Mailing-List: contact open-jpa-dev-help@incubator.apache.org; run by ezmlm
Precedence: bulk
Reply-To: open-jpa-dev@incubator.apache.org
Received-SPF: pass (herse.apache.org: local policy)
Date: Fri, 05 Jan 2007 08:28:39 -0800
From: Craig L Russell <Craig.Russell@Sun.COM>
Subject: Re: race condition in a transaction?
In-reply-to: <7D856CDFE035FF45A0420ACBD71BDD6302C5AFED@repbex02.amer.bea.com>
Sender: Craig.Russell@Sun.COM
To: open-jpa-dev@incubator.apache.org
Message-id: <79E7F997-FA3D-4D0B-BAA0-51CC81FC89A6@SUN.com>
MIME-version: 1.0
Content-type: multipart/signed; protocol="application/pkcs7-signature";
 boundary=Apple-Mail-64-728759594; micalg=sha1
References: <7D856CDFE035FF45A0420ACBD71BDD6302C5AFED@repbex02.amer.bea.com>

--Apple-Mail-64-728759594
Content-Transfer-Encoding: 7bit
Content-Type: text/plain;
	charset=US-ASCII;
	delsp=yes;
	format=flowed

You need to watch out for pessimistic transactions using read- 
committed isolation level, which indeed has a race condition.

It's also not any different to get JPQL UPDATE to work as you want it  
to, with read-committed isolation. All the JPQL does for you is to do  
the same work in QL that you are now doing in Java.

Craig

On Jan 4, 2007, at 10:43 PM, Patrick Linskey wrote:

> Assuming that you're using some sort of locking strategy  
> (pessimistic or
> optimistic), then only one tx will successfully commit.
>
> You should only really use the UPDATE and DELETE JPQL statements for
> bulk operations, not for day-to-day persistence work.
>
> -Patrick
>
> -- 
> Patrick Linskey
> BEA Systems, Inc.
>
> ______________________________________________________________________ 
> _
> Notice:  This email message, together with any attachments, may  
> contain
> information  of  BEA Systems,  Inc.,  its subsidiaries  and   
> affiliated
> entities,  that may be confidential,  proprietary,  copyrighted   
> and/or
> legally privileged, and is intended solely for the use of the  
> individual
> or entity named in this message. If you are not the intended  
> recipient,
> and have received this message in error, please immediately return  
> this
> by email and then delete it.
>
>> -----Original Message-----
>> From: roger.keays [mailto:roger.keays@ninthavenue.com.au]
>> Sent: Thursday, January 04, 2007 4:09 PM
>> To: open-jpa-dev@incubator.apache.org
>> Subject: race condition in a transaction?
>>
>>
>> Hi,
>>
>> I'm just wondering if the following code could be subject to a race
>> condition when accessed by many threads
>>
>> em.getTransaction().begin();
>> bean.setCount(bean.getCount() + 1);
>> em.getTransaction().commit();
>>
>> My understanding is that it would be possible here for two
>> threads to set
>> the same value for the new count (given that each thread has
>> a different
>> em). Is that correct?
>>
>> Do I have to use an UPDATE query to make this function as expected?
>>
>> Thanks,
>>
>> Roger
>> -- 
>> View this message in context:
>> http://www.nabble.com/race-condition-in-a-transaction--tf29229
> 64.html#a8170503
>> Sent from the open-jpa-dev mailing list archive at Nabble.com.
>>
>>

Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:Craig.Russell@sun.com
P.S. A good JDO? O, Gasp!


--Apple-Mail-64-728759594
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-signature;
	name=smime.p7s
Content-Disposition: attachment;
	filename=smime.p7s
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--Apple-Mail-64-728759594--