apache/spark — pull request #418 by marmbrus (2014-04-15 18:20:31+00:00)
Title: Generalize pattern for planning hash joins.

This will be helpful for [SPARK-1495](https://issues.apache.org/jira/browse/SPARK-1495) and other cases where we want to have custom hash join implementations but don't want to repeat the logic for finding the join keys.