Re: Proposal: Commit timestamp

From: José Orlando Pereira <jop(at)lsd(dot)di(dot)uminho(dot)pt>
To: Jan Wieck <JanWieck(at)yahoo(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org, Alfranio Correia <alfranio(at)lsd(dot)di(dot)uminho(dot)pt>, Bruce Momjian <bruce(at)momjian(dot)us>, Theo Schlossnagle <jesus(at)omniti(dot)com>, Jim Nasby <decibel(at)decibel(dot)org>
Subject: Re: Proposal: Commit timestamp
Date: 2007-02-21 16:26:32
Message-ID: 200702211626.33673.jop@lsd.di.uminho.pt
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On Friday 09 February 2007, Jan Wieck wrote:
> I am not sure, I would have to look at what exactly that hook provides.
> The key to a Lamport timestamp is that it is advancing it commit order
> (plus some other things ... of course). If the hook can guarantee that
> the calls are made always in commit order, serialized without any race
> condition possible, it would probably be suitable.

Actually what we do is a bit stronger. We use the commit hook to enforce an
externally defined commit order. In our case, this is defined by a group
communication protocol, which is even allowed to reorder a pair of
transactions originating from the same replica. Therefore, achieving a commit
order that is consistent with a local clock should be straightforward.

Regards,

--
Jose Orlando Pereira

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