Sidenote: the current behaviour allows everyone to have e.g. a heavy lambda attached to a field and fire that one only when needed. If your lambda needs both values, you should update the record specifying both values everywhere. Disclaimer: I'm "a db man" hence not a big fan of computed fields - I prefer triggers on the db. Even when triggers where not available in web2py (and I couldn't write triggers directly on the db), I wrote small functions to help on this kind of things. Now that "triggers" are available on web2py, this kind of "situation" can be easily addressed (and a lot better) with those.
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