From d51f96b16754cad5d2c9a91bb5b5e0673e59ded0 Mon Sep 17 00:00:00 2001 From: unknown Date: Thu, 17 Jan 2013 16:08:05 +0200 Subject: [PATCH] MDEV-3900 Optimizer difference between MySQL and MariaDB with stored functions in WHERE clause of UPDATE or DELETE statements Analysis The reason for the less efficient plan was result of a prior design decision - to limit the eveluation of constant expressions during optimization to only non-expensive ones. With this approach all stored procedures were considered expensive, and were not evaluated during optimization. As a result, SPs didn't participate in range optimization, which resulted in a plan with table scan rather than index range scan. Solution Instead of considering all SPs expensive, consider expensive only those SPs that are non-deterministic. If an SP is deterministic, the optimizer will checj if it is constant, and may eventually evaluate it during optimization. --- mysql-test/r/sp.result | 36 +++++++++++++++++++++++++++++++++--- mysql-test/t/sp.test | 19 +++++++++++++++++++ sql/item_func.cc | 13 +++++++++++++ sql/item_func.h | 5 +++-- 4 files changed, 68 insertions(+), 5 deletions(-) diff --git a/mysql-test/r/sp.result b/mysql-test/r/sp.result index 454be15a1ad..cc5a1f6f65a 100644 --- a/mysql-test/r/sp.result +++ b/mysql-test/r/sp.result @@ -6420,16 +6420,16 @@ id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref c1 c1 5 const 1 Using index EXPLAIN SELECT * FROM t1 WHERE c1=f1(); id select_type table type possible_keys key key_len ref rows Extra -1 SIMPLE t1 ref c1 c1 5 const 0 Using index +1 SIMPLE t1 ref c1 c1 5 const 1 Using index EXPLAIN SELECT * FROM v1 WHERE c1=1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref c1 c1 5 const 1 Using index EXPLAIN SELECT * FROM v1 WHERE c1=f1(); id select_type table type possible_keys key key_len ref rows Extra -1 SIMPLE t1 ref c1 c1 5 const 0 Using index +1 SIMPLE t1 ref c1 c1 5 const 1 Using index EXPLAIN SELECT * FROM t1 WHERE c1=f2(10); id select_type table type possible_keys key key_len ref rows Extra -1 SIMPLE t1 ref c1 c1 5 const 0 Using index +1 SIMPLE t1 ref c1 c1 5 const 1 Using index EXPLAIN SELECT * FROM t1 WHERE c1=f2(c1); id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL c1 5 NULL 5 Using where; Using index @@ -7146,3 +7146,33 @@ c1 c2 count(c3) 2012-03-01 01:00:00 3 1 2012-03-01 02:00:00 3 1 DROP PROCEDURE p1; + +MDEV-3900 Optimizer difference between MySQL and MariaDB with stored functions in WHERE clause of UPDATE or DELETE statements + +CREATE FUNCTION tdn() RETURNS int(7) DETERMINISTIC RETURN to_days(now()); +CREATE TABLE t1 (pk INT NOT NULL AUTO_INCREMENT PRIMARY KEY, daynum INT, a CHAR(1), INDEX(daynum), INDEX(a)) ENGINE=MyISAM; +INSERT INTO t1 (daynum) VALUES (1),(2),(3),(4),(5),(TO_DAYS(NOW())),(7),(8); +INSERT INTO t1 (daynum) SELECT a1.daynum FROM t1 a1, t1 a2, t1 a3, t1 a4, t1 a5; +FLUSH TABLES; +FLUSH STATUS; +SHOW STATUS LIKE '%Handler_read%'; +Variable_name Value +Handler_read_first 0 +Handler_read_key 0 +Handler_read_next 0 +Handler_read_prev 0 +Handler_read_rnd 0 +Handler_read_rnd_deleted 0 +Handler_read_rnd_next 0 +UPDATE t1 SET a = '+' WHERE daynum=tdn(); +SHOW STATUS LIKE '%Handler_read%'; +Variable_name Value +Handler_read_first 0 +Handler_read_key 2 +Handler_read_next 4097 +Handler_read_prev 0 +Handler_read_rnd 0 +Handler_read_rnd_deleted 0 +Handler_read_rnd_next 0 +drop function tdn; +drop table t1; diff --git a/mysql-test/t/sp.test b/mysql-test/t/sp.test index dcfbe127f8a..0fce174ecb7 100644 --- a/mysql-test/t/sp.test +++ b/mysql-test/t/sp.test @@ -8478,3 +8478,22 @@ CALL p1(1); DROP PROCEDURE p1; +--echo +--echo MDEV-3900 Optimizer difference between MySQL and MariaDB with stored functions in WHERE clause of UPDATE or DELETE statements +--echo + +CREATE FUNCTION tdn() RETURNS int(7) DETERMINISTIC RETURN to_days(now()); + +CREATE TABLE t1 (pk INT NOT NULL AUTO_INCREMENT PRIMARY KEY, daynum INT, a CHAR(1), INDEX(daynum), INDEX(a)) ENGINE=MyISAM; +INSERT INTO t1 (daynum) VALUES (1),(2),(3),(4),(5),(TO_DAYS(NOW())),(7),(8); +INSERT INTO t1 (daynum) SELECT a1.daynum FROM t1 a1, t1 a2, t1 a3, t1 a4, t1 a5; + +FLUSH TABLES; +FLUSH STATUS; + +SHOW STATUS LIKE '%Handler_read%'; +UPDATE t1 SET a = '+' WHERE daynum=tdn(); +SHOW STATUS LIKE '%Handler_read%'; + +drop function tdn; +drop table t1; diff --git a/sql/item_func.cc b/sql/item_func.cc index 18d0ce3a822..c1767fb71ca 100644 --- a/sql/item_func.cc +++ b/sql/item_func.cc @@ -6056,6 +6056,19 @@ Item_func_sp::init_result_field(THD *thd) } +/** + @note + Deterministic stored procedures are considered inexpensive. + Consequently such procedures may be evaluated during optimization, + if they are constant (checked by the optimizer). +*/ + +bool Item_func_sp::is_expensive() +{ + return !(m_sp->m_chistics->detistic); +} + + /** @brief Initialize local members with values from the Field interface. diff --git a/sql/item_func.h b/sql/item_func.h index b144b393225..2db8ab76ffe 100644 --- a/sql/item_func.h +++ b/sql/item_func.h @@ -1807,7 +1807,8 @@ private: bool init_result_field(THD *thd); protected: - bool is_expensive_processor(uchar *arg) { return TRUE; } + bool is_expensive_processor(uchar *arg) + { return is_expensive(); } public: @@ -1881,7 +1882,7 @@ public: bool fix_fields(THD *thd, Item **ref); void fix_length_and_dec(void); - bool is_expensive() { return 1; } + bool is_expensive(); inline Field *get_sp_result_field() {