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MDEV-24710 Uninitialized value upon CREATE .. SELECT ... VALUE...

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The failure happened for group by queries when all tables where marked as
'const tables' (tables with 0-1 matching rows) and no row matched the
where clause and there was in addition a direct reference to a field.

In this case the field would not be properly reset and the query would
return 'random data' that happended to be in table->record[0].

Fixed by marking all const tables as null tables in this particular case.

Sergei also provided an extra test case for the code.

@reviewer Sergei Petrunia <psergey@askmonty.org>
This commit is contained in:
Monty 2021-02-27 19:56:46 +02:00
commit 6983ce704b
4 changed files with 135 additions and 10 deletions
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23
mysql-test/main/group_by.test
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@ -2040,6 +2040,29 @@ INSERT INTO t1 VALUES ('2032-10-08');
SELECT d != '2023-03-04' AS f, COUNT(*) FROM t1 GROUP BY d WITH ROLLUP;
DROP TABLE t1;
--echo #
--echo # MDEV-24710 Uninitialized value upon CREATE .. SELECT ... VALUE
--echo #
CREATE TABLE t1 (a VARCHAR(8) NOT NULL DEFAULT '');
INSERT INTO t1 (a) VALUES ('foo');
CREATE TABLE t2 AS SELECT MAX(a) AS f1, a AS f2 FROM t1 WHERE VALUE(a) IS NOT NULL;
SELECT * from t2;
SELECT MAX(a) AS f1, a AS f2 FROM t1 WHERE VALUE(a) IS NOT NULL;
SELECT MAX(a) AS f1, a AS f2 FROM t1 WHERE 1=0;
drop table t1,t2;
--echo # Extra test by to check the fix for MDEV-24710
create table t20 (pk int primary key, a int);
insert into t20 values (1,1);create table t21 (pk int primary key, b int not null);
insert into t21 values (1,1);
create table t22 (a int);
insert into t22 values (1),(2);
select a, (select max(t21.b) from t20 left join t21 on t21.pk=t20.a+10
where t20.pk=1 and rand(123) < 0.5) as SUBQ from t22;
drop table t20, t21, t22;
--echo #
--echo # End of 10.3 tests
--echo #