How to apply dependent fileds filters in appengine datastore?

Question

Representation of my datastore:

key|first|second|
-----------------
xys|55   |34
-----------------
kow|32   |67

If I have to write a sql query then it should be like this:

select * from x where first > second + 20;

How could I write it in appengine datastore ? Is there any way to achieve it by Query.FilterPredicate ?

Answer 1

Based on the fact that all appengine queries must be efficient. I cant see how to avoid a full scan using datastore indexes of those two properties which is not efficient.
the solution is to also store the difference (first-second) then you can filter on the difference > 20.