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  1. MariaDB Server
  2. MDEV-19267

unnecessary scanned all databases for information_schema

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    Details

    • Type: Task
    • Status: Open (View Workflow)
    • Priority: Major
    • Resolution: Unresolved
    • Fix Version/s: None
    • Component/s: Server
    • Labels:
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      Description

      Any query to information_schema is extremely slow because it scans all databases. For example, this query takes over 3 seconds. This bug has been fixed in MySQL 8.0, so I tested in that version using the same data and this same query takes 0.03 seconds.
      https://bugs.mysql.com/bug.php?id=81347

      SELECT `update_time` FROM information_schema.tables;
      ...
      5068 rows in set (3.289 sec)
       
      EXPLAIN SELECT update_time FROM information_schema.tables;
      +------+-------------+--------+------+---------------+------+---------+------+------+----------------------------------------+
      | id   | select_type | table  | type | possible_keys | key  | key_len | ref  | rows | Extra                                  |
      +------+-------------+--------+------+---------------+------+---------+------+------+----------------------------------------+
      |    1 | SIMPLE      | tables | ALL  | NULL          | NULL | NULL    | NULL | NULL | Open_full_table; Scanned all databases |
      +------+-------------+--------+------+---------------+------+---------+------+------+----------------------------------------+
      1 row in set (0.002 sec)
      
      

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              Assignee:
              Unassigned Unassigned
              Reporter:
              llamafilm Elliott Balsley
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                Updated:

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