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  1. Moodle
  2. MDL-65429

Include unsubscribes in the forum subscription cache to improve performance

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      When looking to some DB performance problems @ MDL-65069, it was detected that this query:

      SELECT id, discussion, preference FROM mdl_forum_discussion_subs WHERE userid = $1 AND forum = $2 array (
        0 => '2',
        1 => 107,
      )
      

      Is executed 65 times in a forum/view page plenty of discussions.

      Tracing down the problem... it seems that mod_foum\subscriptions::fill_discussion_subscription_cache() does not cache query misses... and that causes the same query to be executed as many times as discussions are in a page.

      This should be fixed in all supported branches because they are lots of queries for nothing.

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              peterdias Peter Dias
              stronk7 Eloy Lafuente (stronk7)
              Neill Magill Neill Magill
              Andrew Lyons Andrew Lyons
              CiBoT CiBoT
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              Dates

                Created:
                Updated:
                Resolved:
                11/Nov/19

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