Author: dmeil
Date: Wed Aug 31 23:31:05 2011
New Revision: 1163866
URL: http://svn.apache.org/viewvc?rev=1163866&view=rev
Log:
HBASE-4317 book.xml - minor cleanup of MR examples
Modified:
hbase/trunk/src/docbkx/book.xml
Modified: hbase/trunk/src/docbkx/book.xml
URL:
http://svn.apache.org/viewvc/hbase/trunk/src/docbkx/book.xml?rev=1163866&r1=1163865&r2=1163866&view=diff
==============================================================================
--- hbase/trunk/src/docbkx/book.xml (original)
+++ hbase/trunk/src/docbkx/book.xml Wed Aug 31 23:31:05 2011
@@ -126,7 +126,7 @@ TableMapReduceUtil.initTableMapperJob(
job.setOutputFormatClass(NullOutputFormat.class); // because we aren't
emitting anything from mapper
boolean b = job.waitForCompletion(true);
-if ( b == false) {
+if (!b) {
throw new IOException("error with job!");
}
</programlisting>
@@ -169,14 +169,14 @@ TableMapReduceUtil.initTableReducerJob(
job.setNumReduceTasks(0);
boolean b = job.waitForCompletion(true);
-if ( b == false) {
- throw new IOException("error with job!");
+if (!b) {
+ throw new IOException("error with job!");
}
</programlisting>
An explanation is required of what
<classname>TableMapReduceUtil</classname> is doing, especially with the
reducer.
<link
xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/mapreduce/TableOutputFormat.html";>TableOutputFormat</link>
is being used
as the outputFormat class, and several parameters are being set on the
config (e.g., TableOutputFormat.OUTPUT_TABLE), as
- well as setting the reducer output keys to
<classname>ImmutableBytesWritable</classname> and
<classname>Writable</classname>.
+ well as setting the reducer output key to
<classname>ImmutableBytesWritable</classname> and reducer value to
<classname>Writable</classname>.
These could be set by the programmer on the job and conf, but
<classname>TableMapReduceUtil</classname> tries to make things easier.
<para>The following is the example mapper, which will create a
<classname>Put</classname> and matching the input <classname>Result</classname>
and emit it. Note: this is what the CopyTable utility does.
@@ -189,13 +189,12 @@ public static class MyMapper extends Tab
context.write(row, resultToPut(row,value));
}
- private static Put resultToPut(ImmutableBytesWritable key, Result
result)
- throws IOException {
- Put put = new Put(key.get());
- for (KeyValue kv : result.raw()) {
- put.add(kv);
- }
- return put;
+ private static Put resultToPut(ImmutableBytesWritable key, Result
result) throws IOException {
+ Put put = new Put(key.get());
+ for (KeyValue kv : result.raw()) {
+ put.add(kv);
+ }
+ return put;
}
}
</programlisting>
@@ -235,7 +234,7 @@ TableMapReduceUtil.initTableReducerJob(
job.setNumReduceTasks(1); // at least one, adjust as required
boolean b = job.waitForCompletion(true);
-if ( b == false) {
+if (!b) {
throw new IOException("error with job!");
}
</programlisting>
