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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.

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