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HTML
238 lines
8.8 KiB
HTML
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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>More Secondary Key Indices</title>
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<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
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<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
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<link rel="start" href="index.html" title="Berkeley DB Collections Tutorial" />
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<link rel="up" href="UsingSecondaries.html" title="Chapter 3. Using Secondary Indices" />
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<link rel="prev" href="UsingSecondaries.html" title="Chapter 3. Using Secondary Indices" />
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<link rel="next" href="indexedcollections.html" title="Creating Indexed Collections" />
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</head>
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<body>
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<div xmlns="" class="navheader">
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<div class="libver">
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<p>Library Version 11.2.5.2</p>
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</div>
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">
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<span xmlns="http://www.w3.org/1999/xhtml">More Secondary Key Indices</span>
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</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="UsingSecondaries.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 3.
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Using Secondary Indices
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="indexedcollections.html">Next</a></td>
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</tr>
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</table>
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<hr />
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</div>
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<div class="sect1" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h2 class="title" style="clear: both"><a id="openingforeignkeys"></a>
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<span>More Secondary Key Indices</span>
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</h2>
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</div>
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</div>
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</div>
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<p>
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This section builds on the prior section describing secondary key indices.
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Two more secondary key indices are defined for indexing the Shipment record
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by PartNumber and by SupplierNumber.
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</p>
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<p>
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The <code class="classname">SampleDatabase</code> class is extended to open the
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Shipment-by-Part and Shipment-by-Supplier secondary key
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indices.
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</p>
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<a id="index_java_sampledatabase1"></a>
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<pre class="programlisting"><strong class="userinput"><code>import com.sleepycat.bind.serial.SerialSerialKeyCreator;
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import com.sleepycat.db.SecondaryConfig;
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import com.sleepycat.db.SecondaryDatabase;</code></strong>
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...
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public class SampleDatabase
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{
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...
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<strong class="userinput"><code> private static final String SHIPMENT_PART_INDEX =
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"shipment_part_index";
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private static final String SHIPMENT_SUPPLIER_INDEX =
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"shipment_supplier_index";
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...
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private SecondaryDatabase shipmentByPartDb;
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private SecondaryDatabase shipmentBySupplierDb;
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...</code></strong>
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public SampleDatabase(String homeDirectory)
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throws DatabaseException, FileNotFoundException
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{
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...
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SecondaryConfig secConfig = new SecondaryConfig();
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secConfig.setTransactional(true);
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secConfig.setAllowCreate(true);
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secConfig.setType(DatabaseType.BTREE);
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secConfig.setSortedDuplicates(true);
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...
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<strong class="userinput"><code> secConfig.setKeyCreator(
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new ShipmentByPartKeyCreator(javaCatalog,
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ShipmentKey.class,
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ShipmentData.class,
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PartKey.class));
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shipmentByPartDb = env.openSecondaryDatabase(null,
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SHIPMENT_PART_INDEX,
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null,
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shipmentDb,
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secConfig);
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secConfig.setKeyCreator(
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new ShipmentBySupplierKeyCreator(javaCatalog,
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ShipmentKey.class,
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ShipmentData.class,
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SupplierKey.class));
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shipmentBySupplierDb = env.openSecondaryDatabase(null,
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SHIPMENT_SUPPLIER_INDEX,
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null,
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shipmentDb,
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secConfig);</code></strong>
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...
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}
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} </pre>
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<p>
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The statements in this example are very similar to the statements used in
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the previous section for opening a secondary index.
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</p>
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<p>
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The application-defined <code class="classname">ShipmentByPartKeyCreator</code>
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and <code class="classname">ShipmentBySupplierKeyCreator</code> classes are shown below. They
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were used above to configure the secondary database objects.
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</p>
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<a id="index_shipmentbypartkeycreator"></a>
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<pre class="programlisting">public class SampleDatabase
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{
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...
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<strong class="userinput"><code> private static class ShipmentByPartKeyCreator
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extends SerialSerialKeyCreator
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{
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private ShipmentByPartKeyCreator(ClassCatalog catalog,
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Class primaryKeyClass,
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Class valueClass,
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Class indexKeyClass)
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{
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super(catalog, primaryKeyClass, valueClass, indexKeyClass);
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}
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public Object createSecondaryKey(Object primaryKeyInput,
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Object valueInput)
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{
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ShipmentKey shipmentKey = (ShipmentKey) primaryKeyInput;
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return new PartKey(shipmentKey.getPartNumber());
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}
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}
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private static class ShipmentBySupplierKeyCreator
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extends SerialSerialKeyCreator
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{
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private ShipmentBySupplierKeyCreator(ClassCatalog catalog,
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Class primaryKeyClass,
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Class valueClass,
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Class indexKeyClass)
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{
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super(catalog, primaryKeyClass, valueClass, indexKeyClass);
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}
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public Object createSecondaryKey(Object primaryKeyInput,
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Object valueInput)
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{
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ShipmentKey shipmentKey = (ShipmentKey) primaryKeyInput;
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return new SupplierKey(shipmentKey.getSupplierNumber());
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}
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}</code></strong>
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...
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} </pre>
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<p>
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The key creator classes above are almost identical to the one
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defined in the previous section for use with a secondary index. The
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index key fields are different, of course, but the interesting
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difference is that the index keys are extracted from the key, not
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the value, of the Shipment record. This illustrates that an index
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key may be derived from the primary database record key, value, or
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both.
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</p>
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<p>
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The following getter methods return the secondary database
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objects for use by other classes in the example program.
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</p>
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<a id="index_sampledatabasegetters"></a>
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<pre class="programlisting">public class SampleDatabase
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{
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...
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<strong class="userinput"><code> public final SecondaryDatabase getShipmentByPartDatabase()
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{
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return shipmentByPartDb;
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}
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public final SecondaryDatabase getShipmentBySupplierDatabase()
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{
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return shipmentBySupplierDb;
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}</code></strong>
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...
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} </pre>
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<p>
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The following statements close the secondary databases.
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</p>
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<a id="index_close2"></a>
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<pre class="programlisting">public class SampleDatabase
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{
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...
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public void close()
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throws DatabaseException {
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supplierByCityDb.close();
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<strong class="userinput"><code> shipmentByPartDb.close();
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shipmentBySupplierDb.close();</code></strong>
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partDb.close();
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supplierDb.close();
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shipmentDb.close();
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javaCatalog.close();
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env.close();
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}
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...
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} </pre>
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<p>
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Secondary databases must be closed before closing their
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associated primary database.
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</p>
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</div>
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<div class="navfooter">
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<hr />
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<table width="100%" summary="Navigation footer">
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<tr>
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<td width="40%" align="left"><a accesskey="p" href="UsingSecondaries.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="UsingSecondaries.html">Up</a>
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|||
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</td>
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|||
|
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<td width="40%" align="right"> <a accesskey="n" href="indexedcollections.html">Next</a></td>
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|||
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">Chapter 3.
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|||
|
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Using Secondary Indices
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</td>
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<td width="20%" align="center">
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<a accesskey="h" href="index.html">Home</a>
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</td>
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<td width="40%" align="right" valign="top">
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Creating Indexed Collections
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</td>
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</tr>
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</table>
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</div>
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</body>
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</html>
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