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From liancheng <...@git.apache.org>
Subject [GitHub] spark pull request: [SPARK-4785] [SQL] Support udf instance ser/de...
Date Tue, 09 Dec 2014 17:15:48 GMT
Github user liancheng commented on the pull request:

    https://github.com/apache/spark/pull/3640#issuecomment-66319557
  
    The current design of this PR is derived from some background knowledges. I'd like to
provide a brief summary here for future reference.
    
    As mentioned in the PR description, different from Hive 0.12.0, in Hive 0.13.1 UDF/UDAF/UDTF
(aka Hive function) objects should only be initialized once on the driver side and then serialized
to executors. However, not all function objects are serializable (e.g. `GenericUDF` doesn't
implement `Serializable`). Hive 0.13.1 solves this issue with Kryo or XML serializer. Several
utility ser/de methods are provided in class `o.a.h.h.q.e.Utilities` for this purpose. In
this PR we chose Kryo for efficiency. The Kryo serializer used here is created in Hive. Spark
Kryo serializer wasn't used because there's no available `SparkConf` instance.


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