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Evaluate arguments of correlated SubPlans in the referencing ExprState

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Until now we generated an ExprState for each parameter to a SubPlan and
evaluated them one-by-one ExecScanSubPlan. That's sub-optimal as creating lots
of small ExprStates
a) makes JIT compilation more expensive
b) wastes memory
c) is a bit slower to execute

This commit arranges to evaluate parameters to a SubPlan as part of the
ExprState referencing a SubPlan, using the new EEOP_PARAM_SET expression
step. We emit one EEOP_PARAM_SET for each argument to a subplan, just before
the EEOP_SUBPLAN step.

It likely is worth using EEOP_PARAM_SET in other places as well, e.g. for
SubPlan outputs, nestloop parameters and - more ambitiously - to get rid of
ExprContext->domainValue/caseValue/ecxt_agg*.  But that's for later.

Author: Andres Freund <andres@anarazel.de>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Alena Rybakina <lena.ribackina@yandex.ru>
Discussion: https://postgr.es/m/20230225214401.346ancgjqc3zmvek@awork3.anarazel.de
This commit is contained in:
Andres Freund
2024-07-31 18:11:49 -07:00
parent e6a9637488
commit a7f107df2b
8 changed files with 125 additions and 52 deletions
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29
src/backend/executor/nodeSubplan.c
View File

@ -107,7 +107,7 @@ ExecHashSubPlan(SubPlanState *node,
TupleTableSlot *slot;
/* Shouldn't have any direct correlation Vars */
if (subplan->parParam != NIL || node->args != NIL)
if (subplan->parParam != NIL || subplan->args != NIL)
elog(ERROR, "hashed subplan with direct correlation not supported");
/*
@ -231,7 +231,6 @@ ExecScanSubPlan(SubPlanState *node,
TupleTableSlot *slot;
Datum result;
bool found = false; /* true if got at least one subplan tuple */
ListCell *pvar;
ListCell *l;
ArrayBuildStateAny *astate = NULL;
@ -248,26 +247,19 @@ ExecScanSubPlan(SubPlanState *node,
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.)
* We rely on the caller to evaluate plan correlation values, if
* necessary. However we still need to record the fact that the values
* (might have) changed, otherwise the ExecReScan() below won't know that
* nodes need to be rescanned.
*/
Assert(list_length(subplan->parParam) == list_length(node->args));
forboth(l, subplan->parParam, pvar, node->args)
foreach(l, subplan->parParam)
{
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);
}
/*
* Now that we've set up its parameters, we can reset the subplan.
*/
/* with that done, we can reset the subplan */
ExecReScan(planstate);
/*
@ -817,6 +809,10 @@ slotNoNulls(TupleTableSlot *slot)
* 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.
*
* We also rely on ExecInitExpr(), more precisely ExecInitSubPlanExpr(), to
* evaluate input parameters, as that allows them to be evaluated as part of
* the expression referencing the SubPlan.
* ----------------------------------------------------------------
*/
SubPlanState *
@ -844,7 +840,6 @@ ExecInitSubPlan(SubPlan *subplan, PlanState *parent)
/* Initialize subexpressions */
sstate->testexpr = ExecInitExpr((Expr *) subplan->testexpr, parent);
sstate->args = ExecInitExprList(subplan->args, parent);
/*
* initialize my state
@ -1107,7 +1102,7 @@ ExecSetParamPlan(SubPlanState *node, ExprContext *econtext)
elog(ERROR, "ANY/ALL subselect unsupported as initplan");
if (subLinkType == CTE_SUBLINK)
elog(ERROR, "CTE subplans should not be executed via ExecSetParamPlan");
if (subplan->parParam || node->args)
if (subplan->parParam || subplan->args)
elog(ERROR, "correlated subplans should not be executed via ExecSetParamPlan");
/*