[MDEV-3165] LP:888456 - Wrong result with DISTINCT , ANY , subquery_cache=off , NOT NULL Created: 2011-11-10  Updated: 2015-02-02  Resolved: 2012-10-04

Status: Closed
Project: MariaDB Server
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Bug Priority: Major
Reporter: Philip Stoev (Inactive) Assignee: Timour Katchaounov (Inactive)
Resolution: Fixed Votes: 0
Labels: Launchpad

Attachments: XML File LPexportBug888456.xml    

 Description   

The following query:

SELECT *
FROM t2 , t1
WHERE t1.pk != ANY (
SELECT DISTINCT col_int_key
FROM t3
);

incorrectly returns

8 28
9 28
8 29

when executed with semijoin=off and

8 28
9 28
8 29
9 29

otherwise. Repeatable in maria-5.3. Not repeatable in maria-5.2, mysql-5.5

EXPLAIN:

id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t2 ALL NULL NULL NULL NULL 2 100.00
1 PRIMARY t1 ALL NULL NULL NULL NULL 2 100.00 Using where; Using join buffer (flat, BNL join)
2 DEPENDENT SUBQUERY t3 range col_int_key col_int_key 5 NULL 6 100.00 Using where; Using index for group-by
select `test`.`t2`.`col_int_key` AS `col_int_key`,`test`.`t1`.`pk` AS `pk` from `test`.`t2` join `test`.`t1` where <nop>(<in_optimizer>(`test`.`t1`.`pk`,<exists>(select distinct `test`.`t3`.`col_int_key` from `test`.`t3` where ((<cache>(`test`.`t1`.`pk`) <> `test`.`t3`.`col_int_key`) or isnull(`test`.`t3`.`col_int_key`)) having <is_not_null_test>(`test`.`t3`.`col_int_key`))))

minimal switch: subquery_cache=off
full switch: index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=off,derived_merge=off,derived_with_keys=off,firstmatch=on,loosescan=on,materialization=off,in_to_exists=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=off,mrr=off,mrr_cost_based=off,mrr_sort_keys=off,outer_join_with_cache=off,semijoin_with_cache=off,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=off,table_elimination=on

revision-id: <email address hidden>
date: 2011-11-07 16:39:02 +0400
build-date: 2011-11-10 11:21:11 +0200
revno: 3273
branch-nick: maria-5.3

test case:

CREATE TABLE t1 ( a int NOT NULL) ;
INSERT INTO t1 VALUES (28),(29);

CREATE TABLE t2 ( a int) ;
INSERT INTO t2 VALUES (8),(9);

CREATE TABLE t3 ( a int, KEY (a)) ;
INSERT INTO t3 VALUES (1),(1),(1),(4),(4),(5),(5),(8),(8),(9);

SELECT *
FROM t2 , t1
WHERE t1.a != ANY (
        SELECT DISTINCT t3.a
        FROM t3
);

 Comments   
Comment by Oleksandr Byelkin [ 2011-11-29 ]

Re: Wrong result with DISTINCT , ANY , subquery_cache=off , NOT NULL
the problem was in resetting QUICK_GROUP_MIN_MAX_SELECT, fix is:

=== modified file 'sql/opt_range.cc'
— sql/opt_range.cc 2011-11-18 17:35:51 +0000
+++ sql/opt_range.cc 2011-11-29 07:19:01 +0000
@@ -12915,6 +12915,7 @@ int QUICK_GROUP_MIN_MAX_SELECT::reset(vo
int result;
DBUG_ENTER("QUICK_GROUP_MIN_MAX_SELECT::reset");

+ seen_first_key= FALSE;
if (!head->key_read)
{
doing_key_read= 1;

But there is 2 strange things:
1) why the bug is visible only on 5.3?
2) are there something else which should be reset?

Comment by Timour Katchaounov (Inactive) [ 2011-12-08 ]

Re: Wrong result with DISTINCT , ANY , subquery_cache=off , NOT NULL
Replies to the questions above:
1) The bug didn't show in 5.2 with the above test case because loose scan is not
used in 5.2 for this query. However, the bug is present (will post a separate test case).
2) I checked all class members of QUICK_GROUP_MIN_MAX_SELECT, and none of them
controls execution. So I think this is the only member that needs to be reset.

Comment by Timour Katchaounov (Inactive) [ 2011-12-08 ]

Re: Wrong result with DISTINCT , ANY , subquery_cache=off , NOT NULL
The following test case reproduces the bug both in 5.2 and 5.3:

CREATE TABLE t1 ( a int NOT NULL) ;
INSERT INTO t1 VALUES (28),(29),(9);

CREATE TABLE t3 ( a int, KEY (a)) ;
INSERT INTO t3 VALUES (1),(1),(1),(4),(4),(5),(5),(8),(8),(9);

explain select (select t3.a from t3 where t3.a >= t1.a group by t3.a) from t1;
select (select t3.a from t3 where t3.a >= t1.a group by t3.a) from t1;

Comment by Timour Katchaounov (Inactive) [ 2011-12-08 ]

Re: Wrong result with DISTINCT , ANY , subquery_cache=off , NOT NULL
Pushed into MariaDB 5.2.

Comment by Rasmus Johansson (Inactive) [ 2011-12-08 ]

Launchpad bug id: 888456

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