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Be a little smarter in group_clauses_by_indexkey_for_join: detect cases 

where a joinclause is redundant with a restriction clause.  Original coding
believed this was impossible and didn't need to be checked for, but that
was a thinko ...
This commit is contained in:
Tom Lane 2003-12-18 00:22:12 +00:00
parent 422249120d
commit 109a4a603f
1 changed files with 39 additions and 26 deletions
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65
src/backend/optimizer/path/indxpath.c
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@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.149 2003/11/29 19:51:50 pgsql Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.150 2003/12/18 00:22:12 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -600,14 +600,43 @@ group_clauses_by_indexkey_for_join(Query *root,
{
Oid curClass = classes[0];
FastList clausegroup;
int numsources;
List *i;
FastListInit(&clausegroup);
/*
* We can always use plain restriction clauses for the rel. We scan
* these first because we want them first in the clausegroup list
* for the convenience of remove_redundant_join_clauses, which can
* never remove non-join clauses and hence won't be able to get rid
* of a non-join clause if it appears after a join clause it is
* redundant with.
*/
foreach(i, rel->baserestrictinfo)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(i);
/* Can't use pushed-down clauses in outer join */
if (isouterjoin && rinfo->ispusheddown)
continue;
if (match_clause_to_indexcol(rel,
index,
indexcol,
curClass,
rinfo->clause))
FastAppend(&clausegroup, rinfo);
}
/* found anything in base restrict list? */
numsources = (FastListValue(&clausegroup) != NIL) ? 1 : 0;
/* Look for joinclauses that are usable with given outer_relids */
foreach(i, rel->joininfo)
{
JoinInfo *joininfo = (JoinInfo *) lfirst(i);
bool jfoundhere = false;
List *j;
if (!bms_is_subset(joininfo->unjoined_relids, outer_relids))
@ -628,20 +657,21 @@ group_clauses_by_indexkey_for_join(Query *root,
rinfo->clause))
{
FastAppend(&clausegroup, rinfo);
jfound = true;
if (!jfoundhere)
{
jfoundhere = true;
jfound = true;
numsources++;
}
}
}
}
/*
* If we found join clauses in more than one joininfo list, we may
* now have clauses that are known redundant. Get rid of 'em.
* (There is no point in looking at restriction clauses, because
* remove_redundant_join_clauses will never think they are
* redundant, so we do this before adding restriction clauses to
* the clause group.)
* If we found clauses in more than one list, we may now have clauses
* that are known redundant. Get rid of 'em.
*/
if (FastListValue(&clausegroup) != NIL)
if (numsources > 1)
{
List *nl;
@ -651,23 +681,6 @@ group_clauses_by_indexkey_for_join(Query *root,
FastListFromList(&clausegroup, nl);
}
/* We can also use plain restriction clauses for the rel */
foreach(i, rel->baserestrictinfo)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(i);
/* Can't use pushed-down clauses in outer join */
if (isouterjoin && rinfo->ispusheddown)
continue;
if (match_clause_to_indexcol(rel,
index,
indexcol,
curClass,
rinfo->clause))
FastAppend(&clausegroup, rinfo);
}
/*
* If no clauses match this key, we're done; we don't want to look
* at keys to its right.