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From st...@apache.org
Subject svn commit: r1098721 - in /hbase/trunk/src/docbkx: book.xml performance.xml
Date Mon, 02 May 2011 18:35:49 GMT
Author: stack
Date: Mon May  2 18:35:49 2011
New Revision: 1098721

URL: http://svn.apache.org/viewvc?rev=1098721&view=rev
Log:
HBASE-3844 Book.xml (removing link to defunct wiki) and Performance.xml (adding client tip)

Modified:
    hbase/trunk/src/docbkx/book.xml
    hbase/trunk/src/docbkx/performance.xml

Modified: hbase/trunk/src/docbkx/book.xml
URL: http://svn.apache.org/viewvc/hbase/trunk/src/docbkx/book.xml?rev=1098721&r1=1098720&r2=1098721&view=diff
==============================================================================
--- hbase/trunk/src/docbkx/book.xml (original)
+++ hbase/trunk/src/docbkx/book.xml Mon May  2 18:35:49 2011
@@ -1322,8 +1322,7 @@ false
             <answer>
                 <para>
               See the FAQ that is up on the wiki, <link xlink:href="http://wiki.apache.org/hadoop/Hbase/FAQ">HBase
Wiki FAQ</link>
-              as well as the <link xlink:href="http://wiki.apache.org/hadoop/Hbase/Troubleshooting">Troubleshooting</link>
page and
-              the <link xlink:href="http://wiki.apache.org/hadoop/Hbase/FrequentlySeenErrors">Frequently
Seen Errors</link> page.
+              as well as the <link xlink:href="http://wiki.apache.org/hadoop/Hbase/Troubleshooting">Troubleshooting</link>
page.
                 </para>
             </answer>
         </qandaentry>

Modified: hbase/trunk/src/docbkx/performance.xml
URL: http://svn.apache.org/viewvc/hbase/trunk/src/docbkx/performance.xml?rev=1098721&r1=1098720&r2=1098721&view=diff
==============================================================================
--- hbase/trunk/src/docbkx/performance.xml (original)
+++ hbase/trunk/src/docbkx/performance.xml Mon May  2 18:35:49 2011
@@ -189,6 +189,16 @@ public static byte[][] getHexSplits(Stri
       have the cache value be large because it costs more in memory for both
       client and RegionServer, so bigger isn't always better.</para>
     </section>
+    <section xml:id="perf.hbase.client.selection">
+      <title>Scan Attribute Selection</title>
+
+      <para>Whenever a Scan is used to process large numbers of rows (and especially
when used
+      as a MapReduce source), be aware of which attributes are selected.   If <code>scan.addFamily</code>
is called
+      then <emphasis>all</emphasis> of the attributes in the specified ColumnFamily
will be returned to the client.
+      If only a small number of the available attributes are to be processed, then only those
attributes should be specified
+      in the input scan because attribute over-selection is a non-trivial performance penalty
over large datasets.
+      </para>
+    </section>
 
     <section xml:id="perf.hbase.client.scannerclose">
       <title>Close ResultScanners</title>



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