On Sep 19, 2007, at 3:06 PM, Eric Zhang wrote:
I have a job which just wants to take advantage of the sorting
function of
reduce task, so no mapping is required. I am wondering if hadoop
allows to
run a job without running map . If it does, how to do it? and if it
doesn't, could this be a reasonable feature to have?
*Smile* If there are no maps, there is no where to get the input for
the reduce.
I believe your intent is that nothing should happen in the map. You
can do this by using the org.apache.hadoop.mapred.lib.IdentityMapper.
In this case, the map is just passing the input straight to the sort
with no processing at all.
-- Owen
