1 files changed, 27 insertions, 0 deletions
diff --git a/lib/gitlab/background_migration/migrate_stage_index.rb b/lib/gitlab/background_migration/migrate_stage_index.rb
new file mode 100644
index 00000000000..e66fec7b20d
--- /dev/null
+++ b/lib/gitlab/background_migration/migrate_stage_index.rb
@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+# rubocop:disable Style/Documentation
+
+module Gitlab
+  module BackgroundMigration
+    class MigrateStageIndex
+      module Migratable
+        class Stage < ActiveRecord::Base
+          self.table_name = 'ci_stages'
+        end
+      end
+
+      def perform(start_id, stop_id)
+        sql = <<~SQL
+          UPDATE ci_stages
+            SET index =
+              (SELECT stage_idx FROM ci_builds
+                WHERE ci_builds.stage_id = ci_stages.id
+                GROUP BY ci_builds.stage_idx ORDER BY COUNT(*) DESC LIMIT 1)
+          WHERE ci_stages.id BETWEEN #{start_id.to_i} AND #{stop_id.to_i}
+        SQL
+
+        ActiveRecord::Base.connection.execute(sql)
+      end
+    end
+  end
+end