diff options
Diffstat (limited to 'sql/sql_select.cc')
| -rw-r--r-- | sql/sql_select.cc | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/sql/sql_select.cc b/sql/sql_select.cc index 5f8c4dd2e1a..46ef86d5c00 100644 --- a/sql/sql_select.cc +++ b/sql/sql_select.cc @@ -2419,7 +2419,19 @@ merge_key_fields(KEY_FIELD *start,KEY_FIELD *new_fields,KEY_FIELD *end, { if (old->field == new_fields->field) { - if (new_fields->val->used_tables()) + /* + NOTE: below const_item() call really works as "!used_tables()", i.e. + it can return FALSE where it is feasible to make it return TRUE. + + The cause is as follows: Some of the tables are already known to be + const tables (the detection code is in make_join_statistics(), + above the update_ref_and_keys() call), but we didn't propagate + information about this: TABLE::const_table is not set to TRUE, and + Item::update_used_tables() hasn't been called for each item. + The result of this is that we're missing some 'ref' accesses. + TODO: OptimizerTeam: Fix this + */ + if (!new_fields->val->const_item()) { /* If the value matches, we can use the key reference. @@ -2449,7 +2461,8 @@ merge_key_fields(KEY_FIELD *start,KEY_FIELD *new_fields,KEY_FIELD *end, new_fields->null_rejecting); } else if (old->eq_func && new_fields->eq_func && - (old->val->is_null() || new_fields->val->is_null())) + ((old->val->const_item() && old->val->is_null()) || + new_fields->val->is_null())) { /* field = expression OR field IS NULL */ old->level= and_level; |