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From Y G <gymi...@gmail.com>
Subject Re: Is the mapper output type must the same as reducer if combiner is used ?
Date Sun, 22 Nov 2009 09:16:59 GMT
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)
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2009/11/22 Jeff Zhang <zjffdu@gmail.com>

> 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
>

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