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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