MAPREDUCE-2450 introduced, or at least triggers, a significant performance regression in Hive. With MR-2450 the execution time of TestCliDriver.skewjoin goes from 2 minutes to 15 minutes. Reverting this change from the build fixes the issue.
Here's the relevant query:
You can reproduce this by running the following from Hive 8.0 against Hadoop built from branch-23.