Re: 9.1 causing "out of shared memory" error and higher serialization conflicts

Thanks for the heads up.

I'll fix that in Npgsql so it sends the correct isolation level when
running on 9.1+

Sent from my Android phone
On Mar 9, 2012 3:27 PM, "Randy Ficker" <randyficker(at)gmail(dot)com> wrote:

> Hey Marti,
>
> I almost replied that yes, I was 100% sure, since I know my code requests
> the REPEATABLE READ level. However, I figured before I replied, I should
> double-check the SQL statements that were being sent to Postgres.
>
> Then I found this gem in Npgsql:
>
> if (isolation == IsolationLevel.RepeatableRead || isolation ==
> IsolationLevel.Serializable || isolation == IsolationLevel.Snapshot)
> {
> commandText.Append("SERIALIZABLE");
> }
>
> *headslap*. I know this code is fine for 8, but I still would not have
> expected this code to exist in the driver itself instead of just letting
> Postgres do the switch. I guess Npgsql says right on their front page
> "Works with Postgresql 7.x and 8.x" so I shouldn't have assumed it'd behave
> correctly with 9.
>
> So you're right, it turns out I was using SERIALIZABLE after all. I'm
> going to fix this right away. Thanks for the reply!
>
> -----Original Message-----
> From: Marti Raudsepp [mailto:marti(at)juffo(dot)org]
> Sent: Friday, March 09, 2012 9:41 AM
> To: Randy Ficker
> Cc: pgsql-general(at)postgresql(dot)org
> Subject: Re: [GENERAL] 9.1 causing "out of shared memory" error and higher
> serialization conflicts
>
> On Fri, Mar 9, 2012 at 19:16, Randy Ficker <randyficker(at)gmail(dot)com> wrote:
> > Most writing transactions are using the REPEATABLE READ isolation
> > level (the SERIALIZABLE level is not used at all).
>
> Are you 100% sure about this? A major thing that changed in 9.1 was
> implementation for proper SERIALIZABLE isolation, which could indeed cause
> the sort of errors you described. Previously, asking for SERIALIZABLE level
> gave you REPEATABLE READ.
>
> As far as I can tell, the max_pred_locks_per_transaction setting is
> irrelevant for isolation levels lower than SERIALIZABLE.
>
> What's your default_transaction_isolation set to?
>
> Regards,
> Marti
>
>
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