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  1. MariaDB Server
  2. MDEV-29889

mysqldump --tab --header is slow

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    Description

      mysqldump --header --tab wraps the dumping SELECT in UNION ALL + ORDER BY. Which means a filesort (try EXPLAIN), that would make mysqldump notably slower on large tables. This is completely unnecessary, because the ordering of table rows is unimportant.

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          is caused by

          Task - A task that needs to be done. MDEV-22200 mysqldump client: --tab export with column names header row

          • Major - Major loss of function.
          • Closed
          relates to

          Task - A task that needs to be done. MDEV-12879 Please add support for exporting column headers to CSV

          • Minor - Minor loss of function, or other problem where easy workaround is present.
          • Open

          Activity

            Ascending order - Click to sort in descending order
            rmfalves Rui Alves added a comment -

            The ORDER BY that I implemented on the MDEV-22200 has two purposes:

            1. By using a temporary dummy binary sorting variable (0 when at the header row, 1 otherwise) it enforces the header row on the top and prevents it from getting messed up somewhere in the middle of the data rows.

            2. The ordering of data rows is necessary to enforce compability with the --order-by-primary clause.

            rmfalves Rui Alves added a comment - The ORDER BY that I implemented on the MDEV-22200 has two purposes: 1. By using a temporary dummy binary sorting variable (0 when at the header row, 1 otherwise) it enforces the header row on the top and prevents it from getting messed up somewhere in the middle of the data rows. 2. The ordering of data rows is necessary to enforce compability with the --order-by-primary clause.
            danblack Daniel Black added a comment -

            MDEV-12879 as option.

            danblack Daniel Black added a comment - MDEV-12879 as option.
            serg Sergei Golubchik added a comment -

            https://github.com/MariaDB/server/pull/2311/commits/b4d1ff1d3b262a35c1d83acf893544de9ccdaad0 is ok to push

            serg Sergei Golubchik added a comment - https://github.com/MariaDB/server/pull/2311/commits/b4d1ff1d3b262a35c1d83acf893544de9ccdaad0 is ok to push

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              danblack Daniel Black
              serg Sergei Golubchik
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