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Re: nested transactions

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: Manfred Koizar <mkoi-pg(at)aon(dot)at>,PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: nested transactions
Date: 2002-11-29 03:10:57
Message-ID: 200211290310.gAT3Av903644@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Tom Lane wrote:
> > Isn't there some other way we can link these subtransactions together
> > rather than mucking with pg_clog, as we only need the linkage while we
> > mark them all committed?
> 
> You *cannot* expect to do it all in shared memory; you will be blown out
> of the water by the first long transaction that comes along, if you try.
> So the question is not whether we put the status into a file, it is only
> what representation we choose.
> 
> Manfred suggested a separate log file ("pg_subclog" or some such) but
> I really don't see any operational advantage to that.  You still end up
> with 4 bytes per transaction, you're just assuming that putting them
> in a different file makes it better.  I don't see how.

It only becomes better if we can throw away that file (or contents) when
the transaction completes and we have marked all the subtransactions as
completed.  We can't compress pg_clog if we store the parent info in
there.

-- 
  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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Subject: Re: nested transactions
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