Re: Strange Behavior with Serializable Transcations

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От Martijn van Oosterhout
Тема Re: Strange Behavior with Serializable Transcations
Дата
Msg-id 20060628192049.GA6760@svana.org
обсуждение исходный текст
Ответ на Strange Behavior with Serializable Transcations  (Brad Nicholson <bnichols@ca.afilias.info>)
Ответы Re: Strange Behavior with Serializable Transcations  (Tom Lane <tgl@sss.pgh.pa.us>)
Re: Strange Behavior with Serializable Transcations  (Simon Riggs <simon@2ndquadrant.com>)
Список pgsql-general
On Wed, Jun 28, 2006 at 02:48:01PM -0400, Brad Nicholson wrote:
> I'm seeing something fairly unintuitive about serializable transactions.
>
> Taking the following test case:

<snip>

> http://www.postgresql.org/docs/8.1/interactive/transaction-iso.html
>
> "When a transaction is on the serializable level, a SELECT query sees
> only data committed before the transaction began; it never sees either
> uncommitted data or changes committed during transaction execution by
> concurrent transactions."

I think the issue here is that transaction begin is not when you type
"begin" but at your first actual query. You can obviously only start a
transaction once you know what serialisation level you want, and you
don't see that till after the begin.

Hope this helps,
--
Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
> From each according to his ability. To each according to his ability to litigate.

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