1<?xml version="1.0" encoding="UTF-8" standalone="no"?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml"> 4 <head> 5 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> 6 <title>Secondary Indices with Transaction Applications</title> 7 <link rel="stylesheet" href="gettingStarted.css" type="text/css" /> 8 <meta name="generator" content="DocBook XSL Stylesheets V1.62.4" /> 9 <link rel="home" href="index.html" title="Getting Started with Berkeley DB Transaction Processing" /> 10 <link rel="up" href="usingtxns.html" title="Chapter 3. Transaction Basics" /> 11 <link rel="previous" href="txncursor.html" title="Transactional Cursors" /> 12 <link rel="next" href="maxtxns.html" title="Configuring the Transaction Subsystem" /> 13 </head> 14 <body> 15 <div class="navheader"> 16 <table width="100%" summary="Navigation header"> 17 <tr> 18 <th colspan="3" align="center">Secondary Indices with Transaction Applications</th> 19 </tr> 20 <tr> 21 <td width="20%" align="left"><a accesskey="p" href="txncursor.html">Prev</a> </td> 22 <th width="60%" align="center">Chapter 3. Transaction Basics</th> 23 <td width="20%" align="right"> <a accesskey="n" href="maxtxns.html">Next</a></td> 24 </tr> 25 </table> 26 <hr /> 27 </div> 28 <div class="sect1" lang="en" xml:lang="en"> 29 <div class="titlepage"> 30 <div> 31 <div> 32 <h2 class="title" style="clear: both"><a id="txnindices"></a>Secondary Indices with Transaction Applications</h2> 33 </div> 34 </div> 35 <div></div> 36 </div> 37 <p> 38 <span> 39 You 40 </span> 41 42 43 can use transactions with your secondary indices so long as you 44 45 <span> 46 open the secondary index so that it supports transactions (that is, 47 you wrap the database open in a transaction, or use auto commit, 48 in the same way as when you open a primary transactional database). 49 </span> 50 51 52 53 <span> 54 In addition, you must make sure that when you associate the 55 secondary index with the primary database, the association is 56 performed using a transaction. The easiest thing to do here is 57 to simply specify <tt class="literal">DB_AUTO_COMMIT</tt> when you 58 perform the association. 59 </span> 60 </p> 61 <p> 62 All other aspects of using secondary indices with transactions are 63 identical to using secondary indices without transactions. In 64 addition, transaction-protecting 65 <span> 66 cursors opened against secondary indices is performed in 67 exactly the same way as when you use transactional cursors 68 against a primary database. 69 </span> 70 71 See <a href="txncursor.html">Transactional Cursors</a> for details. 72 </p> 73 <p> 74 Note that when you use transactions to protect your database writes, your secondary indices are protected from 75 corruption because updates to the primary and the secondaries are performed in a single atomic transaction. 76 </p> 77 <p> 78 For example: 79 </p> 80 <pre class="programlisting">#include <db_cxx.h> 81 82... 83 84// Environment and primary database open omitted 85... 86 87Db my_index(&envp, 0); // Secondary 88 89// Open the secondary 90my_index.open(NULL, // Transaction pointer 91 "my_secondary.db", // On-disk file that holds the database. 92 NULL, // Optional logical database name 93 DB_BTREE, // Database access method 94 DB_AUTO_COMMIT, // Open flags. 95 0); // File mode (using defaults) 96 97// Now associate the primary and the secondary 98my_database.associate(NULL, // Txn id 99 &my_index, // Associated secondary database 100 get_sales_rep, // Callback used for key extraction. 101 // This is described in the Getting 102 // Started guide. 103 DB_AUTO_COMMIT); // Flags </pre> 104 </div> 105 <div class="navfooter"> 106 <hr /> 107 <table width="100%" summary="Navigation footer"> 108 <tr> 109 <td width="40%" align="left"><a accesskey="p" href="txncursor.html">Prev</a> </td> 110 <td width="20%" align="center"> 111 <a accesskey="u" href="usingtxns.html">Up</a> 112 </td> 113 <td width="40%" align="right"> <a accesskey="n" href="maxtxns.html">Next</a></td> 114 </tr> 115 <tr> 116 <td width="40%" align="left" valign="top">Transactional Cursors </td> 117 <td width="20%" align="center"> 118 <a accesskey="h" href="index.html">Home</a> 119 </td> 120 <td width="40%" align="right" valign="top"> Configuring the Transaction Subsystem</td> 121 </tr> 122 </table> 123 </div> 124 </body> 125</html> 126