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167 lines
6.3 KiB
HTML
167 lines
6.3 KiB
HTML
<?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>Auto Commit</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 Transaction Processing" />
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<link rel="up" href="usingtxns.html" title="Chapter 3. Transaction Basics" />
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<link rel="prev" href="abortresults.html" title="Aborting a Transaction" />
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<link rel="next" href="txncursor.html" title="Transactional 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">Auto Commit</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="abortresults.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 3. Transaction Basics</th>
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<td width="20%" align="right"> <a accesskey="n" href="txncursor.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="autocommit"></a>Auto Commit</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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While transactions are frequently used to provide atomicity to
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multiple database
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<span>
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or store
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</span>
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operations, it is sometimes necessary to perform
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a single database
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<span>
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or store
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</span>
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operation under the control of a transaction.
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Rather than force you to obtain a transaction, perform the single
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write operation, and then either commit or abort the transaction,
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you can automatically group this sequence of events using
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<span class="emphasis"><em>auto commit</em></span>.
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</p>
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<p>
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To use auto commit:
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</p>
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<div class="orderedlist">
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<ol type="1">
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<li>
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<p>
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Open your environment and your databases
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<span>
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or store
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</span>
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so that they support
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transactions. See <a class="xref" href="enabletxn.html" title="Chapter 2. Enabling Transactions">Enabling Transactions</a>
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for details.
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</p>
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</li>
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<li>
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<p>
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Do not provide a transactional handle to the method that is
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performing the database
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<span>
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or store
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</span>
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write operation.
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</p>
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</li>
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</ol>
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</div>
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<p>
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Note that auto commit is not available for cursors. You must always
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open your cursor using a transaction if you want the cursor's
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operations to be transactional protected. See
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<a class="xref" href="txncursor.html" title="Transactional Cursors">Transactional Cursors</a> for details on using
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transactional cursors.
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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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Never have more than one active transaction in your thread
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at a time. This is especially a problem if you mix an
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explicit transaction with another operation that uses auto
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commit. Doing so can result in undetectable deadlocks.
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</p>
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</div>
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<p>
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For example, the following uses auto commit to perform the database write operation:
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</p>
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<pre class="programlisting">package je.txn;
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import com.sleepycat.je.Database;
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import com.sleepycat.je.DatabaseConfig;
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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.Environment;
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import com.sleepycat.je.EnvironmentConfig;
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import java.io.File;
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...
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Database myDatabase = null;
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Environment myEnv = null;
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try {
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EnvironmentConfig myEnvConfig = new EnvironmentConfig();
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myEnvConfig.setTransactional(true);
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myEnv = new Environment(new File("/my/env/home"),
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myEnvConfig);
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// Open the database. Create it if it does not already exist.
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DatabaseConfig dbConfig = new DatabaseConfig();
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dbConfig.setTransactional(true);
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myDatabase = myEnv.openDatabase(null,
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"sampleDatabase",
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dbConfig);
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String keyString = "thekey";
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String dataString = "thedata";
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DatabaseEntry key =
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new DatabaseEntry(keyString.getBytes("UTF-8"));
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DatabaseEntry data =
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new DatabaseEntry(dataString.getBytes("UTF-8"));
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// Perform the write. Because the database was opened to
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// support transactions, this write is performed using auto commit.
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myDatabase.put(null, key, data);
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} catch (DatabaseException de) {
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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="abortresults.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="usingtxns.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="txncursor.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">Aborting a Transaction </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"> Transactional Cursors</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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