Re: Overhead cost of Serializable Snapshot Isolation - Mailing list pgsql-hackers

From Simon Riggs
Subject Re: Overhead cost of Serializable Snapshot Isolation
Date
Msg-id CA+U5nMLo+KL_X3Q9_QCQ3e=i12ioPAQgp3tqfKFDrgKw5gOReA@mail.gmail.com
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In response to Re: Overhead cost of Serializable Snapshot Isolation  ("Kevin Grittner" <Kevin.Grittner@wicourts.gov>)
Responses Re: Overhead cost of Serializable Snapshot Isolation  (Robert Haas <robertmhaas@gmail.com>)
List pgsql-hackers
On Mon, Oct 10, 2011 at 11:31 PM, Kevin Grittner
<Kevin.Grittner@wicourts.gov> wrote:
> Simon Riggs <simon@2ndQuadrant.com> wrote:
>
>> How do we turn it on/off to allow the overhead to be measured?
>
> User REPEATABLE READ transactions or SERIALIZABLE transactions.  The
> easiest way, if you're doing it for all transactions (which I
> recommend) is to set default_transaction_isolation.

Most apps use mixed mode serializable/repeatable read and therefore
can't be changed by simple parameter. Rewriting the application isn't
a sensible solution.

I think it's clear that SSI should have had and still needs an "off
switch" for cases that cause performance problems.

--
 Simon Riggs                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services


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