Return-Path: X-Original-To: apmail-hadoop-mapreduce-user-archive@minotaur.apache.org Delivered-To: apmail-hadoop-mapreduce-user-archive@minotaur.apache.org Received: from mail.apache.org (hermes.apache.org [140.211.11.3]) by minotaur.apache.org (Postfix) with SMTP id 670A97380 for ; Tue, 6 Dec 2011 01:36:42 +0000 (UTC) Received: (qmail 69190 invoked by uid 500); 6 Dec 2011 01:36:41 -0000 Delivered-To: apmail-hadoop-mapreduce-user-archive@hadoop.apache.org Received: (qmail 69153 invoked by uid 500); 6 Dec 2011 01:36:41 -0000 Mailing-List: contact mapreduce-user-help@hadoop.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: mapreduce-user@hadoop.apache.org Delivered-To: mailing list mapreduce-user@hadoop.apache.org Received: (qmail 69144 invoked by uid 99); 6 Dec 2011 01:36:41 -0000 Received: from nike.apache.org (HELO nike.apache.org) (192.87.106.230) by apache.org (qpsmtpd/0.29) with ESMTP; Tue, 06 Dec 2011 01:36:41 +0000 X-ASF-Spam-Status: No, hits=-0.7 required=5.0 tests=RCVD_IN_DNSWL_LOW,SPF_PASS X-Spam-Check-By: apache.org Received-SPF: pass (nike.apache.org: domain of joey@cloudera.com designates 209.85.214.48 as permitted sender) Received: from [209.85.214.48] (HELO mail-bw0-f48.google.com) (209.85.214.48) by apache.org (qpsmtpd/0.29) with ESMTP; Tue, 06 Dec 2011 01:36:34 +0000 Received: by bkas6 with SMTP id s6so1035767bka.35 for ; Mon, 05 Dec 2011 17:36:14 -0800 (PST) MIME-Version: 1.0 Received: by 10.180.103.170 with SMTP id fx10mr15101921wib.56.1323135373888; Mon, 05 Dec 2011 17:36:13 -0800 (PST) Received: by 10.180.0.35 with HTTP; Mon, 5 Dec 2011 17:36:13 -0800 (PST) In-Reply-To: References: Date: Mon, 5 Dec 2011 20:36:13 -0500 Message-ID: Subject: Re: Are the input values (associated with a specific key) of reduce() method sorted? From: Joey Echeverria To: mapreduce-user@hadoop.apache.org Content-Type: text/plain; charset=ISO-8859-1 X-Virus-Checked: Checked by ClamAV on apache.org Hi James, By default, there is no guarantees on value order. Using some of the more advanced API features, you can perform a secondary sort of values. You can read a good example of it here: http://sonerbalkir.blogspot.com/2010/01/simulating-secondary-sort-on-values.html -Joey On Mon, Dec 5, 2011 at 7:55 PM, James Y. Li wrote: > Hi All, > I just begin to use Hadoop framework, and write my reduce() method. Wonder > if the Iterable input values (associated with the input key) are already > sorted. Thanks! > > p.s. I am using the version 0.20.2-cdh3u1 > > -james > > -- > > -- Joseph Echeverria Cloudera, Inc. 443.305.9434