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sync 1.5.101116 includes a collection timestamp query that reliably and simultaneously crashes the mysql servers in production. it appears to stem from the subquery i suggested using here. we have monkeypatched in production a revised query based on the original sync 1.3 query with one single change, specifically "GROUP BY username, collection". this has proven to be sufficient to reap some performance reward of using the available indexes, without crashing the mysql server.
old query still present, and we're having random crashes of mysql in staging when running sync tests, so it's very likely this is the root cause.
Severity: normal → blocker
Created attachment 506418 [details] [diff] [review] Back to the simpler query
Created attachment 506422 [details] [diff] [review] Back to the simpler query added "username" to the group by /
Attachment #506422 - Flags: review?(rsoderberg)
Comment on attachment 506422 [details] [diff] [review] Back to the simpler query Can you provide the resulting SQL query as sent to MySQL by the select() function? r+ otherwise, pending that
SELECT wbo.collection, max(wbo.modified) AS max_1 FROM wbo WHERE wbo.username = %s AND wbo.ttl > %s GROUP BY wbo.username, wbo.collection
Attachment #506422 - Flags: review?(rsoderberg) → review+
Attachment #506422 - Flags: review?(telliott) → review+
Status: NEW → RESOLVED
Last Resolved: 8 years ago
Resolution: --- → FIXED
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