[jira] [Created] (SPARK-2114) Aggregations on raw data

["Sandy Ryza (JIRA)" <ji...@apache.org>]

Sandy Ryza created SPARK-2114:
---------------------------------

             Summary: Aggregations on raw data
                 Key: SPARK-2114
                 URL: https://issues.apache.org/jira/browse/SPARK-2114
             Project: Spark
          Issue Type: New Feature
          Components: Shuffle, Spark Core
    Affects Versions: 1.0.0
            Reporter: Sandy Ryza


For all the ByKey transformations, Spark tasks on the reduce side deserialize every record into a Java object before calling any user function.  

This causes all kinds of problems for garbage collection - when aggregating enough data, objects can escape the young gen and trigger full GCs down the line.  Additionally, when records are spilled, they must be serialized and deserialized multiple times.

It would be helpful to allow aggregations on serialized data - using some sort of RawHasher interface that could implement for hashCode and equals for serialized records.  This would also require encoding record boundaries in the serialized format, which I'm not sure we currently do.



--
This message was sent by Atlassian JIRA
(v6.2#6252)