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  1. MariaDB Server
  2. MDEV-4025

Wrong estimate of rows in the test case for LP bug #934348

Details

    • Bug
    • Status: Closed (View Workflow)
    • Minor
    • Resolution: Fixed
    • 5.3.11
    • 5.3.12
    • Optimizer
    • None

    Description

      The following EXPLAIN command from the test case for LP bug #934348

      EXPLAIN
      		 
      SELECT a FROM t1 t WHERE a IN (SELECT b FROM t1, t2 WHERE b = a)
      		 
      GROUP BY a HAVING a != 'z';

      returns

      id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
      		 
      1	PRIMARY	t	index	idx_a	idx_a	4	NULL	1	Using index
      		 
      ...

      It should return

      id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
      		 
      1	PRIMARY	t	index	idx_a	idx_a	4	NULL	3	Using index

      as the number of rows in the table t1 is equal to 3.

      Attachments

        Activity

          elenst Elena Stepanova added a comment -

          It was fixed in 5.3.12, here is the commit message:

          revno: 3612
          		 
          revision-id: igor@askmonty.org-20130112042634-peaxz8hj6e32rqln
          		 
          parent: wlad@montyprogram.com-20130111114421-j0y44s7tpukn7i9m
          		 
          committer: Igor Babaev <igor@askmonty.org>
          		 
          branch nick: maria-5.3
          		 
          timestamp: Fri 2013-01-11 20:26:34 -0800
          		 
          message:
          		 
            Fixed bug mdev-4025.
          		 
            The bug could lead to a wrong estimate of the number of expected rows
          		 
            in the output of the EXPLAIN commands for queries with GROUP BY.
          		 
            This could be observed in the test case for LP bug 934348.

          elenst Elena Stepanova added a comment - It was fixed in 5.3.12, here is the commit message: revno: 3612 revision-id: igor@askmonty.org-20130112042634-peaxz8hj6e32rqln parent: wlad@montyprogram.com-20130111114421-j0y44s7tpukn7i9m committer: Igor Babaev <igor@askmonty.org> branch nick: maria-5.3 timestamp: Fri 2013-01-11 20:26:34 -0800 message: Fixed bug mdev-4025. The bug could lead to a wrong estimate of the number of expected rows in the output of the EXPLAIN commands for queries with GROUP BY. This could be observed in the test case for LP bug 934348.

          People

            igor Igor Babaev (Inactive)
            igor Igor Babaev (Inactive)
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            Dates

              Created:
              Updated:
              Resolved:

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