Github user kanzhang commented on a diff in the pull request:
https://github.com/apache/spark/pull/1338#discussion_r15153275
--- Diff: docs/programming-guide.md ---
@@ -403,31 +403,30 @@ PySpark SequenceFile support loads an RDD within
Java, and pickles the resulting
<tr><td>BooleanWritable</td><td>bool</td></tr>
<tr><td>BytesWritable</td><td>bytearray</td></tr>
<tr><td>NullWritable</td><td>None</td></tr>
-<tr><td>ArrayWritable</td><td>list of primitives, or tuple of
objects</td></tr>
--- End diff --
We can't write arrays in Scala either (the implicit conversion from Array
to ArrayWritable is marked private). Otherwise, it can be awkward as we can't
read it back since ArrayWritable doesn't have a no-arg constructor. For user
supplied ArrayWritable subtypes, we can read them, it's just they won't be
implicitly converted. Essentially the same support as we have in Python.
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