diff options
Diffstat (limited to 'src/backend/optimizer/path/pathkeys.c')
| -rw-r--r-- | src/backend/optimizer/path/pathkeys.c | 41 |
1 files changed, 24 insertions, 17 deletions
diff --git a/src/backend/optimizer/path/pathkeys.c b/src/backend/optimizer/path/pathkeys.c index 6d7b67bee3d..c6eccddab19 100644 --- a/src/backend/optimizer/path/pathkeys.c +++ b/src/backend/optimizer/path/pathkeys.c @@ -11,7 +11,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/path/pathkeys.c,v 1.24 2000/08/08 15:41:31 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/path/pathkeys.c,v 1.25 2000/09/12 21:06:53 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -694,8 +694,8 @@ find_mergeclauses_for_pathkeys(List *pathkeys, List *restrictinfos) * * 'mergeclauses' is a list of RestrictInfos for mergejoin clauses * that will be used in a merge join. - * 'tlist' is a relation target list for either the inner or outer - * side of the proposed join rel. (Not actually needed anymore) + * 'rel' is the relation the pathkeys will apply to (ie, either the inner + * or outer side of the proposed join rel). * * Returns a pathkeys list that can be applied to the indicated relation. * @@ -706,7 +706,7 @@ find_mergeclauses_for_pathkeys(List *pathkeys, List *restrictinfos) List * make_pathkeys_for_mergeclauses(Query *root, List *mergeclauses, - List *tlist) + RelOptInfo *rel) { List *pathkeys = NIL; List *i; @@ -722,30 +722,37 @@ make_pathkeys_for_mergeclauses(Query *root, Assert(restrictinfo->mergejoinoperator != InvalidOid); /* - * Find the key and sortop needed for this mergeclause. - * - * Both sides of the mergeclause should appear in one of the query's - * pathkey equivalence classes, so it doesn't matter which one we - * use here. + * Which key and sortop is needed for this relation? */ key = (Node *) get_leftop(restrictinfo->clause); sortop = restrictinfo->left_sortop; + if (!IsA(key, Var) || + !intMember(((Var *) key)->varno, rel->relids)) + { + key = (Node *) get_rightop(restrictinfo->clause); + sortop = restrictinfo->right_sortop; + if (!IsA(key, Var) || + !intMember(((Var *) key)->varno, rel->relids)) + elog(ERROR, "make_pathkeys_for_mergeclauses: can't identify which side of mergeclause to use"); + } /* - * Find pathkey sublist for this sort item. We expect to find the - * canonical set including the mergeclause's left and right sides; - * if we get back just the one item, something is rotten. + * Find or create canonical pathkey sublist for this sort item. */ item = makePathKeyItem(key, sortop); pathkey = make_canonical_pathkey(root, item); - Assert(length(pathkey) > 1); /* - * Since the item we just made is not in the returned canonical - * set, we can free it --- this saves a useful amount of storage - * in a big join tree. + * Most of the time we will get back a canonical pathkey set + * including both the mergeclause's left and right sides (the only + * case where we don't is if the mergeclause appeared in an OUTER + * JOIN, which causes us not to generate an equijoin set from it). + * Therefore, most of the time the item we just made is not part + * of the returned structure, and we can free it. This check + * saves a useful amount of storage in a big join tree. */ - pfree(item); + if (item != (PathKeyItem *) lfirst(pathkey)) + pfree(item); pathkeys = lappend(pathkeys, pathkey); } |