Optimize notification timestamp pagination#988
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raymondjacobson
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Jul 7, 2026
## Summary - Bound unread notification polling to the newest 25k single-recipient and 25k multi-recipient candidates before grouping. - Bound first-page and timestamp notification reads to newest candidate groups, then cap expensive validation/JSON aggregation to the newest 100 actions per selected group. - Reuse the read-only transaction with scoped `SET LOCAL enable_seqscan = off` for candidate-limited notification reads, including unread polling. ## Why - Today after PR #988, the remaining failures shifted to first-page `limit=20` and unread `limit=0`, not just timestamp pagination. - Since midnight Pacific on 2026-07-07, Cloud Logging showed 49 `notifications unread query timed out` and 13 `notifications query timed out` messages. - The hot first page for `eJ57D` includes giant groups: roughly 11.7k `save:4281:type:playlist` rows and 12.3k `follow:51` rows inside the newest candidate groups. Candidate rows alone were still too many for the full validation/aggregation stack. ## Live validation - Bounded unread query for `eJ57D` returned count 20 in ~0.6s. - First-page candidate rows without action capping still timed out under the 8s statement timeout when the full filter stack was included. - First-page full filter stack with newest 100 actions per selected group returned a full 20-group page in ~0.42s. ## Product impact - Very large notification groups now return the newest 100 actions for that group in candidate-limited reads instead of trying to return thousands of action rows. - The endpoint still returns the same response shape and group ordering, but giant grouped notifications may include fewer action objects. ## Test plan - `go test ./api -run ^'$'`\n- Attempted `go test ./api -run TestV1Notifications`; blocked locally because the test DB at `localhost:21300` is not running.
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Summary
SET LOCAL enable_seqscan = offso the multi-recipient candidate branch uses the partial GIN path instead of the bad sequential scan plan.Live evidence
notifications query timed out), not unread polling.user_id=51,timestamp=1783054526.961588), the unbounded full page timed out under the 8s read guard.Test plan
go test ./api -run ^'$'