Currently we need to jump through hoops to get the 'raw length' of serializable types for e.g. SequenceFile.Writer.append needs to copy the key/value into a buffer and then check the buffer's size to figure the record/key/value lenghts. Obviously this can be improved to do away with the extra copy if we had types which could be queried for it's raw-length.
Thoughts?
Improvement
Open
Major
Facility to query serializable types such as Writables for 'raw length'
