On Mon, Aug 16, 2010 at 3:21 PM, David Rosenstrauch <dar...@darose.net> wrote: > On 08/16/2010 05:48 PM, Ted Yu wrote: >> >> No. >> >> On Mon, Aug 16, 2010 at 1:25 PM, David >> Rosenstrauch<dar...@darose.net>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 >>> org.apache.hadoop.mapreduce.Mapper)? >>> >>> Thanks, >>> >>> DR > > 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. Tom > > Can you please clarify? > > Thanks, > > DR >
