From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Patches <pgsql-patches(at)postgresql(dot)org> |
Subject: | Re: nested xacts and phantom Xids |
Date: | 2004-06-23 12:57:11 |
Message-ID: | 200406231257.i5NCvB410563@candle.pha.pa.us |
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Lists: | pgsql-hackers pgsql-patches |
Alvaro Herrera wrote:
> On Sun, Jun 20, 2004 at 04:37:16PM -0400, Tom Lane wrote:
> > Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl> writes:
> > > Here I present the nested transactions patch and the phantom Xids patch
> > > that goes with it.
> >
> > I looked at the phantom XIDs stuff a bit. I still have little confidence
> > that the concept is correct :-( but here are some comments on the code
> > level.
>
> Ok. I for one think this got much more complex than I had originally
> thought it would be. I agree the changes to Set/Get Xmin/Xmax are way
> beyond what one would want, but the alternative would be to spread the
> complexity into their callers and I think that would be much worse.
>
> I don't have a lot of confidence in this either. The patch will be
> available in archives if anybody wants to implement this in a cleaner
> and safer way; I'll continue working on the rest of the things you
> pointed out in the subtransactions patch.
I am sorry to have given Alvaro another idea that didn't work. However,
thinking of options, I wonder if instead of phantom xids, we should do
phantom cids. Because only the local backend looks at the command
counter (cid). I think it might be alot cleaner. The phantom cid would
have a tuple bit set indicating that instead of being a cid, it is an
index into an array of cmin/cmax pairs.
--
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
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