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Fix problems with subselects used in GROUP BY expressions, per gripe

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from Philip Warner.  Side effect of change is that GROUP BY expressions
will not be re-evaluated at multiple plan levels anymore, whereas this
sometimes happened with old code.
This commit is contained in:
Tom Lane
2001-10-30 19:58:58 +00:00
parent 512a3aef36
commit 96ca8ffebc
4 changed files with 167 additions and 103 deletions
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40
src/backend/optimizer/plan/planner.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.111 2001/10/28 06:25:45 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.112 2001/10/30 19:58:58 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -173,6 +173,17 @@ subquery_planner(Query *parse, double tuple_fraction)
parse->havingQual = preprocess_expression(parse, parse->havingQual,
EXPRKIND_HAVING);
/*
* Check for ungrouped variables passed to subplans in targetlist and
* HAVING clause (but not in WHERE or JOIN/ON clauses, since those are
* evaluated before grouping). We can't do this any earlier because
* we must use the preprocessed targetlist for comparisons of grouped
* expressions.
*/
if (parse->hasSubLinks &&
(parse->groupClause != NIL || parse->hasAggs))
check_subplans_for_ungrouped_vars(parse);
/*
* A HAVING clause without aggregates is equivalent to a WHERE clause
* (except it can only refer to grouped fields). Transfer any
@ -623,23 +634,10 @@ preprocess_expression(Query *parse, Node *expr, int kind)
#endif
}
/* Expand SubLinks to SubPlans */
if (parse->hasSubLinks)
{
/* Expand SubLinks to SubPlans */
expr = SS_process_sublinks(expr);
if (kind != EXPRKIND_WHERE &&
(parse->groupClause != NIL || parse->hasAggs))
{
/*
* Check for ungrouped variables passed to subplans. Note we
* do NOT do this for subplans in WHERE (or JOIN/ON); it's
* legal there because WHERE is evaluated pre-GROUP.
*/
check_subplans_for_ungrouped_vars(expr, parse);
}
}
/* Replace uplevel vars with Param nodes */
if (PlannerQueryLevel > 1)
expr = SS_replace_correlation_vars(expr);
@ -1122,12 +1120,11 @@ grouping_planner(Query *parse, double tuple_fraction)
/*
* If there are aggregates then the Group node should just return
* the same set of vars as the subplan did (but we can exclude any
* GROUP BY expressions). If there are no aggregates then the
* Group node had better compute the final tlist.
* the same set of vars as the subplan did. If there are no aggs
* then the Group node had better compute the final tlist.
*/
if (parse->hasAggs)
group_tlist = flatten_tlist(result_plan->targetlist);
group_tlist = new_unsorted_tlist(result_plan->targetlist);
else
group_tlist = tlist;
@ -1234,7 +1231,10 @@ grouping_planner(Query *parse, double tuple_fraction)
* where the a+b target will be used by the Sort/Group steps, and the
* other targets will be used for computing the final results. (In the
* above example we could theoretically suppress the a and b targets and
* use only a+b, but it's not really worth the trouble.)
* pass down only c,d,a+b, but it's not really worth the trouble to
* eliminate simple var references from the subplan. We will avoid doing
* the extra computation to recompute a+b at the outer level; see
* replace_vars_with_subplan_refs() in setrefs.c.)
*
* 'parse' is the query being processed.
* 'tlist' is the query's target list.