title: Grails sort params
body: <p>I am using ExtJS4 library to show a grid of paged data served by a Grails controller and returned as JSON. 
  One of the fields is a calculated field that I cannot pass back to the database for a query ... because it's calculated. What is a good solution to implement for this type of column sort request? Other columns I just pass back to the query through : list(params) </p>