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    <td align="right" class="bar"> <!-- InstanceBeginEditable name="Section Title" -->
      <h1>Partitioning</h1>
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      <p><a href="Partitioning.htm">Partitioning</a></p>
      <p><a href="Partitioning.htm#limits"><img src="../../images/blank.gif" width="15" height="10" border="0">Limitations</a></p>
      <p><a href="Partitioning.htm#updates"><img src="../../images/blank.gif" width="15" height="10" border="0">Data 
        Updates</a></p>
      <p><a href="Analysis.htm">1. Analysis</a></p>
      <p><a href="Partition%20the%20Table.htm">2. Partition the Table</a></p>
      <p> <a href="Environment%20File.htm">3. Environment File Entry</a></p>
      <p><a href="Indexing.htm">4. Indexing</a></p>
      <p><a href="Example1.htm">Examples</a></p>
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      <h2 class="line">Step 2 - Partition the Table</h2>
      <p>After determining the best approach to partitioning the table, the table 
        must be physically partitioned. The ODXSQL utility's PARTITION command 
        can be used to perform this task.</p>
      <p><img src="../../images/note.gif" alt="Note: " width="12" height="15" align="left">Omnidex 
        does not require that the actual partitioning of the data be performed 
        using the ODXSQL utility. It is provided as a convenience and is recommended 
        because it can perform the partitioning and at the same time, generate 
        the environment file entries necessary to use and index the partitions.</p>
      <p>This topic focuses solely on partitioning with ODXSQL.</p>
      <p class="line">&nbsp;</p>
      <h3><a name="odxsql" id="odxsql"></a>ODXSQL PARTITION Command</h3>
      <p>The ODXSQL PARTITION command can physically partition a table according 
        to the specified criteria, generating reports detailing exactly how the 
        data was partitioned. At the same time, it can generate the environment 
        file entries necessary to index and search the partitioned table.</p>
      <p>No matter what the underlying database type, the partitions will be created 
        in flat files. These files will be created in either the current working 
        directory or the specified location, if the &quot;in location&quot; clause 
        is passed with the PARTITION command.</p>
      <p>The PARTITION command can divide the table in several different ways:</p>
      <p> <a href="#column"><img src="../../images/arrow2.gif" width="10" height="10" border="0">Partition 
        by column</a></p>
      <p><a href="#equal"><img src="../../images/arrow2.gif" width="10" height="10" border="0">Partition 
        into equal partitions</a></p>
      <p><a href="#equalcolumn"><img src="../../images/arrow2.gif" width="10" height="10" border="0">Partition 
        by column into equal partitions</a></p>
      <p><a href="#validation"><img src="../../images/arrow2.gif" width="10" height="10" border="0">Partiton 
        by valid values</a></p>
      <p><a href="#expressions"><img src="../../images/arrow2.gif" width="10" height="10" border="0">Partition 
        by an expression</a></p>
      <p></p>
      <p><img src="../../images/note.gif" alt="Note: " width="12" height="15" align="left">To 
        assist in the analysis step (<a href="Analysis.htm">Step 1 - Analysis</a>), 
        the REPORT_ONLY option is available for use with the PARTITION command. 
        This will cause ODXSQL to simulate the partition, generating the reports 
        without physically partitioning the table.</p>
      <p>&nbsp;</p>
      <p class="line">&nbsp;</p>
      <h3><a name="column"></a>Partition by Column</h3>
      <p>Partitioning by a column will divide a table into partitions by unique 
        column values. For example, when partitioning by a state column, the table 
        will be split into 50 different partitions, assuming at least one record 
        for each state exists in the table.</p>
      <p>In some instances, this type of partition may be appropriate. However, 
        it does not provide any assurance that the data will be divided evenly 
        or efficiently. For example, partitioning an orders table by the product 
        number without specifying the number of partitions to divided the table 
        into will cause ODXSQL to create a separate partition for each distinct 
        product number.</p>
      <p>The <a href="Example1.htm#column">example</a> will demonstrate how this 
        partition type is performed.</p>
      <p class="line">&nbsp;</p>
      <h3><a name="equal"></a>Partition into Equal Partitions</h3>
      <p>Partitioning into equal partitions will divide a table into the specified 
        number of partitions. However, since no column is specified to be used 
        as the partition qualifier, there is no particular partitioning logic 
        other than an equal or very similar number of rows in each partition.</p>
      <p>In some cases, this may be valid. But without a partition qualifier, 
        queries against this partition will result in a search against all partitions, 
        which negates the benefit of partitioning the data.</p>
      <p>The <a href="Example1.htm#equal">example</a> will demonstrate how this 
        partition type is performed.</p>
      <p class="line">&nbsp;</p>
      <h3><a name="equalcolumn"></a>Partition by Column into Equal Partitions</h3>
      <p>Partitioning by column into equal partitions will group table data by 
        the unique column values of the specified column. It then combines the 
        groups together into the specified number of partitions in such a way 
        that the total number of rows in each partition is uniform, as close as 
        possible.</p>
      <p>This ensures that all rows for a particular column value are kept together 
        in a single partition. When a query is processed against the partitioned 
        table and criteria is specified for the partition column, only the table 
        containing that criteria value will be searched.</p>
      <p>The <a href="Example1.htm#equalcolumn">example</a> will demonstrate how 
        this partition type is performed.</p>
      <p class="line">&nbsp;</p>
      <h3><a name="validation"></a>Partition by Valid Values</h3>
      <p> Partitioning a table using valid values places invalid values into a 
        partition of their own. First export all valid values for the partition 
        qualifier to an OST, attach the OST, then use the validation_column='osttable.column' 
        WITH option in the partition statement.</p>
      <p>The partition should be designed in the same manner as described above, 
        partitioning by column and specifying the number of partitions to generate. 
        Validating the data, however, helps to clean up bad data, which can further 
        improve performance.</p>
      <p>The <a href="Example2.htm#validation">example</a> will demonstrate how 
        this partition type is performed.</p>
      <p class="line">&nbsp;</p>
      <h3><a name="expressions"></a>Partition by an Expression</h3>
      <p> Partitioning a table using an expression provides a little more flexibility 
        in determining how the table will be partitioned. The partition must still 
        occur on a single column, but an expression such as &quot;substring&quot; 
        can be used to determine how the data will be divided.</p>
      <p>Once the expression is evaluated, the data is grouped together into either 
        the specified number of partitions or individual partitions for each expression 
        result.</p>
      <p>The <a href="Example2.htm#expressions">example</a> will demonstrate how 
        this partition type is performed.</p>
      <p>&nbsp;</p>
      <p></p>
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