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From tim likarish <tplikar...@cs.usfca.edu>
Subject GenericWritableComparable?
Date Tue, 21 Jun 2011 17:22:32 GMT

In Tom White's Hadoop book, White discusses Writable collections and
ends the section with the following:

For lists of a single type of Writable, ArrayWritable is
adequate, but to store different types of Writable in a single list, you can use
GenericWritable to wrap the elements in an ArrayWritable. Alternatively, you could
write a general ListWritable using the ideas from MapWritable.

I would like my mapper to emit a key that is a list of different
WritableComparable types.  In addition, the types of the
WritableComparables is not known ahead of time.  Has anyone done any
work on this before?  I've been basing my implementation off of
MapWritable but I was hoping not to reinvent the wheel if possible.


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