Have a table with column quantityonhand which is computed.

COMPUTED BY (quantitypurchased-quantityconsumed)

Now the problem I have is that the column does NOT compute when I
update one of the two columns (purchased or consumed).

Both columns are defined as Int and the computed column is BigInt, and
all have no default.

When I update from a Python program with kinterbasdb the computed
column is not updated.

When I try to update from e.g. IBExpert I get an error that I am
trying to update a read-only column.

I just figured out how to make the Python program work, have to ensure
that neither of the two base columns contain Null.

Shouldn't Firebird (1.5RC2) be able to deal with this? Or am I
doing/or not doing something?

Best regards
Werner