Improve EnqueuerWorker query performance

Updates the EnqueuerWorker query to use LIMIT 10 to
allow it to find the right index due to postgres incorrectly
calculating the optimal query plan.

app/workers/container_registry/migration/enqueuer_worker.rb

@@ -125,17 +125,18 @@ def maximum_capacity
 
       def next_repository
         strong_memoize(:next_repository) do
-          # Using .limit(2)[0] instead of take here. Using a LIMIT 1 caused the query planner to
-          # use an inefficient sequential scan instead of picking an index. LIMIT 2 works around
+          # Using .limit(25)[0] instead of take here. Using a LIMIT 1 and 2 caused the query planner to
+          # use an inefficient sequential scan instead of picking an index. LIMIT 25 works around
           # this issue.
-          # See https://gitlab.com/gitlab-org/gitlab/-/merge_requests/87733 for details.
-          ContainerRepository.ready_for_import.limit(2)[0] # rubocop:disable CodeReuse/ActiveRecord
+          # See https://gitlab.com/gitlab-org/gitlab/-/merge_requests/87733 and
+          # https://gitlab.com/gitlab-org/gitlab/-/merge_requests/90735 for details.
+          ContainerRepository.ready_for_import.limit(25)[0] # rubocop:disable CodeReuse/ActiveRecord
         end
       end
 
       def next_aborted_repository
         strong_memoize(:next_aborted_repository) do
-          ContainerRepository.with_migration_state('import_aborted').limit(2)[0] # rubocop:disable CodeReuse/ActiveRecord
+          ContainerRepository.with_migration_state('import_aborted').limit(25)[0] # rubocop:disable CodeReuse/ActiveRecord
         end
       end
 

spec/workers/container_registry/migration/enqueuer_worker_spec.rb

@@ -158,7 +158,7 @@
 
           expect(worker).to receive(:handle_next_migration).exactly(3).times.and_call_original
 
-          expect { subject }.to make_queries_matching(/LIMIT 2/)
+          expect { subject }.to make_queries_matching(/LIMIT 25/)
 
           expect(container_repository.reload).to be_pre_importing
           expect(container_repository2.reload).to be_pre_importing