Uploaded image for project: 'MariaDB Server'
  1. MariaDB Server
  2. MDEV-10884

Wrong query result with condition pushdown into derived table with ORDER BY ... LIMIT

    XMLWordPrintable

Details

    • Bug
    • Status: Closed (View Workflow)
    • Major
    • Resolution: Fixed
    • 10.2(EOL)
    • 10.2.2
    • Optimizer
    • None

    Description

      Test dataset:

      create table ten(a int);
      insert into ten values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
      select a from ten order by a limit 5;
      +------+
      | a    |
      +------+
      |    0 |
      |    1 |
      |    2 |
      |    3 |
      |    4 |
      +------+
      

      Use the above query in a derived table, without condition_pushdown_for_derived:

      set optimizer_switch='condition_pushdown_for_derived=off';
      Query OK, 0 rows affected (0.00 sec)
       
      select * from (select a from ten order by a limit 5) TBL where TBL.a not in (1,2,3);
      +------+
      | a    |
      +------+
      |    0 |
      |    4 |
      +------+
      

      Enabling condition_pushdown_for_derived:

      set optimizer_switch='condition_pushdown_for_derived=on';
      Query OK, 0 rows affected (0.00 sec)
       
      select * from (select a from ten order by a limit 5) TBL where TBL.a not in (1,2,3);
      +------+
      | a    |
      +------+
      |    0 |
      |    4 |
      |    5 |
      |    6 |
      |    7 |
      +------+
      

      and see rows with id=5 and so forth. It looks like TBL.a not in (1,2,3) was pushed through ORDER BY ... LIMIT, which changes the query result.

      Attachments

        Issue Links

          Activity

            People

              igor Igor Babaev
              psergei Sergei Petrunia
              Votes:
              0 Vote for this issue
              Watchers:
              2 Start watching this issue

              Dates

                Created:
                Updated:
                Resolved:

                Git Integration

                  Error rendering 'com.xiplink.jira.git.jira_git_plugin:git-issue-webpanel'. Please contact your Jira administrators.