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>
