The list of fields used to sort the index. Only boolean, numeric, date and keyword fields with doc_values are allowed here.

The missing parameter specifies how docs which are missing the field should be treated. The missing value can have the following values: Last: Documents without value for the field are sorted last. First: Documents without value for the field are sorted first.

The mode option controls what value, from a multi-value field, is picked to sort the document. The mode option can have the following values: Minimum: Pick the lowest value. Maximum: Pick the highest value.

The sort order to use for each field. The order option can have the following values: Ascending and Descending.