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  1. Moodle
  2. MDL-29589

New $DB method for bulk deleting/updating records using a subselect

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    • MOODLE_21_STABLE, MOODLE_27_STABLE
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      1. Run the database unit tests on all our supported databases.
      2. Run Eloy's test script (from MDL-29520) that tests this sort of delete

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      1. Run the database unit tests on all our supported databases. 2. Run Eloy's test script (from MDL-29520 ) that tests this sort of delete

      Supposed you want to write a query like

      DELETE FROM table WHERE id IN (SELECT ... )
      		 
      -- or
      		 
      UPDATE table SET field = value WHERE id IN (SELECT ... )

      while that is simple to understand, it turns out that database handle that sort of query very badly. (See, for example, MDL-29520 and MDL-32616.)

      The bad news is that there is no standard SQL syntax that works will in all our supported databases, therefore we need a new $DB-> method called delete_records_subselect or delete_records_join_select or something like that, to replace all the one-off hacks we have had to do in those places.

            Unassigned Unassigned
            timhunt Tim Hunt
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              Created:
              Updated:
              Resolved:

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