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Posted to mapreduce-user@hadoop.apache.org by Owen O'Malley <om...@apache.org> on 2010/02/02 17:18:20 UTC
Re: Does the class of the Mapper output need to match the exact class of the specified output?
On Jan 26, 2010, at 5:17 PM, Wilkes, Chris wrote:
> Does this level of checking really need to be done?
For Writables, the simple answer is yes. It happens because the way
you deserialize is to:
Writable obj = ReflectionUtils.newInstance(cls, conf);
obj.readFields(in);
So you need to know the specific class to read into. To support this
use case, there is library code available in Hadoop:
http://bit.ly/9UoZGc
There is work underway to loosen the restriction in trunk, but that is
a long ways from being released.
-- Owen