Improve performance of stale Ci::Runner queries
What does this MR do and why?
Describe in detail what your merge request does and why.
This MR optimizes the query behind the stale
Ci::Runner
scope so that it uses UNION ALL
instead of OR
. This allows making use of the index_ci_runners_on_id_desc_and_contacted_at_desc
and index_ci_runners_on_created_at_and_id_desc
indices. Previously it was only making use of index_ci_runners_on_created_at_and_id_desc
.
Screenshots or screen recordings
Screenshots are required for UI changes, and strongly recommended for all other merge requests.
How to set up and validate locally
Numbered steps to set up and validate the change are strongly suggested.
Database queries
Ci::Runner.stale
Previous query
SQL query
SELECT "ci_runners".*
FROM "ci_runners"
WHERE (ci_runners.created_at < '2022-10-09 13:40:07.110762'
AND (ci_runners.contacted_at IS NULL
OR ci_runners.contacted_at < '2022-10-09 13:40:07.110762'))
Query execution plan
https://postgres.ai/console/gitlab/gitlab-production-ci/sessions/14307/commands/50174
Index Scan using index_ci_runners_on_created_at_and_id_desc on public.ci_runners (cost=0.43..384168.25 rows=1022535 width=282) (actual time=0.030..2481.873 rows=1434475 loops=1)
Index Cond: (ci_runners.created_at < '2022-10-09 13:40:07.110762'::timestamp without time zone)
Filter: ((ci_runners.contacted_at IS NULL) OR (ci_runners.contacted_at < '2022-10-09 13:40:07.110762'::timestamp without time zone))
Rows Removed by Filter: 178676
Buffers: shared hit=967790 read=11 dirtied=8
I/O Timings: read=11.005 write=0.000
New query
SQL query
SELECT "ci_runners".*
FROM "ci_runners"
WHERE "ci_runners"."created_at" < '2022-10-09 16:20:08.524669'
AND "ci_runners"."id" IN (
SELECT "ci_runners"."id"
FROM ((
SELECT "ci_runners"."id"
FROM "ci_runners"
WHERE "ci_runners"."contacted_at" IS NULL)
UNION ALL (
SELECT "ci_runners"."id"
FROM "ci_runners"
WHERE "ci_runners"."contacted_at" < '2022-10-09 16:20:08.524762')) ci_runners)
Query execution plan
https://postgres.ai/console/gitlab/gitlab-production-ci/sessions/14307/commands/50185
Append (cost=0.43..551022.69 rows=1273871 width=282) (actual time=36.163..1985.434 rows=1434488 loops=1)
Buffers: shared hit=891885
I/O Timings: read=0.000 write=0.000
-> Index Scan using index_ci_runners_on_contacted_at_desc_and_id_desc on public.ci_runners (cost=0.43..265788.81 rows=633703 width=282) (actual time=36.162..806.536 rows=708888 loops=1)
Index Cond: (ci_runners.contacted_at IS NULL)
Filter: (ci_runners.created_at < '2022-10-09 14:18:30.26585'::timestamp without time zone)
Rows Removed by Filter: 9854
Buffers: shared hit=257990
I/O Timings: read=0.000 write=0.000
-> Index Scan using index_ci_runners_on_contacted_at_desc_and_id_desc on public.ci_runners ci_runners_1 (cost=0.43..266125.81 rows=640168 width=282) (actual time=0.058..1044.176 rows=725600 loops=1)
Index Cond: (ci_runners_1.contacted_at < '2022-10-09 14:18:30.265939'::timestamp without time zone)
Filter: (ci_runners_1.created_at < '2022-10-09 14:18:30.26585'::timestamp without time zone)
Rows Removed by Filter: 0
Buffers: shared hit=633895
I/O Timings: read=0.000 write=0.000
MR acceptance checklist
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