Re: Problem with identity column & related sequences

Jeff Hoffmann  writes:
> I am using postgresql-12.8.  I am using I am making use of an identity
> column for part of a scripts to process some updated data.  Because of
> the way the script is called I don't necessarily know if this column
> is going to exist in the table I am working on so I have a step that
> will conditionally create the column if it doesn't already exist, i.e.

> alter table mytable add column if not exists unique_id integer
> generated always as identity;

You're right, this sort of thing does not work very well in v12 and
before.  We fixed it in v13, but the changes seemed far too invasive
to risk a back-patch [1].

			regards, tom lane

[1] https://git.postgresql.org/gitweb/?p=postgresql.git&a=commitdiff&h=1281a5c90