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HBASE-3720 Book.xml - porting conceptual-view / physical-view sections of HBaseArchitecture wiki

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git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1087395 13f79535-47bb-0310-9956-ffa450edef68
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Michael Stack 2011-03-31 18:12:04 +00:00
parent 569b5d2335
commit a906560ce0
2 changed files with 98 additions and 3 deletions
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CHANGES.txt
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@ -110,6 +110,8 @@ Release 0.91.0 - Unreleased
calls from HBase (Liyin Tang via Stack) calls from HBase (Liyin Tang via Stack)
HBASE-3717 deprecate HTable isTableEnabled() methods in favor of HBASE-3717 deprecate HTable isTableEnabled() methods in favor of
HBaseAdmin methods (David Butler via Stack) HBaseAdmin methods (David Butler via Stack)
HBASE-3720 Book.xml - porting conceptual-view / physical-view sections of
HBaseArchitecture wiki (Doug Meil via Stack)
TASK TASK
HBASE-3559 Move report of split to master OFF the heartbeat channel HBASE-3559 Move report of split to master OFF the heartbeat channel

99
src/docbkx/book.xml
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@ -302,8 +302,8 @@ public static byte[][] getHexSplits(String startKey, String endKey, int numRegio
<title>Data Model</title> <title>Data Model</title>
<para>In short, applications store data into HBase <link linkend="table">tables</link>. <para>In short, applications store data into HBase <link linkend="table">tables</link>.
Tables are made of <link linkend="row">rows</link> and <emphasis>columns</emphasis>. Tables are made of <link linkend="row">rows</link> and <emphasis>columns</emphasis>.
All colums in HBase belong to a particular All columns in HBase belong to a particular
<link linkend="columnfamily">Column Family</link>. <link linkend="columnfamily">column family</link>.
Table <link linkend="cell">cells</link> -- the intersection of row and column Table <link linkend="cell">cells</link> -- the intersection of row and column
coordinates -- are versioned. coordinates -- are versioned.
A cell’s content is an uninterpreted array of bytes. A cell’s content is an uninterpreted array of bytes.
@ -315,6 +315,99 @@ public static byte[][] getHexSplits(String startKey, String endKey, int numRegio
via the table row key -- its primary key. via the table row key -- its primary key.
</para> </para>
<section xml:id="conceptual.view"><title>Conceptual View</title>
<para>
The following example is a slightly modified form of the one on page
2 of the <link xlink:href="http://labs.google.com/papers/bigtable.html">BigTable</link> paper.
There is a table called <varname>webtable</varname> that contains two column families named
<varname>contents</varname> and <varname>anchor</varname>.
In this example, <varname>anchor</varname> contains two
columns (<varname>anchor:cssnsi.com</varname>, <varname>anchor:my.look.ca</varname>)
and <varname>contents</varname> contains one column (<varname>contents:html</varname>).
<note>
<title>Column Names</title>
<para>
By convention, a column name is made of its column family prefix and a
<emphasis>qualifier</emphasis>. For example, the
column
<emphasis>contents:html</emphasis> is of the column family <varname>contents</varname>
The colon character (<literal
moreinfo="none">:</literal>) delimits the column family from the
column family <emphasis>qualifier</emphasis>.
</para>
</note>
<table frame='all'><title>Table <varname>webtable</varname></title>
<tgroup cols='4' align='left' colsep='1' rowsep='1'>
<colspec colname='c1'/>
<colspec colname='c2'/>
<colspec colname='c3'/>
<colspec colname='c4'/>
<thead>
<row><entry>Row Key</entry><entry>Time Stamp</entry><entry>ColumnFamily <varname>contents</varname></entry><entry>ColumnFamily <varname>anchor</varname></entry></row>
</thead>
<tbody>
<row><entry>"com.cnn.www"</entry><entry>t9</entry><entry></entry><entry><varname>anchor:cnnsi.com</varname> = "CNN"</entry></row>
<row><entry>"com.cnn.www"</entry><entry>t8</entry><entry></entry><entry><varname>anchor:my.look.ca</varname> = "CNN.com"</entry></row>
<row><entry>"com.cnn.www"</entry><entry>t6</entry><entry><varname>contents:html</varname> = "&lt;html&gt;..."</entry><entry></entry></row>
<row><entry>"com.cnn.www"</entry><entry>t5</entry><entry><varname>contents:html</varname> = "&lt;html&gt;..."</entry><entry></entry></row>
<row><entry>"com.cnn.www"</entry><entry>t3</entry><entry><varname>contents:html</varname> = "&lt;html&gt;..."</entry><entry></entry></row>
</tbody>
</tgroup>
</table>
</para>
</section>
<section xml:id="physical.view"><title>Physical View</title>
<para>
Although at a conceptual level tables may be viewed as a sparse set of rows.
Physically they are stored on a per-column family basis. New columns
(i.e., <varname>columnfamily:column</varname>) can be added to any
column family without pre-announcing them.
<table frame='all'><title>ColumnFamily <varname>anchor</varname></title>
<tgroup cols='3' align='left' colsep='1' rowsep='1'>
<colspec colname='c1'/>
<colspec colname='c2'/>
<colspec colname='c3'/>
<thead>
<row><entry>Row Key</entry><entry>Time Stamp</entry><entry>Column Family <varname>anchor</varname></entry></row>
</thead>
<tbody>
<row><entry>"com.cnn.www"</entry><entry>t9</entry><entry><varname>anchor:cnnsi.com</varname> = "CNN"</entry></row>
<row><entry>"com.cnn.www"</entry><entry>t8</entry><entry><varname>anchor:my.look.ca</varname> = "CNN.com"</entry></row>
</tbody>
</tgroup>
</table>
<table frame='all'><title>ColumnFamily <varname>contents</varname></title>
<tgroup cols='3' align='left' colsep='1' rowsep='1'>
<colspec colname='c1'/>
<colspec colname='c2'/>
<colspec colname='c3'/>
<thead>
<row><entry>Row Key</entry><entry>Time Stamp</entry><entry>ColumnFamily "contents:"</entry></row>
</thead>
<tbody>
<row><entry>"com.cnn.www"</entry><entry>t6</entry><entry><varname>contents:html</varname> = "&lt;html&gt;..."</entry><entry></entry></row>
<row><entry>"com.cnn.www"</entry><entry>t5</entry><entry><varname>contents:html</varname> = "&lt;html&gt;..."</entry><entry></entry></row>
<row><entry>"com.cnn.www"</entry><entry>t3</entry><entry><varname>contents:html</varname> = "&lt;html&gt;..."</entry><entry></entry></row>
</tbody>
</tgroup>
</table>
It is important to note in the diagram above that the empty cells shown in the
conceptual view are not stored since they need not be in a column-oriented
storage format. Thus a request for the value of the <varname>contents:html</varname>
column at time stamp <literal>t8</literal> would return no value. Similarly, a
request for an <varname>anchor:my.look.ca</varname> value at time stamp
<literal>t9</literal> would return no value. However, if no timestamp is
supplied, the most recent value for a particular column would be returned
and would also be the first one found since timestamps are stored in
descending order. Thus a request for the values of all columns in the row
<varname>com.cnn.www</varname> if no timestamp is specified would be:
the value of <varname>contents:html</varname> from time stamp
<literal>t6</literal>, the value of <varname>anchor:cnnsi.com</varname>
from time stamp <literal>t9</literal>, the value of
<varname>anchor:my.look.ca</varname> from time stamp <literal>t8</literal>.
</para>
</section>
<section xml:id="table"> <section xml:id="table">
<title>Table</title> <title>Table</title>
<para> <para>
@ -334,7 +427,7 @@ public static byte[][] getHexSplits(String startKey, String endKey, int numRegio
<title>Column Family<indexterm><primary>Column Family</primary></indexterm></title> <title>Column Family<indexterm><primary>Column Family</primary></indexterm></title>
<para> <para>
Columns in HBase are grouped into <emphasis>column families</emphasis>. Columns in HBase are grouped into <emphasis>column families</emphasis>.
All column members of a column family have a common prefix. For example, the All column members of a column family have the same prefix. For example, the
columns <emphasis>courses:history</emphasis> and columns <emphasis>courses:history</emphasis> and
<emphasis>courses:math</emphasis> are both members of the <emphasis>courses:math</emphasis> are both members of the
<emphasis>courses</emphasis> column family. <emphasis>courses</emphasis> column family.