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MapReduce >> mail # user >> How can I sort a file with pairs <Key Value> in reverse order?


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Re: How can I sort a file with pairs <Key Value> in reverse order?
Even with  your answer I can't see how can I sort the data in reverse
order. I forgot to mention that, the output result is produced by one
reduce task. This means that, at any point of the execution of the job,
 the data must be grouped and sorted in descendent order.
On 11 June 2013 13:57, Bhasker Allene <[EMAIL PROTECTED]> wrote:

>  One way to approach is emit Integer.MAX_VALUE - your key as output of
> mapper.
> Example
> Mapper input
> 7 vim
> 2 emacs
> 9 firefox
>
> Mapper output
> (Integer.MAX_VALUE - 7) vim
> (Integer.MAX_VALUE - 2) emacs
> (Integer.MAX_VALUE - 9) firefox
>
> If you need secondary sorting on second part, you have to use composite
> key  and write  your own petitioner, comparator.
>
> Regards,
> Bhasker
>
> On 11/06/2013 11:10, Pedro Sá da Costa wrote:
>
>  I created a MapReduce job example that that uses the sort mechanism of
> hadoop to sort a file by the key in ascending order. This is an example of
> the data:
>
>  7    vim
>  2    emacs
>  9    firefox
>
>  At the end, I get the result:
>
> 2    emacs
> 7    vim
>  9    firefox
>
>
>
> Now I want to sort in reverse order, for the result be:
> 9    firefox
> 7    vim
> 2    emacs
>
>
>
> How can I sort a file with pairs <Key Value> in reverse order?
>
> --
> Best regards,
>
>
>
> --
> Thanks & Regards,
> Bhasker Allene
>
>
--
Best regards,