FAQ
Thanks.

Dev
On Wed, Jul 29, 2009 at 2:27 AM, Todd Lipcon wrote:
On Tue, Jul 28, 2009 at 11:24 AM, Devajyoti Sarkar wrote:

Hi,

In the hadoop documentation it says that all key-value classes need to
implement Writable to allow serialization and de-serialization of outputs
between mappers and reducers. Is this also necessary for key/value pairs
sent between the RecordReader and the Mapper (as well as the Reducer and
the
RecordWriter)? I assume that each of these two cases, classes are
instantiated in the same VM. So is it safe to assume that key/value pairs
are sent by reference instead of serialization/deserialization? If so, my
specific application may get a performance boost. Please do let me know if
this so.
Yes, this is correct. The values that come out of RecordReaders and go into
RecordWriters do not need to implement Writable.

-Todd

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