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Teach planner about some cases where a restriction clause can be

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propagated inside an outer join.  In particular, given
LEFT JOIN ON (A = B) WHERE A = constant, we cannot conclude that
B = constant at the top level (B might be null instead), but we
can nonetheless put a restriction B = constant into the quals for
B's relation, since no inner-side rows not meeting that condition
can contribute to the final result.  Similarly, given
FULL JOIN USING (J) WHERE J = constant, we can't directly conclude
that either input J variable = constant, but it's OK to push such
quals into each input rel.  Per recent gripe from Kim Bisgaard.
Along the way, remove 'valid_everywhere' flag from RestrictInfo,
as on closer analysis it was not being used for anything, and was
defined backwards anyway.
This commit is contained in:
Tom Lane
2005-07-02 23:00:42 +00:00
parent ea1e2b948d
commit cc5e80b8d1
13 changed files with 424 additions and 114 deletions
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17
src/backend/optimizer/plan/planner.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.189 2005/06/10 02:21:04 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.190 2005/07/02 23:00:41 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -194,7 +194,6 @@ subquery_planner(Query *parse, double tuple_fraction,
int saved_planid = PlannerPlanId;
PlannerInfo *root;
Plan *plan;
bool hasOuterJoins;
List *newHaving;
List *lst;
ListCell *l;
@ -228,12 +227,16 @@ subquery_planner(Query *parse, double tuple_fraction,
/*
* Detect whether any rangetable entries are RTE_JOIN kind; if not, we
* can avoid the expense of doing flatten_join_alias_vars(). Also
* check for outer joins --- if none, we can skip
* reduce_outer_joins(). This must be done after we have done
* check for outer joins --- if none, we can skip reduce_outer_joins()
* and some other processing. This must be done after we have done
* pull_up_subqueries, of course.
*
* Note: if reduce_outer_joins manages to eliminate all outer joins,
* root->hasOuterJoins is not reset currently. This is OK since its
* purpose is merely to suppress unnecessary processing in simple cases.
*/
root->hasJoinRTEs = false;
hasOuterJoins = false;
root->hasOuterJoins = false;
foreach(l, parse->rtable)
{
RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
@ -243,7 +246,7 @@ subquery_planner(Query *parse, double tuple_fraction,
root->hasJoinRTEs = true;
if (IS_OUTER_JOIN(rte->jointype))
{
hasOuterJoins = true;
root->hasOuterJoins = true;
/* Can quit scanning once we find an outer join */
break;
}
@ -347,7 +350,7 @@ subquery_planner(Query *parse, double tuple_fraction,
* joins. This step is most easily done after we've done expression
* preprocessing.
*/
if (hasOuterJoins)
if (root->hasOuterJoins)
reduce_outer_joins(root);
/*