diff options
Diffstat (limited to 'src/backend/optimizer/util/clauses.c')
| -rw-r--r-- | src/backend/optimizer/util/clauses.c | 33 |
1 files changed, 27 insertions, 6 deletions
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c index 4fa73a9d223..add29f54d09 100644 --- a/src/backend/optimizer/util/clauses.c +++ b/src/backend/optimizer/util/clauses.c @@ -833,8 +833,8 @@ contain_subplans_walker(Node *node, void *context) * mistakenly think that something like "WHERE random() < 0.5" can be treated * as a constant qualification. * - * XXX we do not examine sub-selects to see if they contain uses of - * mutable functions. It's not real clear if that is correct or not... + * We will recursively look into Query nodes (i.e., SubLink sub-selects) + * but not into SubPlans. See comments for contain_volatile_functions(). */ bool contain_mutable_functions(Node *clause) @@ -931,6 +931,13 @@ contain_mutable_functions_walker(Node *node, void *context) } /* else fall through to check args */ } + else if (IsA(node, Query)) + { + /* Recurse into subselects */ + return query_tree_walker((Query *) node, + contain_mutable_functions_walker, + context, 0); + } return expression_tree_walker(node, contain_mutable_functions_walker, context); } @@ -945,11 +952,18 @@ contain_mutable_functions_walker(Node *node, void *context) * Recursively search for volatile functions within a clause. * * Returns true if any volatile function (or operator implemented by a - * volatile function) is found. This test prevents invalid conversions - * of volatile expressions into indexscan quals. + * volatile function) is found. This test prevents, for example, + * invalid conversions of volatile expressions into indexscan quals. * - * XXX we do not examine sub-selects to see if they contain uses of - * volatile functions. It's not real clear if that is correct or not... + * We will recursively look into Query nodes (i.e., SubLink sub-selects) + * but not into SubPlans. This is a bit odd, but intentional. If we are + * looking at a SubLink, we are probably deciding whether a query tree + * transformation is safe, and a contained sub-select should affect that; + * for example, duplicating a sub-select containing a volatile function + * would be bad. However, once we've got to the stage of having SubPlans, + * subsequent planning need not consider volatility within those, since + * the executor won't change its evaluation rules for a SubPlan based on + * volatility. */ bool contain_volatile_functions(Node *clause) @@ -1047,6 +1061,13 @@ contain_volatile_functions_walker(Node *node, void *context) } /* else fall through to check args */ } + else if (IsA(node, Query)) + { + /* Recurse into subselects */ + return query_tree_walker((Query *) node, + contain_volatile_functions_walker, + context, 0); + } return expression_tree_walker(node, contain_volatile_functions_walker, context); } |