diff options
Diffstat (limited to 'src/backend/optimizer/path/joinpath.c')
| -rw-r--r-- | src/backend/optimizer/path/joinpath.c | 30 |
1 files changed, 19 insertions, 11 deletions
diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c index ac5d4a72d45..6069a34d879 100644 --- a/src/backend/optimizer/path/joinpath.c +++ b/src/backend/optimizer/path/joinpath.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinpath.c,v 1.72 2002/11/24 21:52:14 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinpath.c,v 1.73 2002/11/30 00:08:16 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -701,7 +701,7 @@ match_unsorted_inner(Query *root, /* * hash_inner_and_outer * Create hashjoin join paths by explicitly hashing both the outer and - * inner join relations of each available hash clause. + * inner keys of each available hash clause. * * 'joinrel' is the join relation * 'outerrel' is the outer join relation @@ -719,6 +719,7 @@ hash_inner_and_outer(Query *root, JoinType jointype) { bool isouterjoin; + List *hashclauses; List *i; /* @@ -737,20 +738,18 @@ hash_inner_and_outer(Query *root, } /* + * We need to build only one hashpath for any given pair of outer and + * inner relations; all of the hashable clauses will be used as keys. + * * Scan the join's restrictinfo list to find hashjoinable clauses that - * are usable with this pair of sub-relations. Since we currently - * accept only var-op-var clauses as hashjoinable, we need only check - * the membership of the vars to determine whether a particular clause - * can be used with this pair of sub-relations. This code would need - * to be upgraded if we wanted to allow more-complex expressions in - * hash joins. + * are usable with this pair of sub-relations. */ + hashclauses = NIL; foreach(i, restrictlist) { RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(i); Var *left, *right; - List *hashclauses; if (restrictinfo->hashjoinoperator == InvalidOid) continue; /* not hashjoinable */ @@ -768,6 +767,12 @@ hash_inner_and_outer(Query *root, /* * Check if clause is usable with these input rels. + * + * Since we currently accept only var-op-var clauses as hashjoinable, + * we need only check the membership of the vars to determine whether + * a particular clause can be used with this pair of sub-relations. + * This code would need to be upgraded if we wanted to allow + * more-complex expressions in hash joins. */ if (VARISRELMEMBER(left->varno, outerrel) && VARISRELMEMBER(right->varno, innerrel)) @@ -782,9 +787,12 @@ hash_inner_and_outer(Query *root, else continue; /* no good for these input relations */ - /* always a one-element list of hash clauses */ - hashclauses = makeList1(restrictinfo); + hashclauses = lappend(hashclauses, restrictinfo); + } + /* If we found any usable hashclauses, make a path */ + if (hashclauses) + { /* * We consider both the cheapest-total-cost and * cheapest-startup-cost outer paths. There's no need to consider |