When running in the internal web server, you can use live text to debug your queries. This are the extra livetext fields added to the context. The will always have the form of name starting with filter and then added the table name that is filtered. Then you have three livetext elements that can be shown.

Livefield Filter description
filterTablename.filter A dictionary holding the collective filter used to build the generated filter based on the DG3 filtering rules.
filterTablename.generatedfilter A string holding the filter as it is sent to tablefilter in PRISM.
filterTablename.returnedfilter The value returned form tablefilter in PRISM
filterTablename.errorfilter Error message if filter failed