execMain.c

/*-------------------------------------------------------------------------
 *
 * execMain.c
 *	  top level executor interface routines
 *
 * INTERFACE ROUTINES
 *	ExecutorStart()
 *	ExecutorRun()
 *	ExecutorEnd()
 *
 *	The old ExecutorMain() has been replaced by ExecutorStart(),
 *	ExecutorRun() and ExecutorEnd()
 *
 *	These three procedures are the external interfaces to the executor.
 *	In each case, the query descriptor and the execution state is required
 *	 as arguments
 *
 *	ExecutorStart() must be called at the beginning of any execution of any
 *	query plan and ExecutorEnd() should always be called at the end of
 *	execution of a plan.
 *
 *	ExecutorRun accepts 'feature' and 'count' arguments that specify whether
 *	the plan is to be executed forwards, backwards, and for how many tuples.
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/backend/executor/execMain.c,v 1.79 1999/02/22 19:40:09 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#include <string.h>
#include "postgres.h"
#include "miscadmin.h"

#include "executor/executor.h"
#include "executor/execdefs.h"
#include "executor/execdebug.h"
#include "executor/nodeIndexscan.h"
#include "utils/builtins.h"
#include "utils/palloc.h"
#include "utils/acl.h"
#include "utils/syscache.h"
#include "utils/tqual.h"
#include "parser/parsetree.h"	/* rt_fetch() */
#include "storage/bufmgr.h"
#include "storage/lmgr.h"
#include "storage/smgr.h"
#include "commands/async.h"
/* #include "access/localam.h" */
#include "optimizer/var.h"
#include "access/heapam.h"
#include "access/xact.h"
#include "catalog/heap.h"
#include "commands/trigger.h"

void ExecCheckPerms(CmdType operation, int resultRelation, List *rangeTable,
			   Query *parseTree);


/* decls for local routines only used within this module */
static TupleDesc InitPlan(CmdType operation,
						Query *parseTree,
		 				Plan *plan,
						EState *estate);
static void EndPlan(Plan *plan,
						EState *estate);
static TupleTableSlot *ExecutePlan(EState *estate, Plan *plan,
						CmdType operation, 
						int offsetTuples,
						int numberTuples,
						ScanDirection direction,
						DestReceiver *destfunc);
static void ExecRetrieve(TupleTableSlot *slot,
						DestReceiver *destfunc,
						EState *estate);
static void ExecAppend(TupleTableSlot *slot, ItemPointer tupleid,
		   				EState *estate);
static void ExecDelete(TupleTableSlot *slot, ItemPointer tupleid,
		   				EState *estate);
static void ExecReplace(TupleTableSlot *slot, ItemPointer tupleid,
						EState *estate);

TupleTableSlot *EvalPlanQual(EState *estate, Index rti, ItemPointer tid);
static TupleTableSlot *EvalPlanQualNext(EState *estate);


/* end of local decls */

#ifdef QUERY_LIMIT
static int	queryLimit = ALL_TUPLES;

#undef ALL_TUPLES
#define ALL_TUPLES queryLimit

int
ExecutorLimit(int limit)
{
	return queryLimit = limit;
}

int
ExecutorGetLimit()
{
	return queryLimit;
}

#endif

/* ----------------------------------------------------------------
 *		ExecutorStart
 *
 *		This routine must be called at the beginning of any execution of any
 *		query plan
 *
 *		returns (AttrInfo*) which describes the attributes of the tuples to
 *		be returned by the query.
 *
 * ----------------------------------------------------------------
 */
TupleDesc
ExecutorStart(QueryDesc *queryDesc, EState *estate)
{
	TupleDesc	result;

	/* sanity checks */
	Assert(queryDesc != NULL);

	if (queryDesc->plantree->nParamExec > 0)
	{
		estate->es_param_exec_vals = (ParamExecData *)
			palloc(queryDesc->plantree->nParamExec * sizeof(ParamExecData));
		memset(estate->es_param_exec_vals, 0, queryDesc->plantree->nParamExec * sizeof(ParamExecData));
	}

	/*
	 * Make our own private copy of the current queries snapshot data
	 */
	if (QuerySnapshot == NULL)
		estate->es_snapshot = NULL;
	else
	{
		estate->es_snapshot = (Snapshot)palloc(sizeof(SnapshotData));
		memcpy(estate->es_snapshot, QuerySnapshot, sizeof(SnapshotData));
		if (estate->es_snapshot->xcnt > 0)
		{
			estate->es_snapshot->xip = (TransactionId *)
					palloc(estate->es_snapshot->xcnt * sizeof(TransactionId));
			memcpy(estate->es_snapshot->xip, QuerySnapshot->xip,
					estate->es_snapshot->xcnt * sizeof(TransactionId));
		}
	}

	/*
	 * Initialize the plan
	 */
	result = InitPlan(queryDesc->operation,
					  queryDesc->parsetree,
					  queryDesc->plantree,
					  estate);

	/*
	 * reset buffer refcount.  the current refcounts are saved and will be
	 * restored when ExecutorEnd is called
	 *
	 * this makes sure that when ExecutorRun's are called recursively as for
	 * postquel functions, the buffers pinned by one ExecutorRun will not
	 * be unpinned by another ExecutorRun.
	 */
	BufferRefCountReset(estate->es_refcount);

	return result;
}

/* ----------------------------------------------------------------
 *		ExecutorRun
 *
 *		This is the main routine of the executor module. It accepts
 *		the query descriptor from the traffic cop and executes the
 *		query plan.
 *
 *		ExecutorStart must have been called already.
 *
 *		the different features supported are:
 *			 EXEC_RUN:	retrieve all tuples in the forward direction
 *			 EXEC_FOR:	retrieve 'count' number of tuples in the forward dir
 *			 EXEC_BACK: retrieve 'count' number of tuples in the backward dir
 *			 EXEC_RETONE: return one tuple but don't 'retrieve' it
 *						   used in postquel function processing
 *
 *
 * ----------------------------------------------------------------
 */
TupleTableSlot *
ExecutorRun(QueryDesc *queryDesc, EState *estate, int feature, 
					Node *limoffset, Node *limcount)
{
	CmdType			operation;
	Plan		   *plan;
	TupleTableSlot *result;
	CommandDest		dest;
	DestReceiver   *destfunc;
	int				offset = 0;
	int				count = 0;

	/*
	 *	sanity checks
	 */
	Assert(queryDesc != NULL);

	/*
	 *	extract information from the query descriptor
	 *	and the query feature.
	 */
	operation = queryDesc->operation;
	plan = queryDesc->plantree;
	dest = queryDesc->dest;
	destfunc = DestToFunction(dest);
	estate->es_processed = 0;
	estate->es_lastoid = InvalidOid;

	/*
	 *	FIXME: the dest setup function ought to be handed the tuple desc
	 *  for the tuples to be output, but I'm not quite sure how to get that
	 *  info at this point.  For now, passing NULL is OK because no existing
	 *  dest setup function actually uses the pointer.
	 */
	(*destfunc->setup) (destfunc, (TupleDesc) NULL);

    /*
     *  if given get the offset of the LIMIT clause
     */
    if (limoffset != NULL)
    {
        Const       *coffset;
        Param       *poffset;
        ParamListInfo   paramLI;
		int	 i;
 
		switch (nodeTag(limoffset))
		{
			case T_Const:
				coffset = (Const *)limoffset;
				offset = (int)(coffset->constvalue);
				break;
 
			case T_Param:
				poffset = (Param *)limoffset;
				paramLI = estate->es_param_list_info;
 
				if (paramLI == NULL)
					elog(ERROR, "parameter for limit offset not in executor state");
				for (i = 0; paramLI[i].kind != PARAM_INVALID; i++)
				{
					if (paramLI[i].kind == PARAM_NUM && paramLI[i].id == poffset->paramid)
						break;
				}
				if (paramLI[i].kind == PARAM_INVALID)
					elog(ERROR, "parameter for limit offset not in executor state");
				if (paramLI[i].isnull)
					elog(ERROR, "limit offset cannot be NULL value");
				offset = (int)(paramLI[i].value);
 
				break;
 
			default:
				elog(ERROR, "unexpected node type %d as limit offset", nodeTag(limoffset));
		}
 
		if (offset < 0)
			elog(ERROR, "limit offset cannot be negative");
	}
 
	/*
	 *  if given get the count of the LIMIT clause
	 */
	if (limcount != NULL)
	{
	    Const       *ccount;
	    Param       *pcount;
	    ParamListInfo   paramLI;
	    int     i;
 
	    switch (nodeTag(limcount))
	    {
	        case T_Const:
	            ccount = (Const *)limcount;
	            count = (int)(ccount->constvalue);
	            break;
 
	        case T_Param:
	            pcount = (Param *)limcount;
	            paramLI = estate->es_param_list_info;
 
	            if (paramLI == NULL)
	                elog(ERROR, "parameter for limit count not in executor state");
	            for (i = 0; paramLI[i].kind != PARAM_INVALID; i++)
	            {
	                if (paramLI[i].kind == PARAM_NUM && paramLI[i].id == pcount->paramid)
	                    break;
	            }
	            if (paramLI[i].kind == PARAM_INVALID)
	                elog(ERROR, "parameter for limit count not in executor state");
	            if (paramLI[i].isnull)
	                elog(ERROR, "limit count cannot be NULL value");
	            count = (int)(paramLI[i].value);
 
	            break;
 
	        default:
	            elog(ERROR, "unexpected node type %d as limit count", nodeTag(limcount));
	    }
 
	    if (count < 0)
	        elog(ERROR, "limit count cannot be negative");
	}

	switch (feature)
	{

		case EXEC_RUN:
			result = ExecutePlan(estate,
								 plan,
								 operation,
								 offset,
								 count,
								 ForwardScanDirection,
								 destfunc);
			break;
		case EXEC_FOR:
			result = ExecutePlan(estate,
								 plan,
								 operation,
								 offset,
								 count,
								 ForwardScanDirection,
								 destfunc);
			break;

			/*
			 *		retrieve next n "backward" tuples
			 */
		case EXEC_BACK:
			result = ExecutePlan(estate,
								 plan,
								 operation,
								 offset,
								 count,
								 BackwardScanDirection,
								 destfunc);
			break;

			/*
			 *		return one tuple but don't "retrieve" it.
			 *		(this is used by the rule manager..) -cim 9/14/89
			 */
		case EXEC_RETONE:
			result = ExecutePlan(estate,
								 plan,
								 operation,
								 0,
								 ONE_TUPLE,
								 ForwardScanDirection,
								 destfunc);
			break;
		default:
			result = NULL;
			elog(DEBUG, "ExecutorRun: Unknown feature %d", feature);
			break;
	}

	(*destfunc->cleanup) (destfunc);

	return result;
}

/* ----------------------------------------------------------------
 *		ExecutorEnd
 *
 *		This routine must be called at the end of any execution of any
 *		query plan
 *
 *		returns (AttrInfo*) which describes the attributes of the tuples to
 *		be returned by the query.
 *
 * ----------------------------------------------------------------
 */
void
ExecutorEnd(QueryDesc *queryDesc, EState *estate)
{
	/* sanity checks */
	Assert(queryDesc != NULL);

	EndPlan(queryDesc->plantree, estate);

	/* restore saved refcounts. */
	BufferRefCountRestore(estate->es_refcount);
}

void
ExecCheckPerms(CmdType operation,
			   int resultRelation,
			   List *rangeTable,
			   Query *parseTree)
{
	int			i = 1;
	Oid			relid;
	HeapTuple	htup;
	List	   *lp;
	List	   *qvars,
			   *tvars;
	int32		ok = 1,
				aclcheck_result = -1;
	char	   *opstr;
	NameData	rname;
	char	   *userName;

#define CHECK(MODE)		pg_aclcheck(rname.data, userName, MODE)

	userName = GetPgUserName();

	foreach(lp, rangeTable)
	{
		RangeTblEntry *rte = lfirst(lp);

		if (rte->skipAcl)
		{

			/*
			 * This happens if the access to this table is due to a view
			 * query rewriting - the rewrite handler checked the
			 * permissions against the view owner, so we just skip this
			 * entry.
			 */
			continue;
		}

		relid = rte->relid;
		htup = SearchSysCacheTuple(RELOID,
								   ObjectIdGetDatum(relid),
								   0, 0, 0);
		if (!HeapTupleIsValid(htup))
			elog(ERROR, "ExecCheckPerms: bogus RT relid: %d",
				 relid);
		StrNCpy(rname.data,
				((Form_pg_class) GETSTRUCT(htup))->relname.data,
				NAMEDATALEN);
		if (i == resultRelation)
		{						/* this is the result relation */
			qvars = pull_varnos(parseTree->qual);
			tvars = pull_varnos((Node *) parseTree->targetList);
			if (intMember(resultRelation, qvars) ||
				intMember(resultRelation, tvars))
			{
				/* result relation is scanned */
				ok = ((aclcheck_result = CHECK(ACL_RD)) == ACLCHECK_OK);
				opstr = "read";
				if (!ok)
					break;
			}
			switch (operation)
			{
				case CMD_INSERT:
					ok = ((aclcheck_result = CHECK(ACL_AP)) == ACLCHECK_OK) ||
						((aclcheck_result = CHECK(ACL_WR)) == ACLCHECK_OK);
					opstr = "append";
					break;
				case CMD_DELETE:
				case CMD_UPDATE:
					ok = ((aclcheck_result = CHECK(ACL_WR)) == ACLCHECK_OK);
					opstr = "write";
					break;
				default:
					elog(ERROR, "ExecCheckPerms: bogus operation %d",
						 operation);
			}
		}
		else
		{
			ok = ((aclcheck_result = CHECK(ACL_RD)) == ACLCHECK_OK);
			opstr = "read";
		}
		if (!ok)
			break;
		++i;
	}
	if (!ok)
		elog(ERROR, "%s: %s", rname.data, aclcheck_error_strings[aclcheck_result]);

	if (parseTree != NULL && parseTree->rowMark != NULL)
	{
		foreach(lp, parseTree->rowMark)
		{
			RowMark	   *rm = lfirst(lp);

			if (!(rm->info & ROW_ACL_FOR_UPDATE))
				continue;

			relid = ((RangeTblEntry *)nth(rm->rti - 1, rangeTable))->relid;
			htup = SearchSysCacheTuple(RELOID,
								   ObjectIdGetDatum(relid),
								   0, 0, 0);
			if (!HeapTupleIsValid(htup))
				elog(ERROR, "ExecCheckPerms: bogus RT relid: %d",
					 relid);
			StrNCpy(rname.data,
					((Form_pg_class) GETSTRUCT(htup))->relname.data,
					NAMEDATALEN);
			ok = ((aclcheck_result = CHECK(ACL_WR)) == ACLCHECK_OK);
			opstr = "write";
			if (!ok)
				elog(ERROR, "%s: %s", rname.data, aclcheck_error_strings[aclcheck_result]);
		}
	}
}

/* ===============================================================
 * ===============================================================
						 static routines follow
 * ===============================================================
 * ===============================================================
 */

typedef struct execRowMark
{
	Relation	relation;
	Index		rti;
	char		resname[32];
} execRowMark;

typedef struct evalPlanQual
{
	Plan				   *plan;
	Index					rti;
	EState					estate;
	struct evalPlanQual	   *free;
} evalPlanQual;

/* ----------------------------------------------------------------
 *		InitPlan
 *
 *		Initializes the query plan: open files, allocate storage
 *		and start up the rule manager
 * ----------------------------------------------------------------
 */
static TupleDesc
InitPlan(CmdType operation, Query *parseTree, Plan *plan, EState *estate)
{
	List		   *rangeTable;
	int				resultRelation;
	Relation		intoRelationDesc;
	TupleDesc		tupType;
	List		   *targetList;
	int				len;

	/*
	 *	get information from query descriptor
	 */
	rangeTable = parseTree->rtable;
	resultRelation = parseTree->resultRelation;

#ifndef NO_SECURITY
	ExecCheckPerms(operation, resultRelation, rangeTable, parseTree);
#endif

	/*
	 *	initialize the node's execution state
	 */
	estate->es_range_table = rangeTable;

	/*
	 *	initialize the BaseId counter so node base_id's
	 *	are assigned correctly.  Someday baseid's will have to
	 *	be stored someplace other than estate because they
	 *	should be unique per query planned.
	 */
	estate->es_BaseId = 1;

	/*
	 *	initialize result relation stuff
	 */

	if (resultRelation != 0 && operation != CMD_SELECT)
	{
		/*
		 *	  if we have a result relation, open it and
		 *	  initialize the result relation info stuff.
		 */
		RelationInfo *resultRelationInfo;
		Index		resultRelationIndex;
		RangeTblEntry *rtentry;
		Oid			resultRelationOid;
		Relation	resultRelationDesc;

		resultRelationIndex = resultRelation;
		rtentry = rt_fetch(resultRelationIndex, rangeTable);
		resultRelationOid = rtentry->relid;
		resultRelationDesc = heap_open(resultRelationOid);

		if (resultRelationDesc->rd_rel->relkind == RELKIND_SEQUENCE)
			elog(ERROR, "You can't change sequence relation %s",
				 resultRelationDesc->rd_rel->relname.data);

		LockRelation(resultRelationDesc, RowExclusiveLock);

		resultRelationInfo = makeNode(RelationInfo);
		resultRelationInfo->ri_RangeTableIndex = resultRelationIndex;
		resultRelationInfo->ri_RelationDesc = resultRelationDesc;
		resultRelationInfo->ri_NumIndices = 0;
		resultRelationInfo->ri_IndexRelationDescs = NULL;
		resultRelationInfo->ri_IndexRelationInfo = NULL;

		/*
		 *	open indices on result relation and save descriptors
		 *	in the result relation information..
		 */
		if (operation != CMD_DELETE)
			ExecOpenIndices(resultRelationOid, resultRelationInfo);

		estate->es_result_relation_info = resultRelationInfo;
	}
	else
	{
		/*
		 *		if no result relation, then set state appropriately
		 */
		estate->es_result_relation_info = NULL;
	}

	/*
	 * Have to lock relations selected for update
	 */
	estate->es_rowMark = NULL;
	if (parseTree->rowMark != NULL)
	{
		Relation		relation;
		Oid				relid;
		RowMark		   *rm;
		List		   *l;
		execRowMark	   *erm;

		foreach(l, parseTree->rowMark)
		{
			rm = lfirst(l);
			relid = ((RangeTblEntry *)nth(rm->rti - 1, rangeTable))->relid;
			relation = heap_open(relid);
			LockRelation(relation, RowShareLock);
			if (!(rm->info & ROW_MARK_FOR_UPDATE))
				continue;
			erm = (execRowMark*) palloc(sizeof(execRowMark));
			erm->relation = relation;
			erm->rti = rm->rti;
			sprintf(erm->resname, "ctid%u", rm->rti);
			estate->es_rowMark = lappend(estate->es_rowMark, erm);
		}
	}

	/*
	 *	  initialize the executor "tuple" table.
	 */
	{
		int			nSlots = ExecCountSlotsNode(plan);
		TupleTable	tupleTable = ExecCreateTupleTable(nSlots + 10);		/* why add ten? - jolly */

		estate->es_tupleTable = tupleTable;
	}

	/*
	 *	   initialize the private state information for
	 *	   all the nodes in the query tree.  This opens
	 *	   files, allocates storage and leaves us ready
	 *	   to start processing tuples..
	 */
	ExecInitNode(plan, estate, NULL);

	/*
	 *	   get the tuple descriptor describing the type
	 *	   of tuples to return.. (this is especially important
	 *	   if we are creating a relation with "retrieve into")
	 */
	tupType = ExecGetTupType(plan);		/* tuple descriptor */
	targetList = plan->targetlist;
	len = ExecTargetListLength(targetList);		/* number of attributes */

	/*
	 *	  now that we have the target list, initialize the junk filter
	 *	  if this is a REPLACE or a DELETE query.
	 *	  We also init the junk filter if this is an append query
	 *	  (there might be some rule lock info there...)
	 *	  NOTE: in the future we might want to initialize the junk
	 *	  filter for all queries.
	 *		  SELECT added by daveh@insightdist.com  5/20/98 to allow
	 *		  ORDER/GROUP BY have an identifier missing from the target.
	 */
	{
		bool		junk_filter_needed = false;
		List	   *tlist;

		if (operation == CMD_SELECT)
		{
			foreach(tlist, targetList)
			{
				TargetEntry *tle = lfirst(tlist);

				if (tle->resdom->resjunk)
				{
					junk_filter_needed = true;
					break;
				}
			}
		}

		if (operation == CMD_UPDATE || operation == CMD_DELETE ||
			operation == CMD_INSERT ||
			(operation == CMD_SELECT && junk_filter_needed))
		{
			JunkFilter *j = (JunkFilter *) ExecInitJunkFilter(targetList);

			estate->es_junkFilter = j;

			if (operation == CMD_SELECT)
				tupType = j->jf_cleanTupType;
		}
		else
			estate->es_junkFilter = NULL;
	}

	/*
	 *	initialize the "into" relation
	 */
	intoRelationDesc = (Relation) NULL;

	if (operation == CMD_SELECT)
	{
		char	   *intoName;
		Oid			intoRelationId;
		TupleDesc	tupdesc;

		if (!parseTree->isPortal)
		{

			/*
			 * a select into table
			 */
			if (parseTree->into != NULL)
			{
				/*
				 *	create the "into" relation
				 */
				intoName = parseTree->into;

				/*
				 * have to copy tupType to get rid of constraints
				 */
				tupdesc = CreateTupleDescCopy(tupType);

				intoRelationId = heap_create_with_catalog(intoName,
								  tupdesc, RELKIND_RELATION,parseTree->isTemp);

				FreeTupleDesc(tupdesc);

				/*
				 *	XXX rather than having to call setheapoverride(true)
				 *		and then back to false, we should change the
				 *		arguments to heap_open() instead..
				 */
				setheapoverride(true);

				intoRelationDesc = heap_open(intoRelationId);

				setheapoverride(false);
			}
		}
	}

	estate->es_into_relation_descriptor = intoRelationDesc;

	estate->es_origPlan = plan;
	estate->es_evalPlanQual = NULL;
	estate->es_evTuple = NULL;
	estate->es_useEvalPlan = false;

	return tupType;
}

/* ----------------------------------------------------------------
 *		EndPlan
 *
 *		Cleans up the query plan -- closes files and free up storages
 * ----------------------------------------------------------------
 */
static void
EndPlan(Plan *plan, EState *estate)
{
	RelationInfo *resultRelationInfo;
	Relation	intoRelationDesc;

	/*
	 *	get information from state
	 */
	resultRelationInfo = estate->es_result_relation_info;
	intoRelationDesc = estate->es_into_relation_descriptor;

	/*
	 *	 shut down the query
	 */
	ExecEndNode(plan, plan);

	/*
	 *	  destroy the executor "tuple" table.
	 */
	{
		TupleTable	tupleTable = (TupleTable) estate->es_tupleTable;

		ExecDestroyTupleTable(tupleTable, true);		/* was missing last arg */
		estate->es_tupleTable = NULL;
	}

	/*
	 *	 close the result relations if necessary
	 */
	if (resultRelationInfo != NULL)
	{
		Relation	resultRelationDesc;

		resultRelationDesc = resultRelationInfo->ri_RelationDesc;
		heap_close(resultRelationDesc);

		/*
		 *	close indices on the result relation
		 */
		ExecCloseIndices(resultRelationInfo);
	}

	/*
	 *	 close the "into" relation if necessary
	 */
	if (intoRelationDesc != NULL)
		heap_close(intoRelationDesc);
}

/* ----------------------------------------------------------------
 *		ExecutePlan
 *
 *		processes the query plan to retrieve 'tupleCount' tuples in the
 *		direction specified.
 *		Retrieves all tuples if tupleCount is 0
 *
 *		result is either a slot containing a tuple in the case
 *		of a RETRIEVE or NULL otherwise.
 *
 * ----------------------------------------------------------------
 */

/* the ctid attribute is a 'junk' attribute that is removed before the
   user can see it*/

static TupleTableSlot *
ExecutePlan(EState *estate,
			Plan *plan,
			CmdType operation,
			int offsetTuples,
			int numberTuples,
			ScanDirection direction,
			DestReceiver* destfunc)
{
	JunkFilter *junkfilter;

	TupleTableSlot *slot;
	ItemPointer tupleid = NULL;
	ItemPointerData tuple_ctid;
	int			current_tuple_count;
	TupleTableSlot *result;

	/*
	 *	initialize local variables
	 */
	slot = NULL;
	current_tuple_count = 0;
	result = NULL;

	/*
	 *	Set the direction.
	 */
	estate->es_direction = direction;

	/*
	 *	Loop until we've processed the proper number
	 *	of tuples from the plan..
	 */

	for (;;)
	{
		/*
		 *	Execute the plan and obtain a tuple
		 */
		/* at the top level, the parent of a plan (2nd arg) is itself */
lnext:;
		if (estate->es_useEvalPlan)
		{
			slot = EvalPlanQualNext(estate);
			if (TupIsNull(slot))
				slot = ExecProcNode(plan, plan);
		}
		else
			slot = ExecProcNode(plan, plan);

		/*
		 *	if the tuple is null, then we assume
		 *	there is nothing more to process so
		 *	we just return null...
		 */
		if (TupIsNull(slot))
		{
			result = NULL;
			break;
		}

		/*
		 *  For now we completely execute the plan and skip
		 *  result tuples if requested by LIMIT offset.
		 *  Finally we should try to do it in deeper levels
		 *  if possible (during index scan)
		 *  - Jan
		 */
		if (offsetTuples > 0)
		{
			--offsetTuples;
			continue;
		}

		/*
		 *		if we have a junk filter, then project a new
		 *		tuple with the junk removed.
		 *
		 *		Store this new "clean" tuple in the place of the
		 *		original tuple.
		 *
		 *		Also, extract all the junk information we need.
		 */
		if ((junkfilter = estate->es_junkFilter) != (JunkFilter *) NULL)
		{
			Datum		datum;
			HeapTuple	newTuple;
			bool		isNull;

			/*
			 * extract the 'ctid' junk attribute.
			 */
			if (operation == CMD_UPDATE || operation == CMD_DELETE)
			{
				if (!ExecGetJunkAttribute(junkfilter,
										  slot,
										  "ctid",
										  &datum,
										  &isNull))
					elog(ERROR, "ExecutePlan: NO (junk) `ctid' was found!");

				if (isNull)
					elog(ERROR, "ExecutePlan: (junk) `ctid' is NULL!");

				tupleid = (ItemPointer) DatumGetPointer(datum);
				tuple_ctid = *tupleid;	/* make sure we don't free the
										 * ctid!! */
				tupleid = &tuple_ctid;
			}
			else if (estate->es_rowMark != NULL)
			{
				List		   *l;
				execRowMark	   *erm;
				Buffer			buffer;
				HeapTupleData	tuple;
				TupleTableSlot *newSlot;
				int				test;

lmark:;
				foreach (l, estate->es_rowMark)
				{
					erm = lfirst(l);
					if (!ExecGetJunkAttribute(junkfilter,
											  slot,
											  erm->resname,
											  &datum,
											  &isNull))
						elog(ERROR, "ExecutePlan: NO (junk) `%s' was found!", erm->resname);

					if (isNull)
						elog(ERROR, "ExecutePlan: (junk) `%s' is NULL!", erm->resname);

					tuple.t_self = *((ItemPointer) DatumGetPointer(datum));
					test = heap_mark4update(erm->relation, &tuple, &buffer);
					ReleaseBuffer(buffer);
					switch (test)
					{
						case HeapTupleSelfUpdated:
						case HeapTupleMayBeUpdated:
							break;

						case HeapTupleUpdated:
							if (XactIsoLevel == XACT_SERIALIZABLE)
							{
								elog(ERROR, "Can't serialize access due to concurrent update");
								return(NULL);
							}
							else if (!(ItemPointerEquals(&(tuple.t_self), 
										(ItemPointer)DatumGetPointer(datum))))
							{
 								newSlot = EvalPlanQual(estate, erm->rti, &(tuple.t_self));
								if (!(TupIsNull(newSlot)))
								{
									slot = newSlot;
									estate->es_useEvalPlan = true;
									goto lmark;
								}
							}
							/* 
							 * if tuple was deleted or PlanQual failed
							 * for updated tuple - we have not return
							 * this tuple!
							 */
							goto lnext;

						default:
							elog(ERROR, "Unknown status %u from heap_mark4update", test);
							return(NULL);
					}
				}
			}

			/*
			 * Finally create a new "clean" tuple with all junk attributes
			 * removed
			 */
			newTuple = ExecRemoveJunk(junkfilter, slot);

			slot = ExecStoreTuple(newTuple,		/* tuple to store */
								  slot, /* destination slot */
								  InvalidBuffer,		/* this tuple has no
														 * buffer */
								  true);		/* tuple should be pfreed */
		}						/* if (junkfilter... */

		/*
		 *		now that we have a tuple, do the appropriate thing
		 *		with it.. either return it to the user, add
		 *		it to a relation someplace, delete it from a
		 *		relation, or modify some of it's attributes.
		 */

		switch (operation)
		{
			case CMD_SELECT:
				ExecRetrieve(slot,		/* slot containing tuple */
							 destfunc,	/* destination's tuple-receiver obj */
							 estate);	/* */
				result = slot;
				break;

			case CMD_INSERT:
				ExecAppend(slot, tupleid, estate);
				result = NULL;
				break;

			case CMD_DELETE:
				ExecDelete(slot, tupleid, estate);
				result = NULL;
				break;

			case CMD_UPDATE:
				ExecReplace(slot, tupleid, estate);
				result = NULL;
				break;

			default:
				elog(DEBUG, "ExecutePlan: unknown operation in queryDesc");
				result = NULL;
				break;
		}
		/*
		 *		check our tuple count.. if we've returned the
		 *		proper number then return, else loop again and
		 *		process more tuples..
		 */
		current_tuple_count += 1;
		if (numberTuples == current_tuple_count)
			break;
	}

	/*
	 *	here, result is either a slot containing a tuple in the case
	 *	of a RETRIEVE or NULL otherwise.
	 */
	return result;
}

/* ----------------------------------------------------------------
 *		ExecRetrieve
 *
 *		RETRIEVEs are easy.. we just pass the tuple to the appropriate
 *		print function.  The only complexity is when we do a
 *		"retrieve into", in which case we insert the tuple into
 *		the appropriate relation (note: this is a newly created relation
 *		so we don't need to worry about indices or locks.)
 * ----------------------------------------------------------------
 */
static void
ExecRetrieve(TupleTableSlot *slot,
			 DestReceiver *destfunc,
			 EState *estate)
{
	HeapTuple	tuple;
	TupleDesc	attrtype;

	/*
	 *	get the heap tuple out of the tuple table slot
	 */
	tuple = slot->val;
	attrtype = slot->ttc_tupleDescriptor;

	/*
	 *	insert the tuple into the "into relation"
	 */
	if (estate->es_into_relation_descriptor != NULL)
	{
		heap_insert(estate->es_into_relation_descriptor, tuple);
		IncrAppended();
	}

	/*
	 *	send the tuple to the front end (or the screen)
	 */
	(*destfunc->receiveTuple) (tuple, attrtype, destfunc);
	IncrRetrieved();
	(estate->es_processed)++;
}

/* ----------------------------------------------------------------
 *		ExecAppend
 *
 *		APPENDs are trickier.. we have to insert the tuple into
 *		the base relation and insert appropriate tuples into the
 *		index relations.
 * ----------------------------------------------------------------
 */

static void
ExecAppend(TupleTableSlot *slot,
		   ItemPointer tupleid,
		   EState *estate)
{
	HeapTuple	tuple;
	RelationInfo *resultRelationInfo;
	Relation	resultRelationDesc;
	int			numIndices;
	Oid			newId;

	/*
	 *	get the heap tuple out of the tuple table slot
	 */
	tuple = slot->val;

	/*
	 *	get information on the result relation
	 */
	resultRelationInfo = estate->es_result_relation_info;
	resultRelationDesc = resultRelationInfo->ri_RelationDesc;

	/*
	 *	have to add code to preform unique checking here.
	 *	cim -12/1/89
	 */

	/* BEFORE ROW INSERT Triggers */
	if (resultRelationDesc->trigdesc &&
	resultRelationDesc->trigdesc->n_before_row[TRIGGER_EVENT_INSERT] > 0)
	{
		HeapTuple	newtuple;

		newtuple = ExecBRInsertTriggers(resultRelationDesc, tuple);

		if (newtuple == NULL)	/* "do nothing" */
			return;

		if (newtuple != tuple)	/* modified by Trigger(s) */
		{
			Assert(slot->ttc_shouldFree);
			pfree(tuple);
			slot->val = tuple = newtuple;
		}
	}

	/*
	 * Check the constraints of a tuple
	 */

	if (resultRelationDesc->rd_att->constr)
	{
		ExecConstraints("ExecAppend", resultRelationDesc, tuple, estate);
	}

	/*
	 *	insert the tuple
	 */
	newId = heap_insert(resultRelationDesc,		/* relation desc */
						tuple); /* heap tuple */
	IncrAppended();

	/*
	 *	process indices
	 *
	 *	Note: heap_insert adds a new tuple to a relation.  As a side
	 *	effect, the tupleid of the new tuple is placed in the new
	 *	tuple's t_ctid field.
	 */
	numIndices = resultRelationInfo->ri_NumIndices;
	if (numIndices > 0)
		ExecInsertIndexTuples(slot, &(tuple->t_self), estate, false);
	(estate->es_processed)++;
	estate->es_lastoid = newId;

	/* AFTER ROW INSERT Triggers */
	if (resultRelationDesc->trigdesc &&
	 resultRelationDesc->trigdesc->n_after_row[TRIGGER_EVENT_INSERT] > 0)
		ExecARInsertTriggers(resultRelationDesc, tuple);
}

/* ----------------------------------------------------------------
 *		ExecDelete
 *
 *		DELETE is like append, we delete the tuple and its
 *		index tuples.
 * ----------------------------------------------------------------
 */
static void
ExecDelete(TupleTableSlot *slot,
		   ItemPointer tupleid,
		   EState *estate)
{
	RelationInfo	   *resultRelationInfo;
	Relation			resultRelationDesc;
	ItemPointerData		ctid;
	int					result;

	/*
	 *	get the result relation information
	 */
	resultRelationInfo = estate->es_result_relation_info;
	resultRelationDesc = resultRelationInfo->ri_RelationDesc;

	/* BEFORE ROW DELETE Triggers */
	if (resultRelationDesc->trigdesc &&
	resultRelationDesc->trigdesc->n_before_row[TRIGGER_EVENT_DELETE] > 0)
	{
		bool		dodelete;

		dodelete = ExecBRDeleteTriggers(estate, tupleid);

		if (!dodelete)			/* "do nothing" */
			return;
	}

	/*
	 *	delete the tuple
	 */
ldelete:;
	result = heap_delete(resultRelationDesc, tupleid, &ctid);
	switch (result)
	{
		case HeapTupleSelfUpdated:
			return;

		case HeapTupleMayBeUpdated:
			break;

		case HeapTupleUpdated:
			if (XactIsoLevel == XACT_SERIALIZABLE)
				elog(ERROR, "Can't serialize access due to concurrent update");
			else if (!(ItemPointerEquals(tupleid, &ctid)))
			{
				TupleTableSlot *epqslot = EvalPlanQual(estate, 
						resultRelationInfo->ri_RangeTableIndex, &ctid);

				if (!TupIsNull(epqslot))
				{
					*tupleid = ctid;
					goto ldelete;
				}
			}
			return;

		default:
			elog(ERROR, "Unknown status %u from heap_delete", result);
			return;
	}

	IncrDeleted();
	(estate->es_processed)++;

	/*
	 *	Note: Normally one would think that we have to
	 *		  delete index tuples associated with the
	 *		  heap tuple now..
	 *
	 *		  ... but in POSTGRES, we have no need to do this
	 *		  because the vacuum daemon automatically
	 *		  opens an index scan and deletes index tuples
	 *		  when it finds deleted heap tuples. -cim 9/27/89
	 */

	/* AFTER ROW DELETE Triggers */
	if (resultRelationDesc->trigdesc &&
	 resultRelationDesc->trigdesc->n_after_row[TRIGGER_EVENT_DELETE] > 0)
		ExecARDeleteTriggers(estate, tupleid);

}

/* ----------------------------------------------------------------
 *		ExecReplace
 *
 *		note: we can't run replace queries with transactions
 *		off because replaces are actually appends and our
 *		scan will mistakenly loop forever, replacing the tuple
 *		it just appended..	This should be fixed but until it
 *		is, we don't want to get stuck in an infinite loop
 *		which corrupts your database..
 * ----------------------------------------------------------------
 */
static void
ExecReplace(TupleTableSlot *slot,
			ItemPointer tupleid,
			EState *estate)
{
	HeapTuple			tuple;
	RelationInfo	   *resultRelationInfo;
	Relation			resultRelationDesc;
	ItemPointerData		ctid;
	int					result;
	int					numIndices;

	/*
	 *	abort the operation if not running transactions
	 */
	if (IsBootstrapProcessingMode())
	{
		elog(DEBUG, "ExecReplace: replace can't run without transactions");
		return;
	}

	/*
	 *	get the heap tuple out of the tuple table slot
	 */
	tuple = slot->val;

	/*
	 *	get the result relation information
	 */
	resultRelationInfo = estate->es_result_relation_info;
	resultRelationDesc = resultRelationInfo->ri_RelationDesc;

	/*
	 *	have to add code to preform unique checking here.
	 *	in the event of unique tuples, this becomes a deletion
	 *	of the original tuple affected by the replace.
	 *	cim -12/1/89
	 */

	/* BEFORE ROW UPDATE Triggers */
	if (resultRelationDesc->trigdesc &&
	resultRelationDesc->trigdesc->n_before_row[TRIGGER_EVENT_UPDATE] > 0)
	{
		HeapTuple	newtuple;

		newtuple = ExecBRUpdateTriggers(estate, tupleid, tuple);

		if (newtuple == NULL)	/* "do nothing" */
			return;

		if (newtuple != tuple)	/* modified by Trigger(s) */
		{
			Assert(slot->ttc_shouldFree);
			pfree(tuple);
			slot->val = tuple = newtuple;
		}
	}

	/*
	 * Check the constraints of a tuple
	 */

	if (resultRelationDesc->rd_att->constr)
	{
		ExecConstraints("ExecReplace", resultRelationDesc, tuple, estate);
	}

	/*
	 *	replace the heap tuple
	 */
lreplace:;
	result = heap_replace(resultRelationDesc, tupleid, tuple, &ctid);
	switch (result)
	{
		case HeapTupleSelfUpdated:
			return;

		case HeapTupleMayBeUpdated:
			break;

		case HeapTupleUpdated:
			if (XactIsoLevel == XACT_SERIALIZABLE)
				elog(ERROR, "Can't serialize access due to concurrent update");
			else if (!(ItemPointerEquals(tupleid, &ctid)))
			{
				TupleTableSlot *epqslot = EvalPlanQual(estate, 
						resultRelationInfo->ri_RangeTableIndex, &ctid);

				if (!TupIsNull(epqslot))
				{
					*tupleid = ctid;
					tuple = ExecRemoveJunk(estate->es_junkFilter, epqslot);
					slot = ExecStoreTuple(tuple, slot, InvalidBuffer, true);
					goto lreplace;
				}
			}
			return;

		default:
			elog(ERROR, "Unknown status %u from heap_replace", result);
			return;
	}

	IncrReplaced();
	(estate->es_processed)++;

	/*
	 *	Note: instead of having to update the old index tuples
	 *		  associated with the heap tuple, all we do is form
	 *		  and insert new index tuples..  This is because
	 *		  replaces are actually deletes and inserts and
	 *		  index tuple deletion is done automagically by
	 *		  the vaccuum deamon.. All we do is insert new
	 *		  index tuples.  -cim 9/27/89
	 */

	/*
	 *	process indices
	 *
	 *	heap_replace updates a tuple in the base relation by invalidating
	 *	it and then appending a new tuple to the relation.	As a side
	 *	effect, the tupleid of the new tuple is placed in the new
	 *	tuple's t_ctid field.  So we now insert index tuples using
	 *	the new tupleid stored there.
	 */

	numIndices = resultRelationInfo->ri_NumIndices;
	if (numIndices > 0)
		ExecInsertIndexTuples(slot, &(tuple->t_self), estate, true);

	/* AFTER ROW UPDATE Triggers */
	if (resultRelationDesc->trigdesc &&
	 resultRelationDesc->trigdesc->n_after_row[TRIGGER_EVENT_UPDATE] > 0)
		ExecARUpdateTriggers(estate, tupleid, tuple);
}

#ifdef NOT_USED
static HeapTuple
ExecAttrDefault(Relation rel, HeapTuple tuple)
{
	int			ndef = rel->rd_att->constr->num_defval;
	AttrDefault *attrdef = rel->rd_att->constr->defval;
	ExprContext *econtext = makeNode(ExprContext);
	HeapTuple	newtuple;
	Node	   *expr;
	bool		isnull;
	bool		isdone;
	Datum		val;
	Datum	   *replValue = NULL;
	char	   *replNull = NULL;
	char	   *repl = NULL;
	int			i;

	econtext->ecxt_scantuple = NULL;	/* scan tuple slot */
	econtext->ecxt_innertuple = NULL;	/* inner tuple slot */
	econtext->ecxt_outertuple = NULL;	/* outer tuple slot */
	econtext->ecxt_relation = NULL;		/* relation */
	econtext->ecxt_relid = 0;	/* relid */
	econtext->ecxt_param_list_info = NULL;		/* param list info */
	econtext->ecxt_param_exec_vals = NULL;		/* exec param values */
	econtext->ecxt_range_table = NULL;	/* range table */
	for (i = 0; i < ndef; i++)
	{
		if (!heap_attisnull(tuple, attrdef[i].adnum))
			continue;
		expr = (Node *) stringToNode(attrdef[i].adbin);

		val = ExecEvalExpr(expr, econtext, &isnull, &isdone);

		pfree(expr);

		if (isnull)
			continue;

		if (repl == NULL)
		{
			repl = (char *) palloc(rel->rd_att->natts * sizeof(char));
			replNull = (char *) palloc(rel->rd_att->natts * sizeof(char));
			replValue = (Datum *) palloc(rel->rd_att->natts * sizeof(Datum));
			MemSet(repl, ' ', rel->rd_att->natts * sizeof(char));
		}

		repl[attrdef[i].adnum - 1] = 'r';
		replNull[attrdef[i].adnum - 1] = ' ';
		replValue[attrdef[i].adnum - 1] = val;

	}

	pfree(econtext);

	if (repl == NULL)
		return tuple;

	newtuple = heap_modifytuple(tuple, rel, replValue, replNull, repl);

	pfree(repl);
	pfree(tuple);
	pfree(replNull);
	pfree(replValue);

	return newtuple;

}

#endif

static char *
ExecRelCheck(Relation rel, HeapTuple tuple, EState *estate)
{
	int			ncheck = rel->rd_att->constr->num_check;
	ConstrCheck *check = rel->rd_att->constr->check;
	ExprContext *econtext = makeNode(ExprContext);
	TupleTableSlot *slot = makeNode(TupleTableSlot);
	RangeTblEntry *rte = makeNode(RangeTblEntry);
	List	   *rtlist;
	List	   *qual;
	bool		res;
	int			i;

	slot->val = tuple;
	slot->ttc_shouldFree = false;
	slot->ttc_descIsNew = true;
	slot->ttc_tupleDescriptor = rel->rd_att;
	slot->ttc_buffer = InvalidBuffer;
	slot->ttc_whichplan = -1;
	rte->relname = nameout(&(rel->rd_rel->relname));
	rte->refname = rte->relname;
	rte->relid = RelationGetRelid(rel);
	rte->inh = false;
	rte->inFromCl = true;
	rtlist = lcons(rte, NIL);
	econtext->ecxt_scantuple = slot;	/* scan tuple slot */
	econtext->ecxt_innertuple = NULL;	/* inner tuple slot */
	econtext->ecxt_outertuple = NULL;	/* outer tuple slot */
	econtext->ecxt_relation = rel;		/* relation */
	econtext->ecxt_relid = 0;	/* relid */
	econtext->ecxt_param_list_info = NULL;		/* param list info */
	econtext->ecxt_param_exec_vals = NULL;		/* exec param values */
	econtext->ecxt_range_table = rtlist;		/* range table */

	if (estate->es_result_relation_constraints == NULL)
	{
		estate->es_result_relation_constraints =
				(List **)palloc(ncheck * sizeof(List *));

		for (i = 0; i < ncheck; i++)
		{
			qual = (List *) stringToNode(check[i].ccbin);
			estate->es_result_relation_constraints[i] = qual;
		}
	}

	for (i = 0; i < ncheck; i++)
	{
		qual = estate->es_result_relation_constraints[i];

		res = ExecQual(qual, econtext);

		if (!res)
			return check[i].ccname;
	}

	pfree(slot);
	pfree(rte->relname);
	pfree(rte);
	pfree(rtlist);
	pfree(econtext);

	return (char *) NULL;

}

void
ExecConstraints(char *caller, Relation rel, HeapTuple tuple, EState *estate)
{

	Assert(rel->rd_att->constr);

	if (rel->rd_att->constr->has_not_null)
	{
		int			attrChk;

		for (attrChk = 1; attrChk <= rel->rd_att->natts; attrChk++)
		{
			if (rel->rd_att->attrs[attrChk - 1]->attnotnull && heap_attisnull(tuple, attrChk))
				elog(ERROR, "%s: Fail to add null value in not null attribute %s",
				  caller, rel->rd_att->attrs[attrChk - 1]->attname.data);
		}
	}

	if (rel->rd_att->constr->num_check > 0)
	{
		char	   *failed;

		if ((failed = ExecRelCheck(rel, tuple, estate)) != NULL)
			elog(ERROR, "%s: rejected due to CHECK constraint %s", caller, failed);
	}

	return;
}

TupleTableSlot*
EvalPlanQual(EState *estate, Index rti, ItemPointer tid)
{
	evalPlanQual	   *epq = (evalPlanQual*) estate->es_evalPlanQual;
	evalPlanQual	   *oldepq;
	EState			   *epqstate = NULL;
	Relation			relation;
	Buffer				buffer;
	HeapTupleData		tuple;
	bool				endNode = true;

	Assert(rti != 0);

	if (epq != NULL && epq->rti == 0)
	{
		Assert(!(estate->es_useEvalPlan) && 
				epq->estate.es_evalPlanQual == NULL);
		epq->rti = rti;
		endNode = false;
	}

	/*
	 * If this is request for another RTE - Ra, - then we have to check
	 * wasn't PlanQual requested for Ra already and if so then Ra' row 
	 * was updated again and we have to re-start old execution for Ra 
	 * and forget all what we done after Ra was suspended. Cool? -:))
	 */
	if (epq != NULL && epq->rti != rti && 
		epq->estate.es_evTuple[rti - 1] != NULL)
	{
		do
		{
			/* pop previous PlanQual from the stack */
			epqstate = &(epq->estate);
			oldepq = (evalPlanQual*) epqstate->es_evalPlanQual;
			Assert(oldepq->rti != 0);
			/* stop execution */
			ExecEndNode(epq->plan, epq->plan);
			pfree(epqstate->es_evTuple[epq->rti - 1]);
			epqstate->es_evTuple[epq->rti - 1] = NULL;
			/* push current PQ to freePQ stack */
			oldepq->free = epq;
			epq = oldepq;
		} while (epq->rti != rti);
		estate->es_evalPlanQual = (Pointer) epq;
	}

	/* 
	 * If we are requested for another RTE then we have to suspend
	 * execution of current PlanQual and start execution for new one.
	 */
	if (epq == NULL || epq->rti != rti)
	{
		/* try to reuse plan used previously */
		evalPlanQual   *newepq = (epq != NULL) ? epq->free : NULL;

		if (newepq == NULL)		/* first call or freePQ stack is empty */
		{
			newepq = (evalPlanQual*) palloc(sizeof(evalPlanQual));
			/* Init EState */
			epqstate = &(newepq->estate);
			memset(epqstate, 0, sizeof(EState));
			epqstate->type = T_EState; 
			epqstate->es_direction = ForwardScanDirection;
			epqstate->es_snapshot = estate->es_snapshot;
			epqstate->es_range_table = estate->es_range_table;
			epqstate->es_param_list_info = estate->es_param_list_info;
			if (estate->es_origPlan->nParamExec > 0)
				epqstate->es_param_exec_vals = (ParamExecData *)
							palloc(estate->es_origPlan->nParamExec * 
									sizeof(ParamExecData));
			epqstate->es_tupleTable = 
				ExecCreateTupleTable(estate->es_tupleTable->size);
			epqstate->es_refcount = estate->es_refcount;
			/* ... rest */
			newepq->plan = copyObject(estate->es_origPlan);
			newepq->free = NULL;
			epqstate->es_evTupleNull = (bool*) 
				palloc(length(estate->es_range_table) * sizeof(bool));
			if (epq == NULL)	/* first call */
			{
				epqstate->es_evTuple = (HeapTuple*) 
					palloc(length(estate->es_range_table) * sizeof(HeapTuple));
				memset(epqstate->es_evTuple, 0, 
					length(estate->es_range_table) * sizeof(HeapTuple));
			}
			else
			{
				epqstate->es_evTuple = epq->estate.es_evTuple;
			}
		}
		else
		{
			epqstate = &(newepq->estate);
		}
		/* push current PQ to the stack */
		epqstate->es_evalPlanQual = (Pointer) epq;
		estate->es_evalPlanQual = (Pointer) epq = newepq;
		epq->rti = rti;
		endNode = false;
	}

	epqstate = &(epq->estate);

	/*
	 * Ok - we're requested for the same RTE (-:)).
	 * I'm not sure about ability to use ExecReScan instead of
	 * ExecInitNode, so...
	 */
	if (endNode)
		ExecEndNode(epq->plan, epq->plan);

	/* free old RTE' tuple */
	if (epqstate->es_evTuple[epq->rti - 1] != NULL)
	{
		pfree(epqstate->es_evTuple[epq->rti - 1]);
		epqstate->es_evTuple[epq->rti - 1] = NULL;
	}

	/* ** fetch tid tuple ** */
	if (estate->es_result_relation_info != NULL && 
		estate->es_result_relation_info->ri_RangeTableIndex == rti)
		relation = estate->es_result_relation_info->ri_RelationDesc;
	else
	{
		List   *l;

		foreach (l, estate->es_rowMark)
		{
			if (((execRowMark*) lfirst(l))->rti == rti)
				break;
		}
		relation = ((execRowMark*) lfirst(l))->relation;
	}
	tuple.t_self = *tid;
	for ( ; ; )
	{
		heap_fetch(relation, SnapshotDirty, &tuple, &buffer);
		if (tuple.t_data != NULL)
		{
			TransactionId xwait = SnapshotDirty->xmax;

			if (TransactionIdIsValid(SnapshotDirty->xmin))
				elog(ERROR, "EvalPlanQual: t_xmin is uncommitted ?!");
			/*
			 * If tuple is being updated by other transaction then 
			 * we have to wait for its commit/abort.
			 */
			if (TransactionIdIsValid(xwait))
			{
				ReleaseBuffer(buffer);
				XactLockTableWait(xwait);
				continue;
			}
			/*
			 * Nice! We got tuple - now copy it.
			 */
			if (epqstate->es_evTuple[epq->rti - 1] != NULL)
				pfree(epqstate->es_evTuple[epq->rti - 1]);
			epqstate->es_evTuple[epq->rti - 1] = heap_copytuple(&tuple);
			ReleaseBuffer(buffer);
			break;
		}
		/*
		 * Ops! Invalid tuple. Have to check is it updated or deleted.
		 * Note that it's possible to get invalid SnapshotDirty->tid
		 * if tuple updated by this transaction. Have we to check this ?
		 */
		if (ItemPointerIsValid(&(SnapshotDirty->tid)) && 
			!(ItemPointerEquals(&(tuple.t_self), &(SnapshotDirty->tid))))
		{
			tuple.t_self = SnapshotDirty->tid;	/* updated ... */
			continue;
		}
		/*
		 * Deleted or updated by this transaction. Do not
		 * (re-)start execution of this PQ. Continue previous PQ.
		 */
		oldepq = (evalPlanQual*) epqstate->es_evalPlanQual;
		if (oldepq != NULL)
		{
			Assert(oldepq->rti != 0);
			/* push current PQ to freePQ stack */
			oldepq->free = epq;
			epq = oldepq;
			epqstate = &(epq->estate);
			estate->es_evalPlanQual = (Pointer) epq;
		}
		else
		{									/* this is the first (oldest) PQ
			epq->rti = 0;					 * - mark as free and 
			estate->es_useEvalPlan = false;	 * continue Query execution
			return (NULL);					 */
		}
	}

	if (estate->es_origPlan->nParamExec > 0)
		memset(epqstate->es_param_exec_vals, 0, 
				estate->es_origPlan->nParamExec * sizeof(ParamExecData));
	memset(epqstate->es_evTupleNull, false, 
			length(estate->es_range_table) * sizeof(bool));
	ExecInitNode(epq->plan, epqstate, NULL);

	/*
	 * For UPDATE/DELETE we have to return tid of actual row
	 * we're executing PQ for.
	 */
	*tid = tuple.t_self;

	return (EvalPlanQualNext(estate));
}

static TupleTableSlot* 
EvalPlanQualNext(EState *estate)
{
	evalPlanQual	   *epq = (evalPlanQual*) estate->es_evalPlanQual;
	EState			   *epqstate = &(epq->estate);
	evalPlanQual	   *oldepq;
	TupleTableSlot	   *slot;

	Assert(epq->rti != 0);

lpqnext:;
	slot = ExecProcNode(epq->plan, epq->plan);

	/*
	 * No more tuples for this PQ. Continue previous one.
	 */
	if (TupIsNull(slot))
	{
		ExecEndNode(epq->plan, epq->plan);
		pfree(epqstate->es_evTuple[epq->rti - 1]);
		epqstate->es_evTuple[epq->rti - 1] = NULL;
		/* pop old PQ from the stack */
		oldepq = (evalPlanQual*) epqstate->es_evalPlanQual;
		if (oldepq == (evalPlanQual*) NULL)
		{									/* this is the first (oldest) */
			epq->rti = 0;					/* PQ - mark as free and      */
			estate->es_useEvalPlan = false;	/* continue Query execution   */
			return (NULL);
		}
		Assert(oldepq->rti != 0);
		/* push current PQ to freePQ stack */
		oldepq->free = epq;
		epq = oldepq;
		epqstate = &(epq->estate);
		estate->es_evalPlanQual = (Pointer) epq;
		goto lpqnext;
	}

	return (slot);
}