Bruce Momjian dijo:
> Justin Clift wrote:
> > Alvaro Herrera wrote:
> > 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?
>
> Yes, we could, but if we are going to do that, we may as well just
> automate the dump/reload.
I don't think that's an acceptable solution. It requires too much free
disk space and too much time. On-line upgrading, meaning altering the
databases on a table-by-table basis (or even page-by-page) solves both
problems (binary conversion sure takes less than converting to text
representation and parsing it to binary again).
I think a converting postmaster would be a waste, because it's unneeded
functionality 99.999% of the time. I'm leaning towards an external
program doing the conversion, and the backend just aborting if it finds
old or in-conversion data. The converter should be able to detect that
it has aborted and resume conversion.
What would that converter need:
- the old system catalog (including user defined data)
- the new system catalog (ditto, including the schema)
- the storage manager subsystem
I think that should be enough for converting table files. I'd like to
experiment with something like this when I have some free time. Maybe
next year...
--
Alvaro Herrera (<alvherre[a]atentus.com>)
"I think my standards have lowered enough that now I think 'good design'
is when the page doesn't irritate the living fuck out of me." (JWZ)
