Update the query that looks for stuck pending jobs
What does this MR do?
Related to #339237 (closed)
We have around 500 outdated stuck pending jobs in the database and this is causing a deadlock with the effort of migrating them to the ci_pending_builds table. This MR changes the database query to start dropping of the older builds and catching up to the newer ones.
This change is behind a feature flag and can be disabled if the query proves to be problematic.
Query and execution plans:
I think the previous timeout errors were caused by the wrong index being used(we have some that overlap):
"ci_builds_gitlab_monitor_metrics" btree (status, created_at, project_id) WHERE type::text = 'Ci::Build'::text"index_ci_builds_on_status_and_type_and_runner_id" btree (status, type, runner_id)"index_ci_builds_runner_id_pending_covering" btree (runner_id, id) INCLUDE (project_id) WHERE status::text = 'pending'::text AND type::text = 'Ci::Build'::text
The data that is being searched is pretty small in size, at this moment there are under 10000 pending builds:
gitlabhq_production=> SELECT COUNT(*) FROM "ci_builds" WHERE "ci_builds"."type" = 'Ci::Build' AND "ci_builds"."id" IN (SELECT "ci_builds"."id" FROM "ci_builds" WHERE "ci_builds"."type" = 'Ci::Build' AND ("ci_builds"."status" IN ('pending'))) ;
count
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9134
(1 row)As the worker processes these records, the query planner might decide to use a different index, so I've added a ORDER BY "ci_builds"."created_at" ASC, "ci_builds"."project_id" to the end of the query to force it to use ci_builds_gitlab_monitor_metrics all the time.
Screenshots or Screencasts (strongly suggested)
How to setup and validate locally (strongly suggested)
Does this MR meet the acceptance criteria?
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