You are viewing a plain text version of this content. The canonical link for it is here.
Posted to common-commits@hadoop.apache.org by om...@apache.org on 2008/06/18 01:12:06 UTC
svn commit: r668872 - in /hadoop/core/branches/branch-0.17: CHANGES.txt
src/java/org/apache/hadoop/mapred/Reducer.java
Author: omalley
Date: Tue Jun 17 16:12:06 2008
New Revision: 668872
URL: http://svn.apache.org/viewvc?rev=668872&view=rev
Log:
HADOOP-3522. Merge -r 668866:668867 from trunk to branch 0.17.
Modified:
hadoop/core/branches/branch-0.17/CHANGES.txt
hadoop/core/branches/branch-0.17/src/java/org/apache/hadoop/mapred/Reducer.java
Modified: hadoop/core/branches/branch-0.17/CHANGES.txt
URL: http://svn.apache.org/viewvc/hadoop/core/branches/branch-0.17/CHANGES.txt?rev=668872&r1=668871&r2=668872&view=diff
==============================================================================
--- hadoop/core/branches/branch-0.17/CHANGES.txt (original)
+++ hadoop/core/branches/branch-0.17/CHANGES.txt Tue Jun 17 16:12:06 2008
@@ -28,6 +28,11 @@
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/branches/branch-0.17/src/java/org/apache/hadoop/mapred/Reducer.java
URL: http://svn.apache.org/viewvc/hadoop/core/branches/branch-0.17/src/java/org/apache/hadoop/mapred/Reducer.java?rev=668872&r1=668871&r2=668872&view=diff
==============================================================================
--- hadoop/core/branches/branch-0.17/src/java/org/apache/hadoop/mapred/Reducer.java (original)
+++ hadoop/core/branches/branch-0.17/src/java/org/apache/hadoop/mapred/Reducer.java Tue Jun 17 16:12:06 2008
@@ -169,7 +169,10 @@
* <p>The framework calls this method for each
* <code><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