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From "Stephen Chester (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (JCR-2892) Large fetch sizes have potentially deleterious effects on VM memory requirements when using Oracle
Date Thu, 01 Sep 2011 23:36:09 GMT

    [ https://issues.apache.org/jira/browse/JCR-2892?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13095675#comment-13095675
] 

Stephen Chester commented on JCR-2892:
--------------------------------------

I am also experiencing this issue, and am working on a patch that will add the ability to
specify the fetch size to the configuration options of the relevant classes, with the default
being 10,000.

> Large fetch sizes have potentially deleterious effects on VM memory requirements when
using Oracle
> --------------------------------------------------------------------------------------------------
>
>                 Key: JCR-2892
>                 URL: https://issues.apache.org/jira/browse/JCR-2892
>             Project: Jackrabbit Content Repository
>          Issue Type: Bug
>          Components: jackrabbit-core, sql
>    Affects Versions: 2.2.2
>         Environment: Oracle 10g+
>            Reporter: Christopher Elkins
>
> Since Release 10g, Oracle JDBC drivers use the fetch size to allocate buffers for caching
row data.
> cf. http://www.oracle.com/technetwork/database/enterprise-edition/memory.pdf
> r1060431 hard-codes the fetch size for all ResultSet-returning statements to 10,000.
This value has significant, potentially deleterious, effects on the heap space required for
even moderately-sized repositories. For example, the BUNDLE table (from 'oracle.ddl') has
two columns -- NODE_ID raw(16) and BUNDLE_DATA blob -- which require 16 b and 4 kb of buffer
space, respectively. This requires a buffer of more than 40 mb [(16+4096) * 10000 = 41120000].
> If the issue described in JCR-2832 is truly specific to PostgreSQL, I think its resolution
should be moved to a PostgreSQL-specific ConnectionHelper subclass. Failing that, there should
be a way to override this hard-coded value in OracleConnectionHelper.

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