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

Thanks!
I'll make the changes to Npgsql source code.

Sent from my Android phone
On Mar 9, 2012 7:17 PM, "Randy Ficker" <randyficker(at)gmail(dot)com> wrote:

> Filed:
> http://pgfoundry.org/tracker/index.php?func=detail&aid=1011174&group_id=1000140&atid=590
> ****
>
> ** **
>
> *From:* francisco(dot)figueiredo(dot)jr(at)gmail(dot)com [mailto:
> francisco(dot)figueiredo(dot)jr(at)gmail(dot)com] *On Behalf Of *Francisco Figueiredo Jr.
> *Sent:* Friday, March 09, 2012 12:41 PM
> *To:* Randy Ficker
> *Cc:* Marti Raudsepp; pgsql-general(at)postgresql(dot)org
> *Subject:* RE: [GENERAL] 9.1 causing "out of shared memory" error and
> higher serialization conflicts****
>
> ** **
>
>
> Would you mind to fill a bug report about that and also provide your fix
> so we can apply in the main codebase?
> Thanks in advance! ****
>
> Sent from my Android phone****
>
> On Mar 9, 2012 5:12 PM, "Randy Ficker" <randyficker(at)gmail(dot)com> wrote:****
>
> After deploying a fixed version of Npgsql, the error frequency went
> straight back down to the 8.4 level. Awesome!****
>
> ****
>
> Thanks for the quick replies guys!****
>
> ****
>
> *From:* francisco(dot)figueiredo(dot)jr(at)gmail(dot)com [mailto:
> francisco(dot)figueiredo(dot)jr(at)gmail(dot)com] *On Behalf Of *Francisco Figueiredo Jr.
> *Sent:* Friday, March 09, 2012 10:36 AM
> *To:* Randy Ficker
> *Cc:* pgsql-general(at)postgresql(dot)org; Marti Raudsepp
> *Subject:* Re: [GENERAL] 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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