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  1. MariaDB Server
  2. MDEV-7982

EXPLAIN shows meaningless query plan with Distinct

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      Take the attached dataset and run this query:

      explain  select distinct count(*) from t2 where a between 10 and 20 group by a;
      +------+-------------+-------+-------+---------------+------+---------+------+------+---------------------------------------------------------------------+
      | id   | select_type | table | type  | possible_keys | key  | key_len | ref  | rows | Extra                                                               |
      +------+-------------+-------+-------+---------------+------+---------+------+------+---------------------------------------------------------------------+
      |    1 | SIMPLE      | t2    | range | a             | a    | 5       | NULL |   10 | Using where; Using index; Distinct; Using temporary; Using filesort |
      +------+-------------+-------+-------+---------------+------+---------+------+------+---------------------------------------------------------------------+

      and see an apparently non-sensical output (how can a table use "Distinct" if it
      is the only table in the join?)

      This is repeatable on 10.0.17, didn't check 5.5

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            • Assignee:
              psergey Sergei Petrunia
              Reporter:
              psergey Sergei Petrunia
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