code: def distinct(field)
        if field.nil? == false && field.respond_to?(:to_s)
          # disable counting if it was enabled.
          old_count_value = @count
          @count = nil
          compile_query = compile # temporary store
          # add distinct field
          compile_query[:distinct] = Query.format_field(field).to_sym
          @count = old_count_value
          # perform aggregation
          return client.aggregate_objects(@table, compile_query.as_json, _opts ).result
        else
          raise ArgumentError, "Invalid field name passed to `distinct`."
        end
      end
docs: Queries can be made using distinct, allowing you find unique values for a specified field.
   For this to be performant, please remember to index your database.
   @example
     # Return a set of unique city names
     # for users who are greater than 21 years old
     Parse::Query.all(distinct: :age)
     query = Parse::Query.new("_User")
     query.where :age.gt => 21
     # triggers query
     query.distinct(:city) #=> ["San Diego", "Los Angeles", "San Juan"]
   @note This feature requires use of the Master Key in the API.
   @param field [Symbol|String] The name of the field used for filtering.
   @version 1.8.0