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Diffstat (limited to 'src/backend/executor/nodeForeignscan.c')
| -rw-r--r-- | src/backend/executor/nodeForeignscan.c | 209 |
1 files changed, 209 insertions, 0 deletions
diff --git a/src/backend/executor/nodeForeignscan.c b/src/backend/executor/nodeForeignscan.c new file mode 100644 index 0000000000..c4309a981e --- /dev/null +++ b/src/backend/executor/nodeForeignscan.c @@ -0,0 +1,209 @@ +/*------------------------------------------------------------------------- + * + * nodeForeignscan.c + * Routines to support scans of foreign tables + * + * Portions Copyright (c) 1996-2011, 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" + +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); +} |