2008-10-04 23:56:55 +02:00
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/*-------------------------------------------------------------------------
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*
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* nodeWorktablescan.c
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* routines to handle WorkTableScan nodes.
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*
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2016-01-02 19:33:40 +01:00
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* Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
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2008-10-04 23:56:55 +02:00
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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2010-09-20 22:08:53 +02:00
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* src/backend/executor/nodeWorktablescan.c
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2008-10-04 23:56:55 +02:00
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "executor/execdebug.h"
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#include "executor/nodeWorktablescan.h"
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static TupleTableSlot *WorkTableScanNext(WorkTableScanState *node);
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/* ----------------------------------------------------------------
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* WorkTableScanNext
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*
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* This is a workhorse for ExecWorkTableScan
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* ----------------------------------------------------------------
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*/
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static TupleTableSlot *
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WorkTableScanNext(WorkTableScanState *node)
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{
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TupleTableSlot *slot;
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Tuplestorestate *tuplestorestate;
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/*
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* get information from the estate and scan state
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2008-10-28 18:13:51 +01:00
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*
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* Note: we intentionally do not support backward scan. Although it would
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* take only a couple more lines here, it would force nodeRecursiveunion.c
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* to create the tuplestore with backward scan enabled, which has a
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* performance cost. In practice backward scan is never useful for a
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* worktable plan node, since it cannot appear high enough in the plan
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* tree of a scrollable cursor to be exposed to a backward-scan
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* requirement. So it's not worth expending effort to support it.
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2009-03-27 19:30:21 +01:00
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*
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* Note: we are also assuming that this node is the only reader of the
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* worktable. Therefore, we don't need a private read pointer for the
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* tuplestore, nor do we need to tell tuplestore_gettupleslot to copy.
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2008-10-04 23:56:55 +02:00
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*/
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2012-03-21 22:30:14 +01:00
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Assert(ScanDirectionIsForward(node->ss.ps.state->es_direction));
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2008-10-04 23:56:55 +02:00
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tuplestorestate = node->rustate->working_table;
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/*
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* Get the next tuple from tuplestore. Return NULL if no more tuples.
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*/
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slot = node->ss.ss_ScanTupleSlot;
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2009-03-27 19:30:21 +01:00
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(void) tuplestore_gettupleslot(tuplestorestate, true, false, slot);
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2008-10-04 23:56:55 +02:00
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return slot;
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}
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Re-implement EvalPlanQual processing to improve its performance and eliminate
a lot of strange behaviors that occurred in join cases. We now identify the
"current" row for every joined relation in UPDATE, DELETE, and SELECT FOR
UPDATE/SHARE queries. If an EvalPlanQual recheck is necessary, we jam the
appropriate row into each scan node in the rechecking plan, forcing it to emit
only that one row. The former behavior could rescan the whole of each joined
relation for each recheck, which was terrible for performance, and what's much
worse could result in duplicated output tuples.
Also, the original implementation of EvalPlanQual could not re-use the recheck
execution tree --- it had to go through a full executor init and shutdown for
every row to be tested. To avoid this overhead, I've associated a special
runtime Param with each LockRows or ModifyTable plan node, and arranged to
make every scan node below such a node depend on that Param. Thus, by
signaling a change in that Param, the EPQ machinery can just rescan the
already-built test plan.
This patch also adds a prohibition on set-returning functions in the
targetlist of SELECT FOR UPDATE/SHARE. This is needed to avoid the
duplicate-output-tuple problem. It seems fairly reasonable since the
other restrictions on SELECT FOR UPDATE are meant to ensure that there
is a unique correspondence between source tuples and result tuples,
which an output SRF destroys as much as anything else does.
2009-10-26 03:26:45 +01:00
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/*
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* WorkTableScanRecheck -- access method routine to recheck a tuple in EvalPlanQual
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*/
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static bool
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WorkTableScanRecheck(WorkTableScanState *node, TupleTableSlot *slot)
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{
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/* nothing to check */
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return true;
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}
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2008-10-04 23:56:55 +02:00
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/* ----------------------------------------------------------------
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* ExecWorkTableScan(node)
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*
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* Scans the worktable sequentially and returns the next qualifying tuple.
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Re-implement EvalPlanQual processing to improve its performance and eliminate
a lot of strange behaviors that occurred in join cases. We now identify the
"current" row for every joined relation in UPDATE, DELETE, and SELECT FOR
UPDATE/SHARE queries. If an EvalPlanQual recheck is necessary, we jam the
appropriate row into each scan node in the rechecking plan, forcing it to emit
only that one row. The former behavior could rescan the whole of each joined
relation for each recheck, which was terrible for performance, and what's much
worse could result in duplicated output tuples.
Also, the original implementation of EvalPlanQual could not re-use the recheck
execution tree --- it had to go through a full executor init and shutdown for
every row to be tested. To avoid this overhead, I've associated a special
runtime Param with each LockRows or ModifyTable plan node, and arranged to
make every scan node below such a node depend on that Param. Thus, by
signaling a change in that Param, the EPQ machinery can just rescan the
already-built test plan.
This patch also adds a prohibition on set-returning functions in the
targetlist of SELECT FOR UPDATE/SHARE. This is needed to avoid the
duplicate-output-tuple problem. It seems fairly reasonable since the
other restrictions on SELECT FOR UPDATE are meant to ensure that there
is a unique correspondence between source tuples and result tuples,
which an output SRF destroys as much as anything else does.
2009-10-26 03:26:45 +01:00
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* We call the ExecScan() routine and pass it the appropriate
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* access method functions.
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2008-10-04 23:56:55 +02:00
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* ----------------------------------------------------------------
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*/
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TupleTableSlot *
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ExecWorkTableScan(WorkTableScanState *node)
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{
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2008-10-13 02:41:41 +02:00
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/*
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2009-06-11 16:49:15 +02:00
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* On the first call, find the ancestor RecursiveUnion's state via the
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2014-05-06 18:12:18 +02:00
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* Param slot reserved for it. (We can't do this during node init because
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2009-06-11 16:49:15 +02:00
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* there are corner cases where we'll get the init call before the
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* RecursiveUnion does.)
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2008-10-13 02:41:41 +02:00
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*/
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if (node->rustate == NULL)
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{
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WorkTableScan *plan = (WorkTableScan *) node->ss.ps.plan;
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EState *estate = node->ss.ps.state;
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ParamExecData *param;
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param = &(estate->es_param_exec_vals[plan->wtParam]);
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Assert(param->execPlan == NULL);
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Assert(!param->isnull);
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node->rustate = (RecursiveUnionState *) DatumGetPointer(param->value);
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Assert(node->rustate && IsA(node->rustate, RecursiveUnionState));
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/*
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* The scan tuple type (ie, the rowtype we expect to find in the work
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* table) is the same as the result rowtype of the ancestor
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* RecursiveUnion node. Note this depends on the assumption that
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* RecursiveUnion doesn't allow projection.
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*/
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ExecAssignScanType(&node->ss,
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ExecGetResultType(&node->rustate->ps));
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/*
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2009-06-11 16:49:15 +02:00
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* Now we can initialize the projection info. This must be completed
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* before we can call ExecScan().
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2008-10-13 02:41:41 +02:00
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*/
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ExecAssignScanProjectionInfo(&node->ss);
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}
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Re-implement EvalPlanQual processing to improve its performance and eliminate
a lot of strange behaviors that occurred in join cases. We now identify the
"current" row for every joined relation in UPDATE, DELETE, and SELECT FOR
UPDATE/SHARE queries. If an EvalPlanQual recheck is necessary, we jam the
appropriate row into each scan node in the rechecking plan, forcing it to emit
only that one row. The former behavior could rescan the whole of each joined
relation for each recheck, which was terrible for performance, and what's much
worse could result in duplicated output tuples.
Also, the original implementation of EvalPlanQual could not re-use the recheck
execution tree --- it had to go through a full executor init and shutdown for
every row to be tested. To avoid this overhead, I've associated a special
runtime Param with each LockRows or ModifyTable plan node, and arranged to
make every scan node below such a node depend on that Param. Thus, by
signaling a change in that Param, the EPQ machinery can just rescan the
already-built test plan.
This patch also adds a prohibition on set-returning functions in the
targetlist of SELECT FOR UPDATE/SHARE. This is needed to avoid the
duplicate-output-tuple problem. It seems fairly reasonable since the
other restrictions on SELECT FOR UPDATE are meant to ensure that there
is a unique correspondence between source tuples and result tuples,
which an output SRF destroys as much as anything else does.
2009-10-26 03:26:45 +01:00
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return ExecScan(&node->ss,
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(ExecScanAccessMtd) WorkTableScanNext,
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(ExecScanRecheckMtd) WorkTableScanRecheck);
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2008-10-04 23:56:55 +02:00
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}
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/* ----------------------------------------------------------------
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* ExecInitWorkTableScan
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* ----------------------------------------------------------------
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*/
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WorkTableScanState *
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ExecInitWorkTableScan(WorkTableScan *node, EState *estate, int eflags)
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{
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WorkTableScanState *scanstate;
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/* check for unsupported flags */
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2008-10-28 18:13:51 +01:00
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Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
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2008-10-04 23:56:55 +02:00
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/*
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* WorkTableScan should not have any children.
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*/
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Assert(outerPlan(node) == NULL);
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Assert(innerPlan(node) == NULL);
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/*
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* create new WorkTableScanState for node
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*/
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scanstate = makeNode(WorkTableScanState);
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scanstate->ss.ps.plan = (Plan *) node;
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scanstate->ss.ps.state = estate;
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2008-10-13 02:41:41 +02:00
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scanstate->rustate = NULL; /* we'll set this later */
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2008-10-04 23:56:55 +02:00
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/*
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* Miscellaneous initialization
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*
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* create expression context for node
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*/
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ExecAssignExprContext(estate, &scanstate->ss.ps);
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/*
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* initialize child expressions
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*/
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scanstate->ss.ps.targetlist = (List *)
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ExecInitExpr((Expr *) node->scan.plan.targetlist,
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(PlanState *) scanstate);
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scanstate->ss.ps.qual = (List *)
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ExecInitExpr((Expr *) node->scan.plan.qual,
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(PlanState *) scanstate);
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/*
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* tuple table initialization
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*/
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ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
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ExecInitScanTupleSlot(estate, &scanstate->ss);
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/*
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2008-10-13 02:41:41 +02:00
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* Initialize result tuple type, but not yet projection info.
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2008-10-04 23:56:55 +02:00
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*/
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ExecAssignResultTypeFromTL(&scanstate->ss.ps);
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scanstate->ss.ps.ps_TupFromTlist = false;
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return scanstate;
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}
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/* ----------------------------------------------------------------
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* ExecEndWorkTableScan
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*
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* frees any storage allocated through C routines.
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* ----------------------------------------------------------------
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*/
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void
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ExecEndWorkTableScan(WorkTableScanState *node)
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{
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/*
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* Free exprcontext
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*/
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ExecFreeExprContext(&node->ss.ps);
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/*
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* clean out the tuple table
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*/
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ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
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ExecClearTuple(node->ss.ss_ScanTupleSlot);
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}
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/* ----------------------------------------------------------------
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2010-07-12 19:01:06 +02:00
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* ExecReScanWorkTableScan
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2008-10-04 23:56:55 +02:00
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*
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* Rescans the relation.
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* ----------------------------------------------------------------
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*/
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void
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2010-07-12 19:01:06 +02:00
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ExecReScanWorkTableScan(WorkTableScanState *node)
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2008-10-04 23:56:55 +02:00
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{
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ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
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Re-implement EvalPlanQual processing to improve its performance and eliminate
a lot of strange behaviors that occurred in join cases. We now identify the
"current" row for every joined relation in UPDATE, DELETE, and SELECT FOR
UPDATE/SHARE queries. If an EvalPlanQual recheck is necessary, we jam the
appropriate row into each scan node in the rechecking plan, forcing it to emit
only that one row. The former behavior could rescan the whole of each joined
relation for each recheck, which was terrible for performance, and what's much
worse could result in duplicated output tuples.
Also, the original implementation of EvalPlanQual could not re-use the recheck
execution tree --- it had to go through a full executor init and shutdown for
every row to be tested. To avoid this overhead, I've associated a special
runtime Param with each LockRows or ModifyTable plan node, and arranged to
make every scan node below such a node depend on that Param. Thus, by
signaling a change in that Param, the EPQ machinery can just rescan the
already-built test plan.
This patch also adds a prohibition on set-returning functions in the
targetlist of SELECT FOR UPDATE/SHARE. This is needed to avoid the
duplicate-output-tuple problem. It seems fairly reasonable since the
other restrictions on SELECT FOR UPDATE are meant to ensure that there
is a unique correspondence between source tuples and result tuples,
which an output SRF destroys as much as anything else does.
2009-10-26 03:26:45 +01:00
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ExecScanReScan(&node->ss);
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2008-10-23 17:29:23 +02:00
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2008-10-13 02:41:41 +02:00
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/* No need (or way) to rescan if ExecWorkTableScan not called yet */
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if (node->rustate)
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tuplestore_rescan(node->rustate->working_table);
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2008-10-04 23:56:55 +02:00
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}
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