On Sun, Nov 13, 2011 at 6:57 PM, Florian Pflug <fgp@phlo.org> wrote:
> On Nov13, 2011, at 01:38 , Tom Lane wrote:
>> Just a couple hours ago I was wondering why we create system columns for
>> foreign tables at all. Is there a reasonable prospect that they'll ever
>> be useful? I can see potential value in tableoid, but the others seem
>> pretty dubious --- even if you were fetching from a remote PG server,
>> the XIDs would not be meaningful within our own environment.
>
> At least ctid seems useful too. I've used that in the past as a poor man's
> surrogate primary key.
>
> Also, people have used ctid and xmin in the past to re-find previously
> visited rows and to check whether they've been modified. So there might be
> some value in keeping xmin around also (and make the postgres fdw populate it)
My vote is to nuke 'em all. :-)
I don't think that we want to encourage people to depend on the
existence of system columns any more than they do already.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company