diff options
Diffstat (limited to 'sql')
| -rw-r--r-- | sql/sql_select.cc | 27 |
1 files changed, 25 insertions, 2 deletions
diff --git a/sql/sql_select.cc b/sql/sql_select.cc index 4fa469ce652..860b41731b1 100644 --- a/sql/sql_select.cc +++ b/sql/sql_select.cc @@ -11767,17 +11767,40 @@ evaluate_join_record(JOIN *join, JOIN_TAB *join_tab, first_unmatched->found= 1; for (JOIN_TAB *tab= first_unmatched; tab <= join_tab; tab++) { - if (tab->table->reginfo.not_exists_optimize) - return NESTED_LOOP_NO_MORE_ROWS; /* Check all predicates that has just been activated. */ /* Actually all predicates non-guarded by first_unmatched->found will be re-evaluated again. It could be fixed, but, probably, it's not worth doing now. */ + /* + not_exists_optimize has been created from a + select_cond containing 'is_null'. This 'is_null' + predicate is still present on any 'tab' with + 'not_exists_optimize'. Furthermore, the usual rules + for condition guards also applies for + 'not_exists_optimize' -> When 'is_null==false' we + know all cond. guards are open and we can apply + the 'not_exists_optimize'. + */ + DBUG_ASSERT(!(tab->table->reginfo.not_exists_optimize && + !tab->select_cond)); + if (tab->select_cond && !tab->select_cond->val_int()) { /* The condition attached to table tab is false */ + + if (tab->table->reginfo.not_exists_optimize) + { + /* + When not_exists_optimize is set: No need to further + explore more rows of 'tab' for this partial result. + Any found 'tab' matches are known to evaluate to 'false'. + Returning .._NO_MORE_ROWS will skip rem. 'tab' rows. + */ + return NESTED_LOOP_NO_MORE_ROWS; + } + if (tab == join_tab) found= 0; else |