diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/optimizer/path/clausesel.c | 30 |
1 files changed, 17 insertions, 13 deletions
diff --git a/src/backend/optimizer/path/clausesel.c b/src/backend/optimizer/path/clausesel.c index 6a1dfc229d2..e358c6990e2 100644 --- a/src/backend/optimizer/path/clausesel.c +++ b/src/backend/optimizer/path/clausesel.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/path/clausesel.c,v 1.89 2008/01/01 19:45:50 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/path/clausesel.c,v 1.90 2008/01/11 17:00:45 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -428,7 +428,7 @@ clause_selectivity(PlannerInfo *root, int varRelid, JoinType jointype) { - Selectivity s1 = 1.0; /* default for any unhandled clause type */ + Selectivity s1 = 0.5; /* default for any unhandled clause type */ RestrictInfo *rinfo = NULL; bool cacheable = false; @@ -450,7 +450,7 @@ clause_selectivity(PlannerInfo *root, if (rinfo->pseudoconstant) { if (!IsA(rinfo->clause, Const)) - return s1; + return (Selectivity) 1.0; } /* @@ -517,9 +517,8 @@ clause_selectivity(PlannerInfo *root, { /* * XXX not smart about subquery references... any way to do - * better? + * better than default? */ - s1 = 0.5; } else { @@ -560,8 +559,7 @@ clause_selectivity(PlannerInfo *root, } else { - /* XXX any way to do better? */ - s1 = (Selectivity) 0.5; + /* XXX any way to do better than default? */ } } else if (not_clause(clause)) @@ -601,7 +599,7 @@ clause_selectivity(PlannerInfo *root, s1 = s1 + s2 - s1 * s2; } } - else if (is_opclause(clause)) + else if (is_opclause(clause) || IsA(clause, DistinctExpr)) { Oid opno = ((OpExpr *) clause)->opno; bool is_join_clause; @@ -642,6 +640,15 @@ clause_selectivity(PlannerInfo *root, ((OpExpr *) clause)->args, varRelid); } + + /* + * DistinctExpr has the same representation as OpExpr, but the + * contained operator is "=" not "<>", so we must negate the result. + * This estimation method doesn't give the right behavior for nulls, + * but it's better than doing nothing. + */ + if (IsA(clause, DistinctExpr)) + s1 = 1.0 - s1; } else if (is_funcclause(clause)) { @@ -652,6 +659,7 @@ clause_selectivity(PlannerInfo *root, */ s1 = (Selectivity) 0.3333333; } +#ifdef NOT_USED else if (is_subplan(clause)) { /* @@ -659,11 +667,7 @@ clause_selectivity(PlannerInfo *root, */ s1 = (Selectivity) 0.5; } - else if (IsA(clause, DistinctExpr)) - { - /* can we do better? */ - s1 = (Selectivity) 0.5; - } +#endif else if (IsA(clause, ScalarArrayOpExpr)) { /* First, decide if it's a join clause, same as for OpExpr */ |