HBASE-4504 book.xml - filters
git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1176943 13f79535-47bb-0310-9956-ffa450edef68
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Doug Meil
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2c988abf35
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@ -1236,16 +1236,139 @@ HTable table2 = new HTable(conf2, "myTable");</programlisting>
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see the <link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/client/HTable.html#batch%28java.util.List%29">batch</link> methods on HTable.
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</para>
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</section>
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<section xml:id="client.filter"><title>Filters</title>
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<para><link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/client/Get.html">Get</link> and <link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/client/Scan.html">Scan</link> instances can be
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optionally configured with <link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/Filter.html">filters</link> which are applied on the RegionServer.
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</para>
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</section>
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<section xml:id="client.external"><title>External Clients</title>
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<para>Information on non-Java clients and custom protocols is covered in <xref linkend="external_apis" />
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</para>
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</section>
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</section>
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<section xml:id="client.filter"><title>Client Filters</title>
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<para><link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/client/Get.html">Get</link> and <link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/client/Scan.html">Scan</link> instances can be
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optionally configured with <link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/Filter.html">filters</link> which are applied on the RegionServer.
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</para>
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<para>Filters can be confusing because there are many different types, and it is best to approach them by understanding the groups
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of Filter functionality.
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</para>
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<section xml:id="client.filter.structural"><title>Structural</title>
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<para>Structural Filters contain other Filters.</para>
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<section xml:id="client.filter.structural.fl"><title>FilterList</title>
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<para><link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/FilterList.html">FilterList</link>
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represents a list of Filters with a relationship of <code>FilterList.Operator.MUST_PASS_ALL</code> or
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<code>FilterList.Operator.MUST_PASS_ONE</code> between the Filters. The following example shows an 'or' between two
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Filters (checking for either 'my value' or 'my other value' on the same attribute).
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<programlisting>
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FilterList list = new FilterList(FilterList.Operator.MUST_PASS_ONE);
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SingleColumnValueFilter filter1 = new SingleColumnValueFilter(
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cf,
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column,
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CompareOp.EQUAL,
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Bytes.toBytes("my value")
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);
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list.add(filter1);
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SingleColumnValueFilter filter2 = new SingleColumnValueFilter(
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cf,
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column,
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CompareOp.EQUAL,
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Bytes.toBytes("my other value")
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);
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list.add(filter2);
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scan.setFilter(list);
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</programlisting>
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</para>
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</section>
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</section>
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<section xml:id="client.filter.cv"><title>Column Value</title>
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<section xml:id="client.filter.cv.scvf"><title>SingleColumnValueFilter</title>
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<para><link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/SingleColumnValueFilter.html">SingleColumnValueFilter</link>
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can be used to test column values for equivalence (<code><link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/CompareFilter.CompareOp.html">CompareOp.EQUAL</link>
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</code>), inequality (<code>CompareOp.NOT_EQUAL</code>), or ranges
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(e.g., <code>CompareOp.GREATER</code>). The folowing is example of testing equivalence a column to a String value "my value"...
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<programlisting>
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SingleColumnValueFilter filter = new SingleColumnValueFilter(
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cf,
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column,
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CompareOp.EQUAL,
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Bytes.toBytes("my value")
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);
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scan.setFilter(filter);
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</programlisting>
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</para>
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</section>
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</section>
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<section xml:id="client.filter.cvp"><title>Column Value Comparators</title>
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<para>There are several Comparator classes in the Filter package that deserve special mention.
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These Comparators are used in concert with other Filters, such as <xref linkend="client.filter.cv.scvf" />.
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</para>
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<section xml:id="client.filter.cvp.rcs"><title>RegexStringComparator</title>
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<para><link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/RegexStringComparator.html">RegexStringComparator</link>
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supports regular expressions for value comparisons.
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<programlisting>
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RegexStringComparator comp = new RegexStringComparator("my."); // any value that starts with 'my'
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SingleColumnValueFilter filter = new SingleColumnValueFilter(
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cf,
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column,
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CompareOp.EQUAL,
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comp
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);
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scan.setFilter(filter);
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</programlisting>
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See the Oracle JavaDoc for <link xlink:href="http://download.oracle.com/javase/6/docs/api/java/util/regex/Pattern.html">supported RegEx patterns in Java</link>.
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</para>
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</section>
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<section xml:id="client.filter.cvp.rcs"><title>SubstringComparator</title>
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<para><link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/SubstringComparator.html">SubstringComparator</link>
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can be used to determine if a given substring exists in a value. The comparison is case-insensitive.
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</para>
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<programlisting>
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SubstringComparator comp = new SubstringComparator("y val"); // looking for 'my value'
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SingleColumnValueFilter filter = new SingleColumnValueFilter(
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cf,
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column,
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CompareOp.EQUAL,
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comp
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);
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scan.setFilter(filter);
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</programlisting>
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</section>
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<section xml:id="client.filter.cvp.bfp"><title>BinaryPrefixComparator</title>
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<para>See <link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/BinaryPrefixComparator.html">BinaryPrefixComparator</link>.</para>
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</section>
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<section xml:id="client.filter.cvp.bc"><title>BinaryComparator</title>
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<para>See <link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/BinaryComparator.html">BinaryComparator</link>.</para>
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</section>
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</section>
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<section xml:id="client.filter.kvm"><title>KeyValue Metadata</title>
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<para>As HBase stores data internally as KeyValue pairs, KeyValue Metadata Filters evaluate the existence of keys (i.e., ColumnFamily:Column qualifiers)
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for a row, as opposed to values the previous section.
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</para>
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<section xml:id="client.filter.kvm.ff"><title>FamilyFilter</title>
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<para><link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/FamilyFilter.html">FamilyFilter</link> can be used
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to filter on the ColumnFamily. It is generally a better idea to select ColumnFamilies in the Scan than to do it with a Filter.</para>
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</section>
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<section xml:id="client.filter.kvm.qf"><title>QualifierFilter</title>
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<para><link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/QualifierFilter.html">QualifierFilter</link> can be used
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to filter based on Column (aka Qualifier) name.
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</para>
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</section>
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<section xml:id="client.filter.kvm.cpf"><title>ColumnPrefixFilter</title>
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<para><link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/ColumnPrefixFilter.html">ColumnPrefixFilter</link> can be used
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to filter based on the lead portion of Column (aka Qualifier) names.
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</para>
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</section>
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</section>
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<section xml:id="client.filter.row"><title>RowKey</title>
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<section xml:id="client.filter.row.rf"><title>RowFilter</title>
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<para>It is generally a better idea to use the startRow/stopRow methods on Scan for row selection, however
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<link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/RowFilter.html">RowFilter</link> can also be used.</para>
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</section>
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</section>
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<section xml:id="client.filter.utility"><title>Utility</title>
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<section xml:id="client.filter.utility.fkof"><title>FirstKeyOnlyFilter</title>
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<para>This is primarily used for rowcount jobs.
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See <link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/FirstKeyOnlyFilter.html">FirstKeyOnlyFilter</link>.</para>
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</section>
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</section>
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</section> <!-- client.filter -->
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<section xml:id="master"><title>Master</title>
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<para><code>HMaster</code> is the implementation of the Master Server. The Master server
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