On Thu, Jul 28, 2011 at 5:36 PM, Tom Lane <t...@sss.pgh.pa.us> wrote:
> Michael Nolan <htf...@gmail.com> writes: > > It also appears you cannot group on a column of type xid. > > You can in 8.4 and up. Previous versions only know how to GROUP BY > sortable columns, which requires a btree opclass, which xid doesn't > have and really can't have because it doesn't have a linear ordering. > There is a hash opclass for it, though, so in versions that know how to > GROUP BY using hashing, it'll work. > :sigh: I thought I had done all the tests on my 9.0.4 testbed server too. One of these days I hope to get the production and development servers off 8.2. I more or less understand why xid types don't have a linear ordering from Robert Hass's tutorial at PGCON11. So, a <> operator (either xid,xid or xid,integer) would need to be implemented using the hash opclass, correct? (I don't have a use case for it yet, though.) > > > Would adding a <> operator enable that? > > No, it's pretty irrelevant ... > OK, thanks for putting up with my noobie questions. -- Mike Nolan
