Re: using xmin in a query?

On Thu, Jul 28, 2011 at 5:09 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Michael Nolan <htfoot(at)gmail(dot)com> writes:
> > It seems like we're being inconsistent here in allowing 'where xid =
> > integer' but not allowing 'where xid != integer'.
>
> Well, if you look into pg_operator you'll soon find that there are
> exactly two built-in operators that accept type xid: "=(xid,xid)" and
> "=(xid,integer)" (where I'd say the latter is just a kluge).
> There hasn't previously been any demand to flesh it out more than that.
> Do you have an actual use-case where <> would be helpful, or is this
> just experimentation?
>

I'm not sure yet. I was doing some thinking about ways to do incremental
backups
(at least for inserted/updated rows, deleted rows present a different
challenge),
and was just doing some simple queries to see what worked and what didn't..

It also appears you cannot group on a column of type xid.

Would adding a <> operator enable that?
--
Mike Nolan