Addresses BE maintainer review62214-namespaces-storage-statistics-on-database

- Uses find_each instead of each, as the latter will load all rows into
memory.
- Includes a new spec on UpdateProjectStatistics shared examples to
ensure we're avoiding N+1 queries.
- Changes time Prunding worker is executed as midnight is mostly used by
other workers.

4 files changed, 19 insertions, 5 deletions

diff --git a/app/workers/namespaces/prune_aggregation_schedules_worker.rb b/app/workers/namespaces/prune_aggregation_schedules_worker.rb
index c660727869e..4e40feee702 100644
--- a/app/workers/namespaces/prune_aggregation_schedules_worker.rb
+++ b/app/workers/namespaces/prune_aggregation_schedules_worker.rb
@@ -6,9 +6,9 @@ module Namespaces
     include CronjobQueue
 
     # Worker to prune pending rows on Namespace::AggregationSchedule
-    # It's scheduled to run once a day at midnight.
+    # It's scheduled to run once a day at 1:05am.
     def perform
-      aggregation_schedules.each do |aggregation_schedule|
+      aggregation_schedules.find_each do |aggregation_schedule|
         aggregation_schedule.schedule_root_storage_statistics
       end
     end
diff --git a/app/workers/namespaces/schedule_aggregation_worker.rb b/app/workers/namespaces/schedule_aggregation_worker.rb
index 941149459c7..a4594b84b13 100644
--- a/app/workers/namespaces/schedule_aggregation_worker.rb
+++ b/app/workers/namespaces/schedule_aggregation_worker.rb
@@ -26,8 +26,8 @@ module Namespaces
     # calls UpdateProjectStatistics#schedule_namespace_statistics_worker.
     #
     # The migration and specs fails since NamespaceAggregationSchedule table
-    # does not exist at that point. Technical debt issue:
-    # https://gitlab.com/gitlab-org/gitlab-ce/issues/63775
+    # does not exist at that point.
+    # https://gitlab.com/gitlab-org/gitlab-ce/issues/50712
     def aggregation_schedules_table_exists?
       return true unless Rails.env.test?
 
diff --git a/config/initializers/1_settings.rb b/config/initializers/1_settings.rb
index 5c9ca97534d..bf187e9a282 100644
--- a/config/initializers/1_settings.rb
+++ b/config/initializers/1_settings.rb
@@ -442,7 +442,7 @@ Settings.cron_jobs['schedule_migrate_external_diffs_worker'] ||= Settingslogic.n
 Settings.cron_jobs['schedule_migrate_external_diffs_worker']['cron'] ||= '15 * * * *'
 Settings.cron_jobs['schedule_migrate_external_diffs_worker']['job_class'] = 'ScheduleMigrateExternalDiffsWorker'
 Settings.cron_jobs['namespaces_prune_aggregation_schedules_worker'] ||= Settingslogic.new({})
-Settings.cron_jobs['namespaces_prune_aggregation_schedules_worker']['cron'] ||= '0 0 * * *'
+Settings.cron_jobs['namespaces_prune_aggregation_schedules_worker']['cron'] ||= '5 1 * * *'
 Settings.cron_jobs['namespaces_prune_aggregation_schedules_worker']['job_class'] = 'Namespaces::PruneAggregationSchedulesWorker'
 
 Gitlab.ee do
diff --git a/spec/support/shared_examples/models/update_project_statistics_shared_examples.rb b/spec/support/shared_examples/models/update_project_statistics_shared_examples.rb
index a49d04958e7..aad63982e7a 100644
--- a/spec/support/shared_examples/models/update_project_statistics_shared_examples.rb
+++ b/spec/support/shared_examples/models/update_project_statistics_shared_examples.rb
@@ -74,6 +74,20 @@ shared_examples_for 'UpdateProjectStatistics' do
       subject.save!
     end
 
+    it 'avoids N + 1 queries' do
+      subject.write_attribute(statistic_attribute, read_attribute + delta)
+
+      control_count = ActiveRecord::QueryRecorder.new do
+        subject.save!
+      end
+
+      subject.write_attribute(statistic_attribute, read_attribute + delta)
+
+      expect do
+        subject.save!
+      end.not_to exceed_query_limit(control_count)
+    end
+
     context 'when the feature flag is disabled for the namespace' do
       it 'does not schedule a namespace statistics worker' do
         namespace = subject.project.root_ancestor