| From: | Greg Stark <gsstark(at)mit(dot)edu> |
|---|---|
| To: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
| Cc: | Greg Stark <gsstark(at)mit(dot)edu>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Dead Space Map |
| Date: | 2006-02-28 19:25:12 |
| Message-ID: | 87hd6jwajr.fsf@stark.xeocode.com |
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| Lists: | pgsql-hackers |
Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> Greg Stark wrote:
> >
> > If you commit each update then your tuple might well be visible to other
> > transactions, how would you check that?
>
> You check the xmin/xmax using standard visibility rules.
Would that really find anything? Even putting aside your own transaction
wouldn't it pick up any older transaction that started before yours and is
still running? They can't really see it but short of actually looking at their
snapshots I don't think you can determine that.
--
greg
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