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Re: 7.2.3?

From: Alvaro Herrera <alvherre(at)atentus(dot)com>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: Justin Clift <justin(at)postgresql(dot)org>,Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>,PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: 7.2.3?
Date: 2002-09-29 04:31:38
Message-ID: Pine.LNX.4.44.0209290022370.5621-100000@alvh.no-ip.org (view raw or flat)
Thread:
Lists: pgsql-hackers
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)


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  • Re: 7.2.3? at 2002-09-29 01:23:31 from Bruce Momjian

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