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  1. MariaDB Server
  2. MDEV-30252

Value changed after adding DISTINCT [5.5.62, 10.11.1]

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      Description:
      In theory, the result of sql2(DISTINCT) ⊆ the result of sql1:

      SELECT PI()+~1&f2 AS f1 FROM (SELECT DATE_SUB(DATE_ADD('2009-10-15', INTERVAL 1 MICROSECOND), INTERVAL 1 DAY_SECOND) AS f2 FROM t) AS t1; -- sql1
      SELECT PI()+~1&f2 AS f1 FROM (SELECT DISTINCT DATE_SUB(DATE_ADD('2009-10-15', INTERVAL 1 MICROSECOND), INTERVAL 1 DAY_SECOND) AS f2 FROM t) AS t1; -- sql2
      

      However, the value 20091014235959 changed to 2009 after adding DISTINCT, seems like a logical bug:

      mysql> select version();
      +-----------------------------------------+
      | version()                               |
      +-----------------------------------------+
      | 10.11.1-MariaDB-1:10.11.1+maria~ubu2204 |
      +-----------------------------------------+
      1 row in set (0.00 sec)
       
      mysql> SELECT PI()+~1&f2 AS f1 FROM (SELECT DATE_SUB(DATE_ADD('2009-10-15', INTERVAL 1 MICROSECOND), INTERVAL 1 DAY_SECOND) AS f2 FROM t) AS t1; -- sql1
      +----------------+
      | f1             |
      +----------------+
      | 20091014235959 |
      +----------------+
      1 row in set, 1 warning (0.00 sec)
       
      mysql> SELECT PI()+~1&f2 AS f1 FROM (SELECT DISTINCT DATE_SUB(DATE_ADD('2009-10-15', INTERVAL 1 MICROSECOND), INTERVAL 1 DAY_SECOND) AS f2 FROM t) AS t1; -- sql2
      +------+
      | f1   |
      +------+
      | 2009 |
      +------+
      1 row in set, 2 warnings (0.00 sec)
      

      How to repeat:

      drop table if exists t;
      CREATE TABLE t (c1 INT);
      INSERT INTO t VALUES (1);
       
      SELECT PI()+~1&f2 AS f1 FROM (SELECT DATE_SUB(DATE_ADD('2009-10-15', INTERVAL 1 MICROSECOND), INTERVAL 1 DAY_SECOND) AS f2 FROM t) AS t1; -- sql1
      SELECT PI()+~1&f2 AS f1 FROM (SELECT DISTINCT DATE_SUB(DATE_ADD('2009-10-15', INTERVAL 1 MICROSECOND), INTERVAL 1 DAY_SECOND) AS f2 FROM t) AS t1; -- sql2
      

      Hope these can be helpful for your debugging:
      1. The bug cannot be reproduced after removing the date function (change to '2009-10-15' AS f2);
      2. The bug cannot be reproduced after removing FROM t;
      3. We look for the first version of the bug in all docker images (with format x.x.x) of https://hub.docker.com/_/mariadb/tags
      We found that the bug first occurred in mariadb:5.5.62, it cannot be reproduced in mariadb:5.5.61:

      MariaDB [TEST]> select version();
      +-------------------------+
      | version()               |
      +-------------------------+
      | 5.5.62-MariaDB-1~trusty |
      +-------------------------+
      1 row in set (0.00 sec)
       
      MariaDB [TEST]> SELECT PI()+~1&f2 AS f1 FROM (SELECT DATE_SUB(DATE_ADD('2009-10-15', INTERVAL 1 MICROSECOND), INTERVAL 1 DAY_SECOND) AS f2 FROM t) AS t1; -- sql1
      +----------------+
      | f1             |
      +----------------+
      | 20091014235959 |
      +----------------+
      1 row in set (0.00 sec)
       
      MariaDB [TEST]> SELECT PI()+~1&f2 AS f1 FROM (SELECT DISTINCT DATE_SUB(DATE_ADD('2009-10-15', INTERVAL 1 MICROSECOND), INTERVAL 1 DAY_SECOND) AS f2 FROM t) AS t1; -- sql2
      +------+
      | f1   |
      +------+
      | 2009 |
      +------+
      1 row in set, 1 warning (0.00 sec)
       
      MariaDB [TEST]> select version();
      +-------------------------+
      | version()               |
      +-------------------------+
      | 5.5.61-MariaDB-1~trusty |
      +-------------------------+
      1 row in set (0.00 sec)
       
      MariaDB [TEST]> SELECT PI()+~1&f2 AS f1 FROM (SELECT DATE_SUB(DATE_ADD('2009-10-15', INTERVAL 1 MICROSECOND), INTERVAL 1 DAY_SECOND) AS f2 FROM t) AS t1; -- sql1
      +------+
      | f1   |
      +------+
      |    0 |
      +------+
      1 row in set (0.00 sec)
       
      MariaDB [TEST]> SELECT PI()+~1&f2 AS f1 FROM (SELECT DISTINCT DATE_SUB(DATE_ADD('2009-10-15', INTERVAL 1 MICROSECOND), INTERVAL 1 DAY_SECOND) AS f2 FROM t) AS t1; -- sql2
      +------+
      | f1   |
      +------+
      |    0 |
      +------+
      1 row in set, 1 warning (0.00 sec)
      

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              bar Alexander Barkov
              qaqcatz qaqcatz
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