exports.up = function (knex) {
    return knex('monitor').whereNull('json_path_operator').update('json_path_operator', '==');
};
exports.down = function (knex) {
    // changing the json_path_operator back to null for all '==' is not possible anymore
    // we have lost the context which fields have been set explicitely in >= v2.0 and which would need to be reverted
};