Re: User-facing aspects of serializable transactions

On Wed, May 27, 2009 at 9:00 PM, Kevin Grittner
<Kevin.Grittner@wicourts.gov> wrote:
> Robert Haas <robertmhaas@gmail.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?

I guess my point is that we want to keep the two transaction isolation
levels we have now and add a third one that is "above" what we
currently call SERIALIZABLE.  I don't much care what we call them.

...Robert