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Restructure planning code so that preprocessing of targetlist and quals

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to simplify constant expressions and expand SubLink nodes into SubPlans
is done in a separate routine subquery_planner() that calls union_planner().
We formerly did most of this work in query_planner(), but that's the
wrong place because it may never see the real targetlist.  Splitting
union_planner into two routines also allows us to avoid redundant work
when union_planner is invoked recursively for UNION and inheritance
cases.  Upshot is that it is now possible to do something like
select float8(count(*)) / (select count(*) from int4_tbl)  from int4_tbl
group by f1;
which has never worked before.
This commit is contained in:
Tom Lane
2000-03-21 05:12:12 +00:00
parent aafe86d995
commit 3ee8f7e207
8 changed files with 191 additions and 166 deletions
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13
src/backend/optimizer/prep/prepunion.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/prep/prepunion.c,v 1.46 2000/03/14 23:06:29 thomas Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/prep/prepunion.c,v 1.47 2000/03/21 05:12:06 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -149,8 +149,12 @@ plan_union_queries(Query *parse)
{
Query *union_query = lfirst(ulist);
/* use subquery_planner here because the union'd queries
* have not been preprocessed yet. My goodness this is messy...
*/
union_plans = lappend(union_plans,
union_planner(union_query, tuple_fraction));
subquery_planner(union_query,
tuple_fraction));
union_rts = lappend(union_rts, union_query->rtable);
}
}
@ -185,8 +189,11 @@ plan_union_queries(Query *parse)
{
Query *union_all_query = lfirst(ulist);
/* use subquery_planner here because the union'd queries
* have not been preprocessed yet. My goodness this is messy...
*/
union_plans = lappend(union_plans,
union_planner(union_all_query, -1.0));
subquery_planner(union_all_query, -1.0));
union_rts = lappend(union_rts, union_all_query->rtable);
}
}