[MDL-46826] forum_discussions requires index on course field - Moodle Tracker

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Affected Branches:
MOODLE_26_STABLE, MOODLE_27_STABLE, MOODLE_28_STABLE
Fixed Branches:
MOODLE_26_STABLE, MOODLE_27_STABLE
Pull from Repository:
git://github.com/marinaglancy/moodle.git
Pull Master Branch:
wip-~~MDL-46826~~-master
Pull Master Diff URL:
https://github.com/marinaglancy/moodle/compare/master...wip-MDL-46826-master
Testing Instructions:

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repeat testing from ~~MDL-31089~~, you can limit it to test 2 and test 6 only (group and no-group modes)
master only: verify upgrade to forum version 20140815 works and the index on forum_discussion (course) is created.

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repeat testing from MDL-31089 , you can limit it to test 2 and test 6 only (group and no-group modes) master only: verify upgrade to forum version 20140815 works and the index on forum_discussion (course) is created.

Occasionally, queries pop up which use forum_discussions.course as the filter condition, and join forum_posts and friends to fetch some data.

This does not work very well as there is no index on the course field, so it results in quite poor queries.

The latest case seems to be ~~MDL-31089~~ which has made forum_print_overview a very serious bottleneck, found when testing 2.5 vs 2.7 performance.

An index should be added to the course field to prevent these problems.

has been marked as being related by

MDL-47895 Forum query for course overview block does crazy query which kills our testing server

is a regression caused by

MDL-31089 New posts listing on 'My Moodle' ignores groups.

Participants:: Andrew Lyons, Ankit Agarwal, CiBoT, Eloy Lafuente (stronk7), Marina Glancy, Tony Levi

Component watchers:: David Woloszyn, Huong Nguyen, Jake Dallimore, Meirza, Michael Hawkins, Raquel Ortega, Safat Shahin, Stevani Andolo, Adrian Greeve, Ilya Tregubov, Kevin Percy, Mathew May, Mihail Geshoski, Shamim Rezaie, Matteo Scaramuccia, David Woloszyn, Huong Nguyen, Jake Dallimore, Meirza, Michael Hawkins, Raquel Ortega, Safat Shahin, Stevani Andolo