code: function limitSpec(type, limit, orderByColumns) {
    if (utils.isObject(type)) {
      return type
    }
  
    if (typeof limit !== 'number') {
      limit = parseInt(limit, 10)
    }
  
    if (type !== 'default') {
      throw new FieldError('Currently only DefaultLimitSpec is supported')
    }
    else if (isNaN(limit)) {
      throw new FieldTypeError('limitSpec.limit', 'number')
    }
    else if (!Array.isArray(orderByColumns)) {
      throw new FieldTypeError('limitSpec.columns', 'array')
    }
  
    return {
      type:    type,
      limit:   parseInt(limit, 10),
      columns: orderByColumns
    }
  }
docs: Set limit spec
  
  @see http://druid.io/docs/0.6.120/LimitSpec.html
  @param {string|object} [type=default] Type of LimitSpec or LimitSpec object
  @param {number} [limit] Limit of records
  @param {object[]} [orderByColumns] Sorting columns
  returns {object}