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Re: Upgrading rant.

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Lamar Owen <lamar(dot)owen(at)wgcr(dot)org>, Hannu Krosing <hannu(at)tm(dot)ee>,mlw <pgsql(at)mohawksoft(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Upgrading rant.
Date: 2003-01-06 03:25:21
Message-ID: 200301060325.h063PL026969@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > OK, taking up the pg_upgrade banner, I think there are two things
> > missing from the current code:
> 
> > 1) schema awareness  -- easily fixed with some code
> > 2) need to creat clog files to match incremented xid
> 
> > I can do 1, and I think Tom can help me with 2.
> 
> I was just now wondering whether we really need to do that at all.
> We're already vacuuming the user tables before we bring 'em over.
> What if we VACUUM FREEZE them instead?  Then there are *no* xids of
> interest in the tables being brought over, and no need to screw around
> with the xid counter in the new installation.  That in turn would mean
> no need to mess with its pg_clog files.  I think we'd still need to
> advance the xlog position past the old installation's xlog end, but we
> have the tool for that (pg_resetxlog) already.

VACUUM FREEZE.  Interesting idea.  Did we have that in 7.2?  I never
thought of using it.  Good idea.

Why do we have to do WAL?  Do we have WAL log id's in the tuple headers?
I don't remember.  I don't see them in a quick look.

> > Also, I think we make index format changes more frequently that Tom
> > recollects.  Tom?
> 
> Oh?  Name one... not that they'd be a critical problem anyway, as we
> could easily reconstruct indexes via REINDEX rather than moving them
> over, any time we made such a change.

I remember fixing index problems, and asking folks to rebuild indexes
_after_ we fixed them, so I thought they had a new format.  I guess they
were just broken indexes that had to be rebuilt to get the fix.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

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