From 1a48dd4e2bf0c6353bbf76b1f9b768620e0aa090 Mon Sep 17 00:00:00 2001 From: Georgi Kodinov Date: Wed, 7 Oct 2009 18:03:42 +0300 Subject: [PATCH] Bug #43029: FORCE INDEX FOR ORDER BY is ignored when join buffering is used FORCE INDEX FOR ORDER BY now prevents the optimizer from using join buffering. As a result the optimizer can use indexed access on the first table and doesn't need to sort the complete resultset at the end of the statement. --- mysql-test/r/order_by.result | 31 +++++++++++++++++++++++++++++++ mysql-test/t/order_by.test | 32 ++++++++++++++++++++++++++++++++ sql/sql_base.cc | 6 ++++-- sql/sql_parse.cc | 1 + sql/sql_select.cc | 19 ++++++++++++++----- sql/sql_select.h | 2 ++ sql/table.cc | 25 ++++++++++++++++++++----- sql/table.h | 12 ++++++++++++ 8 files changed, 116 insertions(+), 12 deletions(-) diff --git a/mysql-test/r/order_by.result b/mysql-test/r/order_by.result index 306fce1f3c2..0c72f816c21 100644 --- a/mysql-test/r/order_by.result +++ b/mysql-test/r/order_by.result @@ -1557,3 +1557,34 @@ a 2001 1991 DROP TABLE t1; +# +# Bug #43029: FORCE INDEX FOR ORDER BY is ignored when join buffering +# is used +# +CREATE TABLE t1 (a INT, b INT, KEY (a)); +INSERT INTO t1 VALUES (0, NULL), (1, NULL), (2, NULL), (3, NULL); +INSERT INTO t1 SELECT a+4, b FROM t1; +INSERT INTO t1 SELECT a+8, b FROM t1; +CREATE TABLE t2 (a INT, b INT); +INSERT INTO t2 VALUES (0,NULL), (1,NULL), (2,NULL), (3,NULL), (4,NULL); +INSERT INTO t2 SELECT a+4, b FROM t2; +# shouldn't have "using filesort" +EXPLAIN +SELECT * FROM t1 FORCE INDEX FOR ORDER BY (a), t2 WHERE t1.a < 2 ORDER BY t1.a; +id select_type table type possible_keys key key_len ref rows Extra +1 SIMPLE t1 range a a 5 NULL 2 Using where +1 SIMPLE t2 ALL NULL NULL NULL NULL 10 +# should have "using filesort" +EXPLAIN +SELECT * FROM t1 USE INDEX FOR ORDER BY (a), t2 WHERE t1.a < 2 ORDER BY t1.a; +id select_type table type possible_keys key key_len ref rows Extra +1 SIMPLE t1 range a a 5 NULL 2 Using where; Using temporary; Using filesort +1 SIMPLE t2 ALL NULL NULL NULL NULL 10 Using join buffer +# should have "using filesort" +EXPLAIN +SELECT * FROM t1 FORCE INDEX FOR JOIN (a), t2 WHERE t1.a < 2 ORDER BY t1.a; +id select_type table type possible_keys key key_len ref rows Extra +1 SIMPLE t1 range a a 5 NULL 2 Using where; Using temporary; Using filesort +1 SIMPLE t2 ALL NULL NULL NULL NULL 10 Using join buffer +DROP TABLE t1, t2; +End of 5.1 tests diff --git a/mysql-test/t/order_by.test b/mysql-test/t/order_by.test index cca1e3209cc..ac2bbaaeeac 100644 --- a/mysql-test/t/order_by.test +++ b/mysql-test/t/order_by.test @@ -1402,3 +1402,35 @@ SELECT DISTINCT a FROM t1 WHERE b = 1 ORDER BY c DESC LIMIT 0, 9; SELECT DISTINCT a FROM t1 WHERE b = 1 ORDER BY c DESC LIMIT 0, 9; DROP TABLE t1; + +--echo # +--echo # Bug #43029: FORCE INDEX FOR ORDER BY is ignored when join buffering +--echo # is used +--echo # + +CREATE TABLE t1 (a INT, b INT, KEY (a)); + +INSERT INTO t1 VALUES (0, NULL), (1, NULL), (2, NULL), (3, NULL); +INSERT INTO t1 SELECT a+4, b FROM t1; +INSERT INTO t1 SELECT a+8, b FROM t1; + +CREATE TABLE t2 (a INT, b INT); + +INSERT INTO t2 VALUES (0,NULL), (1,NULL), (2,NULL), (3,NULL), (4,NULL); +INSERT INTO t2 SELECT a+4, b FROM t2; + +--echo # shouldn't have "using filesort" +EXPLAIN +SELECT * FROM t1 FORCE INDEX FOR ORDER BY (a), t2 WHERE t1.a < 2 ORDER BY t1.a; + +--echo # should have "using filesort" +EXPLAIN +SELECT * FROM t1 USE INDEX FOR ORDER BY (a), t2 WHERE t1.a < 2 ORDER BY t1.a; + +--echo # should have "using filesort" +EXPLAIN +SELECT * FROM t1 FORCE INDEX FOR JOIN (a), t2 WHERE t1.a < 2 ORDER BY t1.a; + +DROP TABLE t1, t2; + +--echo End of 5.1 tests diff --git a/sql/sql_base.cc b/sql/sql_base.cc index d1e96fcdbb3..e706bd04ea6 100644 --- a/sql/sql_base.cc +++ b/sql/sql_base.cc @@ -2305,7 +2305,8 @@ bool reopen_name_locked_table(THD* thd, TABLE_LIST* table_list, bool link_in) table->tablenr=thd->current_tablenr++; table->used_fields=0; table->const_table=0; - table->null_row= table->maybe_null= table->force_index= 0; + table->null_row= table->maybe_null= 0; + table->force_index= table->force_index_order= table->force_index_group= 0; table->status=STATUS_NO_RECORD; DBUG_RETURN(FALSE); } @@ -2963,7 +2964,8 @@ TABLE *open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root, table->tablenr=thd->current_tablenr++; table->used_fields=0; table->const_table=0; - table->null_row= table->maybe_null= table->force_index= 0; + table->null_row= table->maybe_null= 0; + table->force_index= table->force_index_order= table->force_index_group= 0; table->status=STATUS_NO_RECORD; table->insert_values= 0; table->fulltext_searched= 0; diff --git a/sql/sql_parse.cc b/sql/sql_parse.cc index 83ef525e3eb..27688e41d4f 100644 --- a/sql/sql_parse.cc +++ b/sql/sql_parse.cc @@ -6258,6 +6258,7 @@ TABLE_LIST *st_select_lex::add_table_to_list(THD *thd, ptr->table_name_length=table->table.length; ptr->lock_type= lock_type; ptr->updating= test(table_options & TL_OPTION_UPDATING); + /* TODO: remove TL_OPTION_FORCE_INDEX as it looks like it's not used */ ptr->force_index= test(table_options & TL_OPTION_FORCE_INDEX); ptr->ignore_leaves= test(table_options & TL_OPTION_IGNORE_LEAVES); ptr->derived= table->sel; diff --git a/sql/sql_select.cc b/sql/sql_select.cc index 3f1432914a0..9dacb2c2ce4 100644 --- a/sql/sql_select.cc +++ b/sql/sql_select.cc @@ -1231,13 +1231,22 @@ JOIN::optimize() (!group_list && tmp_table_param.sum_func_count)) order=0; - // Can't use sort on head table if using row cache + // Can't use sort on head table if using join buffering if (full_join) { - if (group_list) - simple_group=0; - if (order) - simple_order=0; + TABLE *stable= (sort_by_table == (TABLE *) 1 ? + join_tab[const_tables].table : sort_by_table); + /* + FORCE INDEX FOR ORDER BY can be used to prevent join buffering when + sorting on the first table. + */ + if (!stable || !stable->force_index_order) + { + if (group_list) + simple_group= 0; + if (order) + simple_order= 0; + } } /* diff --git a/sql/sql_select.h b/sql/sql_select.h index a0366d47149..3f06b402638 100644 --- a/sql/sql_select.h +++ b/sql/sql_select.h @@ -357,6 +357,8 @@ public: simple_xxxxx is set if ORDER/GROUP BY doesn't include any references to other tables than the first non-constant table in the JOIN. It's also set if ORDER/GROUP BY is empty. + Used for deciding for or against using a temporary table to compute + GROUP/ORDER BY. */ bool simple_order, simple_group; /** diff --git a/sql/table.cc b/sql/table.cc index 04f2a3fbcf8..d2538eb4d59 100644 --- a/sql/table.cc +++ b/sql/table.cc @@ -4637,7 +4637,8 @@ Item_subselect *TABLE_LIST::containing_subselect() (TABLE_LIST::index_hints). Using the information in this tagged list this function sets the members st_table::keys_in_use_for_query, st_table::keys_in_use_for_group_by, st_table::keys_in_use_for_order_by, - st_table::force_index and st_table::covering_keys. + st_table::force_index, st_table::force_index_order, + st_table::force_index_group and st_table::covering_keys. Current implementation of the runtime does not allow mixing FORCE INDEX and USE INDEX, so this is checked here. Then the FORCE INDEX list @@ -4765,14 +4766,28 @@ bool TABLE_LIST::process_index_hints(TABLE *tbl) } /* process FORCE INDEX as USE INDEX with a flag */ + if (!index_order[INDEX_HINT_FORCE].is_clear_all()) + { + tbl->force_index_order= TRUE; + index_order[INDEX_HINT_USE].merge(index_order[INDEX_HINT_FORCE]); + } + + if (!index_group[INDEX_HINT_FORCE].is_clear_all()) + { + tbl->force_index_group= TRUE; + index_group[INDEX_HINT_USE].merge(index_group[INDEX_HINT_FORCE]); + } + + /* + TODO: get rid of tbl->force_index (on if any FORCE INDEX is specified) and + create tbl->force_index_join instead. + Then use the correct force_index_XX instead of the global one. + */ if (!index_join[INDEX_HINT_FORCE].is_clear_all() || - !index_order[INDEX_HINT_FORCE].is_clear_all() || - !index_group[INDEX_HINT_FORCE].is_clear_all()) + tbl->force_index_group || tbl->force_index_order) { tbl->force_index= TRUE; index_join[INDEX_HINT_USE].merge(index_join[INDEX_HINT_FORCE]); - index_order[INDEX_HINT_USE].merge(index_order[INDEX_HINT_FORCE]); - index_group[INDEX_HINT_USE].merge(index_group[INDEX_HINT_FORCE]); } /* apply USE INDEX */ diff --git a/sql/table.h b/sql/table.h index 40372fa91cf..e4a382c799f 100644 --- a/sql/table.h +++ b/sql/table.h @@ -752,6 +752,18 @@ struct st_table { bytes, it would take up 4. */ my_bool force_index; + + /** + Flag set when the statement contains FORCE INDEX FOR ORDER BY + See TABLE_LIST::process_index_hints(). + */ + my_bool force_index_order; + + /** + Flag set when the statement contains FORCE INDEX FOR GROUP BY + See TABLE_LIST::process_index_hints(). + */ + my_bool force_index_group; my_bool distinct,const_table,no_rows; /**