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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)
Sent from Guangzhou, Guangdong, China
Stephen Leacock<http://www.brainyquote.com/quotes/authors/s/stephen_leacock.html>
- "I detest life-insurance agents: they always argue that I shall some
die, which is not so."

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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