| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov> |
| Cc: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Greg Sabino Mullane <greg(at)endpoint(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Overhead cost of Serializable Snapshot Isolation |
| Date: | 2011-10-11 17:11:26 |
| Message-ID: | CA+U5nMLo+KL_X3Q9_QCQ3e=i12ioPAQgp3tqfKFDrgKw5gOReA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, Oct 10, 2011 at 11:31 PM, Kevin Grittner
<Kevin(dot)Grittner(at)wicourts(dot)gov> wrote:
> Simon Riggs <simon(at)2ndQuadrant(dot)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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