execprocnode.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

/*-------------------------------------------------------------------------
 *
 * execProcnode.c
 *	 contains dispatch functions which call the appropriate "initialize",
 *	 "get a tuple", and "cleanup" routines for the given node type.
 *	 If the node has children, then it will presumably call ExecInitNode,
 *	 ExecProcNode, or ExecEndNode on its subnodes and do the appropriate
 *	 processing.
 *
 * 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/execProcnode.c,v 1.51 2005/10/15 02:49:16 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
/*
 *	 INTERFACE ROUTINES
 *		ExecCountSlotsNode -	count tuple slots needed by plan tree
 *		ExecInitNode	-		initialize a plan node and its subplans
 *		ExecProcNode	-		get a tuple by executing the plan node
 *		ExecEndNode		-		shut down a plan node and its subplans
 *
 *	 NOTES
 *		This used to be three files.  It is now all combined into
 *		one file so that it is easier to keep ExecInitNode, ExecProcNode,
 *		and ExecEndNode in sync when new nodes are added.
 *
 *	 EXAMPLE
 *		suppose we want the age of the manager of the shoe department and
 *		the number of employees in that department.  so we have the query:
 *
 *				retrieve (DEPT.no_emps, EMP.age)
 *				where EMP.name = DEPT.mgr and
 *					  DEPT.name = "shoe"
 *
 *		Suppose the planner gives us the following plan:
 *
 *						Nest Loop (DEPT.mgr = EMP.name)
 *						/		\
 *					   /		 \
 *				   Seq Scan		Seq Scan
 *					DEPT		  EMP
 *				(name = "shoe")
 *
 *		ExecStart() is called first.
 *		It calls InitPlan() which calls ExecInitNode() on
 *		the root of the plan -- the nest loop node.
 *
 *	  * ExecInitNode() notices that it is looking at a nest loop and
 *		as the code below demonstrates, it calls ExecInitNestLoop().
 *		Eventually this calls ExecInitNode() on the right and left subplans
 *		and so forth until the entire plan is initialized.	The result
 *		of ExecInitNode() is a plan state tree built with the same structure
 *		as the underlying plan tree.
 *
 *	  * Then when ExecRun() is called, it calls ExecutePlan() which calls
 *		ExecProcNode() repeatedly on the top node of the plan state tree.
 *		Each time this happens, ExecProcNode() will end up calling
 *		ExecNestLoop(), which calls ExecProcNode() on its subplans.
 *		Each of these subplans is a sequential scan so ExecSeqScan() is
 *		called.  The slots returned by ExecSeqScan() may contain
 *		tuples which contain the attributes ExecNestLoop() uses to
 *		form the tuples it returns.
 *
 *	  * Eventually ExecSeqScan() stops returning tuples and the nest
 *		loop join ends.  Lastly, ExecEnd() calls ExecEndNode() which
 *		calls ExecEndNestLoop() which in turn calls ExecEndNode() on
 *		its subplans which result in ExecEndSeqScan().
 *
 *		This should show how the executor works by having
 *		ExecInitNode(), ExecProcNode() and ExecEndNode() dispatch
 *		their work to the appopriate node support routines which may
 *		in turn call these routines themselves on their subplans.
 */
#include "postgres.h"

#include "executor/executor.h"
#include "executor/instrument.h"
#include "executor/nodeAgg.h"
#include "executor/nodeAppend.h"
#include "executor/nodeBitmapAnd.h"
#include "executor/nodeBitmapHeapscan.h"
#include "executor/nodeBitmapIndexscan.h"
#include "executor/nodeBitmapOr.h"
#include "executor/nodeFunctionscan.h"
#include "executor/nodeGroup.h"
#include "executor/nodeHash.h"
#include "executor/nodeHashjoin.h"
#include "executor/nodeIndexscan.h"
#include "executor/nodeLimit.h"
#include "executor/nodeMaterial.h"
#include "executor/nodeMergejoin.h"
#include "executor/nodeNestloop.h"
#include "executor/nodeResult.h"
#include "executor/nodeSeqscan.h"
#include "executor/nodeSetOp.h"
#include "executor/nodeSort.h"
#include "executor/nodeSubplan.h"
#include "executor/nodeSubqueryscan.h"
#include "executor/nodeTidscan.h"
#include "executor/nodeUnique.h"
#include "miscadmin.h"
#include "tcop/tcopprot.h"

/* ------------------------------------------------------------------------
 *		ExecInitNode
 *
 *		Recursively initializes all the nodes in the plan rooted
 *		at 'node'.
 *
 *		Initial States:
 *		  'node' is the plan produced by the query planner
 *		  'estate' is the shared execution state for the query tree
 *
 *		Returns a PlanState node corresponding to the given Plan node.
 * ------------------------------------------------------------------------
 */
PlanState *
ExecInitNode(Plan *node, EState *estate)
{
	PlanState  *result;
	List	   *subps;
	ListCell   *l;

	/*
	 * do nothing when we get to the end of a leaf on tree.
	 */
	if (node == NULL)
		return NULL;

	switch (nodeTag(node))
	{
			/*
			 * control nodes
			 */
		case T_Result:
			result = (PlanState *) ExecInitResult((Result *) node, estate);
			break;

		case T_Append:
			result = (PlanState *) ExecInitAppend((Append *) node, estate);
			break;

		case T_BitmapAnd:
			result = (PlanState *) ExecInitBitmapAnd((BitmapAnd *) node, estate);
			break;

		case T_BitmapOr:
			result = (PlanState *) ExecInitBitmapOr((BitmapOr *) node, estate);
			break;

			/*
			 * scan nodes
			 */
		case T_SeqScan:
			result = (PlanState *) ExecInitSeqScan((SeqScan *) node, estate);
			break;

		case T_IndexScan:
			result = (PlanState *) ExecInitIndexScan((IndexScan *) node, estate);
			break;

		case T_BitmapIndexScan:
			result = (PlanState *) ExecInitBitmapIndexScan((BitmapIndexScan *) node, estate);
			break;

		case T_BitmapHeapScan:
			result = (PlanState *) ExecInitBitmapHeapScan((BitmapHeapScan *) node, estate);
			break;

		case T_TidScan:
			result = (PlanState *) ExecInitTidScan((TidScan *) node, estate);
			break;

		case T_SubqueryScan:
			result = (PlanState *) ExecInitSubqueryScan((SubqueryScan *) node, estate);
			break;

		case T_FunctionScan:
			result = (PlanState *) ExecInitFunctionScan((FunctionScan *) node, estate);
			break;

			/*
			 * join nodes
			 */
		case T_NestLoop:
			result = (PlanState *) ExecInitNestLoop((NestLoop *) node, estate);
			break;

		case T_MergeJoin:
			result = (PlanState *) ExecInitMergeJoin((MergeJoin *) node, estate);
			break;

		case T_HashJoin:
			result = (PlanState *) ExecInitHashJoin((HashJoin *) node, estate);
			break;

			/*
			 * materialization nodes
			 */
		case T_Material:
			result = (PlanState *) ExecInitMaterial((Material *) node, estate);
			break;

		case T_Sort:
			result = (PlanState *) ExecInitSort((Sort *) node, estate);
			break;

		case T_Group:
			result = (PlanState *) ExecInitGroup((Group *) node, estate);
			break;

		case T_Agg:
			result = (PlanState *) ExecInitAgg((Agg *) node, estate);
			break;

		case T_Unique:
			result = (PlanState *) ExecInitUnique((Unique *) node, estate);
			break;

		case T_Hash:
			result = (PlanState *) ExecInitHash((Hash *) node, estate);
			break;

		case T_SetOp:
			result = (PlanState *) ExecInitSetOp((SetOp *) node, estate);
			break;

		case T_Limit:
			result = (PlanState *) ExecInitLimit((Limit *) node, estate);
			break;

		default:
			elog(ERROR, "unrecognized node type: %d", (int) nodeTag(node));
			result = NULL;		/* keep compiler quiet */
			break;
	}

	/*
	 * Initialize any initPlans present in this node.  The planner put them in
	 * a separate list for us.
	 */
	subps = NIL;
	foreach(l, node->initPlan)
	{
		SubPlan    *subplan = (SubPlan *) lfirst(l);
		SubPlanState *sstate;

		Assert(IsA(subplan, SubPlan));
		sstate = ExecInitExprInitPlan(subplan, result);
		ExecInitSubPlan(sstate, estate);
		subps = lappend(subps, sstate);
	}
	result->initPlan = subps;

	/*
	 * Initialize any subPlans present in this node.  These were found by
	 * ExecInitExpr during initialization of the PlanState.  Note we must do
	 * this after initializing initPlans, in case their arguments contain
	 * subPlans (is that actually possible? perhaps not).
	 */
	foreach(l, result->subPlan)
	{
		SubPlanState *sstate = (SubPlanState *) lfirst(l);

		Assert(IsA(sstate, SubPlanState));
		ExecInitSubPlan(sstate, estate);
	}

	/* Set up instrumentation for this node if requested */
	if (estate->es_instrument)
		result->instrument = InstrAlloc(1);

	return result;
}


/* ----------------------------------------------------------------
 *		ExecProcNode
 *
 *		Execute the given node to return a(nother) tuple.
 * ----------------------------------------------------------------
 */
TupleTableSlot *
ExecProcNode(PlanState *node)
{
	TupleTableSlot *result;

	CHECK_FOR_INTERRUPTS();

	if (node->chgParam != NULL) /* something changed */
		ExecReScan(node, NULL); /* let ReScan handle this */

	if (node->instrument)
		InstrStartNode(node->instrument);

	switch (nodeTag(node))
	{
			/*
			 * control nodes
			 */
		case T_ResultState:
			result = ExecResult((ResultState *) node);
			break;

		case T_AppendState:
			result = ExecAppend((AppendState *) node);
			break;

			/* BitmapAndState does not yield tuples */

			/* BitmapOrState does not yield tuples */

			/*
			 * scan nodes
			 */
		case T_SeqScanState:
			result = ExecSeqScan((SeqScanState *) node);
			break;

		case T_IndexScanState:
			result = ExecIndexScan((IndexScanState *) node);
			break;

			/* BitmapIndexScanState does not yield tuples */

		case T_BitmapHeapScanState:
			result = ExecBitmapHeapScan((BitmapHeapScanState *) node);
			break;

		case T_TidScanState:
			result = ExecTidScan((TidScanState *) node);
			break;

		case T_SubqueryScanState:
			result = ExecSubqueryScan((SubqueryScanState *) node);
			break;

		case T_FunctionScanState:
			result = ExecFunctionScan((FunctionScanState *) node);
			break;

			/*
			 * join nodes
			 */
		case T_NestLoopState:
			result = ExecNestLoop((NestLoopState *) node);
			break;

		case T_MergeJoinState: