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Similar to commits7e735035f2
anddddf4cdc33
, this commit makes the order of header file inclusion consistent for backend modules. In the passing, removed a couple of duplicate inclusions. Author: Vignesh C Reviewed-by: Kuntal Ghosh and Amit Kapila Discussion: https://postgr.es/m/CALDaNm2Sznv8RR6Ex-iJO6xAdsxgWhCoETkaYX=+9DW3q0QCfA@mail.gmail.com
1386 lines
41 KiB
C
1386 lines
41 KiB
C
/*-------------------------------------------------------------------------
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*
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* nodeSubplan.c
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* routines to support sub-selects appearing in expressions
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*
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* This module is concerned with executing SubPlan expression nodes, which
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* should not be confused with sub-SELECTs appearing in FROM. SubPlans are
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* divided into "initplans", which are those that need only one evaluation per
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* query (among other restrictions, this requires that they don't use any
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* direct correlation variables from the parent plan level), and "regular"
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* subplans, which are re-evaluated every time their result is required.
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*
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*
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* Portions Copyright (c) 1996-2019, 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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* IDENTIFICATION
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* src/backend/executor/nodeSubplan.c
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*
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*-------------------------------------------------------------------------
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*/
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/*
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* INTERFACE ROUTINES
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* ExecSubPlan - process a subselect
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* ExecInitSubPlan - initialize a subselect
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*/
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#include "postgres.h"
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#include <limits.h>
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#include <math.h>
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#include "access/htup_details.h"
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#include "executor/executor.h"
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#include "executor/nodeSubplan.h"
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#include "miscadmin.h"
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#include "nodes/makefuncs.h"
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#include "nodes/nodeFuncs.h"
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#include "utils/array.h"
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#include "utils/lsyscache.h"
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#include "utils/memutils.h"
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static Datum ExecHashSubPlan(SubPlanState *node,
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ExprContext *econtext,
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bool *isNull);
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static Datum ExecScanSubPlan(SubPlanState *node,
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ExprContext *econtext,
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bool *isNull);
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static void buildSubPlanHash(SubPlanState *node, ExprContext *econtext);
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static bool findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot,
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FmgrInfo *eqfunctions);
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static bool slotAllNulls(TupleTableSlot *slot);
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static bool slotNoNulls(TupleTableSlot *slot);
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/* ----------------------------------------------------------------
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* ExecSubPlan
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*
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* This is the main entry point for execution of a regular SubPlan.
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* ----------------------------------------------------------------
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*/
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Datum
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ExecSubPlan(SubPlanState *node,
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ExprContext *econtext,
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bool *isNull)
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{
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SubPlan *subplan = node->subplan;
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EState *estate = node->planstate->state;
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ScanDirection dir = estate->es_direction;
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Datum retval;
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CHECK_FOR_INTERRUPTS();
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/* Set non-null as default */
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*isNull = false;
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/* Sanity checks */
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if (subplan->subLinkType == CTE_SUBLINK)
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elog(ERROR, "CTE subplans should not be executed via ExecSubPlan");
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if (subplan->setParam != NIL && subplan->subLinkType != MULTIEXPR_SUBLINK)
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elog(ERROR, "cannot set parent params from subquery");
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/* Force forward-scan mode for evaluation */
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estate->es_direction = ForwardScanDirection;
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/* Select appropriate evaluation strategy */
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if (subplan->useHashTable)
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retval = ExecHashSubPlan(node, econtext, isNull);
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else
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retval = ExecScanSubPlan(node, econtext, isNull);
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/* restore scan direction */
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estate->es_direction = dir;
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return retval;
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}
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/*
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* ExecHashSubPlan: store subselect result in an in-memory hash table
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*/
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static Datum
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ExecHashSubPlan(SubPlanState *node,
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ExprContext *econtext,
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bool *isNull)
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{
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SubPlan *subplan = node->subplan;
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PlanState *planstate = node->planstate;
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TupleTableSlot *slot;
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/* Shouldn't have any direct correlation Vars */
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if (subplan->parParam != NIL || node->args != NIL)
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elog(ERROR, "hashed subplan with direct correlation not supported");
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/*
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* If first time through or we need to rescan the subplan, build the hash
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* table.
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*/
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if (node->hashtable == NULL || planstate->chgParam != NULL)
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buildSubPlanHash(node, econtext);
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/*
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* The result for an empty subplan is always FALSE; no need to evaluate
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* lefthand side.
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*/
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*isNull = false;
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if (!node->havehashrows && !node->havenullrows)
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return BoolGetDatum(false);
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/*
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* Evaluate lefthand expressions and form a projection tuple. First we
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* have to set the econtext to use (hack alert!).
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*/
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node->projLeft->pi_exprContext = econtext;
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slot = ExecProject(node->projLeft);
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/*
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* Note: because we are typically called in a per-tuple context, we have
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* to explicitly clear the projected tuple before returning. Otherwise,
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* we'll have a double-free situation: the per-tuple context will probably
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* be reset before we're called again, and then the tuple slot will think
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* it still needs to free the tuple.
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*/
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/*
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* If the LHS is all non-null, probe for an exact match in the main hash
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* table. If we find one, the result is TRUE. Otherwise, scan the
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* partly-null table to see if there are any rows that aren't provably
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* unequal to the LHS; if so, the result is UNKNOWN. (We skip that part
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* if we don't care about UNKNOWN.) Otherwise, the result is FALSE.
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*
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* Note: the reason we can avoid a full scan of the main hash table is
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* that the combining operators are assumed never to yield NULL when both
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* inputs are non-null. If they were to do so, we might need to produce
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* UNKNOWN instead of FALSE because of an UNKNOWN result in comparing the
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* LHS to some main-table entry --- which is a comparison we will not even
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* make, unless there's a chance match of hash keys.
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*/
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if (slotNoNulls(slot))
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{
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if (node->havehashrows &&
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FindTupleHashEntry(node->hashtable,
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slot,
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node->cur_eq_comp,
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node->lhs_hash_funcs) != NULL)
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{
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ExecClearTuple(slot);
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return BoolGetDatum(true);
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}
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if (node->havenullrows &&
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findPartialMatch(node->hashnulls, slot, node->cur_eq_funcs))
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{
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ExecClearTuple(slot);
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*isNull = true;
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return BoolGetDatum(false);
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}
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ExecClearTuple(slot);
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return BoolGetDatum(false);
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}
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/*
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* When the LHS is partly or wholly NULL, we can never return TRUE. If we
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* don't care about UNKNOWN, just return FALSE. Otherwise, if the LHS is
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* wholly NULL, immediately return UNKNOWN. (Since the combining
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* operators are strict, the result could only be FALSE if the sub-select
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* were empty, but we already handled that case.) Otherwise, we must scan
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* both the main and partly-null tables to see if there are any rows that
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* aren't provably unequal to the LHS; if so, the result is UNKNOWN.
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* Otherwise, the result is FALSE.
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*/
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if (node->hashnulls == NULL)
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{
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ExecClearTuple(slot);
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return BoolGetDatum(false);
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}
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if (slotAllNulls(slot))
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{
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ExecClearTuple(slot);
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*isNull = true;
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return BoolGetDatum(false);
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}
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/* Scan partly-null table first, since more likely to get a match */
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if (node->havenullrows &&
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findPartialMatch(node->hashnulls, slot, node->cur_eq_funcs))
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{
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ExecClearTuple(slot);
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*isNull = true;
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return BoolGetDatum(false);
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}
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if (node->havehashrows &&
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findPartialMatch(node->hashtable, slot, node->cur_eq_funcs))
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{
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ExecClearTuple(slot);
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*isNull = true;
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return BoolGetDatum(false);
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}
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ExecClearTuple(slot);
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return BoolGetDatum(false);
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}
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/*
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* ExecScanSubPlan: default case where we have to rescan subplan each time
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*/
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static Datum
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ExecScanSubPlan(SubPlanState *node,
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ExprContext *econtext,
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bool *isNull)
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{
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SubPlan *subplan = node->subplan;
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PlanState *planstate = node->planstate;
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SubLinkType subLinkType = subplan->subLinkType;
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MemoryContext oldcontext;
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TupleTableSlot *slot;
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Datum result;
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bool found = false; /* true if got at least one subplan tuple */
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ListCell *pvar;
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ListCell *l;
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ArrayBuildStateAny *astate = NULL;
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/*
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* MULTIEXPR subplans, when "executed", just return NULL; but first we
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* mark the subplan's output parameters as needing recalculation. (This
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* is a bit of a hack: it relies on the subplan appearing later in its
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* targetlist than any of the referencing Params, so that all the Params
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* have been evaluated before we re-mark them for the next evaluation
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* cycle. But in general resjunk tlist items appear after non-resjunk
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* ones, so this should be safe.) Unlike ExecReScanSetParamPlan, we do
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* *not* set bits in the parent plan node's chgParam, because we don't
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* want to cause a rescan of the parent.
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*/
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if (subLinkType == MULTIEXPR_SUBLINK)
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{
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EState *estate = node->parent->state;
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foreach(l, subplan->setParam)
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{
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int paramid = lfirst_int(l);
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ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);
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prm->execPlan = node;
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}
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*isNull = true;
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return (Datum) 0;
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}
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/* Initialize ArrayBuildStateAny in caller's context, if needed */
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if (subLinkType == ARRAY_SUBLINK)
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astate = initArrayResultAny(subplan->firstColType,
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CurrentMemoryContext, true);
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/*
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* We are probably in a short-lived expression-evaluation context. Switch
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* to the per-query context for manipulating the child plan's chgParam,
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* calling ExecProcNode on it, etc.
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*/
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oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
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/*
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* Set Params of this plan from parent plan correlation values. (Any
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* calculation we have to do is done in the parent econtext, since the
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* Param values don't need to have per-query lifetime.)
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*/
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Assert(list_length(subplan->parParam) == list_length(node->args));
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forboth(l, subplan->parParam, pvar, node->args)
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{
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int paramid = lfirst_int(l);
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ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
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prm->value = ExecEvalExprSwitchContext((ExprState *) lfirst(pvar),
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econtext,
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&(prm->isnull));
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planstate->chgParam = bms_add_member(planstate->chgParam, paramid);
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}
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/*
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* Now that we've set up its parameters, we can reset the subplan.
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*/
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ExecReScan(planstate);
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/*
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* For all sublink types except EXPR_SUBLINK and ARRAY_SUBLINK, the result
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* is boolean as are the results of the combining operators. We combine
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* results across tuples (if the subplan produces more than one) using OR
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* semantics for ANY_SUBLINK or AND semantics for ALL_SUBLINK.
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* (ROWCOMPARE_SUBLINK doesn't allow multiple tuples from the subplan.)
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* NULL results from the combining operators are handled according to the
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* usual SQL semantics for OR and AND. The result for no input tuples is
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* FALSE for ANY_SUBLINK, TRUE for ALL_SUBLINK, NULL for
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* ROWCOMPARE_SUBLINK.
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*
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* For EXPR_SUBLINK we require the subplan to produce no more than one
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* tuple, else an error is raised. If zero tuples are produced, we return
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* NULL. Assuming we get a tuple, we just use its first column (there can
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* be only one non-junk column in this case).
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*
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* For ARRAY_SUBLINK we allow the subplan to produce any number of tuples,
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* and form an array of the first column's values. Note in particular
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* that we produce a zero-element array if no tuples are produced (this is
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* a change from pre-8.3 behavior of returning NULL).
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*/
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result = BoolGetDatum(subLinkType == ALL_SUBLINK);
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*isNull = false;
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for (slot = ExecProcNode(planstate);
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!TupIsNull(slot);
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slot = ExecProcNode(planstate))
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{
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TupleDesc tdesc = slot->tts_tupleDescriptor;
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Datum rowresult;
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bool rownull;
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int col;
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ListCell *plst;
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if (subLinkType == EXISTS_SUBLINK)
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{
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found = true;
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result = BoolGetDatum(true);
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break;
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}
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if (subLinkType == EXPR_SUBLINK)
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{
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/* cannot allow multiple input tuples for EXPR sublink */
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if (found)
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ereport(ERROR,
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(errcode(ERRCODE_CARDINALITY_VIOLATION),
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errmsg("more than one row returned by a subquery used as an expression")));
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found = true;
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/*
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* We need to copy the subplan's tuple in case the result is of
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* pass-by-ref type --- our return value will point into this
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* copied tuple! Can't use the subplan's instance of the tuple
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* since it won't still be valid after next ExecProcNode() call.
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* node->curTuple keeps track of the copied tuple for eventual
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* freeing.
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*/
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if (node->curTuple)
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heap_freetuple(node->curTuple);
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node->curTuple = ExecCopySlotHeapTuple(slot);
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result = heap_getattr(node->curTuple, 1, tdesc, isNull);
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/* keep scanning subplan to make sure there's only one tuple */
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continue;
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}
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if (subLinkType == ARRAY_SUBLINK)
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{
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Datum dvalue;
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bool disnull;
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found = true;
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/* stash away current value */
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Assert(subplan->firstColType == TupleDescAttr(tdesc, 0)->atttypid);
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dvalue = slot_getattr(slot, 1, &disnull);
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astate = accumArrayResultAny(astate, dvalue, disnull,
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subplan->firstColType, oldcontext);
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/* keep scanning subplan to collect all values */
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continue;
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}
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/* cannot allow multiple input tuples for ROWCOMPARE sublink either */
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if (subLinkType == ROWCOMPARE_SUBLINK && found)
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ereport(ERROR,
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(errcode(ERRCODE_CARDINALITY_VIOLATION),
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errmsg("more than one row returned by a subquery used as an expression")));
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found = true;
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/*
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* For ALL, ANY, and ROWCOMPARE sublinks, load up the Params
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* representing the columns of the sub-select, and then evaluate the
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* combining expression.
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*/
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col = 1;
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foreach(plst, subplan->paramIds)
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{
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int paramid = lfirst_int(plst);
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ParamExecData *prmdata;
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prmdata = &(econtext->ecxt_param_exec_vals[paramid]);
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Assert(prmdata->execPlan == NULL);
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prmdata->value = slot_getattr(slot, col, &(prmdata->isnull));
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col++;
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}
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rowresult = ExecEvalExprSwitchContext(node->testexpr, econtext,
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&rownull);
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if (subLinkType == ANY_SUBLINK)
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{
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/* combine across rows per OR semantics */
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if (rownull)
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*isNull = true;
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else if (DatumGetBool(rowresult))
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{
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result = BoolGetDatum(true);
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*isNull = false;
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break; /* needn't look at any more rows */
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}
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}
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else if (subLinkType == ALL_SUBLINK)
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{
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/* combine across rows per AND semantics */
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if (rownull)
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*isNull = true;
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else if (!DatumGetBool(rowresult))
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{
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result = BoolGetDatum(false);
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*isNull = false;
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break; /* needn't look at any more rows */
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}
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}
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else
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{
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/* must be ROWCOMPARE_SUBLINK */
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result = rowresult;
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*isNull = rownull;
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}
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}
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MemoryContextSwitchTo(oldcontext);
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if (subLinkType == ARRAY_SUBLINK)
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{
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/* We return the result in the caller's context */
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result = makeArrayResultAny(astate, oldcontext, true);
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}
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else if (!found)
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{
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/*
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* deal with empty subplan result. result/isNull were previously
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* initialized correctly for all sublink types except EXPR and
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* ROWCOMPARE; for those, return NULL.
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*/
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if (subLinkType == EXPR_SUBLINK ||
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subLinkType == ROWCOMPARE_SUBLINK)
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{
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result = (Datum) 0;
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*isNull = true;
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}
|
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}
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return result;
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}
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|
|
/*
|
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* buildSubPlanHash: load hash table by scanning subplan output.
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|
*/
|
|
static void
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buildSubPlanHash(SubPlanState *node, ExprContext *econtext)
|
|
{
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SubPlan *subplan = node->subplan;
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PlanState *planstate = node->planstate;
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|
int ncols = list_length(subplan->paramIds);
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ExprContext *innerecontext = node->innerecontext;
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MemoryContext oldcontext;
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long nbuckets;
|
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TupleTableSlot *slot;
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Assert(subplan->subLinkType == ANY_SUBLINK);
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|
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/*
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* If we already had any hash tables, reset 'em; otherwise create empty
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* hash table(s).
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*
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* If we need to distinguish accurately between FALSE and UNKNOWN (i.e.,
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* NULL) results of the IN operation, then we have to store subplan output
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* rows that are partly or wholly NULL. We store such rows in a separate
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* hash table that we expect will be much smaller than the main table. (We
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* can use hashing to eliminate partly-null rows that are not distinct. We
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* keep them separate to minimize the cost of the inevitable full-table
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* searches; see findPartialMatch.)
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*
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* If it's not necessary to distinguish FALSE and UNKNOWN, then we don't
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* need to store subplan output rows that contain NULL.
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*/
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|
MemoryContextReset(node->hashtablecxt);
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|
node->hashtable = NULL;
|
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node->hashnulls = NULL;
|
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node->havehashrows = false;
|
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node->havenullrows = false;
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|
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nbuckets = (long) Min(planstate->plan->plan_rows, (double) LONG_MAX);
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|
if (nbuckets < 1)
|
|
nbuckets = 1;
|
|
|
|
if (node->hashtable)
|
|
ResetTupleHashTable(node->hashtable);
|
|
else
|
|
node->hashtable = BuildTupleHashTableExt(node->parent,
|
|
node->descRight,
|
|
ncols,
|
|
node->keyColIdx,
|
|
node->tab_eq_funcoids,
|
|
node->tab_hash_funcs,
|
|
node->tab_collations,
|
|
nbuckets,
|
|
0,
|
|
node->planstate->state->es_query_cxt,
|
|
node->hashtablecxt,
|
|
node->hashtempcxt,
|
|
false);
|
|
|
|
if (!subplan->unknownEqFalse)
|
|
{
|
|
if (ncols == 1)
|
|
nbuckets = 1; /* there can only be one entry */
|
|
else
|
|
{
|
|
nbuckets /= 16;
|
|
if (nbuckets < 1)
|
|
nbuckets = 1;
|
|
}
|
|
|
|
if (node->hashnulls)
|
|
ResetTupleHashTable(node->hashtable);
|
|
else
|
|
node->hashnulls = BuildTupleHashTableExt(node->parent,
|
|
node->descRight,
|
|
ncols,
|
|
node->keyColIdx,
|
|
node->tab_eq_funcoids,
|
|
node->tab_hash_funcs,
|
|
node->tab_collations,
|
|
nbuckets,
|
|
0,
|
|
node->planstate->state->es_query_cxt,
|
|
node->hashtablecxt,
|
|
node->hashtempcxt,
|
|
false);
|
|
}
|
|
|
|
/*
|
|
* We are probably in a short-lived expression-evaluation context. Switch
|
|
* to the per-query context for manipulating the child plan.
|
|
*/
|
|
oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
|
|
|
|
/*
|
|
* Reset subplan to start.
|
|
*/
|
|
ExecReScan(planstate);
|
|
|
|
/*
|
|
* Scan the subplan and load the hash table(s). Note that when there are
|
|
* duplicate rows coming out of the sub-select, only one copy is stored.
|
|
*/
|
|
for (slot = ExecProcNode(planstate);
|
|
!TupIsNull(slot);
|
|
slot = ExecProcNode(planstate))
|
|
{
|
|
int col = 1;
|
|
ListCell *plst;
|
|
bool isnew;
|
|
|
|
/*
|
|
* Load up the Params representing the raw sub-select outputs, then
|
|
* form the projection tuple to store in the hashtable.
|
|
*/
|
|
foreach(plst, subplan->paramIds)
|
|
{
|
|
int paramid = lfirst_int(plst);
|
|
ParamExecData *prmdata;
|
|
|
|
prmdata = &(innerecontext->ecxt_param_exec_vals[paramid]);
|
|
Assert(prmdata->execPlan == NULL);
|
|
prmdata->value = slot_getattr(slot, col,
|
|
&(prmdata->isnull));
|
|
col++;
|
|
}
|
|
slot = ExecProject(node->projRight);
|
|
|
|
/*
|
|
* If result contains any nulls, store separately or not at all.
|
|
*/
|
|
if (slotNoNulls(slot))
|
|
{
|
|
(void) LookupTupleHashEntry(node->hashtable, slot, &isnew);
|
|
node->havehashrows = true;
|
|
}
|
|
else if (node->hashnulls)
|
|
{
|
|
(void) LookupTupleHashEntry(node->hashnulls, slot, &isnew);
|
|
node->havenullrows = true;
|
|
}
|
|
|
|
/*
|
|
* Reset innerecontext after each inner tuple to free any memory used
|
|
* during ExecProject.
|
|
*/
|
|
ResetExprContext(innerecontext);
|
|
}
|
|
|
|
/*
|
|
* Since the projected tuples are in the sub-query's context and not the
|
|
* main context, we'd better clear the tuple slot before there's any
|
|
* chance of a reset of the sub-query's context. Else we will have the
|
|
* potential for a double free attempt. (XXX possibly no longer needed,
|
|
* but can't hurt.)
|
|
*/
|
|
ExecClearTuple(node->projRight->pi_state.resultslot);
|
|
|
|
MemoryContextSwitchTo(oldcontext);
|
|
}
|
|
|
|
/*
|
|
* execTuplesUnequal
|
|
* Return true if two tuples are definitely unequal in the indicated
|
|
* fields.
|
|
*
|
|
* Nulls are neither equal nor unequal to anything else. A true result
|
|
* is obtained only if there are non-null fields that compare not-equal.
|
|
*
|
|
* slot1, slot2: the tuples to compare (must have same columns!)
|
|
* numCols: the number of attributes to be examined
|
|
* matchColIdx: array of attribute column numbers
|
|
* eqFunctions: array of fmgr lookup info for the equality functions to use
|
|
* evalContext: short-term memory context for executing the functions
|
|
*/
|
|
static bool
|
|
execTuplesUnequal(TupleTableSlot *slot1,
|
|
TupleTableSlot *slot2,
|
|
int numCols,
|
|
AttrNumber *matchColIdx,
|
|
FmgrInfo *eqfunctions,
|
|
const Oid *collations,
|
|
MemoryContext evalContext)
|
|
{
|
|
MemoryContext oldContext;
|
|
bool result;
|
|
int i;
|
|
|
|
/* Reset and switch into the temp context. */
|
|
MemoryContextReset(evalContext);
|
|
oldContext = MemoryContextSwitchTo(evalContext);
|
|
|
|
/*
|
|
* We cannot report a match without checking all the fields, but we can
|
|
* report a non-match as soon as we find unequal fields. So, start
|
|
* comparing at the last field (least significant sort key). That's the
|
|
* most likely to be different if we are dealing with sorted input.
|
|
*/
|
|
result = false;
|
|
|
|
for (i = numCols; --i >= 0;)
|
|
{
|
|
AttrNumber att = matchColIdx[i];
|
|
Datum attr1,
|
|
attr2;
|
|
bool isNull1,
|
|
isNull2;
|
|
|
|
attr1 = slot_getattr(slot1, att, &isNull1);
|
|
|
|
if (isNull1)
|
|
continue; /* can't prove anything here */
|
|
|
|
attr2 = slot_getattr(slot2, att, &isNull2);
|
|
|
|
if (isNull2)
|
|
continue; /* can't prove anything here */
|
|
|
|
/* Apply the type-specific equality function */
|
|
if (!DatumGetBool(FunctionCall2Coll(&eqfunctions[i],
|
|
collations[i],
|
|
attr1, attr2)))
|
|
{
|
|
result = true; /* they are unequal */
|
|
break;
|
|
}
|
|
}
|
|
|
|
MemoryContextSwitchTo(oldContext);
|
|
|
|
return result;
|
|
}
|
|
|
|
/*
|
|
* findPartialMatch: does the hashtable contain an entry that is not
|
|
* provably distinct from the tuple?
|
|
*
|
|
* We have to scan the whole hashtable; we can't usefully use hashkeys
|
|
* to guide probing, since we might get partial matches on tuples with
|
|
* hashkeys quite unrelated to what we'd get from the given tuple.
|
|
*
|
|
* Caller must provide the equality functions to use, since in cross-type
|
|
* cases these are different from the hashtable's internal functions.
|
|
*/
|
|
static bool
|
|
findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot,
|
|
FmgrInfo *eqfunctions)
|
|
{
|
|
int numCols = hashtable->numCols;
|
|
AttrNumber *keyColIdx = hashtable->keyColIdx;
|
|
TupleHashIterator hashiter;
|
|
TupleHashEntry entry;
|
|
|
|
InitTupleHashIterator(hashtable, &hashiter);
|
|
while ((entry = ScanTupleHashTable(hashtable, &hashiter)) != NULL)
|
|
{
|
|
CHECK_FOR_INTERRUPTS();
|
|
|
|
ExecStoreMinimalTuple(entry->firstTuple, hashtable->tableslot, false);
|
|
if (!execTuplesUnequal(slot, hashtable->tableslot,
|
|
numCols, keyColIdx,
|
|
eqfunctions,
|
|
hashtable->tab_collations,
|
|
hashtable->tempcxt))
|
|
{
|
|
TermTupleHashIterator(&hashiter);
|
|
return true;
|
|
}
|
|
}
|
|
/* No TermTupleHashIterator call needed here */
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* slotAllNulls: is the slot completely NULL?
|
|
*
|
|
* This does not test for dropped columns, which is OK because we only
|
|
* use it on projected tuples.
|
|
*/
|
|
static bool
|
|
slotAllNulls(TupleTableSlot *slot)
|
|
{
|
|
int ncols = slot->tts_tupleDescriptor->natts;
|
|
int i;
|
|
|
|
for (i = 1; i <= ncols; i++)
|
|
{
|
|
if (!slot_attisnull(slot, i))
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* slotNoNulls: is the slot entirely not NULL?
|
|
*
|
|
* This does not test for dropped columns, which is OK because we only
|
|
* use it on projected tuples.
|
|
*/
|
|
static bool
|
|
slotNoNulls(TupleTableSlot *slot)
|
|
{
|
|
int ncols = slot->tts_tupleDescriptor->natts;
|
|
int i;
|
|
|
|
for (i = 1; i <= ncols; i++)
|
|
{
|
|
if (slot_attisnull(slot, i))
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/* ----------------------------------------------------------------
|
|
* ExecInitSubPlan
|
|
*
|
|
* Create a SubPlanState for a SubPlan; this is the SubPlan-specific part
|
|
* of ExecInitExpr(). We split it out so that it can be used for InitPlans
|
|
* as well as regular SubPlans. Note that we don't link the SubPlan into
|
|
* the parent's subPlan list, because that shouldn't happen for InitPlans.
|
|
* Instead, ExecInitExpr() does that one part.
|
|
* ----------------------------------------------------------------
|
|
*/
|
|
SubPlanState *
|
|
ExecInitSubPlan(SubPlan *subplan, PlanState *parent)
|
|
{
|
|
SubPlanState *sstate = makeNode(SubPlanState);
|
|
EState *estate = parent->state;
|
|
|
|
sstate->subplan = subplan;
|
|
|
|
/* Link the SubPlanState to already-initialized subplan */
|
|
sstate->planstate = (PlanState *) list_nth(estate->es_subplanstates,
|
|
subplan->plan_id - 1);
|
|
|
|
/* ... and to its parent's state */
|
|
sstate->parent = parent;
|
|
|
|
/* Initialize subexpressions */
|
|
sstate->testexpr = ExecInitExpr((Expr *) subplan->testexpr, parent);
|
|
sstate->args = ExecInitExprList(subplan->args, parent);
|
|
|
|
/*
|
|
* initialize my state
|
|
*/
|
|
sstate->curTuple = NULL;
|
|
sstate->curArray = PointerGetDatum(NULL);
|
|
sstate->projLeft = NULL;
|
|
sstate->projRight = NULL;
|
|
sstate->hashtable = NULL;
|
|
sstate->hashnulls = NULL;
|
|
sstate->hashtablecxt = NULL;
|
|
sstate->hashtempcxt = NULL;
|
|
sstate->innerecontext = NULL;
|
|
sstate->keyColIdx = NULL;
|
|
sstate->tab_eq_funcoids = NULL;
|
|
sstate->tab_hash_funcs = NULL;
|
|
sstate->tab_eq_funcs = NULL;
|
|
sstate->tab_collations = NULL;
|
|
sstate->lhs_hash_funcs = NULL;
|
|
sstate->cur_eq_funcs = NULL;
|
|
|
|
/*
|
|
* If this is an initplan or MULTIEXPR subplan, it has output parameters
|
|
* that the parent plan will use, so mark those parameters as needing
|
|
* evaluation. We don't actually run the subplan until we first need one
|
|
* of its outputs.
|
|
*
|
|
* A CTE subplan's output parameter is never to be evaluated in the normal
|
|
* way, so skip this in that case.
|
|
*
|
|
* Note that we don't set parent->chgParam here: the parent plan hasn't
|
|
* been run yet, so no need to force it to re-run.
|
|
*/
|
|
if (subplan->setParam != NIL && subplan->subLinkType != CTE_SUBLINK)
|
|
{
|
|
ListCell *lst;
|
|
|
|
foreach(lst, subplan->setParam)
|
|
{
|
|
int paramid = lfirst_int(lst);
|
|
ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);
|
|
|
|
prm->execPlan = sstate;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If we are going to hash the subquery output, initialize relevant stuff.
|
|
* (We don't create the hashtable until needed, though.)
|
|
*/
|
|
if (subplan->useHashTable)
|
|
{
|
|
int ncols,
|
|
i;
|
|
TupleDesc tupDescLeft;
|
|
TupleDesc tupDescRight;
|
|
Oid *cross_eq_funcoids;
|
|
TupleTableSlot *slot;
|
|
List *oplist,
|
|
*lefttlist,
|
|
*righttlist;
|
|
ListCell *l;
|
|
|
|
/* We need a memory context to hold the hash table(s) */
|
|
sstate->hashtablecxt =
|
|
AllocSetContextCreate(CurrentMemoryContext,
|
|
"Subplan HashTable Context",
|
|
ALLOCSET_DEFAULT_SIZES);
|
|
/* and a small one for the hash tables to use as temp storage */
|
|
sstate->hashtempcxt =
|
|
AllocSetContextCreate(CurrentMemoryContext,
|
|
"Subplan HashTable Temp Context",
|
|
ALLOCSET_SMALL_SIZES);
|
|
/* and a short-lived exprcontext for function evaluation */
|
|
sstate->innerecontext = CreateExprContext(estate);
|
|
/* Silly little array of column numbers 1..n */
|
|
ncols = list_length(subplan->paramIds);
|
|
sstate->keyColIdx = (AttrNumber *) palloc(ncols * sizeof(AttrNumber));
|
|
for (i = 0; i < ncols; i++)
|
|
sstate->keyColIdx[i] = i + 1;
|
|
|
|
/*
|
|
* We use ExecProject to evaluate the lefthand and righthand
|
|
* expression lists and form tuples. (You might think that we could
|
|
* use the sub-select's output tuples directly, but that is not the
|
|
* case if we had to insert any run-time coercions of the sub-select's
|
|
* output datatypes; anyway this avoids storing any resjunk columns
|
|
* that might be in the sub-select's output.) Run through the
|
|
* combining expressions to build tlists for the lefthand and
|
|
* righthand sides.
|
|
*
|
|
* We also extract the combining operators themselves to initialize
|
|
* the equality and hashing functions for the hash tables.
|
|
*/
|
|
if (IsA(subplan->testexpr, OpExpr))
|
|
{
|
|
/* single combining operator */
|
|
oplist = list_make1(subplan->testexpr);
|
|
}
|
|
else if (is_andclause(subplan->testexpr))
|
|
{
|
|
/* multiple combining operators */
|
|
oplist = castNode(BoolExpr, subplan->testexpr)->args;
|
|
}
|
|
else
|
|
{
|
|
/* shouldn't see anything else in a hashable subplan */
|
|
elog(ERROR, "unrecognized testexpr type: %d",
|
|
(int) nodeTag(subplan->testexpr));
|
|
oplist = NIL; /* keep compiler quiet */
|
|
}
|
|
Assert(list_length(oplist) == ncols);
|
|
|
|
lefttlist = righttlist = NIL;
|
|
sstate->tab_eq_funcoids = (Oid *) palloc(ncols * sizeof(Oid));
|
|
sstate->tab_hash_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
|
|
sstate->tab_eq_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
|
|
sstate->tab_collations = (Oid *) palloc(ncols * sizeof(Oid));
|
|
sstate->lhs_hash_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
|
|
sstate->cur_eq_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
|
|
/* we'll need the cross-type equality fns below, but not in sstate */
|
|
cross_eq_funcoids = (Oid *) palloc(ncols * sizeof(Oid));
|
|
|
|
i = 1;
|
|
foreach(l, oplist)
|
|
{
|
|
OpExpr *opexpr = lfirst_node(OpExpr, l);
|
|
Expr *expr;
|
|
TargetEntry *tle;
|
|
Oid rhs_eq_oper;
|
|
Oid left_hashfn;
|
|
Oid right_hashfn;
|
|
|
|
Assert(list_length(opexpr->args) == 2);
|
|
|
|
/* Process lefthand argument */
|
|
expr = (Expr *) linitial(opexpr->args);
|
|
tle = makeTargetEntry(expr,
|
|
i,
|
|
NULL,
|
|
false);
|
|
lefttlist = lappend(lefttlist, tle);
|
|
|
|
/* Process righthand argument */
|
|
expr = (Expr *) lsecond(opexpr->args);
|
|
tle = makeTargetEntry(expr,
|
|
i,
|
|
NULL,
|
|
false);
|
|
righttlist = lappend(righttlist, tle);
|
|
|
|
/* Lookup the equality function (potentially cross-type) */
|
|
cross_eq_funcoids[i - 1] = opexpr->opfuncid;
|
|
fmgr_info(opexpr->opfuncid, &sstate->cur_eq_funcs[i - 1]);
|
|
fmgr_info_set_expr((Node *) opexpr, &sstate->cur_eq_funcs[i - 1]);
|
|
|
|
/* Look up the equality function for the RHS type */
|
|
if (!get_compatible_hash_operators(opexpr->opno,
|
|
NULL, &rhs_eq_oper))
|
|
elog(ERROR, "could not find compatible hash operator for operator %u",
|
|
opexpr->opno);
|
|
sstate->tab_eq_funcoids[i - 1] = get_opcode(rhs_eq_oper);
|
|
fmgr_info(sstate->tab_eq_funcoids[i - 1],
|
|
&sstate->tab_eq_funcs[i - 1]);
|
|
|
|
/* Lookup the associated hash functions */
|
|
if (!get_op_hash_functions(opexpr->opno,
|
|
&left_hashfn, &right_hashfn))
|
|
elog(ERROR, "could not find hash function for hash operator %u",
|
|
opexpr->opno);
|
|
fmgr_info(left_hashfn, &sstate->lhs_hash_funcs[i - 1]);
|
|
fmgr_info(right_hashfn, &sstate->tab_hash_funcs[i - 1]);
|
|
|
|
/* Set collation */
|
|
sstate->tab_collations[i - 1] = opexpr->inputcollid;
|
|
|
|
i++;
|
|
}
|
|
|
|
/*
|
|
* Construct tupdescs, slots and projection nodes for left and right
|
|
* sides. The lefthand expressions will be evaluated in the parent
|
|
* plan node's exprcontext, which we don't have access to here.
|
|
* Fortunately we can just pass NULL for now and fill it in later
|
|
* (hack alert!). The righthand expressions will be evaluated in our
|
|
* own innerecontext.
|
|
*/
|
|
tupDescLeft = ExecTypeFromTL(lefttlist);
|
|
slot = ExecInitExtraTupleSlot(estate, tupDescLeft, &TTSOpsVirtual);
|
|
sstate->projLeft = ExecBuildProjectionInfo(lefttlist,
|
|
NULL,
|
|
slot,
|
|
parent,
|
|
NULL);
|
|
|
|
sstate->descRight = tupDescRight = ExecTypeFromTL(righttlist);
|
|
slot = ExecInitExtraTupleSlot(estate, tupDescRight, &TTSOpsVirtual);
|
|
sstate->projRight = ExecBuildProjectionInfo(righttlist,
|
|
sstate->innerecontext,
|
|
slot,
|
|
sstate->planstate,
|
|
NULL);
|
|
|
|
/*
|
|
* Create comparator for lookups of rows in the table (potentially
|
|
* cross-type comparisons).
|
|
*/
|
|
sstate->cur_eq_comp = ExecBuildGroupingEqual(tupDescLeft, tupDescRight,
|
|
&TTSOpsVirtual, &TTSOpsMinimalTuple,
|
|
ncols,
|
|
sstate->keyColIdx,
|
|
cross_eq_funcoids,
|
|
sstate->tab_collations,
|
|
parent);
|
|
}
|
|
|
|
return sstate;
|
|
}
|
|
|
|
/* ----------------------------------------------------------------
|
|
* ExecSetParamPlan
|
|
*
|
|
* Executes a subplan and sets its output parameters.
|
|
*
|
|
* This is called from ExecEvalParamExec() when the value of a PARAM_EXEC
|
|
* parameter is requested and the param's execPlan field is set (indicating
|
|
* that the param has not yet been evaluated). This allows lazy evaluation
|
|
* of initplans: we don't run the subplan until/unless we need its output.
|
|
* Note that this routine MUST clear the execPlan fields of the plan's
|
|
* output parameters after evaluating them!
|
|
*
|
|
* The results of this function are stored in the EState associated with the
|
|
* ExprContext (particularly, its ecxt_param_exec_vals); any pass-by-ref
|
|
* result Datums are allocated in the EState's per-query memory. The passed
|
|
* econtext can be any ExprContext belonging to that EState; which one is
|
|
* important only to the extent that the ExprContext's per-tuple memory
|
|
* context is used to evaluate any parameters passed down to the subplan.
|
|
* (Thus in principle, the shorter-lived the ExprContext the better, since
|
|
* that data isn't needed after we return. In practice, because initplan
|
|
* parameters are never more complex than Vars, Aggrefs, etc, evaluating them
|
|
* currently never leaks any memory anyway.)
|
|
* ----------------------------------------------------------------
|
|
*/
|
|
void
|
|
ExecSetParamPlan(SubPlanState *node, ExprContext *econtext)
|
|
{
|
|
SubPlan *subplan = node->subplan;
|
|
PlanState *planstate = node->planstate;
|
|
SubLinkType subLinkType = subplan->subLinkType;
|
|
EState *estate = planstate->state;
|
|
ScanDirection dir = estate->es_direction;
|
|
MemoryContext oldcontext;
|
|
TupleTableSlot *slot;
|
|
ListCell *pvar;
|
|
ListCell *l;
|
|
bool found = false;
|
|
ArrayBuildStateAny *astate = NULL;
|
|
|
|
if (subLinkType == ANY_SUBLINK ||
|
|
subLinkType == ALL_SUBLINK)
|
|
elog(ERROR, "ANY/ALL subselect unsupported as initplan");
|
|
if (subLinkType == CTE_SUBLINK)
|
|
elog(ERROR, "CTE subplans should not be executed via ExecSetParamPlan");
|
|
|
|
/*
|
|
* Enforce forward scan direction regardless of caller. It's hard but not
|
|
* impossible to get here in backward scan, so make it work anyway.
|
|
*/
|
|
estate->es_direction = ForwardScanDirection;
|
|
|
|
/* Initialize ArrayBuildStateAny in caller's context, if needed */
|
|
if (subLinkType == ARRAY_SUBLINK)
|
|
astate = initArrayResultAny(subplan->firstColType,
|
|
CurrentMemoryContext, true);
|
|
|
|
/*
|
|
* Must switch to per-query memory context.
|
|
*/
|
|
oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
|
|
|
|
/*
|
|
* Set Params of this plan from parent plan correlation values. (Any
|
|
* calculation we have to do is done in the parent econtext, since the
|
|
* Param values don't need to have per-query lifetime.) Currently, we
|
|
* expect only MULTIEXPR_SUBLINK plans to have any correlation values.
|
|
*/
|
|
Assert(subplan->parParam == NIL || subLinkType == MULTIEXPR_SUBLINK);
|
|
Assert(list_length(subplan->parParam) == list_length(node->args));
|
|
|
|
forboth(l, subplan->parParam, pvar, node->args)
|
|
{
|
|
int paramid = lfirst_int(l);
|
|
ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
|
|
|
|
prm->value = ExecEvalExprSwitchContext((ExprState *) lfirst(pvar),
|
|
econtext,
|
|
&(prm->isnull));
|
|
planstate->chgParam = bms_add_member(planstate->chgParam, paramid);
|
|
}
|
|
|
|
/*
|
|
* Run the plan. (If it needs to be rescanned, the first ExecProcNode
|
|
* call will take care of that.)
|
|
*/
|
|
for (slot = ExecProcNode(planstate);
|
|
!TupIsNull(slot);
|
|
slot = ExecProcNode(planstate))
|
|
{
|
|
TupleDesc tdesc = slot->tts_tupleDescriptor;
|
|
int i = 1;
|
|
|
|
if (subLinkType == EXISTS_SUBLINK)
|
|
{
|
|
/* There can be only one setParam... */
|
|
int paramid = linitial_int(subplan->setParam);
|
|
ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
|
|
|
|
prm->execPlan = NULL;
|
|
prm->value = BoolGetDatum(true);
|
|
prm->isnull = false;
|
|
found = true;
|
|
break;
|
|
}
|
|
|
|
if (subLinkType == ARRAY_SUBLINK)
|
|
{
|
|
Datum dvalue;
|
|
bool disnull;
|
|
|
|
found = true;
|
|
/* stash away current value */
|
|
Assert(subplan->firstColType == TupleDescAttr(tdesc, 0)->atttypid);
|
|
dvalue = slot_getattr(slot, 1, &disnull);
|
|
astate = accumArrayResultAny(astate, dvalue, disnull,
|
|
subplan->firstColType, oldcontext);
|
|
/* keep scanning subplan to collect all values */
|
|
continue;
|
|
}
|
|
|
|
if (found &&
|
|
(subLinkType == EXPR_SUBLINK ||
|
|
subLinkType == MULTIEXPR_SUBLINK ||
|
|
subLinkType == ROWCOMPARE_SUBLINK))
|
|
ereport(ERROR,
|
|
(errcode(ERRCODE_CARDINALITY_VIOLATION),
|
|
errmsg("more than one row returned by a subquery used as an expression")));
|
|
|
|
found = true;
|
|
|
|
/*
|
|
* We need to copy the subplan's tuple into our own context, in case
|
|
* any of the params are pass-by-ref type --- the pointers stored in
|
|
* the param structs will point at this copied tuple! node->curTuple
|
|
* keeps track of the copied tuple for eventual freeing.
|
|
*/
|
|
if (node->curTuple)
|
|
heap_freetuple(node->curTuple);
|
|
node->curTuple = ExecCopySlotHeapTuple(slot);
|
|
|
|
/*
|
|
* Now set all the setParam params from the columns of the tuple
|
|
*/
|
|
foreach(l, subplan->setParam)
|
|
{
|
|
int paramid = lfirst_int(l);
|
|
ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
|
|
|
|
prm->execPlan = NULL;
|
|
prm->value = heap_getattr(node->curTuple, i, tdesc,
|
|
&(prm->isnull));
|
|
i++;
|
|
}
|
|
}
|
|
|
|
if (subLinkType == ARRAY_SUBLINK)
|
|
{
|
|
/* There can be only one setParam... */
|
|
int paramid = linitial_int(subplan->setParam);
|
|
ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
|
|
|
|
/*
|
|
* We build the result array in query context so it won't disappear;
|
|
* to avoid leaking memory across repeated calls, we have to remember
|
|
* the latest value, much as for curTuple above.
|
|
*/
|
|
if (node->curArray != PointerGetDatum(NULL))
|
|
pfree(DatumGetPointer(node->curArray));
|
|
node->curArray = makeArrayResultAny(astate,
|
|
econtext->ecxt_per_query_memory,
|
|
true);
|
|
prm->execPlan = NULL;
|
|
prm->value = node->curArray;
|
|
prm->isnull = false;
|
|
}
|
|
else if (!found)
|
|
{
|
|
if (subLinkType == EXISTS_SUBLINK)
|
|
{
|
|
/* There can be only one setParam... */
|
|
int paramid = linitial_int(subplan->setParam);
|
|
ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
|
|
|
|
prm->execPlan = NULL;
|
|
prm->value = BoolGetDatum(false);
|
|
prm->isnull = false;
|
|
}
|
|
else
|
|
{
|
|
/* For other sublink types, set all the output params to NULL */
|
|
foreach(l, subplan->setParam)
|
|
{
|
|
int paramid = lfirst_int(l);
|
|
ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
|
|
|
|
prm->execPlan = NULL;
|
|
prm->value = (Datum) 0;
|
|
prm->isnull = true;
|
|
}
|
|
}
|
|
}
|
|
|
|
MemoryContextSwitchTo(oldcontext);
|
|
|
|
/* restore scan direction */
|
|
estate->es_direction = dir;
|
|
}
|
|
|
|
/*
|
|
* ExecSetParamPlanMulti
|
|
*
|
|
* Apply ExecSetParamPlan to evaluate any not-yet-evaluated initplan output
|
|
* parameters whose ParamIDs are listed in "params". Any listed params that
|
|
* are not initplan outputs are ignored.
|
|
*
|
|
* As with ExecSetParamPlan, any ExprContext belonging to the current EState
|
|
* can be used, but in principle a shorter-lived ExprContext is better than a
|
|
* longer-lived one.
|
|
*/
|
|
void
|
|
ExecSetParamPlanMulti(const Bitmapset *params, ExprContext *econtext)
|
|
{
|
|
int paramid;
|
|
|
|
paramid = -1;
|
|
while ((paramid = bms_next_member(params, paramid)) >= 0)
|
|
{
|
|
ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
|
|
|
|
if (prm->execPlan != NULL)
|
|
{
|
|
/* Parameter not evaluated yet, so go do it */
|
|
ExecSetParamPlan(prm->execPlan, econtext);
|
|
/* ExecSetParamPlan should have processed this param... */
|
|
Assert(prm->execPlan == NULL);
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Mark an initplan as needing recalculation
|
|
*/
|
|
void
|
|
ExecReScanSetParamPlan(SubPlanState *node, PlanState *parent)
|
|
{
|
|
PlanState *planstate = node->planstate;
|
|
SubPlan *subplan = node->subplan;
|
|
EState *estate = parent->state;
|
|
ListCell *l;
|
|
|
|
/* sanity checks */
|
|
if (subplan->parParam != NIL)
|
|
elog(ERROR, "direct correlated subquery unsupported as initplan");
|
|
if (subplan->setParam == NIL)
|
|
elog(ERROR, "setParam list of initplan is empty");
|
|
if (bms_is_empty(planstate->plan->extParam))
|
|
elog(ERROR, "extParam set of initplan is empty");
|
|
|
|
/*
|
|
* Don't actually re-scan: it'll happen inside ExecSetParamPlan if needed.
|
|
*/
|
|
|
|
/*
|
|
* Mark this subplan's output parameters as needing recalculation.
|
|
*
|
|
* CTE subplans are never executed via parameter recalculation; instead
|
|
* they get run when called by nodeCtescan.c. So don't mark the output
|
|
* parameter of a CTE subplan as dirty, but do set the chgParam bit for it
|
|
* so that dependent plan nodes will get told to rescan.
|
|
*/
|
|
foreach(l, subplan->setParam)
|
|
{
|
|
int paramid = lfirst_int(l);
|
|
ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);
|
|
|
|
if (subplan->subLinkType != CTE_SUBLINK)
|
|
prm->execPlan = node;
|
|
|
|
parent->chgParam = bms_add_member(parent->chgParam, paramid);
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
* ExecInitAlternativeSubPlan
|
|
*
|
|
* Initialize for execution of one of a set of alternative subplans.
|
|
*/
|
|
AlternativeSubPlanState *
|
|
ExecInitAlternativeSubPlan(AlternativeSubPlan *asplan, PlanState *parent)
|
|
{
|
|
AlternativeSubPlanState *asstate = makeNode(AlternativeSubPlanState);
|
|
double num_calls;
|
|
SubPlan *subplan1;
|
|
SubPlan *subplan2;
|
|
Cost cost1;
|
|
Cost cost2;
|
|
ListCell *lc;
|
|
|
|
asstate->subplan = asplan;
|
|
|
|
/*
|
|
* Initialize subplans. (Can we get away with only initializing the one
|
|
* we're going to use?)
|
|
*/
|
|
foreach(lc, asplan->subplans)
|
|
{
|
|
SubPlan *sp = lfirst_node(SubPlan, lc);
|
|
SubPlanState *sps = ExecInitSubPlan(sp, parent);
|
|
|
|
asstate->subplans = lappend(asstate->subplans, sps);
|
|
parent->subPlan = lappend(parent->subPlan, sps);
|
|
}
|
|
|
|
/*
|
|
* Select the one to be used. For this, we need an estimate of the number
|
|
* of executions of the subplan. We use the number of output rows
|
|
* expected from the parent plan node. This is a good estimate if we are
|
|
* in the parent's targetlist, and an underestimate (but probably not by
|
|
* more than a factor of 2) if we are in the qual.
|
|
*/
|
|
num_calls = parent->plan->plan_rows;
|
|
|
|
/*
|
|
* The planner saved enough info so that we don't have to work very hard
|
|
* to estimate the total cost, given the number-of-calls estimate.
|
|
*/
|
|
Assert(list_length(asplan->subplans) == 2);
|
|
subplan1 = (SubPlan *) linitial(asplan->subplans);
|
|
subplan2 = (SubPlan *) lsecond(asplan->subplans);
|
|
|
|
cost1 = subplan1->startup_cost + num_calls * subplan1->per_call_cost;
|
|
cost2 = subplan2->startup_cost + num_calls * subplan2->per_call_cost;
|
|
|
|
if (cost1 < cost2)
|
|
asstate->active = 0;
|
|
else
|
|
asstate->active = 1;
|
|
|
|
return asstate;
|
|
}
|
|
|
|
/*
|
|
* ExecAlternativeSubPlan
|
|
*
|
|
* Execute one of a set of alternative subplans.
|
|
*
|
|
* Note: in future we might consider changing to different subplans on the
|
|
* fly, in case the original rowcount estimate turns out to be way off.
|
|
*/
|
|
Datum
|
|
ExecAlternativeSubPlan(AlternativeSubPlanState *node,
|
|
ExprContext *econtext,
|
|
bool *isNull)
|
|
{
|
|
/* Just pass control to the active subplan */
|
|
SubPlanState *activesp = list_nth_node(SubPlanState,
|
|
node->subplans, node->active);
|
|
|
|
return ExecSubPlan(activesp, econtext, isNull);
|
|
}
|