Re: pgsql: Don't trust NOT NULL on virtual generated columns of partitioned

On 2026-Oct-26, shihao zhong wrote:

> Hi Manu,
>
> Thanks for testing the pg_upgrade, I forgot about that.
>
> I don't think the logic is wrong here, but maybe we can make some
> improvement to the error message. v2 changes
>
> on the partitioned table of each column listed in the file
> =>
> on the partitioned table of each column. In version 18 this is not
> allowed on a table with CHECK constraints, so drop them first and
> add them back afterwards. A list of the problem columns is in the
> file

I think the doc changes here are not ideal; they kinda suggest that there are
numerous different generated column types for which you can have different
generation expressions except for one special case -- rather than one case yes,
one case no. How about something like this?

If a parent column is a generated column, its child column must also
- be a generated column of the same kind (stored or virtual); however,
- the child column can have a different generation expression, except
- that a virtual generated column of a partition must have the same
- generation expression as the partitioned table.
+ be a generated column of the same kind (stored or virtual).
+ In addition, for virtual generated columns, the child column's
+ generation expression must be identical to that of the parent.
+ For stored generated columns, they are allowed to differ.

--
Álvaro Herrera Breisgau, Deutschland — https://www.EnterpriseDB.com/
"I'm impressed how quickly you are fixing this obscure issue. I came from
MS SQL and it would be hard for me to put into words how much of a better job
you all are doing on [PostgreSQL]."
Steve Midgley, http://archives.postgresql.org/pgsql-sql/2008-08/msg00000.php