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Date: Tue, 11 Oct 2011 11:53:11 +0000 (UTC)
From: "Danilo Ghirardelli (Commented) (JIRA)" <jira@apache.org>
To: dev@jackrabbit.apache.org
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Subject: [jira] [Commented] (JCR-2892) Large fetch sizes have potentially
 deleterious effects on VM memory requirements when using Oracle
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    [ https://issues.apache.org/jira/browse/JCR-2892?page=3Dcom.atlassian.j=
ira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=3D131249=
50#comment-13124950 ]=20

Danilo Ghirardelli commented on JCR-2892:
-----------------------------------------

I'm sorry if I wasn't clear, but the value of 100 just worked for my applic=
ation (clustered Magnolia CMS), and it was the maximum fetchSize value that=
 allowed the application to start. Anyway, at 100 the memory occupation was=
 quite high, so maybe that value was good in my case but may crash in other=
 cases. Would it be possible to avoid setting a fetchSize at all (except fo=
r postgresql)? Performance were always good and there was no problem until =
it was set for the first time in JCR-2832...
               =20
> Large fetch sizes have potentially deleterious effects on VM memory requi=
rements 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
>            Assignee: Claus K=C3=B6ll
>             Fix For: 2.2.10, 2.3.1
>
>         Attachments: JCR-2892.patch, oracleFetchSize.patch
>
>
> Since Release 10g, Oracle JDBC drivers use the fetch size to allocate buf=
fers 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 exampl=
e, 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, respec=
tively. This requires a buffer of more than 40 mb [(16+4096) * 10000 =3D 41=
120000].
> If the issue described in JCR-2832 is truly specific to PostgreSQL, I thi=
nk 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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