126 lines
5.2 KiB
HTML
126 lines
5.2 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>Secondary Indices with Transaction Applications</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 V1.62.4" />
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<link rel="home" href="index.html" title="Getting Started with Berkeley DB Transaction Processing" />
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<link rel="up" href="usingtxns.html" title="Chapter 3. Transaction Basics" />
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<link rel="previous" href="txncursor.html" title="Transactional Cursors" />
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<link rel="next" href="maxtxns.html" title="Configuring the Transaction Subsystem" />
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</head>
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<body>
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<div class="navheader">
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">Secondary Indices with Transaction Applications</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="txncursor.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="maxtxns.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="txnindices"></a>Secondary Indices with Transaction Applications</h2>
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</div>
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</div>
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<div></div>
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</div>
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<p>
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<span>
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You
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</span>
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can use transactions with your secondary indices so long as you
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<span>
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open the secondary index so that it supports transactions (that is,
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you wrap the database open in a transaction, or use auto commit,
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in the same way as when you open a primary transactional database).
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</span>
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<span>
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In addition, you must make sure that when you associate the
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secondary index with the primary database, the association is
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performed using a transaction. The easiest thing to do here is
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to simply specify <tt class="literal">DB_AUTO_COMMIT</tt> when you
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perform the association.
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</span>
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</p>
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<p>
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All other aspects of using secondary indices with transactions are
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identical to using secondary indices without transactions. In
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addition, transaction-protecting
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<span>
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cursors opened against secondary indices is performed in
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exactly the same way as when you use transactional cursors
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against a primary database.
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</span>
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See <a href="txncursor.html">Transactional Cursors</a> for details.
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</p>
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<p>
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Note that when you use transactions to protect your database writes, your secondary indices are protected from
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corruption because updates to the primary and the secondaries are performed in a single atomic transaction.
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</p>
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<p>
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For example:
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</p>
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<pre class="programlisting">#include <db_cxx.h>
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...
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// Environment and primary database open omitted
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...
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Db my_index(&envp, 0); // Secondary
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// Open the secondary
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my_index.open(NULL, // Transaction pointer
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"my_secondary.db", // On-disk file that holds the database.
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NULL, // Optional logical database name
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DB_BTREE, // Database access method
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DB_AUTO_COMMIT, // Open flags.
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0); // File mode (using defaults)
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// Now associate the primary and the secondary
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my_database.associate(NULL, // Txn id
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&my_index, // Associated secondary database
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get_sales_rep, // Callback used for key extraction.
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// This is described in the Getting
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// Started guide.
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DB_AUTO_COMMIT); // Flags </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="txncursor.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="maxtxns.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">Transactional Cursors </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"> Configuring the Transaction Subsystem</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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