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>
