execmain.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

/*-------------------------------------------------------------------------
 *
 * 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 *	The old ExecutorMain() has been replaced by ExecutorStart(),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 is required as an argument.
 *
 *	ExecutorStart() must be called at the beginning of execution of any
 *	query plan and ExecutorEnd() should always be called at the end of
 *	execution of a plan.
 *
 *	ExecutorRun accepts direction and count arguments that specify whether
 *	the plan is to be executed forwards, backwards, and for how many tuples.
 *
 * 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/execMain.c,v 1.256.2.6 2006/04/26 23:01:58 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/heapam.h"
#include "access/xlog.h"
#include "catalog/heap.h"
#include "catalog/namespace.h"
#include "commands/tablecmds.h"
#include "commands/tablespace.h"
#include "commands/trigger.h"
#include "executor/execdebug.h"
#include "executor/execdefs.h"
#include "executor/instrument.h"
#include "miscadmin.h"
#include "optimizer/clauses.h"
#include "optimizer/var.h"
#include "parser/parsetree.h"
#include "storage/smgr.h"
#include "utils/acl.h"
#include "utils/guc.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"


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

typedef struct evalPlanQual
{
	Index		rti;
	EState	   *estate;
	PlanState  *planstate;
	struct evalPlanQual *next;	/* stack of active PlanQual plans */
	struct evalPlanQual *free;	/* list of free PlanQual plans */
} evalPlanQual;

/* decls for local routines only used within this module */
static void InitPlan(QueryDesc *queryDesc, bool explainOnly);
static void initResultRelInfo(ResultRelInfo *resultRelInfo,
				  Index resultRelationIndex,
				  List *rangeTable,
				  CmdType operation,
				  bool doInstrument);
static TupleTableSlot *ExecutePlan(EState *estate, PlanState *planstate,
			CmdType operation,
			long numberTuples,
			ScanDirection direction,
			DestReceiver *dest);
static void ExecSelect(TupleTableSlot *slot,
		   DestReceiver *dest,
		   EState *estate);
static void ExecInsert(TupleTableSlot *slot, ItemPointer tupleid,
		   EState *estate);
static void ExecDelete(TupleTableSlot *slot, ItemPointer tupleid,
		   EState *estate);
static void ExecUpdate(TupleTableSlot *slot, ItemPointer tupleid,
		   EState *estate);
static TupleTableSlot *EvalPlanQualNext(EState *estate);
static void EndEvalPlanQual(EState *estate);
static void ExecCheckRTEPerms(RangeTblEntry *rte);
static void ExecCheckXactReadOnly(Query *parsetree);
static void EvalPlanQualStart(evalPlanQual *epq, EState *estate,
				  evalPlanQual *priorepq);
static void EvalPlanQualStop(evalPlanQual *epq);

/* end of local decls */


/* ----------------------------------------------------------------
 *		ExecutorStart
 *
 *		This routine must be called at the beginning of any execution of any
 *		query plan
 *
 * Takes a QueryDesc previously created by CreateQueryDesc (it's not real
 * clear why we bother to separate the two functions, but...).	The tupDesc
 * field of the QueryDesc is filled in to describe the tuples that will be
 * returned, and the internal fields (estate and planstate) are set up.
 *
 * If explainOnly is true, we are not actually intending to run the plan,
 * only to set up for EXPLAIN; so skip unwanted side-effects.
 *
 * NB: the CurrentMemoryContext when this is called will become the parent
 * of the per-query context used for this Executor invocation.
 * ----------------------------------------------------------------
 */
void
ExecutorStart(QueryDesc *queryDesc, bool explainOnly)
{
	EState	   *estate;
	MemoryContext oldcontext;

	/* sanity checks: queryDesc must not be started already */
	Assert(queryDesc != NULL);
	Assert(queryDesc->estate == NULL);

	/*
	 * If the transaction is read-only, we need to check if any writes are
	 * planned to non-temporary tables.
	 */
	if (XactReadOnly && !explainOnly)
		ExecCheckXactReadOnly(queryDesc->parsetree);

	/*
	 * Build EState, switch into per-query memory context for startup.
	 */
	estate = CreateExecutorState();
	queryDesc->estate = estate;

	oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);

	/*
	 * Fill in parameters, if any, from queryDesc
	 */
	estate->es_param_list_info = queryDesc->params;

	if (queryDesc->plantree->nParamExec > 0)
		estate->es_param_exec_vals = (ParamExecData *)
			palloc0(queryDesc->plantree->nParamExec * sizeof(ParamExecData));

	/*
	 * Copy other important information into the EState
	 */
	estate->es_snapshot = queryDesc->snapshot;
	estate->es_crosscheck_snapshot = queryDesc->crosscheck_snapshot;
	estate->es_instrument = queryDesc->doInstrument;

	/*
	 * Initialize the plan state tree
	 */
	InitPlan(queryDesc, explainOnly);

	MemoryContextSwitchTo(oldcontext);
}

/* ----------------------------------------------------------------
 *		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.
 *
 *		If direction is NoMovementScanDirection then nothing is done
 *		except to start up/shut down the destination.  Otherwise,
 *		we retrieve up to 'count' tuples in the specified direction.
 *
 *		Note: count = 0 is interpreted as no portal limit, i.e., run to
 *		completion.
 *
 * ----------------------------------------------------------------
 */
TupleTableSlot *
ExecutorRun(QueryDesc *queryDesc,
			ScanDirection direction, long count)
{
	EState	   *estate;
	CmdType		operation;
	DestReceiver *dest;
	TupleTableSlot *result;
	MemoryContext oldcontext;

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

	estate = queryDesc->estate;

	Assert(estate != NULL);

	/*
	 * Switch into per-query memory context
	 */
	oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);

	/*
	 * extract information from the query descriptor and the query feature.
	 */
	operation = queryDesc->operation;
	dest = queryDesc->dest;

	/*
	 * startup tuple receiver
	 */
	estate->es_processed = 0;
	estate->es_lastoid = InvalidOid;

	(*dest->rStartup) (dest, operation, queryDesc->tupDesc);

	/*
	 * run plan
	 */
	if (direction == NoMovementScanDirection)
		result = NULL;
	else
		result = ExecutePlan(estate,
							 queryDesc->planstate,
							 operation,
							 count,
							 direction,
							 dest);

	/*
	 * shutdown receiver
	 */
	(*dest->rShutdown) (dest);

	MemoryContextSwitchTo(oldcontext);

	return result;
}

/* ----------------------------------------------------------------
 *		ExecutorEnd
 *
 *		This routine must be called at the end of execution of any
 *		query plan
 * ----------------------------------------------------------------
 */
void
ExecutorEnd(QueryDesc *queryDesc)
{
	EState	   *estate;
	MemoryContext oldcontext;

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

	estate = queryDesc->estate;

	Assert(estate != NULL);

	/*
	 * Switch into per-query memory context to run ExecEndPlan
	 */
	oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);

	ExecEndPlan(queryDesc->planstate, estate);

	/*
	 * Must switch out of context before destroying it
	 */
	MemoryContextSwitchTo(oldcontext);

	/*
	 * Release EState and per-query memory context.  This should release
	 * everything the executor has allocated.
	 */
	FreeExecutorState(estate);

	/* Reset queryDesc fields that no longer point to anything */
	queryDesc->tupDesc = NULL;
	queryDesc->estate = NULL;
	queryDesc->planstate = NULL;
}

/* ----------------------------------------------------------------
 *		ExecutorRewind
 *
 *		This routine may be called on an open queryDesc to rewind it
 *		to the start.
 * ----------------------------------------------------------------
 */
void
ExecutorRewind(QueryDesc *queryDesc)
{
	EState	   *estate;
	MemoryContext oldcontext;

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

	estate = queryDesc->estate;

	Assert(estate != NULL);

	/* It's probably not sensible to rescan updating queries */
	Assert(queryDesc->operation == CMD_SELECT);

	/*
	 * Switch into per-query memory context
	 */
	oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);

	/*
	 * rescan plan
	 */
	ExecReScan(queryDesc->planstate, NULL);

	MemoryContextSwitchTo(oldcontext);
}


/*
 * ExecCheckRTPerms
 *		Check access permissions for all relations listed in a range table.
 */
void
ExecCheckRTPerms(List *rangeTable)
{
	ListCell   *l;

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

		ExecCheckRTEPerms(rte);
	}
}

/*
 * ExecCheckRTEPerms
 *		Check access permissions for a single RTE.
 */
static void
ExecCheckRTEPerms(RangeTblEntry *rte)
{
	AclMode		requiredPerms;
	Oid			relOid;
	Oid			userid;

	/*
	 * Only plain-relation RTEs need to be checked here.  Subquery RTEs are
	 * checked by ExecInitSubqueryScan if the subquery is still a separate
	 * subquery --- if it's been pulled up into our query level then the RTEs
	 * are in our rangetable and will be checked here. Function RTEs are
	 * checked by init_fcache when the function is prepared for execution.
	 * Join and special RTEs need no checks.
	 */
	if (rte->rtekind != RTE_RELATION)
		return;

	/*
	 * No work if requiredPerms is empty.
	 */
	requiredPerms = rte->requiredPerms;
	if (requiredPerms == 0)
		return;

	relOid = rte->relid;

	/*
	 * userid to check as: current user unless we have a setuid indication.
	 *
	 * Note: GetUserId() is presently fast enough that there's no harm in
	 * calling it separately for each RTE.	If that stops being true, we could
	 * call it once in ExecCheckRTPerms and pass the userid down from there.
	 * But for now, no need for the extra clutter.
	 */
	userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();

	/*
	 * We must have *all* the requiredPerms bits, so use aclmask not aclcheck.
	 */
	if (pg_class_aclmask(relOid, userid, requiredPerms, ACLMASK_ALL)
		!= requiredPerms)
		aclcheck_error(ACLCHECK_NO_PRIV, ACL_KIND_CLASS,
					   get_rel_name(relOid));
}

/*
 * Check that the query does not imply any writes to non-temp tables.
 */
static void
ExecCheckXactReadOnly(Query *parsetree)
{
	ListCell   *l;

	/*
	 * CREATE TABLE AS or SELECT INTO?
	 *
	 * XXX should we allow this if the destination is temp?
	 */
	if (parsetree->into != NULL)
		goto fail;

	/* Fail if write permissions are requested on any non-temp table */
	foreach(l, parsetree->rtable)
	{
		RangeTblEntry *rte = lfirst(l);

		if (rte->rtekind == RTE_SUBQUERY)
		{
			ExecCheckXactReadOnly(rte->subquery);
			continue;
		}

		if (rte->rtekind != RTE_RELATION)
			continue;

		if ((rte->requiredPerms & (~ACL_SELECT)) == 0)
			continue;

		if (isTempNamespace(get_rel_namespace(rte->relid)))
			continue;

		goto fail;
	}

	return;

fail:
	ereport(ERROR,
			(errcode(ERRCODE_READ_ONLY_SQL_TRANSACTION),
			 errmsg("transaction is read-only")));
}


/* ----------------------------------------------------------------
 *		InitPlan
 *
 *		Initializes the query plan: open files, allocate storage
 *		and start up the rule manager
 * ----------------------------------------------------------------
 */
static void
InitPlan(QueryDesc *queryDesc, bool explainOnly)
{
	CmdType		operation = queryDesc->operation;
	Query	   *parseTree = queryDesc->parsetree;
	Plan	   *plan = queryDesc->plantree;
	EState	   *estate = queryDesc->estate;
	PlanState  *planstate;
	List	   *rangeTable;
	Relation	intoRelationDesc;
	bool		do_select_into;