno++)
	{
		RelationCacheInsert(rels[relno]);
		/* also make a list of their OIDs, for RelationIdIsInInitFile */
		if (!shared)
			initFileRelationIds = lcons_oid(RelationGetRelid(rels[relno]),
											initFileRelationIds);
	}

	pfree(rels);
	FreeFile(fp);

	if (shared)
		criticalSharedRelcachesBuilt = true;
	else
		criticalRelcachesBuilt = true;
	return true;

	/*
	 * init file is broken, so do it the hard way.	We don't bother trying to
	 * free the clutter we just allocated; it's not in the relcache so it
	 * won't hurt.
	 */
read_failed:
	pfree(rels);
	FreeFile(fp);

	return false;
}

/*
 * Write out a new initialization file with the current contents
 * of the relcache.
 */
static void
write_relcache_init_file(bool shared)
{
	FILE	   *fp;
	char		tempfilename[MAXPGPATH];
	char		finalfilename[MAXPGPATH];
	int			magic;
	HASH_SEQ_STATUS status;
	RelIdCacheEnt *idhentry;
	MemoryContext oldcxt;
	int			i;

	/*
	 * We must write a temporary file and rename it into place. Otherwise,
	 * another backend starting at about the same time might crash trying to
	 * read the partially-complete file.
	 */
	if (shared)
	{
		snprintf(tempfilename, sizeof(tempfilename), "global/%s.%d",
				 RELCACHE_INIT_FILENAME, MyProcPid);
		snprintf(finalfilename, sizeof(finalfilename), "global/%s",
				 RELCACHE_INIT_FILENAME);
	}
	else
	{
		snprintf(tempfilename, sizeof(tempfilename), "%s/%s.%d",
				 DatabasePath, RELCACHE_INIT_FILENAME, MyProcPid);
		snprintf(finalfilename, sizeof(finalfilename), "%s/%s",
				 DatabasePath, RELCACHE_INIT_FILENAME);
	}

	unlink(tempfilename);		/* in case it exists w/wrong permissions */

	fp = AllocateFile(tempfilename, PG_BINARY_W);
	if (fp == NULL)
	{
		/*
		 * We used to consider this a fatal error, but we might as well
		 * continue with backend startup ...
		 */
		ereport(WARNING,
				(errcode_for_file_access(),
				 errmsg("could not create relation-cache initialization file \"%s\": %m",
						tempfilename),
			  errdetail("Continuing anyway, but there's something wrong.")));
		return;
	}

	/*
	 * Write a magic number to serve as a file version identifier.	We can
	 * change the magic number whenever the relcache layout changes.
	 */
	magic = RELCACHE_INIT_FILEMAGIC;
	if (fwrite(&magic, 1, sizeof(magic), fp) != sizeof(magic))
		elog(FATAL, "could not write init file");

	/*
	 * Write all the reldescs (in no particular order).
	 */
	hash_seq_init(&status, RelationIdCache);

	initFileRelationIds = NIL;

	while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
	{
		Relation	rel = idhentry->reldesc;
		Form_pg_class relform = rel->rd_rel;

		/* ignore if not correct group */
		if (relform->relisshared != shared)
			continue;

		/* first write the relcache entry proper */
		write_item(rel, sizeof(RelationData), fp);

		/* next write the relation tuple form */
		write_item(relform, CLASS_TUPLE_SIZE, fp);

		/* next, do all the attribute tuple form data entries */
		for (i = 0; i < relform->relnatts; i++)
		{
			write_item(rel->rd_att->attrs[i], ATTRIBUTE_FIXED_PART_SIZE, fp);
		}

		/* next, do the access method specific field */
		write_item(rel->rd_options,
				   (rel->rd_options ? VARSIZE(rel->rd_options) : 0),
				   fp);

		/* If it's an index, there's more to do */
		if (rel->rd_rel->relkind == RELKIND_INDEX)
		{
			Form_pg_am	am = rel->rd_am;

			/* write the pg_index tuple */
			/* we assume this was created by heap_copytuple! */
			write_item(rel->rd_indextuple,
					   HEAPTUPLESIZE + rel->rd_indextuple->t_len,
					   fp);

			/* next, write the access method tuple form */
			write_item(am, sizeof(FormData_pg_am), fp);

			/* next, write the vector of opfamily OIDs */
			write_item(rel->rd_opfamily,
					   relform->relnatts * sizeof(Oid),
					   fp);

			/* next, write the vector of opcintype OIDs */
			write_item(rel->rd_opcintype,
					   relform->relnatts * sizeof(Oid),
					   fp);

			/* next, write the vector of operator OIDs */
			write_item(rel->rd_operator,
					   relform->relnatts * (am->amstrategies * sizeof(Oid)),
					   fp);

			/* next, write the vector of support procedures */
			write_item(rel->rd_support,
				  relform->relnatts * (am->amsupport * sizeof(RegProcedure)),
					   fp);

			/* finally, write the vector of indoption values */
			write_item(rel->rd_indoption,
					   relform->relnatts * sizeof(int16),
					   fp);
		}

		/* also make a list of their OIDs, for RelationIdIsInInitFile */
		if (!shared)
		{
			oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
			initFileRelationIds = lcons_oid(RelationGetRelid(rel),
											initFileRelationIds);
			MemoryContextSwitchTo(oldcxt);
		}
	}

	if (FreeFile(fp))
		elog(FATAL, "could not write init file");

	/*
	 * Now we have to check whether the data we've so painstakingly
	 * accumulated is already obsolete due to someone else's just-committed
	 * catalog changes.  If so, we just delete the temp file and leave it to
	 * the next backend to try again.  (Our own relcache entries will be
	 * updated by SI message processing, but we can't be sure whether what we
	 * wrote out was up-to-date.)
	 *
	 * This mustn't run concurrently with the code that unlinks an init file
	 * and sends SI messages, so grab a serialization lock for the duration.
	 */
	LWLockAcquire(RelCacheInitLock, LW_EXCLUSIVE);

	/* Make sure we have seen all incoming SI messages */
	AcceptInvalidationMessages();

	/*
	 * If we have received any SI relcache invals since backend start, assume
	 * we may have written out-of-date data.
	 */
	if (relcacheInvalsReceived == 0L)
	{
		/*
		 * OK, rename the temp file to its final name, deleting any
		 * previously-existing init file.
		 *
		 * Note: a failure here is possible under Cygwin, if some other
		 * backend is holding open an unlinked-but-not-yet-gone init file. So
		 * treat this as a noncritical failure; just remove the useless temp
		 * file on failure.
		 */
		if (rename(tempfilename, finalfilename) < 0)
			unlink(tempfilename);
	}
	else
	{
		/* Delete the already-obsolete temp file */
		unlink(tempfilename);
	}

	LWLockRelease(RelCacheInitLock);
}

/* write a chunk of data preceded by its length */
static void
write_item(const void *data, Size len, FILE *fp)
{
	if (fwrite(&len, 1, sizeof(len), fp) != sizeof(len))
		elog(FATAL, "could not write init file");
	if (fwrite(data, 1, len, fp) != len)
		elog(FATAL, "could not write init file");
}

/*
 * Detect whether a given relation (identified by OID) is one of the ones
 * we store in the init file.
 *
 * Note that we effectively assume that all backends running in a database
 * would choose to store the same set of relations in the init file;
 * otherwise there are cases where we'd fail to detect the need for an init
 * file invalidation.  This does not seem likely to be a problem in practice.
 */
bool
RelationIdIsInInitFile(Oid relationId)
{
	return list_member_oid(initFileRelationIds, relationId);
}

/*
 * Invalidate (remove) the init file during commit of a transaction that
 * changed one or more of the relation cache entries that are kept in the
 * local init file.
 *
 * To be safe against concurrent inspection or rewriting of the init file,
 * we must take RelCacheInitLock, then remove the old init file, then send
 * the SI messages that include relcache inval for such relations, and then
 * release RelCacheInitLock.  This serializes the whole affair against
 * write_relcache_init_file, so that we can be sure that any other process
 * that's concurrently trying to create a new init file won't move an
 * already-stale version into place after we unlink.  Also, because we unlink
 * before sending the SI messages, a backend that's currently starting cannot
 * read the now-obsolete init file and then miss the SI messages that will
 * force it to update its relcache entries.  (This works because the backend
 * startup sequence gets into the sinval array before trying to load the init
 * file.)
 *
 * We take the lock and do the unlink in RelationCacheInitFilePreInvalidate,
 * then release the lock in RelationCacheInitFilePostInvalidate.  Caller must
 * send any pending SI messages between those calls.
 *
 * Notice this deals only with the local init file, not the shared init file.
 * The reason is that there can never be a "significant" change to the
 * relcache entry of a shared relation; the most that could happen is
 * updates of noncritical fields such as relpages/reltuples.  So, while
 * it's worth updating the shared init file from time to time, it can never
 * be invalid enough to make it necessary to remove it.
 */
void
RelationCacheInitFilePreInvalidate(void)
{
	char		initfilename[MAXPGPATH];

	snprintf(initfilename, sizeof(initfilename), "%s/%s",
			 DatabasePath, RELCACHE_INIT_FILENAME);

	LWLockAcquire(RelCacheInitLock, LW_EXCLUSIVE);

	if (unlink(initfilename) < 0)
	{
		/*
		 * The file might not be there if no backend has been started since
		 * the last removal.  But complain about failures other than ENOENT.
		 * Fortunately, it's not too late to abort the transaction if we
		 * can't get rid of the would-be-obsolete init file.
		 */
		if (errno != ENOENT)
			ereport(ERROR,
					(errcode_for_file_access(),
					 errmsg("could not remove cache file \"%s\": %m",
							initfilename)));
	}
}

void
RelationCacheInitFilePostInvalidate(void)
{
	LWLockRelease(RelCacheInitLock);
}

/*
 * Remove the init files during postmaster startup.
 *
 * We used to keep the init files across restarts, but that is unsafe even in simple
 * crash-recovery cases as there are windows for the init files to become out-of-sync
 * with the database. So now we just remove them during startup and expect the
 * first backend launch to rebuild them. Of course, this has to happen in each
 * database of the cluster.
 */
void
RelationCacheInitFileRemove(void)
{
	char		path[MAXPGPATH];

	/*
	 * We zap the shared cache file too.  In theory it can't get out of sync
	 * enough to be a problem, but in data-corruption cases, who knows ...
	 */
	snprintf(path, sizeof(path), "global/%s",
			 RELCACHE_INIT_FILENAME);
	unlink_initfile(path);

	/* Scan everything in the default tablespace */
	RelationCacheInitFileRemoveInDir("base");
}

/* Process one per-tablespace directory for RelationCacheInitFileRemove */
static void
RelationCacheInitFileRemoveInDir(const char *tblspcpath)
{
	DIR		   *dir;
	struct dirent *de;
	char		initfilename[MAXPGPATH];

	/* Scan the tablespace directory to find per-database directories */
	dir = AllocateDir(tblspcpath);
	if (dir == NULL)
	{
		elog(LOG, "could not open tablespace directory \"%s\": %m",
			 tblspcpath);
		return;
	}

	while ((de = ReadDir(dir, tblspcpath)) != NULL)
	{
		if (strspn(de->d_name, "0123456789") == strlen(de->d_name))
		{
			/* Try to remove the init file in each database */
			snprintf(initfilename, sizeof(initfilename), "%s/%s/%s",
					 tblspcpath, de->d_name, RELCACHE_INIT_FILENAME);
			unlink_initfile(initfilename);
		}
	}

	FreeDir(dir);
}

static void
unlink_initfile(const char *initfilename)
{
	if (unlink(initfilename) < 0)
	{
		/* It might not be there, but log any error other than ENOENT */
		if (errno != ENOENT)
			elog(LOG, "could not remove cache file \"%s\": %m", initfilename);
	}
}

void
RelationGetPTInfo(Relation rel,
	ItemPointer persistentTid,
	int64 *persistentSerialNum)
{
	if (! GpPersistent_SkipXLogInfo(rel->rd_node.relNode) &&
		! rel->rd_segfile0_relationnodeinfo.isPresent)
	{
		elog(ERROR,
			 "required Persistent Table information missing for relation %u/%u/%u",
			 rel->rd_node.spcNode, rel->rd_node.dbNode, rel->rd_node.relNode);
	}

	*persistentTid = rel->rd_segfile0_relationnodeinfo.persistentTid;
	*persistentSerialNum = rel->rd_segfile0_relationnodeinfo.persistentSerialNum;
}