From 385f337c9f39b21dca96ca4770552a10a6d5af24 Mon Sep 17 00:00:00 2001 From: Robert Haas Date: Tue, 8 Dec 2015 12:31:03 -0500 Subject: Allow foreign and custom joins to handle EvalPlanQual rechecks. Commit e7cb7ee14555cc9c5773e2c102efd6371f6f2005 provided basic infrastructure for allowing a foreign data wrapper or custom scan provider to replace a join of one or more tables with a scan. However, this infrastructure failed to take into account the need for possible EvalPlanQual rechecks, and ExecScanFetch would fail an assertion (or just overwrite memory) if such a check was attempted for a plan containing a pushed-down join. To fix, adjust the EPQ machinery to skip some processing steps when scanrelid == 0, making those the responsibility of scan's recheck method, which also has the responsibility in this case of correctly populating the relevant slot. To allow foreign scans to gain control in the right place to make use of this new facility, add a new, optional RecheckForeignScan method. Also, allow a foreign scan to have a child plan, which can be used to correctly populate the slot (or perhaps for something else, but this is the only use currently envisioned). KaiGai Kohei, reviewed by Robert Haas, Etsuro Fujita, and Kyotaro Horiguchi. --- src/backend/executor/nodeForeignscan.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) (limited to 'src/backend/executor/nodeForeignscan.c') diff --git a/src/backend/executor/nodeForeignscan.c b/src/backend/executor/nodeForeignscan.c index 6165e4a6cb4..62959e3a649 100644 --- a/src/backend/executor/nodeForeignscan.c +++ b/src/backend/executor/nodeForeignscan.c @@ -73,6 +73,7 @@ ForeignNext(ForeignScanState *node) static bool ForeignRecheck(ForeignScanState *node, TupleTableSlot *slot) { + FdwRoutine *fdwroutine = node->fdwroutine; ExprContext *econtext; /* @@ -85,6 +86,18 @@ ForeignRecheck(ForeignScanState *node, TupleTableSlot *slot) ResetExprContext(econtext); + /* + * If an outer join is pushed down, RecheckForeignScan may need to store a + * different tuple in the slot, because a different set of columns may go + * to NULL upon recheck. Otherwise, it shouldn't need to change the slot + * contents, just return true or false to indicate whether the quals still + * pass. For simple cases, setting fdw_recheck_quals may be easier than + * providing this callback. + */ + if (fdwroutine->RecheckForeignScan && + !fdwroutine->RecheckForeignScan(node, slot)) + return false; + return ExecQual(node->fdw_recheck_quals, econtext, false); } @@ -205,6 +218,11 @@ ExecInitForeignScan(ForeignScan *node, EState *estate, int eflags) scanstate->fdwroutine = fdwroutine; scanstate->fdw_state = NULL; + /* Initialize any outer plan. */ + if (outerPlan(node)) + outerPlanState(scanstate) = + ExecInitNode(outerPlan(node), estate, eflags); + /* * Tell the FDW to initialize the scan. */ @@ -225,6 +243,10 @@ ExecEndForeignScan(ForeignScanState *node) /* Let the FDW shut down */ node->fdwroutine->EndForeignScan(node); + /* Shut down any outer plan. */ + if (outerPlanState(node)) + ExecEndNode(outerPlanState(node)); + /* Free the exprcontext */ ExecFreeExprContext(&node->ss.ps); @@ -246,7 +268,17 @@ ExecEndForeignScan(ForeignScanState *node) void ExecReScanForeignScan(ForeignScanState *node) { + PlanState *outerPlan = outerPlanState(node); + node->fdwroutine->ReScanForeignScan(node); + /* + * If chgParam of subnode is not null then plan will be re-scanned by + * first ExecProcNode. outerPlan may also be NULL, in which case there + * is nothing to rescan at all. + */ + if (outerPlan != NULL && outerPlan->chgParam == NULL) + ExecReScan(outerPlan); + ExecScanReScan(&node->ss); } -- cgit v1.2.3