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Code

Auto-merged fox for the bug#50843.

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This commit is contained in:
Evgeny Potemkin 2010-02-26 14:19:44 +03:00
commit a0723c0665
3 changed files with 39 additions and 6 deletions
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14
mysql-test/r/innodb_mysql.result
View File

@ -2281,4 +2281,18 @@ CREATE TABLE t1 (a INT PRIMARY KEY) ENGINE=innodb ;
SELECT 1 FROM t1 JOIN t1 a USING(a) GROUP BY t1.a,t1.a;
1
DROP TABLE t1;
#
# Bug#50843: Filesort used instead of clustered index led to
# performance degradation.
#
create table t1(f1 int not null primary key, f2 int) engine=innodb;
create table t2(f1 int not null, key (f1)) engine=innodb;
insert into t1 values (1,1),(2,2),(3,3);
insert into t2 values (1),(2),(3);
explain select t1.* from t1 left join t2 using(f1) group by t1.f1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL PRIMARY 4 NULL 3
1 SIMPLE t2 ref f1 f1 4 test.t1.f1 1 Using index
drop table t1,t2;
#
End of 5.1 tests

12
mysql-test/t/innodb_mysql.test
View File

@ -545,5 +545,17 @@ CREATE TABLE t1 (a INT PRIMARY KEY) ENGINE=innodb ;
SELECT 1 FROM t1 JOIN t1 a USING(a) GROUP BY t1.a,t1.a;
DROP TABLE t1;
--echo #
--echo # Bug#50843: Filesort used instead of clustered index led to
--echo # performance degradation.
--echo #
create table t1(f1 int not null primary key, f2 int) engine=innodb;
create table t2(f1 int not null, key (f1)) engine=innodb;
insert into t1 values (1,1),(2,2),(3,3);
insert into t2 values (1),(2),(3);
explain select t1.* from t1 left join t2 using(f1) group by t1.f1;
drop table t1,t2;
--echo #
--echo End of 5.1 tests

19
sql/sql_select.cc
View File

@ -13306,12 +13306,6 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
*/
if (select_limit >= table_records)
{
/*
filesort() and join cache are usually faster than reading in
index order and not using join cache
*/
if (tab->type == JT_ALL && tab->join->tables > tab->join->const_tables + 1)
DBUG_RETURN(0);
keys= *table->file->keys_to_use_for_scanning();
keys.merge(table->covering_keys);
@ -13461,6 +13455,19 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
}
}
}
/*
filesort() and join cache are usually faster than reading in
index order and not using join cache, except in case that chosen
index is clustered primary key.
*/
if ((select_limit >= table_records) &&
(tab->type == JT_ALL &&
tab->join->tables > tab->join->const_tables + 1) &&
((unsigned) best_key != table->s->primary_key ||
!table->file->primary_key_is_clustered()))
DBUG_RETURN(0);
if (best_key >= 0)
{
bool quick_created= FALSE;