You are viewing a plain text version of this content. The canonical link for it is here.

Posted to common-user@hadoop.apache.org by Cui tony <to...@gmail.com> on 2010/03/31 03:56:00 UTC

question on shuffle and sort

Hi,
  Did all key-value pairs of the map output, which have the same key, will
be sent to the same reducer tasknode?

Re: question on shuffle and sort

Posted by 毛宏 <ma...@gmail.com>.

yes ,indeed

在 2010-03-31三的 09:56 +0800，Cui tony写道：
> Hi,
>   Did all key-value pairs of the map output, which have the same key, will
> be sent to the same reducer tasknode?

Re: question on shuffle and sort

Posted by Ed Mazur <ma...@cs.umass.edu>.

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