diff options
Diffstat (limited to 'sql/sql_lex.cc')
| -rw-r--r-- | sql/sql_lex.cc | 26 |
1 files changed, 24 insertions, 2 deletions
diff --git a/sql/sql_lex.cc b/sql/sql_lex.cc index 6fd6e53424f..fb5307f9e3a 100644 --- a/sql/sql_lex.cc +++ b/sql/sql_lex.cc @@ -3405,7 +3405,23 @@ bool st_select_lex::add_index_hint (THD *thd, char *str, uint length) } -bool st_select_lex::optimize_unflattened_subqueries() +/** + Optimize all subqueries that have not been flattened into semi-joins. + + @details + This functionality is a method of SELECT_LEX instead of JOIN because + SQL statements as DELETE/UPDATE do not have a corresponding JOIN object. + + @see JOIN::optimize_unflattened_subqueries + + @param const_only Restrict subquery optimization to constant subqueries + + @return Operation status + @retval FALSE success. + @retval TRUE error occurred. +*/ + +bool st_select_lex::optimize_unflattened_subqueries(bool const_only) { for (SELECT_LEX_UNIT *un= first_inner_unit(); un; un= un->next_unit()) { @@ -3415,11 +3431,17 @@ bool st_select_lex::optimize_unflattened_subqueries() { if (subquery_predicate->substype() == Item_subselect::IN_SUBS) { - Item_in_subselect *in_subs=(Item_in_subselect*)subquery_predicate; + Item_in_subselect *in_subs= (Item_in_subselect*) subquery_predicate; if (in_subs->is_jtbm_merged) continue; } + if (const_only && !subquery_predicate->const_item()) + { + /* Skip non-constant subqueries if the caller asked so. */ + continue; + } + bool empty_union_result= true; /* If the subquery is a UNION, optimize all the subqueries in the UNION. If |