[JCR-2892] Large fetch sizes have potentially deleterious effects on VM memory requirements when using Oracle

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.2.2
• Fix Version/s: 2.2.10, 2.3.2
• Component/s: jackrabbit-core, sql
• Environment: Oracle 10g+
• Assignee: Claus Köll
• Reporter: Christopher Elkins
• Created: 15/Feb/11 23:04
• Updated: 15/Nov/11 13:50
• Resolved: 13/Oct/11 05:59

Description

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.

Issue Links

• relates to: JCR-3090 setFetchSize() fails in getAllNodeIds()