apache/spark — pull request #1822 by guowei2 (2014-08-07 02:10:16+00:00)
Title: [SPARK-2873] using ExternalAppendOnlyMap to resolve OOM when aggregating

Using ExternalAppendOnlyMap to resolve OOM when aggregating.
Using "spark.shuffle.spill" to open it or not
Hive udaf does not support yet for udaf need Serializable

Join has the same problem. but using ExternalAppendOnlyMap as CoGroupedRDD seems to reduce performance. i try another way by using ExternalAppendOnlyMap. but it needs testing .i will commit it in another batch.