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Implement constant-expression simplification per Bernard

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Frankpitt, plus some improvements from yours truly.  The simplifier depends
on the proiscachable field of pg_proc to tell it whether a function is
safe to pre-evaluate --- things like nextval() are not, for example.
Update pg_proc.h to contain reasonable cacheability information; as of
6.5.* hardly any functions were marked cacheable.  I may have erred too
far in the other direction; see recent mail to pghackers for more info.
This update does not force an initdb, exactly, but you won't see much
benefit from the simplifier until you do one.
This commit is contained in:
Tom Lane
1999-09-26 02:28:44 +00:00
parent 95d3d468ce
commit 40f6524161
7 changed files with 1359 additions and 938 deletions
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39
src/backend/optimizer/plan/planner.c
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@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.68 1999/09/18 19:07:00 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.69 1999/09/26 02:28:27 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -301,7 +301,28 @@ union_planner(Query *parse)
*/
if (parse->havingQual)
{
List *ql;
/*--------------------
* Require the havingQual to contain at least one aggregate function
* (else it could have been done as a WHERE constraint). This check
* used to be much stricter, requiring an aggregate in each clause of
* the CNF-ified qual. However, that's probably overly anal-retentive.
* We now do it first so that we will not complain if there is an
* aggregate but it gets optimized away by eval_const_expressions().
* The agg itself is never const, of course, but consider
* SELECT ... HAVING xyz OR (COUNT(*) > 1)
* where xyz reduces to constant true in a particular query.
* We probably should not refuse this query.
*--------------------
*/
if (pull_agg_clause(parse->havingQual) == NIL)
elog(ERROR, "SELECT/HAVING requires aggregates to be valid");
/* Simplify constant expressions in havingQual */
parse->havingQual = eval_const_expressions(parse->havingQual);
/* Convert the havingQual to implicit-AND normal form */
parse->havingQual = (Node *)
canonicalize_qual((Expr *) parse->havingQual, true);
/* Replace uplevel Vars with Params */
if (PlannerQueryLevel > 1)
@ -323,20 +344,6 @@ union_planner(Query *parse)
parse->targetList))
elog(ERROR, "Sub-SELECT in HAVING clause must use only GROUPed attributes from outer SELECT");
}
/* convert the havingQual to implicit-AND normal form */
parse->havingQual = (Node *)
canonicalize_qual((Expr *) parse->havingQual, true);
/*
* Require an aggregate function to appear in each clause of the
* havingQual (else it could have been done as a WHERE constraint).
*/
foreach(ql, (List *) parse->havingQual)
{
if (pull_agg_clause(lfirst(ql)) == NIL)
elog(ERROR, "SELECT/HAVING requires aggregates to be valid");
}
}
/*