diff options
Diffstat (limited to 'sql/sql_select.cc')
| -rw-r--r-- | sql/sql_select.cc | 26 |
1 files changed, 18 insertions, 8 deletions
diff --git a/sql/sql_select.cc b/sql/sql_select.cc index 164edacc932..2ef7aa13dd8 100644 --- a/sql/sql_select.cc +++ b/sql/sql_select.cc @@ -846,6 +846,7 @@ JOIN::optimize() "Impossible HAVING" : "Impossible WHERE")); zero_result_cause= having_value == Item::COND_FALSE ? "Impossible HAVING" : "Impossible WHERE"; + tables= 0; error= 0; DBUG_RETURN(0); } @@ -2187,11 +2188,12 @@ JOIN::exec() /* With EXPLAIN EXTENDED we have to restore original ref_array for a derived table which is always materialized. - Otherwise we would not be able to print the query correctly. + We also need to do this when we have temp table(s). + Otherwise we would not be able to print the query correctly. */ - if (items0 && - (thd->lex->describe & DESCRIBE_EXTENDED) && - select_lex->linkage == DERIVED_TABLE_TYPE) + if (items0 && (thd->lex->describe & DESCRIBE_EXTENDED) && + (select_lex->linkage == DERIVED_TABLE_TYPE || + exec_tmp_table1 || exec_tmp_table2)) set_items_ref_array(items0); DBUG_VOID_RETURN; @@ -6505,13 +6507,16 @@ make_join_readinfo(JOIN *join, ulonglong options) !(tab->select && tab->select->quick)) { // Only read index tree /* - See bug #26447: "Using the clustered index for a table scan - is always faster than using a secondary index". - */ + It has turned out that the below change, while speeding things + up for disk-bound loads, slows them down for cases when the data + is in disk cache (see BUG#35850): + // See bug #26447: "Using the clustered index for a table scan + // is always faster than using a secondary index". if (table->s->primary_key != MAX_KEY && table->file->primary_key_is_clustered()) tab->index= table->s->primary_key; else + */ tab->index=find_shortest_key(table, & table->covering_keys); tab->read_first_record= join_read_first; tab->type=JT_NEXT; // Read with index_first / index_next @@ -12966,6 +12971,7 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit, uint tablenr= tab - join->join_tab; ha_rows table_records= table->file->stats.records; bool group= join->group && order == join->group_list; + ha_rows ref_key_quick_rows= HA_POS_ERROR; LINT_INIT(best_key_parts); LINT_INIT(best_key_direction); LINT_INIT(best_records); @@ -12999,6 +13005,9 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit, else keys= usable_keys; + if (ref_key >= 0 && table->covering_keys.is_set(ref_key)) + ref_key_quick_rows= table->quick_rows[ref_key]; + read_time= join->best_positions[tablenr].read_time; for (uint i= tablenr+1; i < join->tables; i++) fanout*= join->best_positions[i].records_read; // fanout is always >= 1 @@ -13093,7 +13102,8 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit, index_scan_time < read_time) { ha_rows quick_records= table_records; - if (is_best_covering && !is_covering) + if (is_best_covering && !is_covering || + is_covering && ref_key_quick_rows < select_limit) continue; if (table->quick_keys.is_set(nr)) quick_records= table->quick_rows[nr]; |