1 files changed, 24 insertions, 0 deletions
diff --git a/lib/gitlab/database/subquery.rb b/lib/gitlab/database/subquery.rb
new file mode 100644
index 00000000000..36e4559b554
--- /dev/null
+++ b/lib/gitlab/database/subquery.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Database
+    module Subquery
+      class << self
+        def self_join(relation)
+          t = relation.arel_table
+          t2 = if !Gitlab.rails5?
+                 relation.arel.as('t2')
+               else
+                 # Work around a bug in Rails 5, where LIMIT causes trouble
+                 # See https://gitlab.com/gitlab-org/gitlab-ce/issues/51729
+                 r = relation.limit(nil).arel
+                 r.take(relation.limit_value) if relation.limit_value
+                 r.as('t2')
+               end
+
+          relation.unscoped.joins(t.join(t2).on(t[:id].eq(t2[:id])).join_sources.first)
+        end
+      end
+    end
+  end
+end