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  1. MariaDB Server
  2. MDEV-11333

Expect "Impossible where condition" for WHERE timestamp_field>=DATE_ADD(TIMESTAMP'9999-01-01 00:00:00',INTERVAL 1000 YEAR)

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      Description

      This query returns NULL with a warning about datetime overflow.

      SELECT DATE_ADD(TIMESTAMP'9999-01-01 00:00:00',INTERVAL 1000 YEAR);
      

      If I use now this expression in a WHERE condition on a TIMESTAMP field with DEFAULT CURRENT_TIMESTAMP:

      DROP TABLE IF EXISTS t1;
      CREATE TABLE t1 (a TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP, KEY(a)) ENGINE=MyISAM;
      INSERT INTO t1 VALUES('2001-01-01'),('2002-02-02'),('2003-03-03');
      INSERT INTO t1 VALUES('2001-01-01'),('2002-02-02'),('2003-03-03');
      INSERT INTO t1 VALUES('2001-01-01'),('2002-02-02'),('2003-03-03');
      INSERT INTO t1 VALUES('2001-01-01'),('2002-02-02'),('2003-03-03');
      INSERT INTO t1 VALUES('2001-01-01'),('2002-02-02'),('2003-03-03');
      INSERT INTO t1 VALUES('2001-01-01'),('2002-02-02'),('2003-03-03');
      EXPLAIN SELECT * FROM t1 WHERE a >= DATE_ADD(TIMESTAMP'9999-01-01 00:00:00',INTERVAL 1000 YEAR);
      

      it reports that one row will be checked:

      +------+-------------+-------+-------+---------------+------+---------+------+------+--------------------------+
      | id   | select_type | table | type  | possible_keys | key  | key_len | ref  | rows | Extra                    |
      +------+-------------+-------+-------+---------------+------+---------+------+------+--------------------------+
      |    1 | SIMPLE      | t1    | range | a             | a    | 4       | NULL |    1 | Using where; Using index |
      +------+-------------+-------+-------+---------------+------+---------+------+------+--------------------------+
      

      This is wrong. It should report "Impossible where".

      Note, if I change the condition wrapping DATE_ADD to COALESCE:

      EXPLAIN SELECT * FROM t1 WHERE a >= COALESCE(DATE_ADD(TIMESTAMP'9999-01-01 00:00:00',INTERVAL 1000 YEAR));
      

      it starts to report "Impossible where" correctly:

      +------+-------------+-------+------+---------------+------+---------+------+------+-----------------------------------------------------+
      | id   | select_type | table | type | possible_keys | key  | key_len | ref  | rows | Extra                                               |
      +------+-------------+-------+------+---------------+------+---------+------+------+-----------------------------------------------------+
      |    1 | SIMPLE      | NULL  | NULL | NULL          | NULL | NULL    | NULL | NULL | Impossible WHERE noticed after reading const tables |
      +------+-------------+-------+------+---------------+------+---------+------+------+-----------------------------------------------------+
      

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              • Assignee:
                bar Alexander Barkov
                Reporter:
                bar Alexander Barkov
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                • Created:
                  Updated:
                  Resolved: