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Diffstat (limited to 'doc/development/database/query_recorder.md')
| -rw-r--r-- | doc/development/database/query_recorder.md | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/doc/development/database/query_recorder.md b/doc/development/database/query_recorder.md index 3fc38c10d68..f1540e7e2ae 100644 --- a/doc/development/database/query_recorder.md +++ b/doc/development/database/query_recorder.md @@ -39,12 +39,17 @@ end As an example you might create 5 issues in between counts, which would cause the query count to increase by 5 if an N+1 problem exists. -In some cases the query count might change slightly between runs for unrelated reasons. In this case you might need to test `exceed_query_limit(control_count + acceptable_change)`, but this should be avoided if possible. +In some cases, the query count might change slightly between runs for unrelated reasons. In this case you might need to test `exceed_query_limit(control_count + acceptable_change)`, but this should be avoided if possible. If this test fails, and the control was passed as a `QueryRecorder`, then the failure message indicates where the extra queries are by matching queries on the longest common prefix, grouping similar queries together. +In some cases, N+1 specs have been written to include three requests: first one to +warm the cache, second one to establish a control, third one to validate that +ther are no N+1 queries. Rather than make an extra request to warm the cache, prefer two requests +(control and test) and configure your test to ignore [cached queries](#cached-queries) in N+1 specs. + ## Cached queries By default, QueryRecorder ignores [cached queries](../merge_request_performance_guidelines.md#cached-queries) in the count. However, it may be better to count @@ -62,7 +67,7 @@ end ## Use request specs instead of controller specs -Use a [request spec](https://gitlab.com/gitlab-org/gitlab-foss/tree/master/spec/requests) when writing a N+1 test on the controller level. +Use a [request spec](https://gitlab.com/gitlab-org/gitlab/-/tree/master/spec/requests) when writing a N+1 test on the controller level. Controller specs should not be used to write N+1 tests as the controller is only initialized once per example. This could lead to false successes where subsequent "requests" could have queries reduced (for example, because of memoization). |