[hibernate-dev] RE: scrollableresult OOM problem

[Sanne Grinovero]

thanks John,
hope your back is getting better.
I've asked for more information to the reporter.
I am not expecting the JDBC driver to do the sort, it is a Lucene sort, so as
you said it must be Search's code to keep something around.
Maybe we are ignoring the FORWARD_ONLY.

2008/11/24 John Griffin <jgriffin at thebluezone.net>:
> I've dealt with this problem but only from an Oracle perspective. Using a
> FORWARD_ONLY ScrollMode only allows the rs.next() method call. Any other
> result set record movement method call results in an exception. This allows
> JDBC to fetch x amount of records (set by fetch size) and then get the next
> fetch size etc. This prevents caching of previously fetched records (causing
> OOM with large result sets).
>        Since it is my understanding that Oracle sorts results and generates
> a cursor on the server side, if this really is a problem, somewhere in the
> code we are caching results.
>        The only way I have been able to scroll extremely large results is
> to implement paging. This does not imply that there is state maintained. An
> array of record pointers can do it and there are probably more ways.
>
> I have no way to test this at home and I'm here all week.
>
> My two cents.
>
> John G.
>
>
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>   1. interesting issues in the forum (Sanne Grinovero)
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> ----------------------------------------------------------------------
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> Message: 1
> Date: Mon, 24 Nov 2008 17:17:58 +0100
> From: "Sanne Grinovero" <sanne.grinovero at gmail.com>
> Subject: [hibernate-dev] interesting issues in the forum
> To: "Hardy Ferentschik" <hibernate at ferentschik.de>
> Cc: Hibernate Dev <hibernate-dev at lists.jboss.org>
> Message-ID:
>        <50e5f6250811240817qf3a9f0v84c40b5ae771e3d0 at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
>
> hi Hardy,
> I've been browsing the forums today and found these topics of interest,
> they could be quite important bugs we should fix:
>
> not working correctly with Spring (needs some test, I don't trust this
> report 100%)
> http://forum.hibernate.org/viewtopic.php?t=988828
>
> memory leak on redeploy (quite good information here, but this is
> going to be hard)
> http://forum.hibernate.org/viewtopic.php?p=2400319
>
> sort + scrollableresult appears to load all in memory (never happened
> to me, needs a test)
> http://forum.hibernate.org/viewtopic.php?t=992342
>
> I never used Spring, so can't help there.
> I have no idea about how to solve the ThreadLocal problem: this has to do
> with
> how Hibernate registers eventlisteners and we probably should ask for
> changes there
> Nnot sure if we can change the EM listeners without changing the spec??
> I'm absolutely no expert on other Hibernate modules.
>
> I could try to reproduce the scrollableresult problem, but not this week.
>
>
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