On Tue, Jul 28, 2009 at 11:24 AM, Devajyoti Sarkar <[email protected]> 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
