text: /*-------------------------------------------------------------------------
   *
   * nodeSubplan.c
   *	  routines to support subselects
   *
   * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   * IDENTIFICATION
   *	  $PostgreSQL: pgsql/src/backend/executor/nodeSubplan.c,v 1.70.2.1 2005/11/22 18:23:09 momjian Exp $
   *
   *-------------------------------------------------------------------------
   */
  /*
   *	 INTERFACE ROUTINES
   *		ExecSubPlan  - process a subselect
   *		ExecInitSubPlan - initialize a subselect
   *		ExecEndSubPlan	- shut down a subselect
   */
  #include "postgres.h"
  
  #include "access/heapam.h"
  #include "executor/executor.h"
  #include "executor/nodeSubplan.h"
  #include "nodes/makefuncs.h"
  #include "parser/parse_expr.h"
  #include "utils/array.h"
  #include "utils/datum.h"
  #include "utils/lsyscache.h"
  #include "utils/memutils.h"
  
  
  static Datum ExecHashSubPlan(SubPlanState *node,
  				ExprContext *econtext,
  				bool *isNull);
  static Datum ExecScanSubPlan(SubPlanState *node,
  				ExprContext *econtext,
  				bool *isNull);
  static void buildSubPlanHash(SubPlanState *node);
  static bool findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot);
  static bool slotAllNulls(TupleTableSlot *slot);
  static bool slotNoNulls(TupleTableSlot *slot);
  
  
  /* ----------------------------------------------------------------
   *		ExecSubPlan
   * ----------------------------------------------------------------
   */
  Datum
  ExecSubPlan(SubPlanState *node,
  			ExprContext *econtext,
  			bool *isNull,
  			ExprDoneCond *isDone)
  {
  	SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
  
  	/* Set default values for result flags: non-null, not a set result */
  	*isNull = false;
  	if (isDone)
  		*isDone = ExprSingleResult;
  
  	if (subplan->setParam != NIL)
  		elog(ERROR, "cannot set parent params from subquery");
  
  	if (subplan->useHashTable)
  		return ExecHashSubPlan(node, econtext, isNull);
  	else
  		return ExecScanSubPlan(node, econtext, isNull);
  }
  
  /*
   * ExecHashSubPlan: store subselect result in an in-memory hash table
   */
  static Datum
  ExecHashSubPlan(SubPlanState *node,
  				ExprContext *econtext,
  				bool *isNull)
  {
  	SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
  	PlanState  *planstate = node->planstate;
  	ExprContext *innerecontext = node->innerecontext;
  	TupleTableSlot *slot;
  
  	/* Shouldn't have any direct correlation Vars */
  	if (subplan->parParam != NIL || node->args != NIL)
  		elog(ERROR, "hashed subplan with direct correlation not supported");
  
  	/*
  	 * If first time through or we need to rescan the subplan, build the hash
  	 * table.
  	 */
  	if (node->hashtable == NULL || planstate->chgParam != NULL)
  		buildSubPlanHash(node);
  
  	/*
  	 * The result for an empty subplan is always FALSE; no need to evaluate
  	 * lefthand side.
  	 */
  	*isNull = false;
  	if (!node->havehashrows && !node->havenullrows)
  		return BoolGetDatum(false);
  
  	/*
  	 * Evaluate lefthand expressions and form a projection tuple. First we
  	 * have to set the econtext to use (hack alert!).
  	 */
  	node->projLeft->pi_exprContext = econtext;
  	slot = ExecProject(node->projLeft, NULL);
  
  	/*
  	 * Note: because we are typically called in a per-tuple context, we have
  	 * to explicitly clear the projected tuple before returning. Otherwise,
  	 * we'll have a double-free situation: the per-tuple context will probably
  	 * be reset before we're called again, and then the tuple slot will think
  	 * it still needs to free the tuple.
  	 */
  
  	/*
  	 * Since the hashtable routines will use innerecontext's per-tuple memory
  	 * as working memory, be sure to reset it for each tuple.
  	 */
  	ResetExprContext(innerecontext);
  
  	/*
  	 * If the LHS is all non-null, probe for an exact match in the main hash
  	 * table.  If we find one, the result is TRUE. Otherwise, scan the
  	 * partly-null table to see if there are any rows that aren't provably
  	 * unequal to the LHS; if so, the result is UNKNOWN.  (We skip that part
  	 * if we don't care about UNKNOWN.) Otherwise, the result is FALSE.
  	 *
  	 * Note: the reason we can avoid a full scan of the main hash table is
  	 * that the combining operators are assumed never to yield NULL when both
  	 * inputs are non-null.  If they were to do so, we might need to produce
  	 * UNKNOWN instead of FALSE because of an UNKNOWN result in comparing the
  	 * LHS to some main-table entry --- which is a comparison we will not even
  	 * make, unless there's a chance match of hash keys.
  	 */
  	if (slotNoNulls(slot))
  	{
  		if (node->havehashrows &&
  			LookupTupleHashEntry(node->hashtable, slot, NULL) != NULL)
  		{
  			ExecClearTuple(slot);
  			return BoolGetDatum(true);
  		}
  		if (node->havenullrows &&
  			findPartialMatch(node->hashnulls, slot))
  		{
  			ExecClearTuple(slot);
  			*isNull = true;
  			return BoolGetDatum(false);
  		}
  		ExecClearTuple(slot);
  		return BoolGetDatum(false);
  	}
  
  	/*
  	 * When the LHS is partly or wholly NULL, we can never return TRUE. If we
  	 * don't care about UNKNOWN, just return FALSE.  Otherwise, if the LHS is
  	 * wholly NULL, immediately return UNKNOWN.  (Since the combining
  	 * operators are strict, the result could only be FALSE if the sub-select
  	 * were empty, but we already handled that case.) Otherwise, we must scan
  	 * both the main and partly-null tables to see if there are any rows that
  	 * aren't provably unequal to the LHS; if so, the result is UNKNOWN.
  	 * Otherwise, the result is FALSE.
  	 */
  	if (node->hashnulls == NULL)
  	{
  		ExecClearTuple(slot);
  		return BoolGetDatum(false);
  	}
  	if (slotAllNulls(slot))
  	{
  		ExecClearTuple(slot);
  		*isNull = true;
  		return BoolGetDatum(false);
  	}
  	/* Scan partly-null table first, since more likely to get a match */
  	if (node->havenullrows &&
  		findPartialMatch(node->hashnulls, slot))
  	{
  		ExecClearTuple(slot);
  		*isNull = true;
  		return BoolGetDatum(false);
  	}
  	if (node->havehashrows &&
  		findPartialMatch(node->hashtable, slot))
  	{
  		ExecClearTuple(slot);
  		*isNull = true;
  		return BoolGetDatum(false);
  	}
  	ExecClearTuple(slot);
  	return BoolGetDatum(false);
  }
  
  /*
   * ExecScanSubPlan: default case where we have to rescan subplan each time
   */
  static Datum
  ExecScanSubPlan(SubPlanState *node,
  				ExprContext *econtext,
  				bool *isNull)
  {
  	SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
  	PlanState  *planstate = node->planstate;
  	SubLinkType subLinkType = subplan->subLinkType;
  	bool		useOr = subplan->useOr;
  	MemoryContext oldcontext;
  	TupleTableSlot *slot;
  	Datum		result;
  	bool		found = false;	/* TRUE if got at least one subplan tuple */
  	ListCell   *pvar;
  	ListCell   *l;
  	ArrayBuildState *astate = NULL;
  
  	/*
  	 * We are probably in a short-lived expression-evaluation context. Switch
  	 * to the child plan's per-query context for manipulating its chgParam,
  	 * calling ExecProcNode on it, etc.
  	 */
  	oldcontext = MemoryContextSwitchTo(node->sub_estate->es_query_cxt);
  
  	/*
  	 * Set Params of this plan from parent plan correlation values. (Any
  	 * calculation we have to do is done in the parent econtext, since the
  	 * Param values don't need to have per-query lifetime.)
  	 */
  	Assert(list_length(subplan->parParam) == list_length(node->args));
  
  	forboth(l, subplan->parParam, pvar, node->args)
  	{
  		int			paramid = lfirst_int(l);
  		ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
  
  		prm->value = ExecEvalExprSwitchContext((ExprState *) lfirst(pvar),
  											   econtext,
  											   &(prm->isnull),
  											   NULL);
  		planstate->chgParam = bms_add_member(planstate->chgParam, paramid);
  	}
  
  	ExecReScan(planstate, NULL);
  
  	/*
  	 * For all sublink types except EXPR_SUBLINK and ARRAY_SUBLINK, the result
  	 * is boolean as are the results of the combining operators. We combine
  	 * results within a tuple (if there are multiple columns) using OR
  	 * semantics if "useOr" is true, AND semantics if not. We then combine
  	 * results across tuples (if the subplan produces more than one) using OR
  	 * semantics for ANY_SUBLINK or AND semantics for ALL_SUBLINK.
  	 * (MULTIEXPR_SUBLINK doesn't allow multiple tuples from the subplan.)
  	 * NULL results from the combining operators are handled according to the
  	 * usual SQL semantics for OR and AND.	The result for no input tuples is
  	 * FALSE for ANY_SUBLINK, TRUE for ALL_SUBLINK, NULL for
  	 * MULTIEXPR_SUBLINK.
  	 *
  	 * For EXPR_SUBLINK we require the subplan to produce no more than one
  	 * tuple, else an error is raised. For ARRAY_SUBLINK we allow the subplan
  	 * to produce more than one tuple. In either case, if zero tuples are
  	 * produced, we return NULL. Assuming we get a tuple, we just use its
  	 * first column (there can be only one non-junk column in this case).
  	 */
  	result = BoolGetDatum(subLinkType == ALL_SUBLINK);
  	*isNull = false;
  
  	for (slot = ExecProcNode(planstate);
  		 !TupIsNull(slot);
  		 slot = ExecProcNode(planstate))
  	{
  		TupleDesc	tdesc = slot->tts_tupleDescriptor;
  		Datum		rowresult = BoolGetDatum(!useOr);
  		bool		rownull = false;
  		int			col = 1;
  		ListCell   *plst;
  
  		if (subLinkType == EXISTS_SUBLINK)
  		{
  			found = true;
  			result = BoolGetDatum(true);
  			break;
  		}
  
  		if (subLinkType == EXPR_SUBLINK)
  		{
  			/* cannot allow multiple input tuples for EXPR sublink */
  			if (found)
  				ereport(ERROR,
  						(errcode(ERRCODE_CARDINALITY_VIOLATION),
  						 errmsg("more than one row returned by a subquery used as an expression")));
  			found = true;
  
  			/*
  			 * We need to copy the subplan's tuple in case the result is of
  			 * pass-by-ref type --- our return value will point into this
  			 * copied tuple!  Can't use the subplan's instance of the tuple
  			 * since it won't still be valid after next ExecProcNode() call.
  			 * node->curTuple keeps track of the copied tuple for eventual
  			 * freeing.
  			 */
  			MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
  			if (node->curTuple)
  				heap_freetuple(node->curTuple);
  			node->curTuple = ExecCopySlotTuple(slot);
  			MemoryContextSwitchTo(node->sub_estate->es_query_cxt);
  
  			result = heap_getattr(node->curTuple, col, tdesc, isNull);
  			/* keep scanning subplan to make sure there's only one tuple */
  			continue;
  		}
  
  		if (subLinkType == ARRAY_SUBLINK)
  		{
  			Datum		dvalue;
  			bool		disnull;
  
  			found = true;
  			/* stash away current value */
  			dvalue = slot_getattr(slot, 1, &disnull);
  			astate = accumArrayResult(astate, dvalue, disnull,
  									  tdesc->attrs[0]->atttypid,
  									  oldcontext);
  			/* keep scanning subplan to collect all values */
  			continue;
  		}
  
  		/* cannot allow multiple input tuples for MULTIEXPR sublink either */
  		if (subLinkType == MULTIEXPR_SUBLINK && found)
  			ereport(ERROR,
  					(errcode(ERRCODE_CARDINALITY_VIOLATION),
  					 errmsg("more than one row returned by a subquery used as an expression")));
  
  		found = true;
  
  		/*
  		 * For ALL, ANY, and MULTIEXPR sublinks, iterate over combining
  		 * operators for columns of tuple.
  		 */
  		Assert(list_length(node->exprs) == list_length(subplan->paramIds));
  
  		forboth(l, node->exprs, plst, subplan->paramIds)
  		{
  			ExprState  *exprstate = (ExprState *) lfirst(l);
  			int			paramid = lfirst_int(plst);
  			ParamExecData *prmdata;
  			Datum		expresult;
  			bool		expnull;
  
  			/*
  			 * Load up the Param representing this column of the sub-select.
  			 */
  			prmdata = &(econtext->ecxt_param_exec_vals[paramid]);
  			Assert(prmdata->execPlan == NULL);
  			prmdata->value = slot_getattr(slot, col,
  										  &(prmdata->isnull));
  
  			/*
  			 * Now we can eval the combining operator for this column.
  			 */
  			expresult = ExecEvalExprSwitchContext(exprstate, econtext,
  												  &expnull, NULL);
  
  			/*
  			 * Combine the result into the row result as appropriate.
  			 */
  			if (col == 1)
  			{
  				rowresult = expresult;
  				rownull = expnull;
  			}
  			else if (useOr)
  			{
  				/* combine within row per OR semantics */
  				if (expnull)
  					rownull = true;
  				else if (DatumGetBool(expresult))
  				{
  					rowresult = BoolGetDatum(true);
  					rownull = false;
  					break;		/* needn't look at any more columns */
  				}
  			}
  			else
  			{
  				/* combine within row per AND semantics */
  				if (expnull)
  					rownull = true;
  				else if (!DatumGetBool(expresult))
  				{
  					rowresult = BoolGetDatum(false);
  					rownull = false;
  					break;		/* needn't look at any more columns */
  				}
  			}
  
  			col++;
  		}
  
  		if (subLinkType == ANY_SUBLINK)
  		{
  			/* combine across rows per OR semantics */
  			if (rownull)
  				*isNull = true;
  			else if (DatumGetBool(rowresult))
  			{
  				result = BoolGetDatum(true);
  				*isNull = false;
  				break;			/* needn't look at any more rows */
  			}
  		}
  		else if (subLinkType == ALL_SUBLINK)
  		{
  			/* combine across rows per AND semantics */
  			if (rownull)
  				*isNull = true;
  			else if (!DatumGetBool(rowresult))
  			{
  				result = BoolGetDatum(false);
  				*isNull = false;
  				break;			/* needn't look at any more rows */
  			}
  		}
  		else
  		{
  			/* must be MULTIEXPR_SUBLINK */
  			result = rowresult;
  			*isNull = rownull;
  		}
  	}
  
  	if (!found)
  	{
  		/*
  		 * deal with empty subplan result.	result/isNull were previously
  		 * initialized correctly for all sublink types except EXPR, ARRAY, and
  		 * MULTIEXPR; for those, return NULL.
  		 */
  		if (subLinkType == EXPR_SUBLINK ||
  			subLinkType == ARRAY_SUBLINK ||
  			subLinkType == MULTIEXPR_SUBLINK)
  		{
  			result = (Datum) 0;
  			*isNull = true;
  		}
  	}
  	else if (subLinkType == ARRAY_SUBLINK)
  	{
  		Assert(astate != NULL);
  		/* We return the result in the caller's context */
  		result = makeArrayResult(astate, oldcontext);
  	}
  
  	MemoryContextSwitchTo(oldcontext);
  
  	return result;
  }
  
  /*
   * buildSubPlanHash: load hash table by scanning subplan output.
   */
  static void
  buildSubPlanHash(SubPlanState *node)
  {
  	SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
  	PlanState  *planstate = node->planstate;
  	int			ncols = list_length(node->exprs);
  	ExprContext *innerecontext = node->innerecontext;
  	MemoryContext tempcxt = innerecontext->ecxt_per_tuple_memory;
  	MemoryContext oldcontext;
  	int			nbuckets;
  	TupleTableSlot *slot;
  
  	Assert(subplan->subLinkType == ANY_SUBLINK);
  	Assert(!subplan->useOr);
  
  	/*
  	 * If we already had any hash tables, destroy 'em; then create empty hash
  	 * table(s).
  	 *
  	 * If we need to distinguish accurately between FALSE and UNKNOWN (i.e.,
  	 * NULL) results of the IN operation, then we have to store subplan output
  	 * rows that are partly or wholly NULL.  We store such rows in a separate
  	 * hash table that we expect will be much smaller than the main table. (We
  	 * can use hashing to eliminate partly-null rows that are not distinct.
  	 * We keep them separate to minimize the cost of the inevitable full-table
  	 * searches; see findPartialMatch.)
  	 *
  	 * If it's not necessary to distinguish FALSE and UNKNOWN, then we don't
  	 * need to store subplan output rows that contain NULL.
  	 */
  	MemoryContextReset(node->tablecxt);
  	node->hashtable = NULL;
  	node->hashnulls = NULL;
  	node->havehashrows = false;
  	node->havenullrows = false;
  
  	nbuckets = (int) ceil(planstate->plan->plan_rows);
  	if (nbuckets < 1)
  		nbuckets = 1;
  
  	node->hashtable = BuildTupleHashTable(ncols,
  										  node->keyColIdx,
  										  node->eqfunctions,
  										  node->hashfunctions,
  										  nbuckets,
  										  sizeof(TupleHashEntryData),
  										  node->tablecxt,
  										  tempcxt);
  
  	if (!subplan->unknownEqFalse)
  	{
  		if (ncols == 1)
  			nbuckets = 1;		/* there can only be one entry */
  		else
  		{
  			nbuckets /= 16;
  			if (nbuckets < 1)
  				nbuckets = 1;
  		}
  		node->hashnulls = BuildTupleHashTable(ncols,
  											  node->keyColIdx,
  											  node->eqfunctions,
  											  node->hashfunctions,
  											  nbuckets,
  											  sizeof(TupleHashEntryData),
  											  node->tablecxt,
  											  tempcxt);
  	}
  
  	/*
  	 * We are probably in a short-lived expression-evaluation context. Switch
  	 * to the child plan's per-query context for calling ExecProcNode.
  	 */
  	oldcontext = MemoryContextSwitchTo(node->sub_estate->es_query_cxt);
  
  	/*
  	 * Reset subplan to start.
  	 */
  	ExecReScan(planstate, NULL);
  
  	/*
  	 * Scan the subplan and load the hash table(s).  Note that when there are
  	 * duplicate rows coming out of the sub-select, only one copy is stored.
  	 */
  	for (slot = ExecProcNode(planstate);
  		 !TupIsNull(slot);
  		 slot = ExecProcNode(planstate))
  	{
  		int			col = 1;
  		ListCell   *plst;
  		bool		isnew;
  
  		/*
  		 * Load up the Params representing the raw sub-select outputs, then
  		 * form the projection tuple to store in the hashtable.
  		 */
  		foreach(plst, subplan->paramIds)
  		{
  			int			paramid = lfirst_int(plst);
  			ParamExecData *prmdata;
  
  			prmdata = &(innerecontext->ecxt_param_exec_vals[paramid]);
  			Assert(prmdata->execPlan == NULL);
  			prmdata->value = slot_getattr(slot, col,
  										  &(prmdata->isnull));
  			col++;
  		}
  		slot = ExecProject(node->projRight, NULL);
  
  		/*
  		 * If result contains any nulls, store separately or not at all.
  		 */
  		if (slotNoNulls(slot))
  		{
  			(void) LookupTupleHashEntry(node->hashtable, slot, &isnew);
  			node->havehashrows = true;
  		}
  		else if (node->hashnulls)
  		{
  			(void) LookupTupleHashEntry(node->hashnulls, slot, &isnew);
  			node->havenullrows = true;
  		}
  
  		/*
  		 * Reset innerecontext after each inner tuple to free any memory used
  		 * in hash computation or comparison routines.
  		 */
  		ResetExprContext(innerecontext);
  	}
  
  	/*
  	 * Since the projected tuples are in the sub-query's context and not the
  	 * main context, we'd better clear the tuple slot before there's any
  	 * chance of a reset of the sub-query's context.  Else we will have the
  	 * potential for a double free attempt.  (XXX possibly no longer needed,
  	 * but can't hurt.)
  	 */
  	ExecClearTuple(node->projRight->pi_slot);
  
  	MemoryContextSwitchTo(oldcontext);
  }
  
  /*
   * findPartialMatch: does the hashtable contain an entry that is not
   * provably distinct from the tuple?
   *
   * We have to scan the whole hashtable; we can't usefully use hashkeys
   * to guide probing, since we might get partial matches on tuples with
   * hashkeys quite unrelated to what we'd get from the given tuple.
   */
  static bool
  findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot)
  {
  	int			numCols = hashtable->numCols;
  	AttrNumber *keyColIdx = hashtable->keyColIdx;
  	TupleHashIterator hashiter;
  	TupleHashEntry entry;
  
  	ResetTupleHashIterator(hashtable, &hashiter);
  	while ((entry = ScanTupleHashTable(&hashiter)) != NULL)
  	{
  		ExecStoreTuple(entry->firstTuple, hashtable->tableslot,
  					   InvalidBuffer, false);
  		if (!execTuplesUnequal(hashtable->tableslot, slot,
  							   numCols, keyColIdx,
  							   hashtable->eqfunctions,
  							   hashtable->tempcxt))
  			return true;
  	}
  	return false;
  }
  
  /*
   * slotAllNulls: is the slot completely NULL?
   *
   * This does not test for dropped columns, which is OK because we only
   * use it on projected tuples.
   */
  static bool
  slotAllNulls(TupleTableSlot *slot)
  {
  	int			ncols = slot->tts_tupleDescriptor->natts;
  	int			i;
  
  	for (i = 1; i <= ncols; i++)
  	{
  		if (!slot_attisnull(slot, i))
  			return false;
  	}
  	return true;
  }
  
  /*
   * slotNoNulls: is the slot entirely not NULL?
   *
   * This does not test for dropped columns, which is OK because we only
   * use it on projected tuples.
   */
  static bool
  slotNoNulls(TupleTableSlot *slot)
  {
  	int			ncols = slot->tts_tupleDescriptor->natts;
  	int			i;
  
  	for (i = 1; i <= ncols; i++)
  	{
  		if (slot_attisnull(slot, i))
  			return false;
  	}
  	return true;
  }
  
  /* ----------------------------------------------------------------
   *		ExecInitSubPlan
   * ----------------------------------------------------------------
   */
  void
  ExecInitSubPlan(SubPlanState *node, EState *estate)
  {
  	SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
  	EState	   *sp_estate;
  	MemoryContext oldcontext;
  
  	/*
  	 * Do access checking on the rangetable entries in the subquery.
  	 */
  	ExecCheckRTPerms(subplan->rtable);
  
  	/*
  	 * initialize my state
  	 */
  	node->needShutdown = false;
  	node->curTuple = NULL;
  	node->projLeft = NULL;
  	node->projRight = NULL;
  	node->hashtable = NULL;
  	node->hashnulls = NULL;
  	node->tablecxt = NULL;
  	node->innerecontext = NULL;
  	node->keyColIdx = NULL;
  	node->eqfunctions = NULL;
  	node->hashfunctions = NULL;
  
  	/*
  	 * create an EState for the subplan
  	 *
  	 * The subquery needs its own EState because it has its own rangetable. It
  	 * shares our Param ID space, however.	XXX if rangetable access were done
  	 * differently, the subquery could share our EState, which would eliminate
  	 * some thrashing about in this module...
  	 */
  	sp_estate = CreateExecutorState();
  	node->sub_estate = sp_estate;
  
  	oldcontext = MemoryContextSwitchTo(sp_estate->es_query_cxt);
  
  	sp_estate->es_range_table = subplan->rtable;
  	sp_estate->es_param_list_info = estate->es_param_list_info;
  	sp_estate->es_param_exec_vals = estate->es_param_exec_vals;
  	sp_estate->es_tupleTable =
  		ExecCreateTupleTable(ExecCountSlotsNode(subplan->plan) + 10);
  	sp_estate->es_snapshot = estate->es_snapshot;
  	sp_estate->es_crosscheck_snapshot = estate->es_crosscheck_snapshot;
  	sp_estate->es_instrument = estate->es_instrument;
  
  	/*
  	 * Start up the subplan (this is a very cut-down form of InitPlan())
  	 */
  	node->planstate = ExecInitNode(subplan->plan, sp_estate);
  
  	node->needShutdown = true;	/* now we need to shutdown the subplan */
  
  	MemoryContextSwitchTo(oldcontext);
  
  	/*
  	 * If this plan is un-correlated or undirect correlated one and want to
  	 * set params for parent plan then mark parameters as needing evaluation.
  	 *
  	 * Note that in the case of un-correlated subqueries we don't care about
  	 * setting parent->chgParam here: indices take care about it, for others -
  	 * it doesn't matter...
  	 */
  	if (subplan->setParam != NIL)
  	{
  		ListCell   *lst;
  
  		foreach(lst, subplan->setParam)
  		{
  			int			paramid = lfirst_int(lst);
  			ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);
  
  			prm->execPlan = node;
  		}
  	}
  
  	/*
  	 * If we are going to hash the subquery output, initialize relevant stuff.
  	 * (We don't create the hashtable until needed, though.)
  	 */
  	if (subplan->useHashTable)
  	{
  		int			ncols,
  					i;
  		TupleDesc	tupDesc;
  		TupleTable	tupTable;
  		TupleTableSlot *slot;
  		List	   *lefttlist,
  				   *righttlist,
  				   *leftptlist,
  				   *rightptlist;
  		ListCell   *lexpr;
  
  		/* We need a memory context to hold the hash table(s) */
  		node->tablecxt =
  			AllocSetContextCreate(CurrentMemoryContext,
  								  "Subplan HashTable Context",
  								  ALLOCSET_DEFAULT_MINSIZE,
  								  ALLOCSET_DEFAULT_INITSIZE,
  								  ALLOCSET_DEFAULT_MAXSIZE);
  		/* and a short-lived exprcontext for function evaluation */
  		node->innerecontext = CreateExprContext(estate);
  		/* Silly little array of column numbers 1..n */
  		ncols = list_length(node->exprs);
  		node->keyColIdx = (AttrNumber *) palloc(ncols * sizeof(AttrNumber));
  		for (i = 0; i < ncols; i++)
  			node->keyColIdx[i] = i + 1;
  
  		/*
  		 * We use ExecProject to evaluate the lefthand and righthand
  		 * expression lists and form tuples.  (You might think that we could
  		 * use the sub-select's output tuples directly, but that is not the
  		 * case if we had to insert any run-time coercions of the sub-select's
  		 * output datatypes; anyway this avoids storing any resjunk columns
  		 * that might be in the sub-select's output.) Run through the
  		 * combining expressions to build tlists for the lefthand and
  		 * righthand sides.  We need both the ExprState list (for ExecProject)
  		 * and the underlying parse Exprs (for ExecTypeFromTL).
  		 *
  		 * We also extract the combining operators themselves to initialize
  		 * the equality and hashing functions for the hash tables.
  		 */
  		lefttlist = righttlist = NIL;
  		leftptlist = rightptlist = NIL;
  		node->eqfunctions = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
  		node->hashfunctions = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
  		i = 1;
  		foreach(lexpr, node->exprs)
  		{
  			FuncExprState *fstate = (FuncExprState *) lfirst(lexpr);
  			OpExpr	   *opexpr = (OpExpr *) fstate->xprstate.expr;
  			ExprState  *exstate;
  			Expr	   *expr;
  			TargetEntry *tle;
  			GenericExprState *tlestate;
  			Oid			hashfn;
  
  			Assert(IsA(fstate, FuncExprState));
  			Assert(IsA(opexpr, OpExpr));
  			Assert(list_length(fstate->args) == 2);
  
  			/* Process lefthand argument */
  			exstate = (ExprState *) linitial(fstate->args);
  			expr = exstate->expr;
  			tle = makeTargetEntry(expr,
  								  i,
  								  NULL,
  								  false);
  			tlestate = makeNode(GenericExprState);
  			tlestate->xprstate.expr = (Expr *) tle;
  			tlestate->xprstate.evalfunc = NULL;
  			tlestate->arg = exstate;
  			lefttlist = lappend(lefttlist, tlestate);
  			leftptlist = lappend(leftptlist, tle);
  
  			/* Process righthand argument */
  			exstate = (ExprState *) lsecond(fstate->args);
  			expr = exstate->expr;
  			tle = makeTargetEntry(expr,
  								  i,
  								  NULL,
  								  false);
  			tlestate = makeNode(GenericExprState);
  			tlestate->xprstate.expr = (Expr *) tle;
  			tlestate->xprstate.evalfunc = NULL;
  			tlestate->arg = exstate;
  			righttlist = lappend(righttlist, tlestate);
  			rightptlist = lappend(rightptlist, tle);
  
  			/* Lookup the combining function */
  			fmgr_info(opexpr->opfuncid, &node->eqfunctions[i - 1]);
  			node->eqfunctions[i - 1].fn_expr = (Node *) opexpr;
  
  			/* Lookup the associated hash function */
  			hashfn = get_op_hash_function(opexpr->opno);
  			if (!OidIsValid(hashfn))
  				elog(ERROR, "could not find hash function for hash operator %u",
  					 opexpr->opno);
  			fmgr_info(hashfn, &node->hashfunctions[i - 1]);
  
  			i++;
  		}
  
  		/*
  		 * Create a tupletable to hold these tuples.  (Note: we never bother
  		 * to free the tupletable explicitly; that's okay because it will
  		 * never store raw disk tuples that might have associated buffer pins.
  		 * The only resource involved is memory, which will be cleaned up by
  		 * freeing the query context.)
  		 */
  		tupTable = ExecCreateTupleTable(2);
  
  		/*
  		 * Construct tupdescs, slots and projection nodes for left and right
  		 * sides.  The lefthand expressions will be evaluated in the parent
  		 * plan node's exprcontext, which we don't have access to here.
  		 * Fortunately we can just pass NULL for now and fill it in later
  		 * (hack alert!).  The righthand expressions will be evaluated in our
  		 * own innerecontext.
  		 */
  		tupDesc = ExecTypeFromTL(leftptlist, false);
  		slot = ExecAllocTableSlot(tupTable);
  		ExecSetSlotDescriptor(slot, tupDesc, true);
  		node->projLeft = ExecBuildProjectionInfo(lefttlist,
  												 NULL,
  												 slot);
  
  		tupDesc = ExecTypeFromTL(rightptlist, false);
  		slot = ExecAllocTableSlot(tupTable);
  		ExecSetSlotDescriptor(slot, tupDesc, true);
  		node->projRight = ExecBuildProjectionInfo(righttlist,
  												  node->innerecontext,
  												  slot);
  	}
  }
  
  /* ----------------------------------------------------------------
   *		ExecSetParamPlan
   *
   *		Executes an InitPlan subplan and sets its output parameters.
   *
   * This is called from ExecEvalParam() when the value of a PARAM_EXEC
   * parameter is requested and the param's execPlan field is set (indicating
   * that the param has not yet been evaluated).	This allows lazy evaluation
   * of initplans: we don't run the subplan until/unless we need its output.
   * Note that this routine MUST clear the execPlan fields of the plan's
   * output parameters after evaluating them!
   * ----------------------------------------------------------------
   */
  void
  ExecSetParamPlan(SubPlanState *node, ExprContext *econtext)
  {
  	SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
  	PlanState  *planstate = node->planstate;
  	SubLinkType subLinkType = subplan->subLinkType;
  	MemoryContext oldcontext;
  	TupleTableSlot *slot;
  	ListCell   *l;
  	bool		found = false;
  	ArrayBuildState *astate = NULL;
  
  	/*
  	 * Must switch to child query's per-query memory context.
  	 */
  	oldcontext = MemoryContextSwitchTo(node->sub_estate->es_query_cxt);
  
  	if (subLinkType == ANY_SUBLINK ||
  		subLinkType == ALL_SUBLINK)
  		elog(ERROR, "ANY/ALL subselect unsupported as initplan");
  
  	if (planstate->chgParam != NULL)
  		ExecReScan(planstate, NULL);
  
  	for (slot = ExecProcNode(planstate);
  		 !TupIsNull(slot);
  		 slot = ExecProcNode(planstate))
  	{
  		TupleDesc	tdesc = slot->tts_tupleDescriptor;
  		int			i = 1;
  
  		if (subLinkType == EXISTS_SUBLINK)
  		{
  			/* There can be only one param... */
  			int			paramid = linitial_int(subplan->setParam);
  			ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
  
  			prm->execPlan = NULL;
  			prm->value = BoolGetDatum(true);
  			prm->isnull = false;
  			found = true;
  			break;
  		}
  
  		if (subLinkType == ARRAY_SUBLINK)
  		{
  			Datum		dvalue;
  			bool		disnull;
  
  			found = true;
  			/* stash away current value */
  			dvalue = slot_getattr(slot, 1, &disnull);
  			astate = accumArrayResult(astate, dvalue, disnull,
  									  tdesc->attrs[0]->atttypid,
  									  oldcontext);
  			/* keep scanning subplan to collect all values */
  			continue;
  		}
  
  		if (found &&
  			(subLinkType == EXPR_SUBLINK ||
  			 subLinkType == MULTIEXPR_SUBLINK))
  			ereport(ERROR,
  					(errcode(ERRCODE_CARDINALITY_VIOLATION),
  					 errmsg("more than one row returned by a subquery used as an expression")));
  
  		found = true;
  
  		/*
  		 * We need to copy the subplan's tuple into our own context, in case
  		 * any of the params are pass-by-ref type --- the pointers stored in
  		 * the param structs will point at this copied tuple! node->curTuple
  		 * keeps track of the copied tuple for eventual freeing.
  		 */
  		MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
  		if (node->curTuple)
  			heap_freetuple(node->curTuple);
  		node->curTuple = ExecCopySlotTuple(slot);
  		MemoryContextSwitchTo(node->sub_estate->es_query_cxt);
  
  		/*
  		 * Now set all the setParam params from the columns of the tuple
  		 */
  		foreach(l, subplan->setParam)
  		{
  			int			paramid = lfirst_int(l);
  			ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
  
  			prm->execPlan = NULL;
  			prm->value = heap_getattr(node->curTuple, i, tdesc,
  									  &(prm->isnull));
  			i++;
  		}
  	}
  
  	if (!found)
  	{
  		if (subLinkType == EXISTS_SUBLINK)
  		{
  			/* There can be only one param... */
  			int			paramid = linitial_int(subplan->setParam);
  			ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
  
  			prm->execPlan = NULL;
  			prm->value = BoolGetDatum(false);
  			prm->isnull = false;
  		}
  		else
  		{
  			foreach(l, subplan->setParam)
  			{
  				int			paramid = lfirst_int(l);
  				ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
  
  				prm->execPlan = NULL;
  				prm->value = (Datum) 0;
  				prm->isnull = true;
  			}
  		}
  	}
  	else if (subLinkType == ARRAY_SUBLINK)
  	{
  		/* There can be only one param... */
  		int			paramid = linitial_int(subplan->setParam);
  		ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
  
  		Assert(astate != NULL);
  		prm->execPlan = NULL;
  		/* We build the result in query context so it won't disappear */
  		prm->value = makeArrayResult(astate, econtext->ecxt_per_query_memory);
  		prm->isnull = false;
  	}
  
  	MemoryContextSwitchTo(oldcontext);
  }
  
  /* ----------------------------------------------------------------
   *		ExecEndSubPlan
   * ----------------------------------------------------------------
   */
  void
  ExecEndSubPlan(SubPlanState *node)
  {
  	if (node->needShutdown)
  	{
  		MemoryContext oldcontext;
  
  		oldcontext = MemoryContextSwitchTo(node->sub_estate->es_query_cxt);
  		ExecEndPlan(node->planstate, node->sub_estate);
  		MemoryContextSwitchTo(oldcontext);
  		FreeExecutorState(node->sub_estate);
  		node->sub_estate = NULL;
  		node->planstate = NULL;
  		node->needShutdown = false;
  	}
  }
  
  /*
   * Mark an initplan as needing recalculation
   */
  void
  ExecReScanSetParamPlan(SubPlanState *node, PlanState *parent)
  {
  	PlanState  *planstate = node->planstate;
  	SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
  	EState	   *estate = parent->state;
  	ListCell   *l;
  
  	/* sanity checks */
  	if (subplan->parParam != NIL)
  		elog(ERROR, "direct correlated subquery unsupported as initplan");
  	if (subplan->setParam == NIL)
  		elog(ERROR, "setParam list of initplan is empty");
  	if (bms_is_empty(planstate->plan->extParam))
  		elog(ERROR, "extParam set of initplan is empty");
  
  	/*
  	 * Don't actually re-scan: ExecSetParamPlan does it if needed.
  	 */
  
  	/*
  	 * Mark this subplan's output parameters as needing recalculation
  	 */
  	foreach(l, subplan->setParam)
  	{
  		int			paramid = lfirst_int(l);
  		ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);
  
  		prm->execPlan = node;
  		parent->chgParam = bms_add_member(parent->chgParam, paramid);
  	}
  }
  