[MDEV-8671] Wrong result for SELECT..WHERE varchar_column=' 1' AND (varchar_column XOR '1') - Jira

This script:

DROP TABLE IF EXISTS t1;

CREATE TABLE t1 (a VARCHAR(10) CHARACTER SET cp1251 COLLATE cp1251_ukrainian_ci);

INSERT INTO t1 VALUES (' 1'),('`1');

SELECT * FROM t1 WHERE (a XOR '0');

returns one row:

+------+

| a    |

+------+

|  1   |

+------+

Now if I make the WHERE condition even stricter:

SELECT * FROM t1 WHERE a=' 1' AND (a XOR '0');

it erroneously returns two rows:

+------+

| a    |

+------+

|  1   |

| `1   |

+------+

blocks

MDEV-8728 Fix a number of problems in equal field and equal expression propagation