Fix notification query plan for users with domain blocks #7981

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lambadalambda merged 2 commits from fix/domain-block-subplan-cost into develop

2026-09-02 13:41:41 +00:00

lambadalambda commented

2026-09-02 09:42:57 +00:00

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keep_following_or_not_domain_blocked/2 uses ? = ANY(SELECT ap_id FROM users JOIN following_relationships ...). Postgres folds that hashed sub-plan's startup cost into the actor index scan and charges it on every rescan of the nested loop, so for a user with a long follow list the index plan is estimated ~1000x too high and can lose to a plan that materialises every active user per candidate row.

Wrapping the subselect in ARRAY(...) makes it an InitPlan, evaluated and costed once.

Measured on a 312 GB instance, /api/v1/notifications for a user with 20k notifications and 2.3k follows:

	planner cost	actual
materialise-users plan (chosen at work_mem 64MB)	339,878	3.8 s
index plan, before	373,199	74 ms
index plan, after	17,255	4.8 ms

Adds a test for the followed-actor exception through Notification.for_user/1.

`keep_following_or_not_domain_blocked/2` uses `? = ANY(SELECT ap_id FROM users JOIN following_relationships ...)`. Postgres folds that hashed sub-plan's startup cost into the actor index scan and charges it on every rescan of the nested loop, so for a user with a long follow list the index plan is estimated ~1000x too high and can lose to a plan that materialises every active user per candidate row. Wrapping the subselect in `ARRAY(...)` makes it an InitPlan, evaluated and costed once. Measured on a 312 GB instance, `/api/v1/notifications` for a user with 20k notifications and 2.3k follows: | | planner cost | actual | |---|---|---| | materialise-users plan (chosen at work_mem 64MB) | 339,878 | 3.8 s | | index plan, before | 373,199 | 74 ms | | index plan, after | 17,255 | 4.8 ms | Adds a test for the followed-actor exception through `Notification.for_user/1`.

lambadalambda added 1 commit

2026-09-02 09:42:57 +00:00

fix(notifications): cost the followed-accounts subselect once

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635bc19ac8

Wrap the followed ap_ids subselect in keep_following_or_not_domain_blocked
in ARRAY(...) so it becomes an InitPlan. As a plain subselect the planner
charged its startup per rescan of the actor lookup, which could make
Notification.for_user pick a plan that scans every active user per row.

lambadalambda added 1 commit

2026-09-02 10:19:28 +00:00

Merge branch 'develop' into fix/domain-block-subplan-cost

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