diff options
Diffstat (limited to 'src/backend/optimizer/util/restrictinfo.c')
| -rw-r--r-- | src/backend/optimizer/util/restrictinfo.c | 28 |
1 files changed, 25 insertions, 3 deletions
diff --git a/src/backend/optimizer/util/restrictinfo.c b/src/backend/optimizer/util/restrictinfo.c index bc1fcc36464..bdcc338d609 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 1.15 2002/11/24 21:52:14 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/util/restrictinfo.c,v 1.16 2003/01/24 03:58:43 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -17,6 +17,7 @@ #include "optimizer/clauses.h" #include "optimizer/paths.h" #include "optimizer/restrictinfo.h" +#include "optimizer/var.h" /* @@ -101,6 +102,13 @@ get_actual_join_clauses(List *restrictinfo_list, * equality between any set member on the left and any member on the right; * by transitivity, all the rest are then equal. * + * However, clauses that are of the form "var expr = const expr" cannot be + * eliminated as redundant. This is because when there are const expressions + * in a pathkey set, generate_implied_equalities() suppresses "var = var" + * clauses in favor of "var = const" clauses. We cannot afford to drop any + * of the latter, even though they might seem redundant by the pathkey + * membership test. + * * 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 @@ -120,7 +128,7 @@ remove_redundant_join_clauses(Query *root, List *restrictinfo_list, { RestrictInfo *rinfo = (RestrictInfo *) lfirst(item); - /* eliminate duplicates */ + /* always eliminate duplicates */ if (member(rinfo, result)) continue; @@ -132,6 +140,7 @@ remove_redundant_join_clauses(Query *root, List *restrictinfo_list, cache_mergeclause_pathkeys(root, rinfo); + /* do the cheap tests first */ foreach(olditem, result) { RestrictInfo *oldrinfo = (RestrictInfo *) lfirst(olditem); @@ -148,7 +157,20 @@ remove_redundant_join_clauses(Query *root, List *restrictinfo_list, } if (redundant) - continue; + { + /* + * 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. + */ + if (rinfo->left_relids) + continue; /* var = var, so redundant */ + if (contain_var_clause(get_leftop(rinfo->clause)) && + contain_var_clause(get_rightop(rinfo->clause))) + continue; /* var = var, so redundant */ + /* else var = const, not redundant */ + } } /* otherwise, add it to result list */ |