diff options
Diffstat (limited to 'src/backend/optimizer/util/restrictinfo.c')
| -rw-r--r-- | src/backend/optimizer/util/restrictinfo.c | 57 |
1 files changed, 45 insertions, 12 deletions
diff --git a/src/backend/optimizer/util/restrictinfo.c b/src/backend/optimizer/util/restrictinfo.c index 0c21e94e688..d3aa8098bde 100644 --- a/src/backend/optimizer/util/restrictinfo.c +++ b/src/backend/optimizer/util/restrictinfo.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/util/restrictinfo.c,v 1.19 2003/08/04 02:40:01 momjian Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/util/restrictinfo.c,v 1.19.4.1 2007/07/31 19:54:27 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -23,6 +23,8 @@ static bool join_clause_is_redundant(Query *root, RestrictInfo *rinfo, List *reference_list, + Relids outer_relids, + Relids inner_relids, JoinType jointype); @@ -105,6 +107,8 @@ get_actual_join_clauses(List *restrictinfo_list, */ List * remove_redundant_join_clauses(Query *root, List *restrictinfo_list, + Relids outer_relids, + Relids inner_relids, JoinType jointype) { List *result = NIL; @@ -115,7 +119,9 @@ remove_redundant_join_clauses(Query *root, List *restrictinfo_list, RestrictInfo *rinfo = (RestrictInfo *) lfirst(item); /* drop it if redundant with any prior clause */ - if (join_clause_is_redundant(root, rinfo, result, jointype)) + if (join_clause_is_redundant(root, rinfo, result, + outer_relids, inner_relids, + jointype)) continue; /* otherwise, add it to result list */ @@ -143,6 +149,8 @@ List * select_nonredundant_join_clauses(Query *root, List *restrictinfo_list, List *reference_list, + Relids outer_relids, + Relids inner_relids, JoinType jointype) { List *result = NIL; @@ -153,7 +161,9 @@ select_nonredundant_join_clauses(Query *root, RestrictInfo *rinfo = (RestrictInfo *) lfirst(item); /* drop it if redundant with any reference clause */ - if (join_clause_is_redundant(root, rinfo, reference_list, jointype)) + if (join_clause_is_redundant(root, rinfo, reference_list, + outer_relids, inner_relids, + jointype)) continue; /* otherwise, add it to result list */ @@ -185,6 +195,12 @@ select_nonredundant_join_clauses(Query *root, * of the latter, even though they might seem redundant by the pathkey * membership test. * + * Also, we cannot eliminate clauses wherein one side mentions vars from + * both relations, as in "WHERE t1.f1 = t2.f1 AND t1.f1 = t1.f2 - t2.f2". + * In this example, "t1.f2 - t2.f2" could not have been computed at all + * before forming the join of t1 and t2, so it certainly wasn't constrained + * earlier. + * * 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 @@ -194,6 +210,8 @@ static bool join_clause_is_redundant(Query *root, RestrictInfo *rinfo, List *reference_list, + Relids outer_relids, + Relids inner_relids, JoinType jointype) { /* always consider exact duplicates redundant */ @@ -228,16 +246,31 @@ join_clause_is_redundant(Query *root, if (redundant) { /* - * It looks redundant, now check for "var = const" case. If - * left_relids/right_relids are set, then there are definitely - * vars on both sides; else we must check the hard way. + * It looks redundant, now check for special cases. This is + * ugly and slow because of the mistaken decision to not set + * left_relids/right_relids all the time, as 8.0 and up do. + * Not going to change that in 7.x though. */ - if (rinfo->left_relids) - return true; /* var = var, so redundant */ - if (contain_var_clause(get_leftop(rinfo->clause)) && - contain_var_clause(get_rightop(rinfo->clause))) - return true; /* var = var, so redundant */ - /* else var = const, not redundant */ + Relids left_relids = rinfo->left_relids; + Relids right_relids = rinfo->right_relids; + + if (left_relids == NULL) + left_relids = pull_varnos(get_leftop(rinfo->clause)); + if (right_relids == NULL) + right_relids = pull_varnos(get_rightop(rinfo->clause)); + + if (bms_is_empty(left_relids) || bms_is_empty(right_relids)) + return false; /* var = const, so not redundant */ + + /* check for either side mentioning both rels */ + if (bms_overlap(left_relids, outer_relids) && + bms_overlap(left_relids, inner_relids)) + return false; /* clause LHS uses both, so not redundant */ + if (bms_overlap(right_relids, outer_relids) && + bms_overlap(right_relids, inner_relids)) + return false; /* clause RHS uses both, so not redundant */ + + return true; /* else it really is redundant */ } } |