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MDEV-3900 Optimizer difference between MySQL and MariaDB with stored functions in WHERE clause of UPDATE or DELETE statements

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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.
This commit is contained in:
unknown
2013-01-17 16:08:05 +02:00
parent 8a296e6ca2
commit d51f96b167
4 changed files with 68 additions and 5 deletions
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36
mysql-test/r/sp.result
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@@ -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;

19
mysql-test/t/sp.test
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@@ -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;

13
sql/item_func.cc
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@@ -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.

5
sql/item_func.h
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@@ -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()
{