Uploaded image for project: 'MariaDB Server'
  1. MariaDB Server
  2. MDEV-4119

Remove duplicate ORDER BY/GROUP BY column references

    XMLWordPrintable

Details

    • 10.1.6-2, 10.1.8-1

    Description

      Currently the optimizer doesn't cannot take into account duplicate column references in the GROUP/ORDER BY clauses. As a result, queries like:

      select a col1, a col2 from t1 group by col1, col2;

      will not use an index on t1(a), even though the duplicate columns
      do not change the meaning of the query.

      This is a simple task to remove duplicates in the order/group lists.
      Care should be taken of queries with the ROLLUP modifier.

      There is already an implementation attached to this task. The implementation has to be verified/changed so that:

      • it takes care of queries with ROLLUP,
      • it is verified that the place where duplicate removal is done covers all cases when it can and should be done,
      • there is sufficient coverage with test cases.

      Attachments

        Activity

          People

            monty Michael Widenius
            timour Timour Katchaounov (Inactive)
            Votes:
            2 Vote for this issue
            Watchers:
            5 Start watching this issue

            Dates

              Created:
              Updated:

              Git Integration

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