Add a 10 ms bucket for SQL timings

This allows us to calculate quantiles of SQL timings more accurately,
instead of a lot of timings being assigned to the 50 ms bucket.

changelogs/unreleased/tweak-sql-buckets.yml

@@ -0,0 +1,5 @@
+---
+title: Add a 10 ms bucket for SQL timings
+merge_request:
+author:
+type: changed

lib/gitlab/metrics/subscribers/active_record.rb

@@ -20,7 +20,7 @@ module Gitlab
         define_histogram :gitlab_sql_duration_seconds do
           docstring 'SQL time'
           base_labels Transaction::BASE_LABELS
-          buckets [0.05, 0.1, 0.25, 0.5, 1.0, 2.5, 5.0]
+          buckets [0.01, 0.05, 0.1, 0.25, 0.5, 1.0, 2.5, 5.0]
         end
 
         def current_transaction