+ALTER TABLE tb_tariffs ADD change_policy_timeout DM_MOMENT DEFAULT '1970-01-01 00:00:00';
+
+UPDATE tb_tariffs SET change_policy = 'allow', change_policy_timeout = '1970-01-01 00:00:00';
+
+ALTER TABLE tb_tariffs ALTER COLUMN change_policy DROP DEFAULT;
+ALTER TABLE tb_tariffs ALTER COLUMN change_policy_timeout DROP DEFAULT;