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.
Yes, I know that doesn't fit our existing model of 'all in one' system
catalogs. And the solution doesn't present itself readily -- but one day
someone will see the way to do this, and it will be good. It _will_ involve
refactoring the system catalog schema so that user 'system catalog' metadata
and system 'system catalog' data aren't codependent. A more modular data
storage approach at a level above the existing broken storage manager
modularity will result, and things will be different.
However, the number of messages on this subject has increased; one day it will
become an important feature worthy of core developer attention. That will be
a happy day for me, as well as many others. I have not the time to do it
myself; but I can be a gadfly, at least. In the meantime we have pg_upgrade
for the future 7.3 -> 7.4 upgrade.
--
Lamar Owen
WGCR Internet Radio
1 Peter 4:11
