"Christopher Kings-Lynne" <chriskl@familyhealth.com.au> writes:
> Messing about with ADD COLUMN...
> I'm not certain how to re-evaluate the default expression for each
> row?
Basically you'll want to apply ExecEvalExpr (or perhaps
ExecEvalExprSwitchContext) to the "cooked" expression tree.
Look at the execution of per-row constraints in ADD CONSTRAINT;
should be very very similar.
regards, tom lane