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From Paul Joseph <pjos...@gmail.com>
Subject Re: thought I had fixe it
Date Wed, 26 Oct 2011 20:32:47 GMT
Hi there,

In connection with this issue where the user does a query that returns a 
large number of results...as Jasha points out below the correct thing is 
to implement paging logic that returns results only as demanded.

Is there anything already done in Cocoon OJB that uses this approach and 
which I can leverage?

Paul

On 10/24/2011 12:22 PM, Jasha Joachimsthal wrote:
> The first question that comes to my mind: why would you need 25000 
> objects as query result? Can't you do 1 query that only returns the 
> total possible amount of objects and another query that returns e.g. 
> the first 10 results and build in some paging logic for the next 10.
>
> Jasha Joachimsthal
>
> Europe - Amsterdam - Oosteinde 11, 1017 WT Amsterdam - +31(0)20 522 4466
> US - Boston - 1 Broadway, Cambridge, MA 02142 - +1 877 414 4776 (toll 
> free)
>
> www.onehippo.com <http://www.onehippo.com/>
>
>
> On 24 October 2011 18:13, Paul Joseph <pjoseph@gmail.com 
> <mailto:pjoseph@gmail.com>> wrote:
>
>     I think you hit the nail on the head.
>
>     I assumed that the memory is freed at session time out. I did not
>     realize this was not the case.
>
>     I know what the culprit is in this case--the array that I use to
>     store the objects returned from the query.
>
>     I do this in two places--once in the business logic (java code)
>     and once in the flow script.
>
>     The code in the java business logic is as follows--the item of
>     interest is a "Task".  How would I optimize it in terms of memory
>     collection?
>
>     public Object[] getSearchResults() throws Exception {
>
>        Object[] results = getSearchResultBeans(sql_query);
>
>            Vector secureResults = new Vector();
>
>            for (int n=0; n < results.length; n++) {
>
>                Task t = (Task)results[n];
>
>                if (securityManager.canIViewTask(t)) secureResults.add(t);
>
>            }
>
>        return secureResults.toArray();
>
>     }
>
>     On 10/24/2011 11:50 AM, Nathaniel, Alfred wrote:
>
>         Hi Paul,
>
>         I don't think that it is a database issue.
>         It is rather the question where the application places the
>         large amounts of data and how it is cleaned up.
>
>         I interprete your statements that it is placed in the session
>         object assuming that the memory is freed at session timeout.
>         Unfortunately that is not the case.
>
>         The session timeout is a security feature to force a new login
>         if the same user comes back after a longish idle time.
>         There is no guarantee that the container will actually delete
>         the session object at the session timeout.
>         As long as there is a reference to the session object GC
>         cannot free the attached memory.
>
>         You will have to find a way that the application keeps the
>         data only for the duration of a request, or use another
>         mechanism to limit the memory requirements.
>
>         HTH, Alfred.
>
>         -----Original Message-----
>         From: Paul Joseph [mailto:pjoseph@gmail.com
>         <mailto:pjoseph@gmail.com>]
>         Sent: Montag, 24. Oktober 2011 17:16
>         To: users@cocoon.apache.org <mailto:users@cocoon.apache.org>
>         Subject: thought I had fixe it
>
>         Hi there,
>
>         I thought I had fixed this memory issue but...
>
>         I am using Tomcat 6 in a Windows 32 bit environment (Windows
>         2003)  with
>         Cocoon 2.1.11 and Java 1.6, agains Postgresql 8.4 with the latest
>         Postgres 9.1, JDBC 4 driver.
>
>
>         The behavior is this:
>
>         The user fires of a LARGE query that returns 25,000 large objects.
>
>         The user repeats this 20 times within 5 minutes to show me he
>         can freeze
>         the app.
>
>         On the 20th time, it says out of memory (heap space).
>
>
>         The JVM indicates that it is maxed to the limit specified in
>         Xms and
>         that there is only about 2MB of memory free.
>
>         I then ask her to log off.
>
>         The session time out is set to 20 minutes.
>
>         But even after an hour, the memory is not reclaimed by the
>         JVM--it still
>         reports that only about 2MB is still free.
>
>         Is the fact that it is not reclaiming memory an indication of
>         a memory leak?
>
>         I am using the following settings in my repository.database:
>
>         <jdbc-connection-descriptor
>         jcd-alias="WebApp"
>         default-connection="true"
>         platform="PostgreSQL"
>         jdbc-level="4.0"
>         driver="org.postgresql.Driver"
>         protocol="jdbc"
>         subprotocol="postgresql"
>         dbalias="//localhost:5432/WebApp"
>         username="******"
>         password="******"
>         eager-release="false"
>         batch-mode="false">
>
>         <connection-pool maxActive="200" validationQuery="" />
>         <sequence-manager
>         className="org.apache.ojb.broker.util.sequence.SequenceManagerNextValImpl"
>         />
>         </jdbc-connection-descriptor>
>
>
>         Thanks much!
>         Paul
>
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