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From omal...@apache.org
Subject svn commit: r668867 - in /hadoop/core/trunk: CHANGES.txt src/mapred/org/apache/hadoop/mapred/Reducer.java
Date Tue, 17 Jun 2008 22:56:51 GMT
Author: omalley
Date: Tue Jun 17 15:56:50 2008
New Revision: 668867

URL: http://svn.apache.org/viewvc?rev=668867&view=rev
Log:
HADOOP-3522. Improve documentation on reduce pointing out that
input keys and values will be reused.

Modified:
    hadoop/core/trunk/CHANGES.txt
    hadoop/core/trunk/src/mapred/org/apache/hadoop/mapred/Reducer.java

Modified: hadoop/core/trunk/CHANGES.txt
URL: http://svn.apache.org/viewvc/hadoop/core/trunk/CHANGES.txt?rev=668867&r1=668866&r2=668867&view=diff
==============================================================================
--- hadoop/core/trunk/CHANGES.txt (original)
+++ hadoop/core/trunk/CHANGES.txt Tue Jun 17 15:56:50 2008
@@ -630,6 +630,11 @@
     default, to clear the state of the serializer between objects.
     (tomwhite via omalley)
 
+  IMPROVEMENTS
+
+    HADOOP-3522. Improve documentation on reduce pointing out that
+    input keys and values will be reused. (omalley)
+
 Release 0.17.0 - 2008-05-18
 
   INCOMPATIBLE CHANGES

Modified: hadoop/core/trunk/src/mapred/org/apache/hadoop/mapred/Reducer.java
URL: http://svn.apache.org/viewvc/hadoop/core/trunk/src/mapred/org/apache/hadoop/mapred/Reducer.java?rev=668867&r1=668866&r2=668867&view=diff
==============================================================================
--- hadoop/core/trunk/src/mapred/org/apache/hadoop/mapred/Reducer.java (original)
+++ hadoop/core/trunk/src/mapred/org/apache/hadoop/mapred/Reducer.java Tue Jun 17 15:56:50
2008
@@ -169,7 +169,10 @@
    * <p>The framework calls this method for each 
    * <code>&lt;key, (list of values)></code> pair in the grouped inputs.
    * Output values must be of the same type as input values.  Input keys must 
-   * not be altered.  Typically all values are combined into zero or one value.
+   * not be altered. The framework will <b>reuse</b> the key and value objects
+   * that are passed into the reduce, therefore the application should clone
+   * the objects they want to keep a copy of. In many cases, all values are 
+   * combined into zero or one value.
    * </p>
    *   
    * <p>Output pairs are collected with calls to  



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