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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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37
src/backend/optimizer/plan/planmain.c
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@@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planmain.c,v 1.44 1999/09/13 00:17:25 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planmain.c,v 1.45 1999/09/26 02:28:27 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -66,24 +66,41 @@ query_planner(Query *root,
List *level_tlist;
Plan *subplan;
if (PlannerQueryLevel > 1)
{
/* should copy be made ? */
tlist = (List *) SS_replace_correlation_vars((Node *) tlist);
qual = (List *) SS_replace_correlation_vars((Node *) qual);
}
if (root->hasSubLinks)
qual = (List *) SS_process_sublinks((Node *) qual);
/*
* Simplify constant expressions in both targetlist and qual.
*
* Note that at this point the qual has not yet been converted to
* implicit-AND form, so we can apply eval_const_expressions directly.
* Also note that we need to do this before SS_process_sublinks,
* because that routine inserts bogus "Const" nodes.
*/
tlist = (List *) eval_const_expressions((Node *) tlist);
qual = (List *) eval_const_expressions((Node *) qual);
/*
* Canonicalize the qual, and convert it to implicit-AND format.
*/
qual = canonicalize_qual((Expr *) qual, true);
#ifdef OPTIMIZER_DEBUG
printf("After canonicalize_qual()\n");
pprint(qual);
#endif
/* Replace uplevel vars with Param nodes */
if (PlannerQueryLevel > 1)
{
tlist = (List *) SS_replace_correlation_vars((Node *) tlist);
qual = (List *) SS_replace_correlation_vars((Node *) qual);
}
/* Expand SubLinks to SubPlans */
if (root->hasSubLinks)
qual = (List *) SS_process_sublinks((Node *) qual);
/*
* Pull out any non-variable qualifications so these can be put in the
* topmost result node.
* topmost result node. (Any *really* non-variable quals will probably
* have been optimized away by eval_const_expressions(). What we're
* looking for here is quals that depend only on outer-level vars...)
*/
qual = pull_constant_clauses(qual, &constant_qual);