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HBASE-4573 book.xml, Put to KeyValue examples. 

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1181880 13f79535-47bb-0310-9956-ffa450edef68
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Doug Meil 2011-10-11 16:40:04 +00:00
parent 6d68cece01
commit 90e9e2f057
1 changed files with 34 additions and 2 deletions
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36
src/docbkx/book.xml
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@ -609,8 +609,8 @@ admin.enableTable(table);
<para>Another common question is whether one should prefer rows or columns. The context is typically in extreme cases of wide
tables, such as having 1 row with 1 million attributes, or 1 million rows with 1 columns apiece.
</para>
<para>Winner: Rows (generally speaking). To be clear, this guideline is in the context is in extremely wide cases, not where
one needs to store a few dozen or hundred columns.
<para>Winner: Rows (generally speaking). To be clear, this guideline is in the context is in extremely wide cases, not in the
standard use-case where one needs to store a few dozen or hundred columns.
</para>
</section>
</section>
@ -1687,6 +1687,38 @@ scan.setFilter(filter);
</para>
<para>For more information, see the <link xlink:href="http://hbase.apache.org/xref/org/apache/hadoop/hbase/KeyValue.html">KeyValue source code</link>.
</para>
<section xml:id="keyvalue.example"><title>Example</title>
<para>To emphasize the points above, examine what happens with two Puts for two different columns for the same row:</para>
<itemizedlist>
<listitem>Put #1: <code>rowkey=row1, cf:attr1=value1</code></listitem>
<listitem>Put #2: <code>rowkey=row1, cf:attr2=value2</code></listitem>
</itemizedlist>
<para>Even though these are for the same row, a KeyValue is created for each column:</para>
<para>Key portion for Put #1:
<itemizedlist>
<listitem>rowlength (4)</listitem>
<listitem>row (row1)</listitem>
<listitem>columnfamilylength (2)</listitem>
<listitem>columnfamily (cf)</listitem>
<listitem>columnqualifier (attr1)</listitem>
<listitem>timestamp (server time of Put)</listitem>
<listitem>keytype (Put)</listitem>
</itemizedlist>
</para>
<para>Key portion for Put #2:
<itemizedlist>
<listitem>rowlength (4)</listitem>
<listitem>row (row1)</listitem>
<listitem>columnfamilylength (2)</listitem>
<listitem>columnfamily (cf)</listitem>
<listitem>columnqualifier (attr2)</listitem>
<listitem>timestamp (server time of Put)</listitem>
<listitem>keytype (Put)</listitem>
</itemizedlist>
</para>
</section>
<para>It is critical to understand that the rowkey, ColumnFamily, and column (aka columnqualifier) are embedded within
the KeyValue instance. The longer these identifiers are, the bigger the KeyValue is.</para>
</section>
<section xml:id="compaction">
<title>Compaction</title>