On 10/10/07, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> "Marko Kreen" <markokr@gmail.com> writes:
> > IMHO the core operations are already as stable as PostgreSQL use
> > of MVCC, as the module just exports backend internal state...
>
> Well, it exports backend internal state that did not exist before 8.2
> (ie, XID epoch). So it doesn't seem all that set in stone to me.
Ok. Lets say the API concepts are 6-7 years old. The epoch was
a only thing missing in API ca. 2 years ago (the 8byte txid was
written on 8.0), so now the API is complete.
> > Another thing can can be done is more compact representation for
> > txid_snapshot type, but that also won't affect core operation.
>
> That's another thing that's likely to become very much harder to change
> once it's in core. People keep threatening to produce a working
> in-place-upgrade process, and once that's reality the on-disk
> representation of core types is going to be hard to change.
Good point. But txid_snapshot happens to have couple of free
bits that can be used to create backwards compatibility, so I
don't think that could be a big problem.
Anyway, the in-place upgrade seems a month-two away couple of
years now :)
--
marko