| From: | Bruno Wolff III <bruno(at)wolff(dot)to> |
|---|---|
| To: | Simon Riggs <simon(at)2ndquadrant(dot)com>, Brad Nicholson <bnichols(at)ca(dot)afilias(dot)info>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Strange Behavior with Serializable Transcations |
| Date: | 2006-06-30 04:53:47 |
| Message-ID: | 20060630045347.GA7653@wolff.to |
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| Lists: | pgsql-general |
On Thu, Jun 29, 2006 at 14:27:30 +0200,
Martijn van Oosterhout <kleptog(at)svana(dot)org> wrote:
> On Thu, Jun 29, 2006 at 01:21:19PM +0100, Simon Riggs wrote:
> > The issue is the difference between start of transaction and time when
> > the serializable snapshot is taken. Since BEGIN and other commands may
> > be issued as separate network requests it makes sense to defer taking
> > the snapshot until the first time it is needed. The transaction is still
> > serializable, just that the manual is worded slightly incorrectly with
> > regards the exact timing.
>
> I've always interpreted it as "there exists a serialised order for the
> transactions" but the database makes no guarentees about what it might
> be. I can't think of any real world case where you actually care about
> the order, just as long as one exists.
Postgres' serializable mode doesn't guaranty that. To get that effect you
may need to do some extra locking.
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