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Push qual clauses containing subplans to the back of the qual list

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at each plan node.  Per gripe from Ross Reedstrom.
This commit is contained in:
Tom Lane
2002-11-15 02:37:08 +00:00
parent a530644e4b
commit 779eb54142
1 changed files with 42 additions and 1 deletions
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43
src/backend/optimizer/plan/createplan.c
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@@ -10,7 +10,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/createplan.c,v 1.119 2002/09/18 21:35:21 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/createplan.c,v 1.119.2.1 2002/11/15 02:37:08 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -69,6 +69,7 @@ static Node *fix_indxqual_operand(Node *node, int baserelid,
IndexOptInfo *index,
Oid *opclass);
static List *switch_outer(List *clauses);
static List *order_qual_clauses(Query *root, List *clauses);
static void copy_path_costsize(Plan *dest, Path *src);
static void copy_plan_costsize(Plan *dest, Plan *src);
static SeqScan *make_seqscan(List *qptlist, List *qpqual, Index scanrelid);
@@ -177,6 +178,9 @@ create_scan_plan(Query *root, Path *best_path)
*/
scan_clauses = get_actual_clauses(best_path->parent->baserestrictinfo);
/* Sort clauses into best execution order */
scan_clauses = order_qual_clauses(root, scan_clauses);
switch (best_path->pathtype)
{
case T_SeqScan:
@@ -1178,6 +1182,43 @@ switch_outer(List *clauses)
return t_list;
}
/*
* order_qual_clauses
* Given a list of qual clauses that will all be evaluated at the same
* plan node, sort the list into the order we want to check the quals
* in at runtime.
*
* Ideally the order should be driven by a combination of execution cost and
* selectivity, but unfortunately we have so little information about
* execution cost of operators that it's really hard to do anything smart.
* For now, we just move any quals that contain SubPlan references (but not
* InitPlan references) to the end of the list.
*/
static List *
order_qual_clauses(Query *root, List *clauses)
{
List *nosubplans;
List *withsubplans;
List *l;
/* No need to work hard if the query is subselect-free */
if (!root->hasSubLinks)
return clauses;
nosubplans = withsubplans = NIL;
foreach(l, clauses)
{
Node *clause = lfirst(l);
if (contain_subplans(clause))
withsubplans = lappend(withsubplans, clause);
else
nosubplans = lappend(nosubplans, clause);
}
return nconc(nosubplans, withsubplans);
}
/*
* Copy cost and size info from a Path node to the Plan node created from it.
* The executor won't use this info, but it's needed by EXPLAIN.