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/*-------------------------------------------------------------------------
*
* nodeWorktablescan.c
* routines to handle WorkTableScan nodes.
*
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/executor/nodeWorktablescan.c,v 1.7 2009/06/11 14:48:57 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "executor/execdebug.h"
#include "executor/nodeWorktablescan.h"
static TupleTableSlot *WorkTableScanNext(WorkTableScanState *node);
/* ----------------------------------------------------------------
* WorkTableScanNext
*
* This is a workhorse for ExecWorkTableScan
* ----------------------------------------------------------------
*/
static TupleTableSlot *
WorkTableScanNext(WorkTableScanState *node)
{
TupleTableSlot *slot;
EState *estate;
Tuplestorestate *tuplestorestate;
/*
* get information from the estate and scan state
*
* Note: we intentionally do not support backward scan. Although it would
* take only a couple more lines here, it would force nodeRecursiveunion.c
* to create the tuplestore with backward scan enabled, which has a
* performance cost. In practice backward scan is never useful for a
* worktable plan node, since it cannot appear high enough in the plan
* tree of a scrollable cursor to be exposed to a backward-scan
* requirement. So it's not worth expending effort to support it.
*
* Note: we are also assuming that this node is the only reader of the
* worktable. Therefore, we don't need a private read pointer for the
* tuplestore, nor do we need to tell tuplestore_gettupleslot to copy.
*/
estate = node->ss.ps.state;
Assert(ScanDirectionIsForward(estate->es_direction));
tuplestorestate = node->rustate->working_table;
/*
* Get the next tuple from tuplestore. Return NULL if no more tuples.
*/
slot = node->ss.ss_ScanTupleSlot;
(void) tuplestore_gettupleslot(tuplestorestate, true, false, slot);
return slot;
}
/* ----------------------------------------------------------------
* ExecWorkTableScan(node)
*
* Scans the worktable sequentially and returns the next qualifying tuple.
* It calls the ExecScan() routine and passes it the access method
* which retrieves tuples sequentially.
* ----------------------------------------------------------------
*/
TupleTableSlot *
ExecWorkTableScan(WorkTableScanState *node)
{
/*
* On the first call, find the ancestor RecursiveUnion's state via the
* Param slot reserved for it. (We can't do this during node init because
* there are corner cases where we'll get the init call before the
* RecursiveUnion does.)
*/
if (node->rustate == NULL)
{
WorkTableScan *plan = (WorkTableScan *) node->ss.ps.plan;
EState *estate = node->ss.ps.state;
ParamExecData *param;
param = &(estate->es_param_exec_vals[plan->wtParam]);
Assert(param->execPlan == NULL);
Assert(!param->isnull);
node->rustate = (RecursiveUnionState *) DatumGetPointer(param->value);
Assert(node->rustate && IsA(node->rustate, RecursiveUnionState));
/*
* The scan tuple type (ie, the rowtype we expect to find in the work
* table) is the same as the result rowtype of the ancestor
* RecursiveUnion node. Note this depends on the assumption that
* RecursiveUnion doesn't allow projection.
*/
ExecAssignScanType(&node->ss,
ExecGetResultType(&node->rustate->ps));
/*
* Now we can initialize the projection info. This must be completed
* before we can call ExecScan().
*/
ExecAssignScanProjectionInfo(&node->ss);
}
/*
* use WorkTableScanNext as access method
*/
return ExecScan(&node->ss, (ExecScanAccessMtd) WorkTableScanNext);
}
/* ----------------------------------------------------------------
* ExecInitWorkTableScan
* ----------------------------------------------------------------
*/
WorkTableScanState *
ExecInitWorkTableScan(WorkTableScan *node, EState *estate, int eflags)
{
WorkTableScanState *scanstate;
/* check for unsupported flags */
Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
/*
* WorkTableScan should not have any children.
*/
Assert(outerPlan(node) == NULL);
Assert(innerPlan(node) == NULL);
/*
* create new WorkTableScanState for node
*/
scanstate = makeNode(WorkTableScanState);
scanstate->ss.ps.plan = (Plan *) node;
scanstate->ss.ps.state = estate;
scanstate->rustate = NULL; /* we'll set this later */
/*
* Miscellaneous initialization
*
* create expression context for node
*/
ExecAssignExprContext(estate, &scanstate->ss.ps);
/*
* initialize child expressions
*/
scanstate->ss.ps.targetlist = (List *)
ExecInitExpr((Expr *) node->scan.plan.targetlist,
(PlanState *) scanstate);
scanstate->ss.ps.qual = (List *)
ExecInitExpr((Expr *) node->scan.plan.qual,
(PlanState *) scanstate);
#define WORKTABLESCAN_NSLOTS 2
/*
* tuple table initialization
*/
ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
ExecInitScanTupleSlot(estate, &scanstate->ss);
/*
* Initialize result tuple type, but not yet projection info.
*/
ExecAssignResultTypeFromTL(&scanstate->ss.ps);
scanstate->ss.ps.ps_TupFromTlist = false;
return scanstate;
}
int
ExecCountSlotsWorkTableScan(WorkTableScan *node)
{
return ExecCountSlotsNode(outerPlan(node)) +
ExecCountSlotsNode(innerPlan(node)) +
WORKTABLESCAN_NSLOTS;
}
/* ----------------------------------------------------------------
* ExecEndWorkTableScan
*
* frees any storage allocated through C routines.
* ----------------------------------------------------------------
*/
void
ExecEndWorkTableScan(WorkTableScanState *node)
{
/*
* Free exprcontext
*/
ExecFreeExprContext(&node->ss.ps);
/*
* clean out the tuple table
*/
ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
ExecClearTuple(node->ss.ss_ScanTupleSlot);
}
/* ----------------------------------------------------------------
* ExecWorkTableScanReScan
*
* Rescans the relation.
* ----------------------------------------------------------------
*/
void
ExecWorkTableScanReScan(WorkTableScanState *node, ExprContext *exprCtxt)
{
ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
node->ss.ps.ps_TupFromTlist = false;
/* No need (or way) to rescan if ExecWorkTableScan not called yet */
if (node->rustate)
tuplestore_rescan(node->rustate->working_table);
}
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