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/*-------------------------------------------------------------------------
*
* nodeForeignscan.c
* Routines to support scans of foreign tables
*
* Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/executor/nodeForeignscan.c
*
*-------------------------------------------------------------------------
*/
/*
* INTERFACE ROUTINES
*
* ExecForeignScan scans a foreign table.
* ExecInitForeignScan creates and initializes state info.
* ExecReScanForeignScan rescans the foreign relation.
* ExecEndForeignScan releases any resources allocated.
*/
#include "postgres.h"
#include "executor/executor.h"
#include "executor/nodeForeignscan.h"
#include "foreign/fdwapi.h"
#include "utils/rel.h"
static TupleTableSlot *ForeignNext(ForeignScanState *node);
static bool ForeignRecheck(ForeignScanState *node, TupleTableSlot *slot);
/* ----------------------------------------------------------------
* ForeignNext
*
* This is a workhorse for ExecForeignScan
* ----------------------------------------------------------------
*/
static TupleTableSlot *
ForeignNext(ForeignScanState *node)
{
TupleTableSlot *slot;
ForeignScan *plan = (ForeignScan *) node->ss.ps.plan;
ExprContext *econtext = node->ss.ps.ps_ExprContext;
MemoryContext oldcontext;
/* Call the Iterate function in short-lived context */
oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
slot = node->fdwroutine->IterateForeignScan(node);
MemoryContextSwitchTo(oldcontext);
/*
* If any system columns are requested, we have to force the tuple into
* physical-tuple form to avoid "cannot extract system attribute from
* virtual tuple" errors later. We also insert a valid value for
* tableoid, which is the only actually-useful system column.
*/
if (plan->fsSystemCol && !TupIsNull(slot))
{
HeapTuple tup = ExecMaterializeSlot(slot);
tup->t_tableOid = RelationGetRelid(node->ss.ss_currentRelation);
}
return slot;
}
/*
* ForeignRecheck -- access method routine to recheck a tuple in EvalPlanQual
*/
static bool
ForeignRecheck(ForeignScanState *node, TupleTableSlot *slot)
{
/* There are no access-method-specific conditions to recheck. */
return true;
}
/* ----------------------------------------------------------------
* ExecForeignScan(node)
*
* Fetches the next tuple from the FDW, checks local quals, and
* returns it.
* We call the ExecScan() routine and pass it the appropriate
* access method functions.
* ----------------------------------------------------------------
*/
TupleTableSlot *
ExecForeignScan(ForeignScanState *node)
{
return ExecScan((ScanState *) node,
(ExecScanAccessMtd) ForeignNext,
(ExecScanRecheckMtd) ForeignRecheck);
}
/* ----------------------------------------------------------------
* ExecInitForeignScan
* ----------------------------------------------------------------
*/
ForeignScanState *
ExecInitForeignScan(ForeignScan *node, EState *estate, int eflags)
{
ForeignScanState *scanstate;
Relation currentRelation;
FdwRoutine *fdwroutine;
/* check for unsupported flags */
Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
/*
* create state structure
*/
scanstate = makeNode(ForeignScanState);
scanstate->ss.ps.plan = (Plan *) node;
scanstate->ss.ps.state = estate;
/*
* Miscellaneous initialization
*
* create expression context for node
*/
ExecAssignExprContext(estate, &scanstate->ss.ps);
scanstate->ss.ps.ps_TupFromTlist = false;
/*
* 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);
/*
* tuple table initialization
*/
ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
ExecInitScanTupleSlot(estate, &scanstate->ss);
/*
* open the base relation and acquire appropriate lock on it.
*/
currentRelation = ExecOpenScanRelation(estate, node->scan.scanrelid);
scanstate->ss.ss_currentRelation = currentRelation;
/*
* get the scan type from the relation descriptor.
*/
ExecAssignScanType(&scanstate->ss, RelationGetDescr(currentRelation));
/*
* Initialize result tuple type and projection info.
*/
ExecAssignResultTypeFromTL(&scanstate->ss.ps);
ExecAssignScanProjectionInfo(&scanstate->ss);
/*
* Acquire function pointers from the FDW's handler, and init fdw_state.
*/
fdwroutine = GetFdwRoutineByRelId(RelationGetRelid(currentRelation));
scanstate->fdwroutine = fdwroutine;
scanstate->fdw_state = NULL;
/*
* Tell the FDW to initiate the scan.
*/
fdwroutine->BeginForeignScan(scanstate, eflags);
return scanstate;
}
/* ----------------------------------------------------------------
* ExecEndForeignScan
*
* frees any storage allocated through C routines.
* ----------------------------------------------------------------
*/
void
ExecEndForeignScan(ForeignScanState *node)
{
/* Let the FDW shut down */
node->fdwroutine->EndForeignScan(node);
/* Free the exprcontext */
ExecFreeExprContext(&node->ss.ps);
/* clean out the tuple table */
ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
ExecClearTuple(node->ss.ss_ScanTupleSlot);
/* close the relation. */
ExecCloseScanRelation(node->ss.ss_currentRelation);
}
/* ----------------------------------------------------------------
* ExecReScanForeignScan
*
* Rescans the relation.
* ----------------------------------------------------------------
*/
void
ExecReScanForeignScan(ForeignScanState *node)
{
node->fdwroutine->ReScanForeignScan(node);
ExecScanReScan(&node->ss);
}
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