: Yes that worked, thanks Alan. The consistency of this api is "challenging".
It's important to understand what's happening here. fl, by default, only returns "stored" fields -- but you can also request "psuedo-fields" such as the results of functions, or the result of a "Doc Transformer" ... http://wiki.apache.org/solr/CommonQueryParameters#fl On the other side of things, the ExtenalFileField has some very special behavior that allows it to be used as the input to a function, but it does not act as a true stored or indexed field -- it's completley external to the index... https://lucene.apache.org/solr/4_3_1/solr-core/org/apache/solr/schema/ExternalFileField.html The syntax Alan suggested tells the solr response writer to generate a psuedo-field for each doc in the response which contains the results of a function call -- that function just so happens to be a simple field() function that returns the numeric value of the specified field name -- which works for EFF since (as mentioned before) EFF can be used as the input to any function. -Hoss
