[hibernate-dev] RE: scrollableresult OOM problem

John Griffin jgriffin at thebluezone.net
Mon Nov 24 12:44:52 EST 2008

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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Today's Topics:

   1. interesting issues in the forum (Sanne Grinovero)


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>
	<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%)

memory leak on redeploy (quite good information here, but this is
going to be hard)

sort + scrollableresult appears to load all in memory (never happened
to me, needs a test)

I never used Spring, so can't help there.
I have no idea about how to solve the ThreadLocal problem: this has to do
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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