-Re: Null mapper?
Tom White 2010-08-18, 21:31
On Mon, Aug 16, 2010 at 3:21 PM, David Rosenstrauch <[EMAIL PROTECTED]> wrote:
> On 08/16/2010 05:48 PM, Ted Yu wrote:
>> On Mon, Aug 16, 2010 at 1:25 PM, David
>> Rosenstrauch<[EMAIL PROTECTED]>wrote:
>>> Is it possible for a M/R job to have no mapper? i.e.:
>>> job.setMapperClass(null)? Or is it required that one at least use an
>>> "identity mapper" (i.e., plain vanilla
> Um ...
> Sorry, but I'm not clear. Which of the 2 questions were you answering "no"
> to? :-)
> I'm guessing the first.? i.e., I can't have a null mapper. So then I need
> to supply a org.apache.hadoop.mapreduce.Mapper as a "no-op" mapper?
org.apache.hadoop.mapreduce.Mapper is the identity mapper: it simply
emits the key-value pairs it was passed. The old API equivalent is
org.apache.hadoop.mapred.lib.IdentityMapper, which is the default.
> Can you please clarify?