mirror of
https://github.com/berkeleydb/je.git
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129 lines
4.8 KiB
HTML
129 lines
4.8 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>Deleting Secondary Database Records</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="Getting Started with Berkeley DB Java Edition" />
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<link rel="up" href="indexes.html" title="Chapter 10. Secondary Databases" />
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<link rel="prev" href="readSecondary.html" title="Reading Secondary Databases" />
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<link rel="next" href="secondaryCursor.html" title="Using Secondary Cursors" />
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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 12.2.7.5</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">Deleting Secondary Database Records</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="readSecondary.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 10. Secondary Databases</th>
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<td width="20%" align="right"> <a accesskey="n" href="secondaryCursor.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="secondaryDelete"></a>Deleting Secondary Database Records</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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In general, you
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<span>can</span>
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not modify a secondary database directly. In
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order to modify a secondary database, you should modify the primary
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database and simply allow JE to manage the secondary modifications for you.
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</p>
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<p>
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However, as a convenience, you can delete
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<code class="classname">SecondaryDatabase</code>
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records directly. Doing so causes the associated primary key/data pair to be deleted.
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This in turn causes JE to delete all
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<code class="classname">SecondaryDatabase</code>
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records that reference the primary record.
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</p>
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<p>
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You can use the
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<code class="methodname">SecondaryDatabase.delete()</code>
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method to delete a secondary database record. Note that if your
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<code class="classname">SecondaryDatabase</code>
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contains duplicate records, then deleting a record from the set of
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duplicates causes all of the duplicates to be deleted as well.
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</p>
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<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
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<h3 class="title">Note</h3>
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<p>
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<span><code class="methodname">SecondaryDatabase.delete()</code> causes the
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previously described delete operations to occur
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</span>
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only if the primary database is opened for write access.
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</p>
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</div>
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<p>For example:</p>
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<a id="je_index7"></a>
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<pre class="programlisting">package je.gettingStarted;
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import com.sleepycat.je.DatabaseEntry;
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import com.sleepycat.je.DatabaseException;
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import com.sleepycat.je.OperationStatus;
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import com.sleepycat.je.SecondaryDatabase;
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...
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try {
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// Omitting all database and environment opens
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...
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String searchName = "John Doe";
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DatabaseEntry searchKey =
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new DatabaseEntry(searchName.getBytes("UTF-8"));
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// Delete the first secondary record that uses "John Doe" as
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// a key. This causes the primary record referenced by this secondary
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// record to be deleted.
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OperationStatus retVal = mySecondaryDatabase.delete(null, searchKey);
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} catch (Exception e) {
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// Exception handling goes here
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}</pre>
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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="readSecondary.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="indexes.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="secondaryCursor.html">Next</a></td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">Reading Secondary Databases </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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<span>Using Secondary Cursors</span>
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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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