Tom Lane <> writes:

> Robert Haas <> writes:
>> Right.  If there were a DEFAULT on the new column that would of course
>> be different, and you can also do thinks like CHECK (a != b) here.
>> However, if the CHECK constraint does not reference any column other
>> than the newly-added one, and if the new column will have the same
>> value for every row either because there is no default or because the
>> default is a constant,
> ... and if the CHECK expression is immutable ...

Doesn't it have to be already?  Otherwise a value accepted at one point
in time could suddenly violate the constraint later, even though it
never changed.


"A disappointingly low fraction of the human race is,
 at any given time, on fire." - Stig Sandbeck Mathisen

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