-Re: Is the mapper output type must the same as reducer if combiner is used ?
Karthik Kambatla 2009-11-22, 15:12
I have never tried it, but the following must also be possible.
map: (k1,v1) -> list(k2,v2)
combine: (k2 ,list(v2)) -> list(k3,v3)
reduce: (k3 ,list(v3)) -> list(k4,v4)
On Sun, Nov 22, 2009 at 4:16 AM, Y G <[EMAIL PROTECTED]> wrote:
> if your combiner is the same as reducer,the output type of mapper must the
> same as
> the input type of reducer.
> map: (k1,v1) -> list(k2,v2)
> combine: (k2 ,list(v2)) -> list(k2,v2)
> reduce: (k2 ,list(v2)) -> list(k3,v3)
> Sent from Guangzhou, Guangdong, China
> Stephen Leacock<
> - "I detest life-insurance agents: they always argue that I shall some
> die, which is not so."
> 2009/11/22 Jeff Zhang <[EMAIL PROTECTED]>
> > Hi all,
> > As I know, Combiner is used in the mapper task, and most of the time,
> > combiner is the same as reducer.
> > So if combiner is used, the output type of mapper task must the same as
> > reducer task, is it right ?
> > Thank you
> > Jeff Zhang