Re: ERROR: attribute number 6 exceeds number of columns 5

At Tue, 26 Nov 2019 10:49:11 -0500, Tom Lane <tgl@sss.pgh.pa.us> wrote in 
> 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.

Something like this works?

ALTER TABLE gtest25 ADD COLUMN x int, ADD COLUMN y int GENERATED ALWAYS AS (x * 4) STORED;
ERROR:  column "x" does not exist
DETAIL:  An expression cannot reference columns added in the same command.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center