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Fixed the bug mdev-7599.

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At some conditions the function opt_sum_query() can apply MIN/MAX
optimizations to to Item_sum objects of a select These optimizations
becomes invalid if this select is the subquery of an IN subquery
predicate that is converted to a EXISTS subquery. Thus in this case
the MIX/MAX optimizations that have been applied in opt_sum_query()
must be rolled back.
This bug appeared in 5.3 when the code for the cost base choice between
materialization and in-to-exists transformation of non-correlated
IN subqueries was introduced. Before this code in-to-exists
transformations were always performed before the call of opt_sum_query().
This commit is contained in:
Igor Babaev 2017-05-15 09:51:01 -07:00
parent 9495e018fb
commit e0352fb079
7 changed files with 124 additions and 0 deletions
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43
mysql-test/r/subselect_mat_cost_bugs.result
View File

@ -379,6 +379,7 @@ drop table t3, t4, t5;
#
# LP BUG#858038 The result of a query with NOT IN subquery depends on the state of the optimizer switch
#
set @optimizer_switch_save= @@optimizer_switch;
create table t1 (c1 char(2) not null, c2 char(2));
create table t2 (c3 char(2), c4 char(2));
insert into t1 values ('a1', 'b1');
@ -400,6 +401,7 @@ id select_type table type possible_keys key key_len ref rows Extra
select * from t1 where c1 = 'a2' and (c1, c2) not in (select * from t2);
c1 c2
drop table t1, t2;
set optimizer_switch= @optimizer_switch_save;
#
# MDEV-12673: cost-based choice between materialization and in-to-exists
#
@ -442,3 +444,44 @@ id select_type table type possible_keys key key_len ref rows Extra
2 DEPENDENT SUBQUERY t3 const PRIMARY PRIMARY 4 const 1
2 DEPENDENT SUBQUERY t2 index NULL i2 11 NULL 2 Using where; Using index
DROP TABLE t1,t2,t3;
#
# MDEV-7599: in-to-exists chosen after min/max optimization
#
set @optimizer_switch_save= @@optimizer_switch;
CREATE TABLE t1 (a INT, KEY(a)) ENGINE=MyISAM;
INSERT INTO t1 VALUES (1),(2);
CREATE TABLE t2 (b INT, c INT) ENGINE=MyISAM;
INSERT INTO t2 VALUES (1,6),(2,4), (8,9);
SELECT * FROM t2 WHERE b != ALL (SELECT MIN(a) FROM t1, t2 WHERE t2.c = t2.b);
b c
EXPLAIN EXTENDED SELECT * FROM t2 WHERE b != ALL (SELECT MIN(a) FROM t1, t2 WHERE t2.c = t2.b);
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t2 ALL NULL NULL NULL NULL 3 100.00 Using where
2 MATERIALIZED t1 index NULL a 5 NULL 2 100.00 Using index
2 MATERIALIZED t2 ALL NULL NULL NULL NULL 3 100.00 Using where; Using join buffer (flat, BNL join)
Warnings:
Note 1003 select `test`.`t2`.`b` AS `b`,`test`.`t2`.`c` AS `c` from `test`.`t2` where (not(<expr_cache><`test`.`t2`.`b`>(<in_optimizer>(`test`.`t2`.`b`,`test`.`t2`.`b` in ( <materialize> (select min(`test`.`t1`.`a`) from `test`.`t1` join `test`.`t2` where (`test`.`t2`.`c` = `test`.`t2`.`b`) ), <primary_index_lookup>(`test`.`t2`.`b` in <temporary table> on distinct_key where ((`test`.`t2`.`b` = `<subquery2>`.`MIN(a)`))))))))
set optimizer_switch= 'materialization=off';
SELECT * FROM t2 WHERE b != ALL (SELECT MIN(a) FROM t1, t2 WHERE t2.c = t2.b);
b c
EXPLAIN EXTENDED SELECT * FROM t2 WHERE b != ALL (SELECT MIN(a) FROM t1, t2 WHERE t2.c = t2.b);
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t2 ALL NULL NULL NULL NULL 3 100.00 Using where
2 DEPENDENT SUBQUERY t1 index NULL a 5 NULL 2 100.00 Using index
2 DEPENDENT SUBQUERY t2 ALL NULL NULL NULL NULL 3 100.00 Using where; Using join buffer (flat, BNL join)
Warnings:
Note 1003 select `test`.`t2`.`b` AS `b`,`test`.`t2`.`c` AS `c` from `test`.`t2` where (not(<expr_cache><`test`.`t2`.`b`>(<in_optimizer>(`test`.`t2`.`b`,<exists>(select min(`test`.`t1`.`a`) from `test`.`t1` join `test`.`t2` where (`test`.`t2`.`c` = `test`.`t2`.`b`) having trigcond((<cache>(`test`.`t2`.`b`) = <ref_null_helper>(min(`test`.`t1`.`a`)))))))))
set optimizer_switch= @optimizer_switch_save;
DROP TABLE t1,t2;
CREATE TABLE t1 (f1 varchar(10)) ENGINE=MyISAM;
INSERT INTO t1 VALUES ('foo'),('bar');
CREATE TABLE t2 (f2 varchar(10), key(f2)) ENGINE=MyISAM;
INSERT INTO t2 VALUES ('baz'),('qux');
CREATE TABLE t3 (f3 varchar(10)) ENGINE=MyISAM;
INSERT INTO t3 VALUES ('abc'),('def');
SELECT * FROM t1
WHERE f1 = ALL( SELECT MAX(t2a.f2)
FROM t2 AS t2a INNER JOIN t2 t2b INNER JOIN t3
ON (f3 = t2b.f2) );
f1
DROP TABLE t1,t2,t3;

44
mysql-test/t/subselect_mat_cost_bugs.test
View File

@ -406,6 +406,8 @@ drop table t3, t4, t5;
--echo # LP BUG#858038 The result of a query with NOT IN subquery depends on the state of the optimizer switch
--echo #
set @optimizer_switch_save= @@optimizer_switch;
create table t1 (c1 char(2) not null, c2 char(2));
create table t2 (c3 char(2), c4 char(2));
@ -425,6 +427,8 @@ select * from t1 where c1 = 'a2' and (c1, c2) not in (select * from t2);
drop table t1, t2;
set optimizer_switch= @optimizer_switch_save;
--echo #
--echo # MDEV-12673: cost-based choice between materialization and in-to-exists
--echo #
@ -463,3 +467,43 @@ SELECT * FROM t1 WHERE i1 NOT IN (
);
DROP TABLE t1,t2,t3;
--echo #
--echo # MDEV-7599: in-to-exists chosen after min/max optimization
--echo #
set @optimizer_switch_save= @@optimizer_switch;
CREATE TABLE t1 (a INT, KEY(a)) ENGINE=MyISAM;
INSERT INTO t1 VALUES (1),(2);
CREATE TABLE t2 (b INT, c INT) ENGINE=MyISAM;
INSERT INTO t2 VALUES (1,6),(2,4), (8,9);
let $q=
SELECT * FROM t2 WHERE b != ALL (SELECT MIN(a) FROM t1, t2 WHERE t2.c = t2.b);
eval $q;
eval EXPLAIN EXTENDED $q;
set optimizer_switch= 'materialization=off';
eval $q;
eval EXPLAIN EXTENDED $q;
set optimizer_switch= @optimizer_switch_save;
DROP TABLE t1,t2;
CREATE TABLE t1 (f1 varchar(10)) ENGINE=MyISAM;
INSERT INTO t1 VALUES ('foo'),('bar');
CREATE TABLE t2 (f2 varchar(10), key(f2)) ENGINE=MyISAM;
INSERT INTO t2 VALUES ('baz'),('qux');
CREATE TABLE t3 (f3 varchar(10)) ENGINE=MyISAM;
INSERT INTO t3 VALUES ('abc'),('def');
SELECT * FROM t1
WHERE f1 = ALL( SELECT MAX(t2a.f2)
FROM t2 AS t2a INNER JOIN t2 t2b INNER JOIN t3
ON (f3 = t2b.f2) );
DROP TABLE t1,t2,t3;

21
sql/item_subselect.cc
View File

@ -2493,6 +2493,27 @@ bool Item_in_subselect::inject_in_to_exists_cond(JOIN *join_arg)
DBUG_ENTER("Item_in_subselect::inject_in_to_exists_cond");
DBUG_ASSERT(thd == join_arg->thd);
if (select_lex->min_max_opt_list.elements)
{
/*
MIN/MAX optimizations have been applied to Item_sum objects
of the subquery this subquery predicate in opt_sum_query().
Injection of new condition invalidates this optimizations.
Thus those optimizations must be rolled back.
*/
List_iterator_fast<Item_sum> it(select_lex->min_max_opt_list);
Item_sum *item;
while ((item= it++))
{
item->clear();
item->reset_forced_const();
}
if (where_item)
where_item->update_used_tables();
if (having_item)
having_item->update_used_tables();
}
if (where_item)
{
List<Item> *and_args= NULL;

1
sql/item_sum.h
View File

@ -454,6 +454,7 @@ public:
used_tables_cache= 0;
forced_const= TRUE;
}
void reset_forced_const() { forced_const= FALSE; }
virtual bool const_item() const { return forced_const; }
virtual bool const_during_execution() const { return false; }
virtual void print(String *str, enum_query_type query_type);

9
sql/opt_sum.cc
View File

@ -253,6 +253,8 @@ int opt_sum_query(THD *thd,
int error= 0;
DBUG_ENTER("opt_sum_query");
thd->lex->current_select->min_max_opt_list.empty();
if (conds)
where_tables= conds->used_tables();
@ -444,7 +446,14 @@ int opt_sum_query(THD *thd,
item_sum->aggregator_clear();
}
else
{
item_sum->reset_and_add();
/*
Save a reference to the item for possible rollback
of the min/max optimizations for this select
*/
thd->lex->current_select->min_max_opt_list.push_back(item_sum);
}
item_sum->make_const();
recalc_const_item= 1;
break;

1
sql/sql_lex.cc
View File

@ -1875,6 +1875,7 @@ void st_select_lex::init_query()
leaf_tables_prep.empty();
leaf_tables.empty();
item_list.empty();
min_max_opt_list.empty();
join= 0;
having= prep_having= where= prep_where= 0;
olap= UNSPECIFIED_OLAP_TYPE;

5
sql/sql_lex.h
View File

@ -766,6 +766,11 @@ public:
*/
List<Item_func_match> *ftfunc_list;
List<Item_func_match> ftfunc_list_alloc;
/*
The list of items to which MIN/MAX optimizations of opt_sum_query()
have been applied. Used to rollback those optimizations if it's needed.
*/
List<Item_sum> min_max_opt_list;
JOIN *join; /* after JOIN::prepare it is pointer to corresponding JOIN */
List<TABLE_LIST> top_join_list; /* join list of the top level */
List<TABLE_LIST> *join_list; /* list for the currently parsed join */