Re: [Bug]Vacuum full silently NULL out fast default columns

SATYANARAYANA NARLAPURAM <satyanarlapuram(at)gmail(dot)com> writes:
> VACUUM FULL silently turns columns added via ALTER TABLE ... ADD COLUMN ...
> DEFAULT <const> into NULL
> on all pre-existing rows. The issue exists for other operations like
> CLUSTER, REPACK.

That is a seriously awful bug. Fortunately it is not in any shipping
release. A quick bisect run agrees that it broke here:

28d534e2ae0ac888b5460f977a10cd9bb017ef98 is the first bad commit
commit 28d534e2ae0ac888b5460f977a10cd9bb017ef98 (HEAD)
Author: Álvaro Herrera <alvherre(at)kurilemu(dot)de>
Date: Mon Apr 6 21:55:08 2026 +0200

Add CONCURRENTLY option to REPACK

> Patch attached. Added a regression test in fast_default.sql covering
> VACUUM FULL, CLUSTER, and REPACK on a table with fast-default columns
> including a NOT NULL CHECK column.

I don't know if this is the best code fix (I don't like putting extra
checks into a loop condition like this). But I agree we need some
more tests covering this area.

regards, tom lane