Re: User-facing aspects of serializable transactions

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "Robert Haas" <robertmhaas(at)gmail(dot)com>
Cc: "Jeff Davis" <pgsql(at)j-davis(dot)com>,<pgsql-hackers(at)postgresql(dot)org>
Subject: Re: User-facing aspects of serializable transactions
Date: 2009-05-28 01:00:03
Message-ID: 4A1D9BC3.EE98.0025.1@wicourts.gov
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Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

> I think we should introduce a new value for SET TRANSACTION
ISOLATION
> LEVEL, maybe SNAPSHOT, intermediate between READ COMMITTED and
> SERIALIZABLE.

The standard defines such a level, and calls it REPEATABLE READ.
Snapshot semantics are more strict than required for that level, which
is something you are allowed to get when you request a given level, so
it seems clear to me that when you request REPEATABLE READ mode, you
should get our current snapshot behavior. I'm not clear on what the
benefit would be of aliasing that with SNAPSHOT. If there is a
benefit, fine; if not, why add it?

-Kevin

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