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From Utkarsh Gupta <Utkarsh_Gu...@infosys.com>
Subject RE: Limitation of key-value pairs for a particular key.
Date Fri, 18 Jan 2013 09:25:24 GMT
You are right
Actually we were expecting the values to be sorted.
We tried to reproduce the problem by this simple code
private final IntWritable one=new IntWritable(1);
        private Text word=new Text();
        public void map(LongWritable key,Text value, Context context) throws IOException,
InterruptedException {
            int N=30000;
            for(int i=0;i<N;i++)
For smaller N numbers were in order but for N 3000000 order was not maintained

From: Harsh J [mailto:harsh@cloudera.com]
Sent: Thursday, January 17, 2013 1:57 AM
To: mapreduce-user
Subject: RE: Limitation of key-value pairs for a particular key.

We don't sort values (only keys) nor apply any manual limits in MR. Can your post a reproduceable
test case to support your suspicion?
On Jan 16, 2013 4:34 PM, "Utkarsh Gupta" <Utkarsh_Gupta@infosys.com<mailto:Utkarsh_Gupta@infosys.com>>
Thanks for the response. There was some issues with my code. I have checked that in detail.
All the values of map are present in reducer but not in sorted order. This case happens if
the number of values are too large for a key.


From: Vinod Kumar Vavilapalli [mailto:vinodkv@hortonworks.com<mailto:vinodkv@hortonworks.com>]
Sent: Thursday, January 10, 2013 11:00 PM
To: mapreduce-user@hadoop.apache.org<mailto:mapreduce-user@hadoop.apache.org>
Subject: Re: Limitation of key-value pairs for a particular key.

There isn't any limit like that. Can you reproduce this consistently? If so, please file a

It will definitely help if you can provide a test case which can reproduce this issue.


On Thu, Jan 10, 2013 at 12:41 AM, Utkarsh Gupta <Utkarsh_Gupta@infosys.com<mailto:Utkarsh_Gupta@infosys.com>>

I am using Apache Hadoop 1.0.4 on a 10 node cluster of commodity machines with Ubuntu 12.04
Server edition. I am having a issue with my map reduce code. While debugging I found that
the reducer can take 262145 values for a particular key. If more values are there, they seem
to be corrupted. I checked the values while emitting from map and again checked in reducer.
I am wondering is there any such kind of limitation in the Hadoop or is it a configuration

Thanks and Regards
Utkarsh Gupta

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