Edit File: txnindices.html
<?xml version="1.0" encoding="UTF-8" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title>Secondary Indices with Transaction Applications</title> <link rel="stylesheet" href="gettingStarted.css" type="text/css" /> <meta name="generator" content="DocBook XSL Stylesheets V1.62.4" /> <link rel="home" href="index.html" title="Getting Started with Berkeley DB Transaction Processing" /> <link rel="up" href="usingtxns.html" title="Chapter 3. Transaction Basics" /> <link rel="previous" href="txncursor.html" title="Transactional Cursors" /> <link rel="next" href="maxtxns.html" title="Configuring the Transaction Subsystem" /> </head> <body> <div class="navheader"> <table width="100%" summary="Navigation header"> <tr> <th colspan="3" align="center">Secondary Indices with Transaction Applications</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="txncursor.html">Prev</a> </td> <th width="60%" align="center">Chapter 3. Transaction Basics</th> <td width="20%" align="right"> <a accesskey="n" href="maxtxns.html">Next</a></td> </tr> </table> <hr /> </div> <div class="sect1" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h2 class="title" style="clear: both"><a id="txnindices"></a>Secondary Indices with Transaction Applications</h2> </div> </div> <div></div> </div> <p> <span> You </span> can use transactions with your secondary indices so long as you <span> open the secondary index so that it supports transactions (that is, you wrap the database open in a transaction, or use auto commit, in the same way as when you open a primary transactional database). </span> <span> In addition, you must make sure that when you associate the secondary index with the primary database, the association is performed using a transaction. The easiest thing to do here is to simply specify <tt class="literal">DB_AUTO_COMMIT</tt> when you perform the association. </span> </p> <p> All other aspects of using secondary indices with transactions are identical to using secondary indices without transactions. In addition, transaction-protecting <span> cursors opened against secondary indices is performed in exactly the same way as when you use transactional cursors against a primary database. </span> See <a href="txncursor.html">Transactional Cursors</a> for details. </p> <p> Note that when you use transactions to protect your database writes, your secondary indices are protected from corruption because updates to the primary and the secondaries are performed in a single atomic transaction. </p> <p> For example: </p> <pre class="programlisting">#include <db.h> ... DB_ENV *envp; /* Environment pointer */ DB *dbp, *sdbp; /* Primary and secondary DB handles */ u_int32_t flags; /* Primary database open flags */ int ret; /* Function return value */ /* Environment and primary database opens omitted */ /* Secondary */ ret = db_create(&sdbp, envp, 0); if (ret != 0) { /* Error handling goes here */ } /* open the secondary database */ ret = sdbp->open(sdbp, /* DB structure pointer */ NULL, /* Transaction pointer */ "my_secdb.db", /* On-disk file that holds the database. */ NULL, /* Optional logical database name */ DB_BTREE, /* Database access method */ DB_AUTO_COMMIT, /* Open flags */ 0); /* File mode (using defaults) */ if (ret != 0) { /* Error handling goes here */ } /* Now associate the secondary to the primary */ dbp->associate(dbp, /* Primary database */ NULL, /* TXN id */ sdbp, /* Secondary database */ get_sales_rep, /* Callback used for key creation. This * is described in the Getting Started * guide. */ DB_AUTO_COMMIT);/* Flags */</pre> </div> <div class="navfooter"> <hr /> <table width="100%" summary="Navigation footer"> <tr> <td width="40%" align="left"><a accesskey="p" href="txncursor.html">Prev</a> </td> <td width="20%" align="center"> <a accesskey="u" href="usingtxns.html">Up</a> </td> <td width="40%" align="right"> <a accesskey="n" href="maxtxns.html">Next</a></td> </tr> <tr> <td width="40%" align="left" valign="top">Transactional Cursors </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> <td width="40%" align="right" valign="top"> Configuring the Transaction Subsystem</td> </tr> </table> </div> </body> </html>
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