A named expression that can be evaluated at search time. Can be used to sort the search results, define other expressions, or return computed information in the search results.
Names must begin with a letter and can contain the following characters: a-z (lowercase), 0-9, and _ (underscore).
Length constraints: Minimum length of 1. Maximum length of 64.
The expression to evaluate for sorting while processing a search request. The
Length constraints: Minimum length of 1. Maximum length of 10240.