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Caching in effect. Below are sequential attempt at accessing a forums heavy course course-v1:IDBx+IDB6x+2015_T2 where the comment count of the pinned posts are ~4000. Each of the 20 threads it is trying to load (limit=20), is taking too long for a query. When running the query without the count, because of the limit and skip, results are return very quickly. Count seems to be taking up a lot of time?
Looks like it is trying to retrieve the count of all comments with with the matching comment_thread_id in order to get the comment_count. This is horribly inefficient.
