HBASE-3720 Book.xml - porting conceptual-view / physical-view sections of HBaseArchitecture wiki
git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1087395 13f79535-47bb-0310-9956-ffa450edef68
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Michael Stack
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@ -110,6 +110,8 @@ Release 0.91.0 - Unreleased
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calls from HBase (Liyin Tang via Stack)
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HBASE-3717 deprecate HTable isTableEnabled() methods in favor of
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HBaseAdmin methods (David Butler via Stack)
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HBASE-3720 Book.xml - porting conceptual-view / physical-view sections of
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HBaseArchitecture wiki (Doug Meil via Stack)
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TASK
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HBASE-3559 Move report of split to master OFF the heartbeat channel
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@ -302,8 +302,8 @@ public static byte[][] getHexSplits(String startKey, String endKey, int numRegio
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<title>Data Model</title>
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<para>In short, applications store data into HBase <link linkend="table">tables</link>.
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Tables are made of <link linkend="row">rows</link> and <emphasis>columns</emphasis>.
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All colums in HBase belong to a particular
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<link linkend="columnfamily">Column Family</link>.
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All columns in HBase belong to a particular
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<link linkend="columnfamily">column family</link>.
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Table <link linkend="cell">cells</link> -- the intersection of row and column
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coordinates -- are versioned.
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A cell’s content is an uninterpreted array of bytes.
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@ -315,6 +315,99 @@ public static byte[][] getHexSplits(String startKey, String endKey, int numRegio
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via the table row key -- its primary key.
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</para>
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<section xml:id="conceptual.view"><title>Conceptual View</title>
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<para>
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The following example is a slightly modified form of the one on page
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2 of the <link xlink:href="http://labs.google.com/papers/bigtable.html">BigTable</link> paper.
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There is a table called <varname>webtable</varname> that contains two column families named
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<varname>contents</varname> and <varname>anchor</varname>.
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In this example, <varname>anchor</varname> contains two
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columns (<varname>anchor:cssnsi.com</varname>, <varname>anchor:my.look.ca</varname>)
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and <varname>contents</varname> contains one column (<varname>contents:html</varname>).
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<note>
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<title>Column Names</title>
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<para>
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By convention, a column name is made of its column family prefix and a
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<emphasis>qualifier</emphasis>. For example, the
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column
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<emphasis>contents:html</emphasis> is of the column family <varname>contents</varname>
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The colon character (<literal
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moreinfo="none">:</literal>) delimits the column family from the
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column family <emphasis>qualifier</emphasis>.
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</para>
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</note>
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<table frame='all'><title>Table <varname>webtable</varname></title>
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<tgroup cols='4' align='left' colsep='1' rowsep='1'>
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<colspec colname='c1'/>
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<colspec colname='c2'/>
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<colspec colname='c3'/>
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<colspec colname='c4'/>
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<thead>
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<row><entry>Row Key</entry><entry>Time Stamp</entry><entry>ColumnFamily <varname>contents</varname></entry><entry>ColumnFamily <varname>anchor</varname></entry></row>
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</thead>
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<tbody>
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<row><entry>"com.cnn.www"</entry><entry>t9</entry><entry></entry><entry><varname>anchor:cnnsi.com</varname> = "CNN"</entry></row>
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<row><entry>"com.cnn.www"</entry><entry>t8</entry><entry></entry><entry><varname>anchor:my.look.ca</varname> = "CNN.com"</entry></row>
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<row><entry>"com.cnn.www"</entry><entry>t6</entry><entry><varname>contents:html</varname> = "<html>..."</entry><entry></entry></row>
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<row><entry>"com.cnn.www"</entry><entry>t5</entry><entry><varname>contents:html</varname> = "<html>..."</entry><entry></entry></row>
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<row><entry>"com.cnn.www"</entry><entry>t3</entry><entry><varname>contents:html</varname> = "<html>..."</entry><entry></entry></row>
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</tbody>
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</tgroup>
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</table>
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</para>
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</section>
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<section xml:id="physical.view"><title>Physical View</title>
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<para>
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Although at a conceptual level tables may be viewed as a sparse set of rows.
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Physically they are stored on a per-column family basis. New columns
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(i.e., <varname>columnfamily:column</varname>) can be added to any
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column family without pre-announcing them.
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<table frame='all'><title>ColumnFamily <varname>anchor</varname></title>
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<tgroup cols='3' align='left' colsep='1' rowsep='1'>
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<colspec colname='c1'/>
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<colspec colname='c2'/>
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<colspec colname='c3'/>
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<thead>
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<row><entry>Row Key</entry><entry>Time Stamp</entry><entry>Column Family <varname>anchor</varname></entry></row>
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</thead>
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<tbody>
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<row><entry>"com.cnn.www"</entry><entry>t9</entry><entry><varname>anchor:cnnsi.com</varname> = "CNN"</entry></row>
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<row><entry>"com.cnn.www"</entry><entry>t8</entry><entry><varname>anchor:my.look.ca</varname> = "CNN.com"</entry></row>
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</tbody>
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</tgroup>
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</table>
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<table frame='all'><title>ColumnFamily <varname>contents</varname></title>
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<tgroup cols='3' align='left' colsep='1' rowsep='1'>
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<colspec colname='c1'/>
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<colspec colname='c2'/>
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<colspec colname='c3'/>
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<thead>
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<row><entry>Row Key</entry><entry>Time Stamp</entry><entry>ColumnFamily "contents:"</entry></row>
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</thead>
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<tbody>
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<row><entry>"com.cnn.www"</entry><entry>t6</entry><entry><varname>contents:html</varname> = "<html>..."</entry><entry></entry></row>
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<row><entry>"com.cnn.www"</entry><entry>t5</entry><entry><varname>contents:html</varname> = "<html>..."</entry><entry></entry></row>
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<row><entry>"com.cnn.www"</entry><entry>t3</entry><entry><varname>contents:html</varname> = "<html>..."</entry><entry></entry></row>
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</tbody>
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</tgroup>
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</table>
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It is important to note in the diagram above that the empty cells shown in the
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conceptual view are not stored since they need not be in a column-oriented
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storage format. Thus a request for the value of the <varname>contents:html</varname>
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column at time stamp <literal>t8</literal> would return no value. Similarly, a
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request for an <varname>anchor:my.look.ca</varname> value at time stamp
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<literal>t9</literal> would return no value. However, if no timestamp is
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supplied, the most recent value for a particular column would be returned
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and would also be the first one found since timestamps are stored in
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descending order. Thus a request for the values of all columns in the row
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<varname>com.cnn.www</varname> if no timestamp is specified would be:
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the value of <varname>contents:html</varname> from time stamp
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<literal>t6</literal>, the value of <varname>anchor:cnnsi.com</varname>
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from time stamp <literal>t9</literal>, the value of
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<varname>anchor:my.look.ca</varname> from time stamp <literal>t8</literal>.
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</para>
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</section>
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<section xml:id="table">
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<title>Table</title>
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<para>
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@ -334,7 +427,7 @@ public static byte[][] getHexSplits(String startKey, String endKey, int numRegio
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<title>Column Family<indexterm><primary>Column Family</primary></indexterm></title>
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<para>
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Columns in HBase are grouped into <emphasis>column families</emphasis>.
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All column members of a column family have a common prefix. For example, the
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All column members of a column family have the same prefix. For example, the
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columns <emphasis>courses:history</emphasis> and
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<emphasis>courses:math</emphasis> are both members of the
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<emphasis>courses</emphasis> column family.
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