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  1. MariaDB Server
  2. MDEV-5197

Feature Request: optimize away LIKE '%%'

        Details

        • Type: Task
        • Status: Open
        • Priority: Minor
        • Resolution: Unresolved
        • Fix Version/s: 10.1
        • Component/s: None
        • Labels:

          Description

          Some scripts compose SQL queries without checking if some input fields are empty. As a result, they can produce queries containing LIKE '%%'. This clause does not appear to be optimized away:

          MariaDB [test]> EXPLAIN EXTENDED SELECT c FROM t WHERE c LIKE '%%';
+------+-------------+-------+------+---------------+------+---------+------+------+----------+-------------+
| id   | select_type | table | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra       |
+------+-------------+-------+------+---------------+------+---------+------+------+----------+-------------+
|    1 | SIMPLE      | t     | ALL  | NULL          | NULL | NULL    | NULL | 5 |   100.00 | Using where |
+------+-------------+-------+------+---------------+------+---------+------+------+----------+-------------+
1 row in set, 1 warning (0.05 sec)

Note (Code 1003): select `test`.`t`.`c` AS `c` from `test`.`t` where (`test`.`t`.`c` like '%%')

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                  • Assignee:
                    Unassigned
                    Reporter:
                    f_razzoli Federico Razzoli
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                    • Created:
                      Updated: