diff options
Diffstat (limited to 'src/backend/optimizer/path/pathkeys.c')
| -rw-r--r-- | src/backend/optimizer/path/pathkeys.c | 65 |
1 files changed, 32 insertions, 33 deletions
diff --git a/src/backend/optimizer/path/pathkeys.c b/src/backend/optimizer/path/pathkeys.c index b254598fcf3..abc50ef14d0 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 - * $PostgreSQL: pgsql/src/backend/optimizer/path/pathkeys.c,v 1.79 2006/10/04 00:29:54 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/path/pathkeys.c,v 1.79.2.1 2008/01/09 20:50:11 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -423,15 +423,16 @@ sub_generate_join_implications(PlannerInfo *root, false); /* - * We can remove explicit tests of this outer-join qual, too, - * since we now have tests forcing each of its sides to the same - * value. + * We used to think we could remove explicit tests of this + * outer-join qual, too, since we now have tests forcing each of + * its sides to the same value. However, that fails in some + * corner cases where lower outer joins could cause one of the + * variables to go to NULL. (BUG in 8.2 through 8.2.6.) + * So now we just leave it in place, but mark it with selectivity + * 1.0 so that we don't underestimate the join size output --- + * it's mostly redundant with the constant constraints. */ - process_implied_equality(root, - leftop, rightop, - rinfo->left_sortop, rinfo->right_sortop, - rinfo->left_relids, rinfo->right_relids, - true); + rinfo->this_selec = 1.0; /* * And recurse to see if we can deduce anything from INNERVAR = @@ -465,15 +466,16 @@ sub_generate_join_implications(PlannerInfo *root, false); /* - * We can remove explicit tests of this outer-join qual, too, - * since we now have tests forcing each of its sides to the same - * value. + * We used to think we could remove explicit tests of this + * outer-join qual, too, since we now have tests forcing each of + * its sides to the same value. However, that fails in some + * corner cases where lower outer joins could cause one of the + * variables to go to NULL. (BUG in 8.2 through 8.2.6.) + * So now we just leave it in place, but mark it with selectivity + * 1.0 so that we don't underestimate the join size output --- + * it's mostly redundant with the constant constraints. */ - process_implied_equality(root, - leftop, rightop, - rinfo->left_sortop, rinfo->right_sortop, - rinfo->left_relids, rinfo->right_relids, - true); + rinfo->this_selec = 1.0; /* * And recurse to see if we can deduce anything from INNERVAR = @@ -542,25 +544,22 @@ sub_generate_join_implications(PlannerInfo *root, rinfo->right_sortop, rinfo->right_relids, false); - /* ... and remove COALESCE() = CONSTANT */ - process_implied_const_eq(root, equi_key_set, relids, - item1, - sortop1, - item1_relids, - true); /* - * We can remove explicit tests of this outer-join qual, too, - * since we now have tests forcing each of its sides to the - * same value. + * We used to think we could remove explicit tests of this + * outer-join qual, too, since we now have tests forcing each + * of its sides to the same value. However, that fails in + * some corner cases where lower outer joins could cause one + * of the variables to go to NULL. (BUG in 8.2 through + * 8.2.6.) So now we just leave it in place, but mark it with + * selectivity 1.0 so that we don't underestimate the join + * size output --- it's mostly redundant with the constant + * constraints. + * + * Ideally we'd do that for the COALESCE() = CONSTANT rinfo, + * too, but we don't have easy access to that here. */ - process_implied_equality(root, - leftop, rightop, - rinfo->left_sortop, - rinfo->right_sortop, - rinfo->left_relids, - rinfo->right_relids, - true); + rinfo->this_selec = 1.0; /* * And recurse to see if we can deduce anything from LEFTVAR = |