Good idea.  I tried this with a more general approach.  This introduces two new methods ```get_field_type``` and ```get_field_query```.  ```get_field_query``` returns the query class for the given field, or ```SubstringQuery``` if none is defined.  ```get_field_type``` returns the type of the field -if defined- or ```unicode`` if undefined.  ```get_field_type``` is ATM only used by the ```NumericQuery``` to provide for correct formatting ...