classMergeRequestDiffAddIndex<ActiveRecord::MigrationincludeGitlab::Database::MigrationHelpersdisable_ddl_transaction!# Set this constant to true if this migration requires downtime.DOWNTIME=falsedefupadd_concurrent_index:merge_request_diffs,:merge_request_idenddefdownifindex_exists?(:merge_request_diffs,:merge_request_id)remove_index:merge_request_diffs,:merge_request_idendendend