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From "Jones, Nick" <nick.jo...@amd.com>
Subject Re: question on shuffle and sort
Date Wed, 31 Mar 2010 02:11:32 GMT
Something to keep in mind though, sorting is appropriate to the key type. Text will be sorted
lexicographically.

Nick Jones


----- Original Message -----
From: Ed Mazur <mazur@cs.umass.edu>
To: common-user@hadoop.apache.org <common-user@hadoop.apache.org>
Sent: Tue Mar 30 21:07:29 2010
Subject: Re: question on shuffle and sort

On Tue, Mar 30, 2010 at 9:56 PM, Cui tony wrote:
>  Did all key-value pairs of the map output, which have the same key, will
> be sent to the same reducer tasknode?

Yes, this is at the core of the MapReduce model. There is one call to
the user reduce function per unique map output key. This grouping is
achieved by sorting which means you see keys in increasing order.

Ed



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