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Improvement
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Resolution: Fixed
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Minor
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4.0.4
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MOODLE_400_STABLE
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MOODLE_400_STABLE
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After updating to Moodle 4.0, we noticed slow queries on mdl_comments in the database.
These always have the same query as cause:
SELECT c.*
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FROM mdl_comments c
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WHERE c.commentarea = 'question' |
AND c.component = 'qbank_comment' |
AND c.itemid = '1234' |
The query came with MDL-71642 for backup of questions in core.
We have now observed the query in production for a few days and see a payload of 25% to about 60% on the database.
The cause for this behavior could be a missing index on
commentarea, component, itemid
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