From e0dbec1ce38688e25cab3720044d6e7e676381f6 Mon Sep 17 00:00:00 2001 From: Sergei Petrunia Date: Fri, 2 Dec 2022 18:21:52 +0300 Subject: [PATCH] MDEV-29129: Performance regression starting in 10.6: select order by limit ... The cause of regression was handling for ROWNUM() function. For queries like SELECT ROWNUM() FROM ... ORDER BY ... ROWNUM() should be computed before the ORDER BY. The computation was moved to be before the ORDER BY for any entries in the select list that had RAND_TABLE_BIT set. This had a negative impact on queries in form: SELECT sp_func() FROM t1 ORDER BY ... LIMIT n where sp_func() is NOT declared as DETERMINISTIC (and so has RAND_TABLE_BIT set). The fix is to require evaluation for sorting only for the ROWNUM() function. Functions that just have RAND_TABLE_BIT() can be computed after ORDER BY ... LIMIT is applied. (think about a possible index that satisfies the ORDER BY clause. In that case, the the rows would be read in the needed order and we would stop after reading LIMIT rows, achieving the same effect). --- mysql-test/main/derived_view.result | 2 +- mysql-test/main/having.result | 6 ++--- mysql-test/main/show_explain.result | 6 ++--- mysql-test/main/sp.result | 40 +++++++++++++++++++++++++++++ mysql-test/main/sp.test | 37 ++++++++++++++++++++++++++ mysql-test/main/user_var.result | 4 +-- sql/sql_base.cc | 2 ++ sql/sql_lex.cc | 2 ++ sql/sql_lex.h | 3 +++ sql/sql_select.cc | 4 +-- sql/sql_select.h | 5 ---- 11 files changed, 94 insertions(+), 17 deletions(-) diff --git a/mysql-test/main/derived_view.result b/mysql-test/main/derived_view.result index 50f6d381dd6..15a7784c890 100644 --- a/mysql-test/main/derived_view.result +++ b/mysql-test/main/derived_view.result @@ -2696,7 +2696,7 @@ ON p.id = g.p_random ORDER BY gallery_name ASC ; id select_type table type possible_keys key key_len ref rows Extra -1 PRIMARY ALL NULL NULL NULL NULL 10 Using temporary; Using filesort +1 PRIMARY ALL NULL NULL NULL NULL 10 Using filesort 1 PRIMARY p eq_ref PRIMARY PRIMARY 4 g.p_random 1 Using where 2 DERIVED gal ALL NULL NULL NULL NULL 10 3 DEPENDENT SUBQUERY pi ref gallery_id gallery_id 4 test.gal.id 4 Using temporary; Using filesort diff --git a/mysql-test/main/having.result b/mysql-test/main/having.result index ac26d69543d..d7cbadd5e75 100644 --- a/mysql-test/main/having.result +++ b/mysql-test/main/having.result @@ -834,13 +834,13 @@ test.t1 analyze status Engine-independent statistics collected test.t1 analyze status OK explain SELECT t, next_seq_value() r FROM t1 FORCE INDEX(t) GROUP BY t HAVING r = 1 ORDER BY t1.u; id select_type table type possible_keys key key_len ref rows Extra -1 SIMPLE t1 ALL NULL NULL NULL NULL 8 Using temporary; Using filesort +1 SIMPLE t1 index NULL t 5 NULL 8 Using temporary; Using filesort SELECT t, next_seq_value() r FROM t1 FORCE INDEX(t) GROUP BY t HAVING r = 1 ORDER BY t1.u; t r 10 1 12 1 -14 1 -16 1 +15 1 +17 1 DROP TABLE t1; DROP FUNCTION next_seq_value; DROP TABLE series; diff --git a/mysql-test/main/show_explain.result b/mysql-test/main/show_explain.result index 317a12ef311..6ad93930448 100644 --- a/mysql-test/main/show_explain.result +++ b/mysql-test/main/show_explain.result @@ -1007,7 +1007,7 @@ SELECT a+SLEEP(0.01) FROM t1 WHERE a IN ( 255, 0 ) OR b BETWEEN 6 AND 129 ORDER BY b; id select_type table type possible_keys key key_len ref rows Extra -1 SIMPLE t1 index_merge a,b a,b 5,5 NULL 8 Using sort_union(a,b); Using where; Using temporary; Using filesort +1 SIMPLE t1 index_merge a,b a,b 5,5 NULL 8 Using sort_union(a,b); Using where; Using filesort set @show_explain_probe_select_id=1; SET debug_dbug='+d,show_explain_probe_join_exec_start'; SELECT a+SLEEP(0.01) FROM t1 @@ -1016,7 +1016,7 @@ ORDER BY b; connection default; show explain for $thr2; id select_type table type possible_keys key key_len ref rows Extra -1 SIMPLE t1 index_merge a,b a,b 5,5 NULL 8 Using sort_union(a,b); Using where; Using temporary; Using filesort +1 SIMPLE t1 index_merge a,b a,b 5,5 NULL 8 Using sort_union(a,b); Using where; Using filesort Warnings: Note 1003 SELECT a+SLEEP(0.01) FROM t1 WHERE a IN ( 255, 0 ) OR b BETWEEN 6 AND 129 @@ -1039,7 +1039,7 @@ ORDER BY b; connection default; show explain for $thr2; id select_type table type possible_keys key key_len ref rows Extra -1 SIMPLE t1 index_merge a,b a,b 5,5 NULL 8 Using sort_union(a,b); Using where; Using temporary; Using filesort +1 SIMPLE t1 index_merge a,b a,b 5,5 NULL 8 Using sort_union(a,b); Using where; Using filesort Warnings: Note 1003 SELECT a+SLEEP(0.01) FROM t1 WHERE a IN ( 255, 0 ) OR b BETWEEN 6 AND 129 diff --git a/mysql-test/main/sp.result b/mysql-test/main/sp.result index b14551d35c7..88df800b0e0 100644 --- a/mysql-test/main/sp.result +++ b/mysql-test/main/sp.result @@ -8932,3 +8932,43 @@ ERROR 42000: PROCEDURE does not support subqueries or stored functions DROP TABLE t1; # End of 10.4 tests # +# +# MDEV-29129: Performance regression starting in 10.6: unlimited "select order by limit" +# +CREATE TABLE t1 ( +lookupId int primary key, +value varchar(255) +); +insert into t1 select seq, seq from seq_1_to_100; +# Note: the function is intentionally NOT declared as DETERMINISTIC +CREATE FUNCTION f1(LOOKUPID_IN INT) RETURNS varchar(255) CHARSET utf8 +BEGIN +DECLARE LOOKUP_VALUE VARCHAR(255); +SET LOOKUP_VALUE = (SELECT value FROM t1 WHERE lookupId = LOOKUPID_IN); +set @counter=@counter+1; +RETURN LOOKUP_VALUE; +END; +// +create table t2 ( +col1 int, +col2 int +); +insert into t2 select mod(seq,100), seq from seq_1_to_1000; +explain +select f1(col1) from t2 order by col2 desc limit 5; +id select_type table type possible_keys key key_len ref rows Extra +1 SIMPLE t2 ALL NULL NULL NULL NULL 1000 Using filesort +set @counter=0; +select f1(col1) from t2 order by col2 desc limit 5; +f1(col1) +NULL +99 +98 +97 +96 +# Must show 5, not 1000: +select @counter; +@counter +5 +drop function f1; +drop table t1,t2; diff --git a/mysql-test/main/sp.test b/mysql-test/main/sp.test index b71cfe11d58..baf89eeaba5 100644 --- a/mysql-test/main/sp.test +++ b/mysql-test/main/sp.test @@ -10519,3 +10519,40 @@ DROP TABLE t1; --echo # End of 10.4 tests --echo # + +--echo # +--echo # MDEV-29129: Performance regression starting in 10.6: unlimited "select order by limit" +--echo # + +CREATE TABLE t1 ( + lookupId int primary key, + value varchar(255) +); +insert into t1 select seq, seq from seq_1_to_100; + +-- echo # Note: the function is intentionally NOT declared as DETERMINISTIC +delimiter //; +CREATE FUNCTION f1(LOOKUPID_IN INT) RETURNS varchar(255) CHARSET utf8 +BEGIN + DECLARE LOOKUP_VALUE VARCHAR(255); + SET LOOKUP_VALUE = (SELECT value FROM t1 WHERE lookupId = LOOKUPID_IN); + set @counter=@counter+1; + RETURN LOOKUP_VALUE; +END; +// +delimiter ;// + +create table t2 ( + col1 int, + col2 int +); +insert into t2 select mod(seq,100), seq from seq_1_to_1000; + +explain +select f1(col1) from t2 order by col2 desc limit 5; +set @counter=0; +select f1(col1) from t2 order by col2 desc limit 5; +--echo # Must show 5, not 1000: +select @counter; +drop function f1; +drop table t1,t2; diff --git a/mysql-test/main/user_var.result b/mysql-test/main/user_var.result index 924c252b951..a5837996c19 100644 --- a/mysql-test/main/user_var.result +++ b/mysql-test/main/user_var.result @@ -372,14 +372,14 @@ insert into t1 (b) values (10), (30), (10), (10); set @var := 0; explain select if(b=@var, 999, b) , @var := b from t1 order by b; id select_type table type possible_keys key key_len ref rows Extra -1 SIMPLE t1 ALL NULL NULL NULL NULL 4 Using temporary; Using filesort +1 SIMPLE t1 ALL NULL NULL NULL NULL 4 Using filesort set @var := 0; select if(b=@var, 999, b) , @var := b from t1 order by b; if(b=@var, 999, b) @var := b 10 10 -10 10 30 30 999 10 +999 10 drop table t1; create temporary table t1 (id int); insert into t1 values (2), (3), (3), (4); diff --git a/sql/sql_base.cc b/sql/sql_base.cc index dfca2500d6d..5de9782fd09 100644 --- a/sql/sql_base.cc +++ b/sql/sql_base.cc @@ -7738,6 +7738,8 @@ bool setup_fields(THD *thd, Ref_ptr_array ref_pointer_array, thd->lex->current_select->select_list_tables|= item->used_tables(); thd->lex->used_tables|= item->used_tables(); thd->lex->current_select->cur_pos_in_select_list++; + + thd->lex->current_select->rownum_in_field_list |= item->with_rownum_func(); } thd->lex->current_select->is_item_list_lookup= save_is_item_list_lookup; thd->lex->current_select->cur_pos_in_select_list= UNDEF_POS; diff --git a/sql/sql_lex.cc b/sql/sql_lex.cc index 520982f93b6..b743141598f 100644 --- a/sql/sql_lex.cc +++ b/sql/sql_lex.cc @@ -3002,6 +3002,8 @@ void st_select_lex::init_query() prep_leaf_list_state= UNINIT; bzero((char*) expr_cache_may_be_used, sizeof(expr_cache_may_be_used)); select_list_tables= 0; + rownum_in_field_list= 0; + window_specs.empty(); window_funcs.empty(); tvc= 0; diff --git a/sql/sql_lex.h b/sql/sql_lex.h index e4fe1465c57..82453ad8259 100644 --- a/sql/sql_lex.h +++ b/sql/sql_lex.h @@ -1344,6 +1344,9 @@ public: */ table_map select_list_tables; + /* Set to 1 if any field in field list has ROWNUM() */ + bool rownum_in_field_list; + /* namp of nesting SELECT visibility (for aggregate functions check) */ nesting_map name_visibility_map; table_map with_dep; diff --git a/sql/sql_select.cc b/sql/sql_select.cc index 60b2641e670..446f6e83b0d 100644 --- a/sql/sql_select.cc +++ b/sql/sql_select.cc @@ -434,7 +434,6 @@ void JOIN::init(THD *thd_arg, List &fields_arg, no_order= 0; simple_order= 0; simple_group= 0; - rand_table_in_field_list= 0; ordered_index_usage= ordered_index_void; need_distinct= 0; skip_sort_order= 0; @@ -1434,7 +1433,6 @@ JOIN::prepare(TABLE_LIST *tables_init, COND *conds_init, uint og_num, &all_fields, &select_lex->pre_fix, 1)) DBUG_RETURN(-1); thd->lex->current_select->context_analysis_place= save_place; - rand_table_in_field_list= select_lex->select_list_tables & RAND_TABLE_BIT; if (setup_without_group(thd, ref_ptrs, tables_list, select_lex->leaf_tables, fields_list, @@ -14807,7 +14805,7 @@ remove_const(JOIN *join,ORDER *first_order, COND *cond, and some wrong results so better to leave the code as it was related to ROLLUP. */ - *simple_order= !join->rand_table_in_field_list; + *simple_order= !join->select_lex->rownum_in_field_list; if (join->only_const_tables()) return change_list ? 0 : first_order; // No need to sort diff --git a/sql/sql_select.h b/sql/sql_select.h index c9e0fa25421..3332bc78b6c 100644 --- a/sql/sql_select.h +++ b/sql/sql_select.h @@ -1420,11 +1420,6 @@ public: GROUP/ORDER BY. */ bool simple_order, simple_group; - /* - Set to 1 if any field in field list has RAND_TABLE set. For example if - if one uses RAND() or ROWNUM() in field list - */ - bool rand_table_in_field_list; /* ordered_index_usage is set if an ordered index access