[MDEV-6302] Wrong result set when using GROUP BY FROM_UNIXTIME(...)+0 - Jira

This script returns from results:

DROP TABLE IF EXISTS t1;

CREATE TABLE t1 (a DATE) ENGINE=MyISAM;

INSERT INTO t1 VALUES ('2005-05-04'),('2000-02-23');

SELECT a, FROM_UNIXTIME(CONCAT(a,'10')) AS f1, FROM_UNIXTIME(CONCAT(a,'10'))+0 AS f2 FROM t1;

SELECT * FROM t1 GROUP BY FROM_UNIXTIME(CONCAT(a,'10'))+0;

The first SELECT returns:

+------------+---------------------+------------------------------------------------+

| a          | f1                  | f2                                             |

+------------+---------------------+------------------------------------------------+

| 2005-05-04 | 1970-01-01 03:33:25 | 19700101033325.0000000000000000000000000000000 |

| 2000-02-23 | 1970-01-01 03:33:20 | 19700101033320.0000000000000000000000000000000 |

+------------+---------------------+------------------------------------------------+

Notice, the number of fractional digits in "f2" looks excessive.

The second SELECT returns:

+------------+

| a          |

+------------+

| 2005-05-04 |

+------------+

This is wrong, because the two values in "f2" in the previous SELECT
are unique. The expected result in this SELECT should return two rows.

More similar failures:

DROP TABLE IF EXISTS t1;

CREATE TABLE t1 (a DATE) ENGINE=MyISAM;

INSERT INTO t1 VALUES ('2005-05-04'),('2000-02-23');

SELECT * FROM t1 GROUP BY FROM_UNIXTIME(concat(a,'10'))/1;

A related problem:

DROP TABLE IF EXISTS t1,t2;

CREATE TABLE t1 (a DATE);

INSERT INTO t1 VALUES ('2005-05-04');

SELECT CHAR_LENGTH(CONCAT(FROM_UNIXTIME(CONCAT(a,'10')) MOD FROM_UNIXTIME(CONCAT(a,'10')))) AS f2 FROM t1;

CREATE TABLE t2 AS SELECT CONCAT(FROM_UNIXTIME(CONCAT(a,'10')) MOD FROM_UNIXTIME(CONCAT(a,'10'))) AS f2 FROM t1;

SHOW WARNINGS;

SHOW COLUMNS IN t2;

returns warnings:

+---------+------+-----------------------------------------+

| Level   | Code | Message                                 |

+---------+------+-----------------------------------------+

| Warning | 1265 | Data truncated for column 'f2' at row 1 |

+---------+------+-----------------------------------------+

which happens because the column is too short (26),
while CHAR_LENGTH() in the above query returns 27:

+-------+---------------+------+-----+---------+-------+

| Field | Type          | Null | Key | Default | Extra |

+-------+---------------+------+-----+---------+-------+

| f2    | varbinary(26) | YES  |     | NULL    |       |

+-------+---------------+------+-----+---------+-------+

Transition	Time In Source Status	Execution Times

Alexander Barkov made transition - 2014-07-28 12:46

Open

Closed

54d 3h 52m

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