2011-09-13 17:44:24 +00:00
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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>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 V1.73.2" />
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<link rel="start" 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="prev" 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 xmlns="" class="navheader">
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<div class="libver">
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2012-11-14 21:35:20 +00:00
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<p>Library Version 11.2.5.3</p>
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2011-09-13 17:44:24 +00:00
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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">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>
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<p>
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You 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 <code class="literal">DB_AUTO_COMMIT</code> 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 class="xref" href="txncursor.html" title="Transactional Cursors">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.h>
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...
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DB_ENV *envp; /* Environment pointer */
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DB *dbp, *sdbp; /* Primary and secondary DB handles */
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u_int32_t flags; /* Primary database open flags */
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int ret; /* Function return value */
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/* Environment and primary database opens omitted */
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/* Secondary */
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ret = db_create(&sdbp, envp, 0);
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if (ret != 0) {
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/* Error handling goes here */
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}
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/* open the secondary database */
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ret = sdbp->open(sdbp, /* DB structure pointer */
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NULL, /* Transaction pointer */
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"my_secdb.db", /* On-disk file that holds the
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* 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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if (ret != 0) {
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/* Error handling goes here */
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}
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/* Now associate the secondary to the primary */
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dbp->associate(dbp, /* Primary database */
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NULL, /* TXN id */
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sdbp, /* Secondary database */
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get_sales_rep, /* Callback used for key creation. This
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* is described in the Getting Started
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* 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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|
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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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|
|
|
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</table>
|
|
|
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</div>
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</body>
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</html>
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