A hash join modification patch is under review for 8.4 that needs performance testing. We would appreciate help with this testing.
A testing version of the patch is attached in addition to testing instructions and where to retrieve a sample data set. The basic idea of the patch is that it reduces disk operations for large multi-batch hash joins where there is skew in the probe relation. The patch collects statistics on performance benefits when using the optimization.
--
Ramon Lawrence and Bryce Cutt