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Fix db load on usersCommunities table #3826
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Every time anybody loaded the community view we would run a query that
would go through all the members of a community (that was quick), then
filter them by e.g. `isMember = true` (that was slow for big communities)
and then order them by `r.desc('reputation')`. (that was also slow)
Together, the filter and the orderBy meant that we would read a couple
tens of thousands of records when somebody opened a large communities
community view. Multiply that by concurrent users pointed at the
platform and you've got a perfect storm of traffic we can't handle.
This patch fixes it by introducing a couple new indexes on the
usersCommunities table:
- `communityIdAndIsMember`
- `communityIdAndIsModerator`
- `...IsOwner`
- `...IsTeamMember` (moderator or owner)
Those four indexes allow us to efficiently query all the data we
commonly need.
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Status
Deploy after merge (delete what needn't be deployed)
Run database migrations (delete if no migration was added)
YES
Every time anybody loaded the community view we would run a query that would go through all the members of a community (that was quick), then filter them by e.g.
isMember = true(that was slow for big communities) and then order them byr.desc('reputation'). (that was also slow)Together, the filter and the orderBy meant that we would read a couple tens of thousands of records when somebody opened a large communities community view. Multiply that by concurrent users pointed at the platform and you've got a perfect storm of traffic we can't handle.
This patch fixes it by introducing a couple new indexes on the usersCommunities table:
communityIdAndIsMembercommunityIdAndIsModerator...IsOwner...IsTeamMember(moderator or owner)Those four indexes allow us to efficiently query all the data we commonly need.