Andreas Joseph Krogh <andreas@visena.com> writes:
> Run the attached script and you'll get: 
> psql -f error.sql -d test 
> psql:error.sql:37: ERROR: attribute number 6 exceeds number of columns 5
Hmm, interesting.  IMO, that *should* have thrown an error, but of
course not that one.  The ADD COLUMN operations are all processed
in parallel, so it's not okay for one of them to have a GENERATED
expression that refers to another one of the new columns.  But you
should have gotten a "no such column" type of error, not a run-time
cross-check failure.
            regards, tom lane