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Restructure planning of nestloop inner indexscans so that the set of usable

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joinclauses is determined accurately for each join.  Formerly, the code only
considered joinclauses that used all of the rels from the outer side of the
join; thus for example
	FROM (a CROSS JOIN b) JOIN c ON (c.f1 = a.x AND c.f2 = b.y)
could not exploit a two-column index on c(f1,f2), since neither of the
qual clauses would be in the joininfo list it looked in.  The new code does
this correctly, and also is able to eliminate redundant clauses, thus fixing
the problem noted 24-Oct-02 by Hans-Jürgen Schönig.
This commit is contained in:
Tom Lane
2002-11-24 21:52:15 +00:00
parent 6bfc09baf4
commit 04c8785c7b
19 changed files with 742 additions and 579 deletions
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66
src/backend/optimizer/util/relnode.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/util/relnode.c,v 1.40 2002/10/12 22:24:49 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/util/relnode.c,v 1.41 2002/11/24 21:52:14 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -17,8 +17,8 @@
#include "optimizer/cost.h"
#include "optimizer/joininfo.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/plancat.h"
#include "optimizer/restrictinfo.h"
#include "optimizer/tlist.h"
#include "parser/parsetree.h"
@ -152,7 +152,8 @@ make_base_rel(Query *root, int relid)
rel->baserestrictcost = 0;
rel->outerjoinset = NIL;
rel->joininfo = NIL;
rel->innerjoin = NIL;
rel->index_outer_relids = NIL;
rel->index_inner_paths = NIL;
/* Check type of rtable entry */
switch (rte->rtekind)
@ -365,7 +366,8 @@ build_join_rel(Query *root,
joinrel->baserestrictcost = 0;
joinrel->outerjoinset = NIL;
joinrel->joininfo = NIL;
joinrel->innerjoin = NIL;
joinrel->index_outer_relids = NIL;
joinrel->index_inner_paths = NIL;
/* Is there a join RTE matching this join? */
joinrterel = find_other_rel_for_join(root, joinrelids);
@ -529,9 +531,8 @@ build_joinrel_restrictlist(Query *root,
RelOptInfo *inner_rel,
JoinType jointype)
{
List *result = NIL;
List *result;
List *rlist;
List *item;
/*
* Collect all the clauses that syntactically belong at this level.
@ -549,59 +550,8 @@ build_joinrel_restrictlist(Query *root,
* mergejoinable clause, it's possible that it is redundant with
* previous clauses (see optimizer/README for discussion). We detect
* that case and omit the redundant clause from the result list.
*
* We can detect redundant mergejoinable clauses very cheaply by using
* their left and right pathkeys, which uniquely identify the sets of
* equijoined variables in question. All the members of a pathkey set
* that are in the left relation have already been forced to be equal;
* likewise for those in the right relation. So, we need to have only
* one clause that checks equality between any set member on the left
* and any member on the right; by transitivity, all the rest are then
* equal.
*
* Weird special case: if we have two clauses that seem redundant
* except one is pushed down into an outer join and the other isn't,
* then they're not really redundant, because one constrains the
* joined rows after addition of null fill rows, and the other doesn't.
*/
foreach(item, rlist)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(item);
/* eliminate duplicates */
if (member(rinfo, result))
continue;
/* check for redundant merge clauses */
if (rinfo->mergejoinoperator != InvalidOid)
{
bool redundant = false;
List *olditem;
cache_mergeclause_pathkeys(root, rinfo);
foreach(olditem, result)
{
RestrictInfo *oldrinfo = (RestrictInfo *) lfirst(olditem);
if (oldrinfo->mergejoinoperator != InvalidOid &&
rinfo->left_pathkey == oldrinfo->left_pathkey &&
rinfo->right_pathkey == oldrinfo->right_pathkey &&
(rinfo->ispusheddown == oldrinfo->ispusheddown ||
!IS_OUTER_JOIN(jointype)))
{
redundant = true;
break;
}
}
if (redundant)
continue;
}
/* otherwise, add it to result list */
result = lappend(result, rinfo);
}
result = remove_redundant_join_clauses(root, rlist, jointype);
freeList(rlist);