Re: Proposal: Commit timestamp

From: "Zeugswetter Andreas ADI SD" <ZeugswetterA(at)spardat(dot)at>
To: "Jan Wieck" <JanWieck(at)Yahoo(dot)com>, "Markus Schiltknecht" <markus(at)bluegap(dot)ch>
Cc: "Theo Schlossnagle" <jesus(at)omniti(dot)com>, "Peter Eisentraut" <peter_e(at)gmx(dot)net>, <pgsql-hackers(at)postgresql(dot)org>, "Bruce Momjian" <bruce(at)momjian(dot)us>, "Jim Nasby" <decibel(at)decibel(dot)org>
Subject: Re: Proposal: Commit timestamp
Date: 2007-02-08 09:35:47
Message-ID: E1539E0ED7043848906A8FF995BDA57901C13135@m0143.s-mxs.net
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> Yes, yes, and yes ... but aside from the problem that you use the very

> ambiguous word "timestamp" (which somehow suggests using a "clock" of
> some sort), isn't the "begin" timestamp of a long running transaction

imho a begin timestamp is near useless

> worse than the "commit" timestamp, when all its work got visible to
the
> outside world instantaneously?

This is one of the areas I am still worried about. Is one commit lamport
timestamp enough ?
I think for some conflict resolutions we need to look at the
row level, and resolve conflicts per row and not per transaction
(yes, this means that a tx might get partially replicated).

What I am trying to lead at is: maybe an infrastructure to produce
wieck lamport timestamps, that can be used in different places like
commit hooks and column defaults, would be of more general use. Maybe
such
a column could be a system column that is not visible with "select *"
for those cases where commit is not enough. And a commit hook could
insert it into clog like storage.

Andreas

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