optimize Section#summarize_without_students #30552
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- Remove unnecesary 'ORDER BY' relation from scope to improve query. - Use `#size` instead of `#length` to use `COUNT` instead of fetching full association collection.
Codecov Report
@@ Coverage Diff @@
## staging #30552 +/- ##
===========================================
+ Coverage 73.21% 76.8% +3.58%
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Files 2058 680 -1378
Lines 112978 27786 -85192
Branches 3495 0 -3495
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- Hits 82721 21340 -61381
+ Misses 26995 6446 -20549
+ Partials 3262 0 -3262
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davidsbailey
approved these changes
Aug 30, 2019
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This PR improves the performance of
section#summarize_without_students, used by the home page for signed-in users within a section:#sizeinstead of#lengthto useCOUNTinstead of fetching full association.I've also replaced
uniqwithdistinct, theuniqalias is deprecated and will be removed in Rails 5.1.Students within large sections (10k+ students) were seeing ~20 second load times for the home page due to this unoptimized query. Benchmarking
#summarize_without_studentsagainst a single section of 10,000 students, this PR provides a ~70x improvement, which should make this page once again usable for students in large sections.