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The reason for doing so is that it will allow expression evaluation to optimize based on the underlying tupledesc. In particular it will allow to JIT tuple deforming together with the expression itself. For that expression initialization needs to be moved after the relevant slots are initialized - mostly unproblematic, except in the case of nodeWorktablescan.c. After doing so there's no need for ExecAssignResultType() and ExecAssignResultTypeFromTL() anymore, as all former callers have been converted to create a slot with a fixed descriptor. When creating a slot with a fixed descriptor, tts_values/isnull can be allocated together with the main slot, reducing allocation overhead and increasing cache density a bit. Author: Andres Freund Discussion: https://postgr.es/m/20171206093717.vqdxe5icqttpxs3p@alap3.anarazel.de
198 lines
5.3 KiB
C
198 lines
5.3 KiB
C
/*-------------------------------------------------------------------------
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*
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* nodeNamedtuplestorescan.c
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* routines to handle NamedTuplestoreScan nodes.
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*
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* Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
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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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* src/backend/executor/nodeNamedtuplestorescan.c
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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/nodeNamedtuplestorescan.h"
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#include "miscadmin.h"
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#include "utils/queryenvironment.h"
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static TupleTableSlot *NamedTuplestoreScanNext(NamedTuplestoreScanState *node);
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/* ----------------------------------------------------------------
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* NamedTuplestoreScanNext
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*
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* This is a workhorse for ExecNamedTuplestoreScan
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* ----------------------------------------------------------------
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*/
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static TupleTableSlot *
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NamedTuplestoreScanNext(NamedTuplestoreScanState *node)
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{
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TupleTableSlot *slot;
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/* We intentionally do not support backward scan. */
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Assert(ScanDirectionIsForward(node->ss.ps.state->es_direction));
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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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(void) tuplestore_gettupleslot(node->relation, true, false, slot);
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return slot;
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}
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/*
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* NamedTuplestoreScanRecheck -- access method routine to recheck a tuple in
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* EvalPlanQual
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*/
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static bool
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NamedTuplestoreScanRecheck(NamedTuplestoreScanState *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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/* ----------------------------------------------------------------
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* ExecNamedTuplestoreScan(node)
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*
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* Scans the CTE sequentially and returns the next qualifying tuple.
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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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* ----------------------------------------------------------------
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*/
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static TupleTableSlot *
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ExecNamedTuplestoreScan(PlanState *pstate)
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{
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NamedTuplestoreScanState *node = castNode(NamedTuplestoreScanState, pstate);
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return ExecScan(&node->ss,
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(ExecScanAccessMtd) NamedTuplestoreScanNext,
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(ExecScanRecheckMtd) NamedTuplestoreScanRecheck);
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}
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/* ----------------------------------------------------------------
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* ExecInitNamedTuplestoreScan
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* ----------------------------------------------------------------
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*/
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NamedTuplestoreScanState *
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ExecInitNamedTuplestoreScan(NamedTuplestoreScan *node, EState *estate, int eflags)
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{
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NamedTuplestoreScanState *scanstate;
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EphemeralNamedRelation enr;
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/* check for unsupported flags */
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Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
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/*
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* NamedTuplestoreScan 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 NamedTuplestoreScanState for node
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*/
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scanstate = makeNode(NamedTuplestoreScanState);
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scanstate->ss.ps.plan = (Plan *) node;
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scanstate->ss.ps.state = estate;
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scanstate->ss.ps.ExecProcNode = ExecNamedTuplestoreScan;
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enr = get_ENR(estate->es_queryEnv, node->enrname);
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if (!enr)
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elog(ERROR, "executor could not find named tuplestore \"%s\"",
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node->enrname);
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Assert(enr->reldata);
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scanstate->relation = (Tuplestorestate *) enr->reldata;
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scanstate->tupdesc = ENRMetadataGetTupDesc(&(enr->md));
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scanstate->readptr =
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tuplestore_alloc_read_pointer(scanstate->relation, EXEC_FLAG_REWIND);
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/*
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* The new read pointer copies its position from read pointer 0, which
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* could be anywhere, so explicitly rewind it.
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*/
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tuplestore_rescan(scanstate->relation);
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/*
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* XXX: Should we add a function to free that read pointer when done?
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*
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* This was attempted, but it did not improve performance or memory usage
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* in any tested cases.
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*/
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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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* Tuple table and result type initialization. The scan tuple type is
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* specified for the tuplestore.
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*/
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ExecInitResultTupleSlotTL(estate, &scanstate->ss.ps);
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ExecInitScanTupleSlot(estate, &scanstate->ss, scanstate->tupdesc);
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/*
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* initialize child expressions
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*/
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scanstate->ss.ps.qual =
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ExecInitQual(node->scan.plan.qual, (PlanState *) scanstate);
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/*
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* Initialize projection.
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*/
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ExecAssignScanProjectionInfo(&scanstate->ss);
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return scanstate;
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}
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/* ----------------------------------------------------------------
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* ExecEndNamedTuplestoreScan
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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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ExecEndNamedTuplestoreScan(NamedTuplestoreScanState *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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* ExecReScanNamedTuplestoreScan
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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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ExecReScanNamedTuplestoreScan(NamedTuplestoreScanState *node)
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{
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Tuplestorestate *tuplestorestate = node->relation;
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ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
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ExecScanReScan(&node->ss);
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/*
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* Rewind my own pointer.
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*/
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tuplestore_select_read_pointer(tuplestorestate, node->readptr);
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tuplestore_rescan(tuplestorestate);
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}
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