"Christopher Kings-Lynne" <chriskl@familyhealth.com.au> writes:
> The one big programming difficulty I see is the process of running through
> all the existing tuples in the relation the column was added to and
> evaluating the default for each row.
Basically you wanna do an "UPDATE tab SET col = <default expr>". I'd
suggest letting the existing machinery handle as much of that as
possible.
regards, tom lane