From 07b39aaf0e4f59705b205f40aa616ee8f5724a58 Mon Sep 17 00:00:00 2001
From: dsyer <dsyer@2e8e966d-6415-0410-94b9-dc4e65435d03>
Date: Tue, 5 Oct 2010 15:55:03 +0000
Subject: [PATCH] BATCH-1531: add docs to user guide and javadocs

---
 .../core/partition/support/PartitionNameProvider.java |  8 ++++++++
 src/site/docbook/reference/scalability.xml            | 11 +++++++++++
 2 files changed, 19 insertions(+)

diff --git a/spring-batch-core/src/main/java/org/springframework/batch/core/partition/support/PartitionNameProvider.java b/spring-batch-core/src/main/java/org/springframework/batch/core/partition/support/PartitionNameProvider.java
index fa1457302..19571d404 100644
--- a/spring-batch-core/src/main/java/org/springframework/batch/core/partition/support/PartitionNameProvider.java
+++ b/spring-batch-core/src/main/java/org/springframework/batch/core/partition/support/PartitionNameProvider.java
@@ -25,6 +25,14 @@ import java.util.Collection;
  * interface if a partitioner extends {@link SimplePartitioner} and re-uses the
  * default partition names.
  * </p>
+ * <p>
+ * If a partitioner does implement this interface, however, on a restart the
+ * {@link Partitioner#partition(int)} method will not be called again, instead
+ * the partitions will be re-used from the last execution, and matched by name
+ * with the results of {@link PartitionNameProvider#getPartitionNames(int)}.
+ * This can be a useful performance optimisation if the partitioning process is
+ * expensive.
+ * </p>
  * 
  * @author Dave Syer
  * 
diff --git a/src/site/docbook/reference/scalability.xml b/src/site/docbook/reference/scalability.xml
index a34516490..fec314c81 100644
--- a/src/site/docbook/reference/scalability.xml
+++ b/src/site/docbook/reference/scalability.xml
@@ -340,6 +340,17 @@
       <classname>Job</classname>), and the suffix is just a counter. There is
       a <classname>SimplePartitioner</classname> in the framework that uses
       this convention.</para>
+
+      <para>An optional interface
+      <classname>PartitioneNameProvider</classname> can be used to
+      provide the partition names separately from the partitions
+      themselves.  If a <classname>Partitioner</classname> implements
+      this interface then on a restart only the names will be queried.
+      If partitioning is expensive this can be a useful optimisation.
+      Obviously the names provided by the
+      <classname>PartitioneNameProvider</classname> must match those
+      provided by the <classname>Partitioner</classname>.</para>
+
     </section>
 
     <section id="bindingInputDataToSteps">