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From t...@apache.org
Subject svn commit: r1102184 - in /hadoop/mapreduce/trunk: CHANGES.txt src/docs/src/documentation/content/xdocs/streaming.xml
Date Thu, 12 May 2011 07:15:41 GMT
Author: todd
Date: Thu May 12 07:15:41 2011
New Revision: 1102184

URL: http://svn.apache.org/viewvc?rev=1102184&view=rev
Log:
MAPREDUCE-2410. Add entry to streaming FAQ about how streaming reducers receive keys. Contributed
by Harsh J Chouraria.

Modified:
    hadoop/mapreduce/trunk/CHANGES.txt
    hadoop/mapreduce/trunk/src/docs/src/documentation/content/xdocs/streaming.xml

Modified: hadoop/mapreduce/trunk/CHANGES.txt
URL: http://svn.apache.org/viewvc/hadoop/mapreduce/trunk/CHANGES.txt?rev=1102184&r1=1102183&r2=1102184&view=diff
==============================================================================
--- hadoop/mapreduce/trunk/CHANGES.txt (original)
+++ hadoop/mapreduce/trunk/CHANGES.txt Thu May 12 07:15:41 2011
@@ -90,6 +90,9 @@ Trunk (unreleased changes)
     MAPREDUCE-869. Documentation for config to set map/reduce task environment
     (Alejandro Abdelnur via todd)
 
+    MAPREDUCE-2410. Add entry to streaming FAQ about how streaming reducers
+    receive keys. (Harsh J Chouraria via todd)
+
   OPTIMIZATIONS
     
     MAPREDUCE-2026. Make JobTracker.getJobCounters() and

Modified: hadoop/mapreduce/trunk/src/docs/src/documentation/content/xdocs/streaming.xml
URL: http://svn.apache.org/viewvc/hadoop/mapreduce/trunk/src/docs/src/documentation/content/xdocs/streaming.xml?rev=1102184&r1=1102183&r2=1102184&view=diff
==============================================================================
--- hadoop/mapreduce/trunk/src/docs/src/documentation/content/xdocs/streaming.xml (original)
+++ hadoop/mapreduce/trunk/src/docs/src/documentation/content/xdocs/streaming.xml Thu May
12 07:15:41 2011
@@ -785,6 +785,15 @@ For details see <a href="mapred_tutorial
 </p>
 </section>
 
+<!-- QUESTION -->
+<section>
+<title>How does the use of streaming differ from the Java MapReduce API?</title>
+<p>
+    The Java MapReduce API provides a higher level API that lets the developer focus on writing
map and reduce functions that act upon a pair of key and associated value(s). The Java API
takes care of the iteration over the data source behind the scenes.
+    In streaming, the framework pours in the input data over the stdin to the mapper/reduce
program, and thus these programs ought to be written from the reading (via stdin) iteration
level. A practical consequence of this is that reducers for streaming need to be able to deal
with different input keys.
+    Some alternative interfaces for particular programming languages can be found <a href="http://wiki.apache.org/hadoop/HadoopStreaming/AlternativeInterfaces">here</a>.
+</p>
+</section>
 
 <!-- QUESTION -->
 <section>



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