Re: nested xacts and phantom Xids

Alvaro Herrera wrote:
> On Sun, Jun 20, 2004 at 04:37:16PM -0400, Tom Lane wrote:
> > Alvaro Herrera <alvherre@dcc.uchile.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.

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