text: exports.up = function(knex) {
  	return knex.schema.hasColumn('urls', 'updatedAt').then(exists => {
  		if (!exists) {
  			return knex.schema.table('urls', table => {
  				switch (knex.client.config.client) {
  					case 'mysql':
  					case 'mysql2':
  						table.timestamp('updatedAt').defaultTo(knex.fn.now());
  						break;
  					default:
  						table.timestamp('updatedAt');
  						break;
  				}
  			});
  		}
  	});
  };
  
  exports.down = function(knex) {
  	return knex.schema.hasColumn('urls', 'updatedAt').then(exists => {
  		if (exists) {
  			return knex.schema.table('urls', table => {
  				table.dropColumn('updatedAt');
  			});
  		}
  	});
  };
  