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From Devaraj k <devara...@huawei.com>
Subject RE: Grouping comparator
Date Mon, 04 Jun 2012 12:33:20 GMT
If you don't specify grouping comparator for your Job, it uses the Output Key Comparator class
for grouping.

This comparator should be provided if the equivalence rules for keys sorting the intermediates
are different from those for grouping keys.


From: Ajay Srivastava [Ajay.Srivastava@guavus.com]
Sent: Monday, June 04, 2012 4:26 PM
To: common-user@hadoop.apache.org
Subject: Grouping comparator


Can someone please explain default implementation of grouping comparator i.e. if I do not
specify a custom grouping comparator then which comparator is called to decide the grouping
for reducer.
I searched a lot on web but could not find a satisfactory explanation for its default implementation.

Ajay Srivastava

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