Since Release 10g, Oracle JDBC drivers use the fetch size to allocate buffers for caching row data.
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.