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From "Christopher Elkins (JIRA)" <j...@apache.org>
Subject [jira] Created: (JCR-2892) Large fetch sizes have potentially deleterious effects on VM memory requirements when using Oracle
Date Tue, 15 Feb 2011 23:05:57 GMT
Large fetch sizes have potentially deleterious effects on VM memory requirements when using
Oracle
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                 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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