Re: determine snapshot after obtaining locks for first statement

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
Cc: "Markus Wanner" <markus(at)bluegap(dot)ch>, "Robert Haas" <robertmhaas(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: determine snapshot after obtaining locks for first statement
Date: 2009-12-17 16:59:59
Message-ID: 3541.1261069199@sss.pgh.pa.us
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"Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> writes:
> Thanks for the clarification. That does not work for SERIALIZABLE
> at all, because other tables or rows referenced in that first
> statement would be using the original snapshot. Indeed, the
> behavior under READ COMMITTED could be astonishing in certain
> circumstances as it breaks atomicity:

Yup. That is stated fairly clearly already in the description of
READ COMMITTED mode, no?
http://developer.postgresql.org/pgdocs/postgres/transaction-iso.html#XACT-READ-COMMITTED

regards, tom lane

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