Unverified Commit aafe5c12 authored by
Update composite pipelines index to include "id"
This updates the composite index on ci_pipelines (project_id, ref, status) to also include the "id" column at the end. Adding this column to the index drastically improves the performance of queries used for getting the latest pipeline for a particular branch. For example, on project dashboards we'll run a query like the following: SELECT ci_pipelines.* FROM ci_pipelines WHERE ci_pipelines.project_id = 13083 AND ci_pipelines.ref = 'master' AND ci_pipelines.status = 'success' ORDER BY ci_pipelines.id DESC LIMIT 1; Limit (cost=0.43..58.88 rows=1 width=224) (actual time=26.956..26.956 rows=1 loops=1) Buffers: shared hit=6544 dirtied=16 -> Index Scan Backward using ci_pipelines_pkey on ci_pipelines (cost=0.43..830922.89 rows=14216 width=224) (actual time=26.954..26.954 rows=1 loops=1) Filter: ((project_id = 13083) AND ((ref)::text = 'master'::text) AND ((status)::text = 'success'::text)) Rows Removed by Filter: 6476 Buffers: shared hit=6544 dirtied=16 Planning time: 1.484 ms Execution time: 27.000 ms Because of the lack of "id" in the index we end up scanning over the primary key index, then applying a filter to filter out any remaining rows. The more pipelines a GitLab instance has the slower this will get. By adding "id" to the mentioned composite index we can change the above plan into the following: Limit (cost=0.56..2.01 rows=1 width=224) (actual time=0.034..0.034 rows=1 loops=1) Buffers: shared hit=5 -> Index Scan Backward using yorick_test on ci_pipelines (cost=0.56..16326.37 rows=11243 width=224) (actual time=0.033..0.033 rows=1 loops=1) Index Cond: ((project_id = 13083) AND ((ref)::text = 'master'::text) AND ((status)::text = 'success'::text)) Buffers: shared hit=5 Planning time: 0.695 ms Execution time: 0.061 ms This in turn leads to a best-case improvement of roughly 25 milliseconds, give or take a millisecond or two.
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