Merge branch...

Merge branch '39054-activerecord-statementinvalid-pg-querycanceled-error-canceling-statement-due-to-statement-timeout' into 'master'

Resolve "ActiveRecord::StatementInvalid: PG::QueryCanceled: ERROR:  canceling statement due to statement timeout"

Closes #39054

See merge request gitlab-org/gitlab-ce!15063

app/models/merge_request.rb

@@ -878,7 +878,7 @@ class MergeRequest < ActiveRecord::Base
   #
   def all_commit_shas
     if persisted?
-      column_shas = MergeRequestDiffCommit.where(merge_request_diff: merge_request_diffs).pluck('DISTINCT(sha)')
+      column_shas = MergeRequestDiffCommit.where(merge_request_diff: merge_request_diffs).limit(10_000).pluck('sha')
       serialised_shas = merge_request_diffs.where.not(st_commits: nil).flat_map(&:commit_shas)
 
       (column_shas + serialised_shas).uniq

changelogs/unreleased/39054-activerecord-statementinvalid-pg-querycanceled-error-canceling-statement-due-to-statement-timeout.yml

+---
+title: Stop merge requests with thousands of commits from timing out
+merge_request: 15063
+author:
+type: performance