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From "Christiaan (JIRA)" <j...@apache.org>
Subject [jira] Commented: (OPENJPA-441) Memory increase when deleting objects
Date Thu, 29 Nov 2007 12:43:43 GMT

    [ https://issues.apache.org/jira/browse/OPENJPA-441?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12546703
] 

Christiaan commented on OPENJPA-441:
------------------------------------

Patrick,
in org.apache.openjpa.jdbc.sql.RowImpl the generated sql is cached in _sql. When dealing with
many objects  of the same type in one transaction all having a similar modification  (eg.
they are deleted or a field is updated) there is quite some memory overhead for caching this
sql, since each object (or RowImpl) caches the same sql. In the attached sql it basically
comes down to 2 sql statements which are duplicated many times.

I think there are two options to improve this:
1) reuse the sql instead of duplicating it
2) not cache it, possibly in certain conditions eg, when many objects of the same type are
involved, but generated it each time it is needed;

Option 2) is probably the most straight forward. The caching is probably done for a reason
but I wonder if generating the sql when needed has that much performance impact?

> Memory increase when deleting objects
> -------------------------------------
>
>                 Key: OPENJPA-441
>                 URL: https://issues.apache.org/jira/browse/OPENJPA-441
>             Project: OpenJPA
>          Issue Type: Bug
>    Affects Versions: 1.0.0
>         Environment: Kodo 4.1.4, JDK 6, ms sql server 2005, JTDS 1.2
>            Reporter: Christiaan
>         Attachments: results.ZIP, TestCaseMemoryAndDelete.zip
>
>
> This isssue is based on issue:
> http://issues.apache.org/jira/browse/OPENJPA-439
> When executing a delete on objects which all have been loaded into memory, the memory
usage is doubled when calling pm.deletePersistentAll().
> The same testcase can be used which is attached to the linked issue.

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