1 files changed, 44 insertions, 0 deletions
diff --git a/lib/gitlab/background_migration/schedule_diff_files_deletion.rb b/lib/gitlab/background_migration/schedule_diff_files_deletion.rb
new file mode 100644
index 00000000000..609cf19187c
--- /dev/null
+++ b/lib/gitlab/background_migration/schedule_diff_files_deletion.rb
@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+# rubocop:disable Style/Documentation
+
+module Gitlab
+  module BackgroundMigration
+    class ScheduleDiffFilesDeletion
+      class MergeRequestDiff < ActiveRecord::Base
+        self.table_name = 'merge_request_diffs'
+
+        belongs_to :merge_request
+
+        include EachBatch
+      end
+
+      DIFF_BATCH_SIZE = 5_000
+      INTERVAL = 5.minutes
+      MIGRATION = 'DeleteDiffFiles'
+
+      def perform
+        diffs = MergeRequestDiff
+          .from("(#{diffs_collection.to_sql}) merge_request_diffs")
+          .where('merge_request_diffs.id != merge_request_diffs.latest_merge_request_diff_id')
+          .select(:id)
+
+        diffs.each_batch(of: DIFF_BATCH_SIZE) do |relation, index|
+          ids = relation.pluck(:id)
+
+          BackgroundMigrationWorker.perform_in(index * INTERVAL, MIGRATION, [ids])
+        end
+      end
+
+      private
+
+      def diffs_collection
+        MergeRequestDiff
+          .joins(:merge_request)
+          .where("merge_requests.state = 'merged'")
+          .where('merge_requests.latest_merge_request_diff_id IS NOT NULL')
+          .where("merge_request_diffs.state NOT IN ('without_files', 'empty')")
+          .select('merge_requests.latest_merge_request_diff_id, merge_request_diffs.id')
+      end
+    end
+  end
+end