postgres/src/backend/executor/execUtils.c

/*-------------------------------------------------------------------------
 *
 * execUtils.c
 *	  miscellaneous executor utility routines
 *
 * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  src/backend/executor/execUtils.c
 *
 *-------------------------------------------------------------------------
 */
/*
 * INTERFACE ROUTINES
 *		CreateExecutorState		Create/delete executor working state
 *		FreeExecutorState
 *		CreateExprContext
 *		CreateStandaloneExprContext
 *		FreeExprContext
 *		ReScanExprContext
 *
 *		ExecAssignExprContext	Common code for plan node init routines.
 *		ExecAssignResultType
 *		etc
 *
 *		ExecOpenScanRelation	Common code for scan node init routines.
 *		ExecCloseScanRelation
 *
 *		RegisterExprContextCallback    Register function shutdown callback
 *		UnregisterExprContextCallback  Deregister function shutdown callback
 *
 *	 NOTES
 *		This file has traditionally been the place to stick misc.
 *		executor support stuff that doesn't really go anyplace else.
 */

#include "postgres.h"

#include "access/relscan.h"
#include "access/transam.h"
#include "executor/executor.h"
#include "nodes/nodeFuncs.h"
#include "parser/parsetree.h"
#include "utils/memutils.h"
#include "utils/rel.h"


static bool get_last_attnums(Node *node, ProjectionInfo *projInfo);
static void ShutdownExprContext(ExprContext *econtext, bool isCommit);


/* ----------------------------------------------------------------
 *				 Executor state and memory management functions
 * ----------------------------------------------------------------
 */

/* ----------------
 *		CreateExecutorState
 *
 *		Create and initialize an EState node, which is the root of
 *		working storage for an entire Executor invocation.
 *
 * Principally, this creates the per-query memory context that will be
 * used to hold all working data that lives till the end of the query.
 * Note that the per-query context will become a child of the caller's
 * CurrentMemoryContext.
 * ----------------
 */
EState *
CreateExecutorState(void)
{
	EState	   *estate;
	MemoryContext qcontext;
	MemoryContext oldcontext;

	/*
	 * Create the per-query context for this Executor run.
	 */
	qcontext = AllocSetContextCreate(CurrentMemoryContext,
									 "ExecutorState",
									 ALLOCSET_DEFAULT_MINSIZE,
									 ALLOCSET_DEFAULT_INITSIZE,
									 ALLOCSET_DEFAULT_MAXSIZE);

	/*
	 * Make the EState node within the per-query context.  This way, we don't
	 * need a separate pfree() operation for it at shutdown.
	 */
	oldcontext = MemoryContextSwitchTo(qcontext);

	estate = makeNode(EState);

	/*
	 * Initialize all fields of the Executor State structure
	 */
	estate->es_direction = ForwardScanDirection;
	estate->es_snapshot = InvalidSnapshot;		/* caller must initialize this */
	estate->es_crosscheck_snapshot = InvalidSnapshot;	/* no crosscheck */
	estate->es_range_table = NIL;
	estate->es_plannedstmt = NULL;

	estate->es_junkFilter = NULL;

	estate->es_output_cid = (CommandId) 0;

	estate->es_result_relations = NULL;
	estate->es_num_result_relations = 0;
	estate->es_result_relation_info = NULL;

	estate->es_trig_target_relations = NIL;
	estate->es_trig_tuple_slot = NULL;
	estate->es_trig_oldtup_slot = NULL;
	estate->es_trig_newtup_slot = NULL;

	estate->es_param_list_info = NULL;
	estate->es_param_exec_vals = NULL;

	estate->es_query_cxt = qcontext;

	estate->es_tupleTable = NIL;

	estate->es_rowMarks = NIL;

	estate->es_processed = 0;
	estate->es_lastoid = InvalidOid;

	estate->es_top_eflags = 0;
	estate->es_instrument = 0;
	estate->es_finished = false;

	estate->es_exprcontexts = NIL;

	estate->es_subplanstates = NIL;

	estate->es_auxmodifytables = NIL;

	estate->es_per_tuple_exprcontext = NULL;

	estate->es_epqTuple = NULL;
	estate->es_epqTupleSet = NULL;
	estate->es_epqScanDone = NULL;

	/*
	 * Return the executor state structure
	 */
	MemoryContextSwitchTo(oldcontext);

	return estate;
}

/* ----------------
 *		FreeExecutorState
 *
 *		Release an EState along with all remaining working storage.
 *
 * Note: this is not responsible for releasing non-memory resources,
 * such as open relations or buffer pins.  But it will shut down any
 * still-active ExprContexts within the EState.  That is sufficient
 * cleanup for situations where the EState has only been used for expression
 * evaluation, and not to run a complete Plan.
 *
 * This can be called in any memory context ... so long as it's not one
 * of the ones to be freed.
 * ----------------
 */
void
FreeExecutorState(EState *estate)
{
	/*
	 * Shut down and free any remaining ExprContexts.  We do this explicitly
	 * to ensure that any remaining shutdown callbacks get called (since they
	 * might need to release resources that aren't simply memory within the
	 * per-query memory context).
	 */
	while (estate->es_exprcontexts)
	{
		/*
		 * XXX: seems there ought to be a faster way to implement this than
		 * repeated list_delete(), no?
		 */
		FreeExprContext((ExprContext *) linitial(estate->es_exprcontexts),
						true);
		/* FreeExprContext removed the list link for us */
	}

	/*
	 * Free the per-query memory context, thereby releasing all working
	 * memory, including the EState node itself.
	 */
	MemoryContextDelete(estate->es_query_cxt);
}

/* ----------------
 *		CreateExprContext
 *
 *		Create a context for expression evaluation within an EState.
 *
 * An executor run may require multiple ExprContexts (we usually make one
 * for each Plan node, and a separate one for per-output-tuple processing
 * such as constraint checking).  Each ExprContext has its own "per-tuple"
 * memory context.
 *
 * Note we make no assumption about the caller's memory context.
 * ----------------
 */
ExprContext *
CreateExprContext(EState *estate)
{
	ExprContext *econtext;
	MemoryContext oldcontext;

	/* Create the ExprContext node within the per-query memory context */
	oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);

	econtext = makeNode(ExprContext);

	/* Initialize fields of ExprContext */
	econtext->ecxt_scantuple = NULL;
	econtext->ecxt_innertuple = NULL;
	econtext->ecxt_outertuple = NULL;

	econtext->ecxt_per_query_memory = estate->es_query_cxt;

	/*
	 * Create working memory for expression evaluation in this context.
	 */
	econtext->ecxt_per_tuple_memory =
		AllocSetContextCreate(estate->es_query_cxt,
							  "ExprContext",
							  ALLOCSET_DEFAULT_MINSIZE,
							  ALLOCSET_DEFAULT_INITSIZE,
							  ALLOCSET_DEFAULT_MAXSIZE);

	econtext->ecxt_param_exec_vals = estate->es_param_exec_vals;
	econtext->ecxt_param_list_info = estate->es_param_list_info;

	econtext->ecxt_aggvalues = NULL;
	econtext->ecxt_aggnulls = NULL;

	econtext->caseValue_datum = (Datum) 0;
	econtext->caseValue_isNull = true;

	econtext->domainValue_datum = (Datum) 0;
	econtext->domainValue_isNull = true;

	econtext->ecxt_estate = estate;

	econtext->ecxt_callbacks = NULL;

	/*
	 * Link the ExprContext into the EState to ensure it is shut down when the
	 * EState is freed.  Because we use lcons(), shutdowns will occur in
	 * reverse order of creation, which may not be essential but can't hurt.
	 */
	estate->es_exprcontexts = lcons(econtext, estate->es_exprcontexts);

	MemoryContextSwitchTo(oldcontext);

	return econtext;
}

/* ----------------
 *		CreateStandaloneExprContext
 *
 *		Create a context for standalone expression evaluation.
 *
 * An ExprContext made this way can be used for evaluation of expressions
 * that contain no Params, subplans, or Var references (it might work to
 * put tuple references into the scantuple field, but it seems unwise).
 *
 * The ExprContext struct is allocated in the caller's current memory
 * context, which also becomes its "per query" context.
 *
 * It is caller's responsibility to free the ExprContext when done,
 * or at least ensure that any shutdown callbacks have been called
 * (ReScanExprContext() is suitable).  Otherwise, non-memory resources
 * might be leaked.
 * ----------------
 */
ExprContext *
CreateStandaloneExprContext(void)
{
	ExprContext *econtext;

	/* Create the ExprContext node within the caller's memory context */
	econtext = makeNode(ExprContext);

	/* Initialize fields of ExprContext */
	econtext->ecxt_scantuple = NULL;
	econtext->ecxt_innertuple = NULL;
	econtext->ecxt_outertuple = NULL;

	econtext->ecxt_per_query_memory = CurrentMemoryContext;

	/*
	 * Create working memory for expression evaluation in this context.
	 */
	econtext->ecxt_per_tuple_memory =
		AllocSetContextCreate(CurrentMemoryContext,
							  "ExprContext",
							  ALLOCSET_DEFAULT_MINSIZE,
							  ALLOCSET_DEFAULT_INITSIZE,
							  ALLOCSET_DEFAULT_MAXSIZE);

	econtext->ecxt_param_exec_vals = NULL;
	econtext->ecxt_param_list_info = NULL;

	econtext->ecxt_aggvalues = NULL;
	econtext->ecxt_aggnulls = NULL;

	econtext->caseValue_datum = (Datum) 0;
	econtext->caseValue_isNull = true;

	econtext->domainValue_datum = (Datum) 0;
	econtext->domainValue_isNull = true;

	econtext->ecxt_estate = NULL;

	econtext->ecxt_callbacks = NULL;

	return econtext;
}

/* ----------------
 *		FreeExprContext
 *
 *		Free an expression context, including calling any remaining
 *		shutdown callbacks.
 *
 * Since we free the temporary context used for expression evaluation,
 * any previously computed pass-by-reference expression result will go away!
 *
 * If isCommit is false, we are being called in error cleanup, and should
 * not call callbacks but only release memory.  (It might be better to call
 * the callbacks and pass the isCommit flag to them, but that would require
 * more invasive code changes than currently seems justified.)
 *
 * Note we make no assumption about the caller's memory context.
 * ----------------
 */
void
FreeExprContext(ExprContext *econtext, bool isCommit)
{
	EState	   *estate;

	/* Call any registered callbacks */
	ShutdownExprContext(econtext, isCommit);
	/* And clean up the memory used */
	MemoryContextDelete(econtext->ecxt_per_tuple_memory);
	/* Unlink self from owning EState, if any */
	estate = econtext->ecxt_estate;
	if (estate)
		estate->es_exprcontexts = list_delete_ptr(estate->es_exprcontexts,
												  econtext);
	/* And delete the ExprContext node */
	pfree(econtext);
}

/*
 * ReScanExprContext
 *
 *		Reset an expression context in preparation for a rescan of its
 *		plan node.  This requires calling any registered shutdown callbacks,
 *		since any partially complete set-returning-functions must be canceled.
 *
 * Note we make no assumption about the caller's memory context.
 */
void
ReScanExprContext(ExprContext *econtext)
{
	/* Call any registered callbacks */
	ShutdownExprContext(econtext, true);
	/* And clean up the memory used */
	MemoryContextReset(econtext->ecxt_per_tuple_memory);
}

/*
 * Build a per-output-tuple ExprContext for an EState.
 *
 * This is normally invoked via GetPerTupleExprContext() macro,
 * not directly.
 */
ExprContext *
MakePerTupleExprContext(EState *estate)
{
	if (estate->es_per_tuple_exprcontext == NULL)
		estate->es_per_tuple_exprcontext = CreateExprContext(estate);

	return estate->es_per_tuple_exprcontext;
}


/* ----------------------------------------------------------------
 *				 miscellaneous node-init support functions
 *
 * Note: all of these are expected to be called with CurrentMemoryContext
 * equal to the per-query memory context.
 * ----------------------------------------------------------------
 */

/* ----------------
 *		ExecAssignExprContext
 *
 *		This initializes the ps_ExprContext field.  It is only necessary
 *		to do this for nodes which use ExecQual or ExecProject
 *		because those routines require an econtext. Other nodes that
 *		don't have to evaluate expressions don't need to do this.
 * ----------------
 */
void
ExecAssignExprContext(EState *estate, PlanState *planstate)
{
	planstate->ps_ExprContext = CreateExprContext(estate);
}

/* ----------------
 *		ExecAssignResultType
 * ----------------
 */
void
ExecAssignResultType(PlanState *planstate, TupleDesc tupDesc)
{
	TupleTableSlot *slot = planstate->ps_ResultTupleSlot;

	ExecSetSlotDescriptor(slot, tupDesc);
}

/* ----------------
 *		ExecAssignResultTypeFromTL
 * ----------------
 */
void
ExecAssignResultTypeFromTL(PlanState *planstate)
{
	bool		hasoid;
	TupleDesc	tupDesc;

	if (ExecContextForcesOids(planstate, &hasoid))
	{
		/* context forces OID choice; hasoid is now set correctly */
	}
	else
	{
		/* given free choice, don't leave space for OIDs in result tuples */
		hasoid = false;
	}

	/*
	 * ExecTypeFromTL needs the parse-time representation of the tlist, not a
	 * list of ExprStates.  This is good because some plan nodes don't bother
	 * to set up planstate->targetlist ...
	 */
	tupDesc = ExecTypeFromTL(planstate->plan->targetlist, hasoid);
	ExecAssignResultType(planstate, tupDesc);
}

/* ----------------
 *		ExecGetResultType
 * ----------------
 */
TupleDesc
ExecGetResultType(PlanState *planstate)
{
	TupleTableSlot *slot = planstate->ps_ResultTupleSlot;

	return slot->tts_tupleDescriptor;
}

/* ----------------
 *		ExecBuildProjectionInfo
 *
 * Build a ProjectionInfo node for evaluating the given tlist in the given
 * econtext, and storing the result into the tuple slot.  (Caller must have
 * ensured that tuple slot has a descriptor matching the tlist!)  Note that
 * the given tlist should be a list of ExprState nodes, not Expr nodes.
 *
 * inputDesc can be NULL, but if it is not, we check to see whether simple
 * Vars in the tlist match the descriptor.  It is important to provide
 * inputDesc for relation-scan plan nodes, as a cross check that the relation
 * hasn't been changed since the plan was made.  At higher levels of a plan,
 * there is no need to recheck.
 * ----------------
 */
ProjectionInfo *
ExecBuildProjectionInfo(List *targetList,
						ExprContext *econtext,
						TupleTableSlot *slot,
						TupleDesc inputDesc)
{
	ProjectionInfo *projInfo = makeNode(ProjectionInfo);
	int			len = ExecTargetListLength(targetList);
	int		   *workspace;
	int		   *varSlotOffsets;
	int		   *varNumbers;
	int		   *varOutputCols;
	List	   *exprlist;
	int			numSimpleVars;
	bool		directMap;
	ListCell   *tl;

	projInfo->pi_exprContext = econtext;
	projInfo->pi_slot = slot;
	/* since these are all int arrays, we need do just one palloc */
	workspace = (int *) palloc(len * 3 * sizeof(int));
	projInfo->pi_varSlotOffsets = varSlotOffsets = workspace;
	projInfo->pi_varNumbers = varNumbers = workspace + len;
	projInfo->pi_varOutputCols = varOutputCols = workspace + len * 2;
	projInfo->pi_lastInnerVar = 0;
	projInfo->pi_lastOuterVar = 0;
	projInfo->pi_lastScanVar = 0;

	/*
	 * We separate the target list elements into simple Var references and
	 * expressions which require the full ExecTargetList machinery.  To be a
	 * simple Var, a Var has to be a user attribute and not mismatch the
	 * inputDesc.  (Note: if there is a type mismatch then ExecEvalScalarVar
	 * will probably throw an error at runtime, but we leave that to it.)
	 */
	exprlist = NIL;
	numSimpleVars = 0;
	directMap = true;
	foreach(tl, targetList)
	{
		GenericExprState *gstate = (GenericExprState *) lfirst(tl);
		Var		   *variable = (Var *) gstate->arg->expr;
		bool		isSimpleVar = false;

		if (variable != NULL &&
			IsA(variable, Var) &&
			variable->varattno > 0)
		{
			if (!inputDesc)
				isSimpleVar = true;		/* can't check type, assume OK */
			else if (variable->varattno <= inputDesc->natts)
			{
				Form_pg_attribute attr;

				attr = inputDesc->attrs[variable->varattno - 1];
				if (!attr->attisdropped && variable->vartype == attr->atttypid)
					isSimpleVar = true;
			}
		}

		if (isSimpleVar)
		{
			TargetEntry *tle = (TargetEntry *) gstate->xprstate.expr;
			AttrNumber	attnum = variable->varattno;

			varNumbers[numSimpleVars] = attnum;
			varOutputCols[numSimpleVars] = tle->resno;
			if (tle->resno != numSimpleVars + 1)
				directMap = false;

			switch (variable->varno)
			{
				case INNER_VAR:
					varSlotOffsets[numSimpleVars] = offsetof(ExprContext,
															 ecxt_innertuple);
					if (projInfo->pi_lastInnerVar < attnum)
						projInfo->pi_lastInnerVar = attnum;
					break;

				case OUTER_VAR:
					varSlotOffsets[numSimpleVars] = offsetof(ExprContext,
															 ecxt_outertuple);
					if (projInfo->pi_lastOuterVar < attnum)
						projInfo->pi_lastOuterVar = attnum;
					break;

					/* INDEX_VAR is handled by default case */

				default:
					varSlotOffsets[numSimpleVars] = offsetof(ExprContext,
															 ecxt_scantuple);
					if (projInfo->pi_lastScanVar < attnum)
						projInfo->pi_lastScanVar = attnum;
					break;
			}
			numSimpleVars++;
		}
		else
		{
			/* Not a simple variable, add it to generic targetlist */
			exprlist = lappend(exprlist, gstate);
			/* Examine expr to include contained Vars in lastXXXVar counts */
			get_last_attnums((Node *) variable, projInfo);
		}
	}
	projInfo->pi_targetlist = exprlist;
	projInfo->pi_numSimpleVars = numSimpleVars;
	projInfo->pi_directMap = directMap;

	if (exprlist == NIL)
		projInfo->pi_itemIsDone = NULL; /* not needed */
	else
		projInfo->pi_itemIsDone = (ExprDoneCond *)
			palloc(len * sizeof(ExprDoneCond));

	return projInfo;
}

/*
 * get_last_attnums: expression walker for ExecBuildProjectionInfo
 *
 *	Update the lastXXXVar counts to be at least as large as the largest
 *	attribute numbers found in the expression
 */
static bool
get_last_attnums(Node *node, ProjectionInfo *projInfo)
{
	if (node == NULL)
		return false;
	if (IsA(node, Var))
	{
		Var		   *variable = (Var *) node;
		AttrNumber	attnum = variable->varattno;

		switch (variable->varno)
		{
			case INNER_VAR:
				if (projInfo->pi_lastInnerVar < attnum)
					projInfo->pi_lastInnerVar = attnum;
				break;

			case OUTER_VAR:
				if (projInfo->pi_lastOuterVar < attnum)
					projInfo->pi_lastOuterVar = attnum;
				break;

				/* INDEX_VAR is handled by default case */

			default:
				if (projInfo->pi_lastScanVar < attnum)
					projInfo->pi_lastScanVar = attnum;
				break;
		}
		return false;
	}

	/*
	 * Don't examine the arguments or filters of Aggrefs or WindowFuncs,
	 * because those do not represent expressions to be evaluated within the
	 * overall targetlist's econtext.  GroupingFunc arguments are never
	 * evaluated at all.
	 */
	if (IsA(node, Aggref))
		return false;
	if (IsA(node, WindowFunc))
		return false;
	if (IsA(node, GroupingFunc))
		return false;
	return expression_tree_walker(node, get_last_attnums,
								  (void *) projInfo);
}

/* ----------------
 *		ExecAssignProjectionInfo
 *
 * forms the projection information from the node's targetlist
 *
 * Notes for inputDesc are same as for ExecBuildProjectionInfo: supply it
 * for a relation-scan node, can pass NULL for upper-level nodes
 * ----------------
 */
void
ExecAssignProjectionInfo(PlanState *planstate,
						 TupleDesc inputDesc)
{
	planstate->ps_ProjInfo =
		ExecBuildProjectionInfo(planstate->targetlist,
								planstate->ps_ExprContext,
								planstate->ps_ResultTupleSlot,
								inputDesc);
}


/* ----------------
 *		ExecFreeExprContext
 *
 * A plan node's ExprContext should be freed explicitly during executor
 * shutdown because there may be shutdown callbacks to call.  (Other resources
 * made by the above routines, such as projection info, don't need to be freed
 * explicitly because they're just memory in the per-query memory context.)
 *
 * However ... there is no particular need to do it during ExecEndNode,
 * because FreeExecutorState will free any remaining ExprContexts within
 * the EState.  Letting FreeExecutorState do it allows the ExprContexts to
 * be freed in reverse order of creation, rather than order of creation as
 * will happen if we delete them here, which saves O(N^2) work in the list
 * cleanup inside FreeExprContext.
 * ----------------
 */
void
ExecFreeExprContext(PlanState *planstate)
{
	/*
	 * Per above discussion, don't actually delete the ExprContext. We do
	 * unlink it from the plan node, though.
	 */
	planstate->ps_ExprContext = NULL;
}

/* ----------------------------------------------------------------
 *		the following scan type support functions are for
 *		those nodes which are stubborn and return tuples in
 *		their Scan tuple slot instead of their Result tuple
 *		slot..  luck fur us, these nodes do not do projections
 *		so we don't have to worry about getting the ProjectionInfo
 *		right for them...  -cim 6/3/91
 * ----------------------------------------------------------------
 */

/* ----------------
 *		ExecAssignScanType
 * ----------------
 */
void
ExecAssignScanType(ScanState *scanstate, TupleDesc tupDesc)
{
	TupleTableSlot *slot = scanstate->ss_ScanTupleSlot;

	ExecSetSlotDescriptor(slot, tupDesc);
}

/* ----------------
 *		ExecAssignScanTypeFromOuterPlan
 * ----------------
 */
void
ExecAssignScanTypeFromOuterPlan(ScanState *scanstate)
{
	PlanState  *outerPlan;
	TupleDesc	tupDesc;

	outerPlan = outerPlanState(scanstate);
	tupDesc = ExecGetResultType(outerPlan);

	ExecAssignScanType(scanstate, tupDesc);
}


/* ----------------------------------------------------------------
 *				  Scan node support
 * ----------------------------------------------------------------
 */

/* ----------------------------------------------------------------
 *		ExecRelationIsTargetRelation
 *
 *		Detect whether a relation (identified by rangetable index)
 *		is one of the target relations of the query.
 * ----------------------------------------------------------------
 */
bool
ExecRelationIsTargetRelation(EState *estate, Index scanrelid)
{
	ResultRelInfo *resultRelInfos;
	int			i;

	resultRelInfos = estate->es_result_relations;
	for (i = 0; i < estate->es_num_result_relations; i++)
	{
		if (resultRelInfos[i].ri_RangeTableIndex == scanrelid)
			return true;
	}
	return false;
}

/* ----------------------------------------------------------------
 *		ExecOpenScanRelation
 *
 *		Open the heap relation to be scanned by a base-level scan plan node.
 *		This should be called during the node's ExecInit routine.
 *
 * By default, this acquires AccessShareLock on the relation.  However,
 * if the relation was already locked by InitPlan, we don't need to acquire
 * any additional lock.  This saves trips to the shared lock manager.
 * ----------------------------------------------------------------
 */
Relation
ExecOpenScanRelation(EState *estate, Index scanrelid, int eflags)
{
	Relation	rel;
	Oid			reloid;
	LOCKMODE	lockmode;

	/*
	 * Determine the lock type we need.  First, scan to see if target relation
	 * is a result relation.  If not, check if it's a FOR UPDATE/FOR SHARE
	 * relation.  In either of those cases, we got the lock already.
	 */
	lockmode = AccessShareLock;
	if (ExecRelationIsTargetRelation(estate, scanrelid))
		lockmode = NoLock;
	else
	{
		/* Keep this check in sync with InitPlan! */
		ExecRowMark *erm = ExecFindRowMark(estate, scanrelid, true);

		if (erm != NULL && erm->relation != NULL)
			lockmode = NoLock;
	}

	/* Open the relation and acquire lock as needed */
	reloid = getrelid(scanrelid, estate->es_range_table);
	rel = heap_open(reloid, lockmode);

	/*
	 * Complain if we're attempting a scan of an unscannable relation, except
	 * when the query won't actually be run.  This is a slightly klugy place
	 * to do this, perhaps, but there is no better place.
	 */
	if ((eflags & (EXEC_FLAG_EXPLAIN_ONLY | EXEC_FLAG_WITH_NO_DATA)) == 0 &&
		!RelationIsScannable(rel))
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				 errmsg("materialized view \"%s\" has not been populated",
						RelationGetRelationName(rel)),
				 errhint("Use the REFRESH MATERIALIZED VIEW command.")));

	return rel;
}

/* ----------------------------------------------------------------
 *		ExecCloseScanRelation
 *
 *		Close the heap relation scanned by a base-level scan plan node.
 *		This should be called during the node's ExecEnd routine.
 *
 * Currently, we do not release the lock acquired by ExecOpenScanRelation.
 * This lock should be held till end of transaction.  (There is a faction
 * that considers this too much locking, however.)
 *
 * If we did want to release the lock, we'd have to repeat the logic in
 * ExecOpenScanRelation in order to figure out what to release.
 * ----------------------------------------------------------------
 */
void
ExecCloseScanRelation(Relation scanrel)
{
	heap_close(scanrel, NoLock);
}

/*
 * UpdateChangedParamSet
 *		Add changed parameters to a plan node's chgParam set
 */
void
UpdateChangedParamSet(PlanState *node, Bitmapset *newchg)
{
	Bitmapset  *parmset;

	/*
	 * The plan node only depends on params listed in its allParam set. Don't
	 * include anything else into its chgParam set.
	 */
	parmset = bms_intersect(node->plan->allParam, newchg);

	/*
	 * Keep node->chgParam == NULL if there's not actually any members; this
	 * allows the simplest possible tests in executor node files.
	 */
	if (!bms_is_empty(parmset))
		node->chgParam = bms_join(node->chgParam, parmset);
	else
		bms_free(parmset);
}

/*
 * Register a shutdown callback in an ExprContext.
 *
 * Shutdown callbacks will be called (in reverse order of registration)
 * when the ExprContext is deleted or rescanned.  This provides a hook
 * for functions called in the context to do any cleanup needed --- it's
 * particularly useful for functions returning sets.  Note that the
 * callback will *not* be called in the event that execution is aborted
 * by an error.
 */
void
RegisterExprContextCallback(ExprContext *econtext,
							ExprContextCallbackFunction function,
							Datum arg)
{
	ExprContext_CB *ecxt_callback;

	/* Save the info in appropriate memory context */
	ecxt_callback = (ExprContext_CB *)
		MemoryContextAlloc(econtext->ecxt_per_query_memory,
						   sizeof(ExprContext_CB));

	ecxt_callback->function = function;
	ecxt_callback->arg = arg;

	/* link to front of list for appropriate execution order */
	ecxt_callback->next = econtext->ecxt_callbacks;
	econtext->ecxt_callbacks = ecxt_callback;
}

/*
 * Deregister a shutdown callback in an ExprContext.
 *
 * Any list entries matching the function and arg will be removed.
 * This can be used if it's no longer necessary to call the callback.
 */
void
UnregisterExprContextCallback(ExprContext *econtext,
							  ExprContextCallbackFunction function,
							  Datum arg)
{
	ExprContext_CB **prev_callback;
	ExprContext_CB *ecxt_callback;

	prev_callback = &econtext->ecxt_callbacks;

	while ((ecxt_callback = *prev_callback) != NULL)
	{
		if (ecxt_callback->function == function && ecxt_callback->arg == arg)
		{
			*prev_callback = ecxt_callback->next;
			pfree(ecxt_callback);
		}
		else
			prev_callback = &ecxt_callback->next;
	}
}

/*
 * Call all the shutdown callbacks registered in an ExprContext.
 *
 * The callback list is emptied (important in case this is only a rescan
 * reset, and not deletion of the ExprContext).
 *
 * If isCommit is false, just clean the callback list but don't call 'em.
 * (See comment for FreeExprContext.)
 */
static void
ShutdownExprContext(ExprContext *econtext, bool isCommit)
{
	ExprContext_CB *ecxt_callback;
	MemoryContext oldcontext;

	/* Fast path in normal case where there's nothing to do. */
	if (econtext->ecxt_callbacks == NULL)
		return;

	/*
	 * Call the callbacks in econtext's per-tuple context.  This ensures that
	 * any memory they might leak will get cleaned up.
	 */
	oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);

	/*
	 * Call each callback function in reverse registration order.
	 */
	while ((ecxt_callback = econtext->ecxt_callbacks) != NULL)
	{
		econtext->ecxt_callbacks = ecxt_callback->next;
		if (isCommit)
			(*ecxt_callback->function) (ecxt_callback->arg);
		pfree(ecxt_callback);
	}

	MemoryContextSwitchTo(oldcontext);
}