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Fixed LP bug #934342.

Browse source 
An outer join query with a semi-join subquery could return a wrong result
if the optimizer chose to materialize the subquery.
It happened because when substituting for the best field into a ref item
used to build access keys not all COND_EQUAL objects that could be employed
at substitution were checked.

Also refined some code in the function check_join_cache_usage to make it
safer.
This commit is contained in:
Igor Babaev 2012-02-18 16:06:38 -08:00
parent bbb3527635
commit cd81f57830
3 changed files with 150 additions and 5 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

80
mysql-test/r/subselect_sj_jcl6.result
View file

@ -2753,6 +2753,86 @@ DROP table t1, t2;
set @@optimizer_switch= @os_912513;
set @@join_cache_level= @jcl_912513;
# End
#
# BUG#934342: outer join + semijoin materialization
# + join_cache_level > 2
#
CREATE TABLE t1 (a varchar(1), b varchar(1), INDEX idx_a(a) );
INSERT INTO t1 VALUES ('v','v'), ('w','w'), ('t','t');
CREATE TABLE t2 (c varchar(1), INDEX idx_c(c) );
INSERT INTO t2 VALUES ('v'), ('v'), ('s'), ('j');
CREATE TABLE t3 (c varchar(1), d varchar(1), INDEX idx_c(c) );
INSERT INTO t3 VALUES ('v','v'), ('v','v'), ('s','s'), ('j','j');
INSERT INTO t3 VALUES ('m','m'), ('d','d'), ('k','k'), ('m','m');
set @tmp_otimizer_switch= @@optimizer_switch;
set @tmp_join_cache_level=@@join_cache_level;
set optimizer_switch = 'materialization=on,semijoin=on,join_cache_hashed=on';
set join_cache_level=0;
EXPLAIN
SELECT * FROM t1 LEFT JOIN t2 ON (c = b)
WHERE (a, b) IN (SELECT a, b FROM t1 t);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL idx_a NULL NULL NULL 3
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 10 func,func 1
1 PRIMARY t2 ref idx_c idx_c 4 test.t1.b 2 Using where; Using index
2 MATERIALIZED t ALL idx_a NULL NULL NULL 3
SELECT * FROM t1 LEFT JOIN t2 ON (c = b)
WHERE (a, b) IN (SELECT a, b FROM t1 t);
a b c
v v v
v v v
w w NULL
t t NULL
EXPLAIN
SELECT * FROM t1 LEFT JOIN t3 ON (c = b)
WHERE (a, b) IN (SELECT a, b FROM t1 t);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL idx_a NULL NULL NULL 3
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 10 func,func 1
1 PRIMARY t3 ref idx_c idx_c 4 test.t1.b 2 Using where
2 MATERIALIZED t ALL idx_a NULL NULL NULL 3
SELECT * FROM t1 LEFT JOIN t3 ON (c = b)
WHERE (a, b) IN (SELECT a, b FROM t1 t);
a b c d
v v v v
v v v v
w w NULL NULL
t t NULL NULL
set join_cache_level=6;
EXPLAIN
SELECT * FROM t1 LEFT JOIN t2 ON (c = b)
WHERE (a, b) IN (SELECT a, b FROM t1 t);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL idx_a NULL NULL NULL 3
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 10 func,func 1
1 PRIMARY t2 ref idx_c idx_c 4 test.t1.b 2 Using where; Using index
2 MATERIALIZED t ALL idx_a NULL NULL NULL 3
SELECT * FROM t1 LEFT JOIN t2 ON (c = b)
WHERE (a, b) IN (SELECT a, b FROM t1 t);
a b c
v v v
v v v
w w NULL
t t NULL
EXPLAIN
SELECT * FROM t1 LEFT JOIN t3 ON (c = b)
WHERE (a, b) IN (SELECT a, b FROM t1 t);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL idx_a NULL NULL NULL 3
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 10 func,func 1
1 PRIMARY t3 ref idx_c idx_c 4 test.t1.b 2 Using where; Using join buffer (flat, BKA join); Key-ordered Rowid-ordered scan
2 MATERIALIZED t ALL idx_a NULL NULL NULL 3
SELECT * FROM t1 LEFT JOIN t3 ON (c = b)
WHERE (a, b) IN (SELECT a, b FROM t1 t);
a b c d
v v v v
v v v v
w w NULL NULL
t t NULL NULL
set optimizer_switch=@tmp_optimizer_switch;
set join_cache_level=@tmp_join_cache_level;
DROP TABLE t1,t2,t3;
# End
set join_cache_level=default;
show variables like 'join_cache_level';
Variable_name Value

54
mysql-test/t/subselect_sj_jcl6.test
View file

@ -116,6 +116,60 @@ set @@join_cache_level= @jcl_912513;
--echo # End
--echo #
--echo # BUG#934342: outer join + semijoin materialization
--echo # + join_cache_level > 2
--echo #
CREATE TABLE t1 (a varchar(1), b varchar(1), INDEX idx_a(a) );
INSERT INTO t1 VALUES ('v','v'), ('w','w'), ('t','t');
CREATE TABLE t2 (c varchar(1), INDEX idx_c(c) );
INSERT INTO t2 VALUES ('v'), ('v'), ('s'), ('j');
CREATE TABLE t3 (c varchar(1), d varchar(1), INDEX idx_c(c) );
INSERT INTO t3 VALUES ('v','v'), ('v','v'), ('s','s'), ('j','j');
INSERT INTO t3 VALUES ('m','m'), ('d','d'), ('k','k'), ('m','m');
set @tmp_otimizer_switch= @@optimizer_switch;
set @tmp_join_cache_level=@@join_cache_level;
set optimizer_switch = 'materialization=on,semijoin=on,join_cache_hashed=on';
set join_cache_level=0;
EXPLAIN
SELECT * FROM t1 LEFT JOIN t2 ON (c = b)
WHERE (a, b) IN (SELECT a, b FROM t1 t);
SELECT * FROM t1 LEFT JOIN t2 ON (c = b)
WHERE (a, b) IN (SELECT a, b FROM t1 t);
EXPLAIN
SELECT * FROM t1 LEFT JOIN t3 ON (c = b)
WHERE (a, b) IN (SELECT a, b FROM t1 t);
SELECT * FROM t1 LEFT JOIN t3 ON (c = b)
WHERE (a, b) IN (SELECT a, b FROM t1 t);
set join_cache_level=6;
EXPLAIN
SELECT * FROM t1 LEFT JOIN t2 ON (c = b)
WHERE (a, b) IN (SELECT a, b FROM t1 t);
SELECT * FROM t1 LEFT JOIN t2 ON (c = b)
WHERE (a, b) IN (SELECT a, b FROM t1 t);
EXPLAIN
SELECT * FROM t1 LEFT JOIN t3 ON (c = b)
WHERE (a, b) IN (SELECT a, b FROM t1 t);
SELECT * FROM t1 LEFT JOIN t3 ON (c = b)
WHERE (a, b) IN (SELECT a, b FROM t1 t);
set optimizer_switch=@tmp_optimizer_switch;
set join_cache_level=@tmp_join_cache_level;
DROP TABLE t1,t2,t3;
--echo # End
set join_cache_level=default;
show variables like 'join_cache_level';

21
sql/sql_select.cc
View file

@ -1266,9 +1266,20 @@ JOIN::optimize()
Item *ref_item= *ref_item_ptr;
if (!ref_item->used_tables() && !(select_options & SELECT_DESCRIBE))
continue;
COND_EQUAL *equals= tab->first_inner ? tab->first_inner->cond_equal :
cond_equal;
ref_item= substitute_for_best_equal_field(tab, ref_item, equals, map2table);
COND_EQUAL *equals= cond_equal;
JOIN_TAB *first_inner= tab->first_inner;
while (equals)
{
ref_item= substitute_for_best_equal_field(tab, ref_item,
equals, map2table);
if (first_inner)
{
equals= first_inner->cond_equal;
first_inner= first_inner->first_upper;
}
else
equals= 0;
}
ref_item->update_used_tables();
if (*ref_item_ptr != ref_item)
{
@ -9213,7 +9224,7 @@ uint check_join_cache_usage(JOIN_TAB *tab,
Check whether table tab and the previous one belong to the same nest of
inner tables and if so do not use join buffer when joining table tab.
*/
if (tab->first_inner)
if (tab->first_inner && tab != tab->first_inner)
{
for (JOIN_TAB *first_inner= tab[-1].first_inner;
first_inner;
@ -9223,7 +9234,7 @@ uint check_join_cache_usage(JOIN_TAB *tab,
goto no_join_cache;
}
}
else if (tab->first_sj_inner_tab &&
else if (tab->first_sj_inner_tab && tab != tab->first_sj_inner_tab &&
tab->first_sj_inner_tab == tab[-1].first_sj_inner_tab)
goto no_join_cache;
}