diff options
Diffstat (limited to 'src/backend/optimizer/util/clauses.c')
| -rw-r--r-- | src/backend/optimizer/util/clauses.c | 75 |
1 files changed, 74 insertions, 1 deletions
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c index 52dd8c22ca7..bfeb3375701 100644 --- a/src/backend/optimizer/util/clauses.c +++ b/src/backend/optimizer/util/clauses.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.230 2007/01/17 17:25:52 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.231 2007/01/22 01:35:20 tgl Exp $ * * HISTORY * AUTHOR DATE MAJOR EVENT @@ -64,6 +64,7 @@ typedef struct static bool contain_agg_clause_walker(Node *node, void *context); static bool count_agg_clauses_walker(Node *node, AggClauseCounts *counts); static bool expression_returns_set_walker(Node *node, void *context); +static bool expression_returns_set_rows_walker(Node *node, double *count); static bool contain_subplans_walker(Node *node, void *context); static bool contain_mutable_functions_walker(Node *node, void *context); static bool contain_volatile_functions_walker(Node *node, void *context); @@ -566,6 +567,78 @@ expression_returns_set_walker(Node *node, void *context) context); } +/* + * expression_returns_set_rows + * Estimate the number of rows in a set result. + * + * We use the product of the rowcount estimates of all the functions in + * the given tree. The result is 1 if there are no set-returning functions. + */ +double +expression_returns_set_rows(Node *clause) +{ + double result = 1; + + (void) expression_returns_set_rows_walker(clause, &result); + return result; +} + +static bool +expression_returns_set_rows_walker(Node *node, double *count) +{ + if (node == NULL) + return false; + if (IsA(node, FuncExpr)) + { + FuncExpr *expr = (FuncExpr *) node; + + if (expr->funcretset) + *count *= get_func_rows(expr->funcid); + } + if (IsA(node, OpExpr)) + { + OpExpr *expr = (OpExpr *) node; + + if (expr->opretset) + { + set_opfuncid(expr); + *count *= get_func_rows(expr->opfuncid); + } + } + + /* Avoid recursion for some cases that can't return a set */ + if (IsA(node, Aggref)) + return false; + if (IsA(node, DistinctExpr)) + return false; + if (IsA(node, ScalarArrayOpExpr)) + return false; + if (IsA(node, BoolExpr)) + return false; + if (IsA(node, SubLink)) + return false; + if (IsA(node, SubPlan)) + return false; + if (IsA(node, ArrayExpr)) + return false; + if (IsA(node, RowExpr)) + return false; + if (IsA(node, RowCompareExpr)) + return false; + if (IsA(node, CoalesceExpr)) + return false; + if (IsA(node, MinMaxExpr)) + return false; + if (IsA(node, XmlExpr)) + return false; + if (IsA(node, NullIfExpr)) + return false; + + return expression_tree_walker(node, expression_returns_set_rows_walker, + (void *) count); +} + + /***************************************************************************** * Subplan clause manipulation *****************************************************************************/ |