On Sun, 2002-09-29 at 07:19, Lamar Owen wrote:
> On Saturday 28 September 2002 09:23 pm, Bruce Momjian wrote:
> > Justin Clift wrote:
> > > Alvaro Herrera wrote:
> > > > I agree with Lamar that upgrading is a very difficult process right
>
> > > As a "simple for the user approach", would it be
> > > too-difficult-to-bother-with to add to the postmaster an ability to
> > > start up with the data files from the previous version, for it to
> > > recognise an old data format automatically, then for it to do the
> > > conversion process of the old data format to the new one before going
> > > any further?
>
> > > Sounds like a pain to create initially, but nifty in the end.
>
> > Yes, we could, but if we are going to do that, we may as well just
> > automate the dump/reload.
>
> Automating the dump/reload is fraught with pitfalls. Been there; done that;
> got the t-shirt. The dump from the old version many times requires
> hand-editing for cases where the complexity is above a certain threshold.
> The 7.2->7.3 threshold is just a little lower than normal.
>
> Our whole approach to the system catalog is wrong for what Justin (and many
> others would like to see).
>
> With MySQL, for instance, one can migrate on a table-by-table basis from one
> table type to another. As older table types are continuously supported, one
> can upgrade each table in turn as you need the featureset supported by that
> tabletype.
The initial Postgres design had a notion of StorageManager's, which
should make this very easy indeed, if it had been kept working .
IIRC the black box nature of storage manager interface was broken at
latest when adding WAL (if it had really been there in the first place).
----------------------
Hannu