Re: IdentityMapper

[Doug Cutting]

Stefan Groschupf wrote:
what is the reason that each job that has no mapper defined runs the  
IdentityMapper?
Handling different formats (as discussed) between mapping and  reducing 
is difficult.
Having one job that just map in the one format and having another job  
that just reduce
in a other format would be a nice workaround of the format problem  but 
the IdentityMapper makes this workaround impossible.

Stefan,

I don't understand the problem here.  Some map function is required for 
any data to make it to reduce.  IdentityMapper simply copies all map 
input without altering it.  How does this cause you problems?  Would you 
prefer a NullMapper by default, that does nothing?  That would result in 
no output sent to reduce.

Thanks,

Doug