1 files changed, 29 insertions, 0 deletions
diff --git a/lib/gitlab/background_migration/replace_blocked_by_links.rb b/lib/gitlab/background_migration/replace_blocked_by_links.rb
new file mode 100644
index 00000000000..26626aaef79
--- /dev/null
+++ b/lib/gitlab/background_migration/replace_blocked_by_links.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+# rubocop:disable Style/Documentation
+
+module Gitlab
+  module BackgroundMigration
+    class ReplaceBlockedByLinks
+      class IssueLink < ActiveRecord::Base
+        self.table_name = 'issue_links'
+      end
+
+      def perform(start_id, stop_id)
+        blocked_by_links = IssueLink.where(id: start_id..stop_id).where(link_type: 2)
+
+        ActiveRecord::Base.transaction do
+          # if there is duplicit bi-directional relation (issue2 is blocked by issue1
+          # and issue1 already links issue2), then we can just delete 'blocked by'.
+          # This should be rare as we have a pre-create check which checks if issues are
+          # already linked
+          blocked_by_links
+            .joins('INNER JOIN issue_links as opposite_links ON issue_links.source_id = opposite_links.target_id AND issue_links.target_id = opposite_links.source_id')
+            .where('opposite_links.link_type': 1)
+            .delete_all
+
+          blocked_by_links.update_all('source_id=target_id,target_id=source_id,link_type=1')
+        end
+      end
+    end
+  end
+end