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Detect case where an outer join can be reduced to a plain inner join

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because there are WHERE clauses that will reject the null-extended rows.
Per suggestion from Brandon Craig Rhodes, 19-Nov-02.
This commit is contained in:
Tom Lane
2003-02-09 23:57:19 +00:00
parent 43785a434e
commit b5956a2f22
3 changed files with 378 additions and 15 deletions
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26
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 1.145 2003/02/09 00:30:39 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.146 2003/02/09 23:57:19 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -144,6 +144,7 @@ subquery_planner(Query *parse, double tuple_fraction)
{
List *saved_initplan = PlannerInitPlan;
int saved_planid = PlannerPlanId;
bool hasOuterJoins;
Plan *plan;
List *newHaving;
List *lst;
@ -172,10 +173,12 @@ 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().
* 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 pull_up_subqueries, of course.
*/
parse->hasJoinRTEs = false;
hasOuterJoins = false;
foreach(lst, parse->rtable)
{
RangeTblEntry *rte = (RangeTblEntry *) lfirst(lst);
@ -183,7 +186,12 @@ subquery_planner(Query *parse, double tuple_fraction)
if (rte->rtekind == RTE_JOIN)
{
parse->hasJoinRTEs = true;
break;
if (IS_OUTER_JOIN(rte->jointype))
{
hasOuterJoins = true;
/* Can quit scanning once we find an outer join */
break;
}
}
}
@ -244,15 +252,23 @@ subquery_planner(Query *parse, double tuple_fraction)
}
parse->havingQual = (Node *) newHaving;
/*
* If we have any outer joins, try to reduce them to plain inner joins.
* This step is most easily done after we've done expression preprocessing.
*/
if (hasOuterJoins)
reduce_outer_joins(parse);
/*
* See if we can simplify the jointree; opportunities for this may come
* from having pulled up subqueries, or from flattening explicit JOIN
* syntax. We must do this after flattening JOIN alias variables, since
* eliminating explicit JOIN nodes from the jointree will cause
* get_relids_for_join() to fail.
* get_relids_for_join() to fail. But it should happen after
* reduce_outer_joins, anyway.
*/
parse->jointree = (FromExpr *)
preprocess_jointree(parse, (Node *) parse->jointree);
simplify_jointree(parse, (Node *) parse->jointree);
/*
* Do the main planning. If we have an inherited target relation,