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>Release 2.0: converting applications</title> 7 <link rel="stylesheet" href="gettingStarted.css" type="text/css" /> 8 <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /> 9 <link rel="start" href="index.html" title="Berkeley DB Programmer's Reference Guide" /> 10 <link rel="up" href="upgrade_2_0_toc.html" title="Chapter��32.��Upgrading Berkeley DB 1.85 or 1.86 applications to Berkeley DB 2.0" /> 11 <link rel="prev" href="upgrade_2_0_system.html" title="Release 2.0: system integration" /> 12 <link rel="next" href="upgrade_2_0_disk.html" title="Release 2.0: Upgrade Requirements" /> 13 </head> 14 <body> 15 <div class="navheader"> 16 <table width="100%" summary="Navigation header"> 17 <tr> 18 <th colspan="3" align="center">Release 2.0: converting applications</th> 19 </tr> 20 <tr> 21 <td width="20%" align="left"><a accesskey="p" href="upgrade_2_0_system.html">Prev</a>��</td> 22 <th width="60%" align="center">Chapter��32.��Upgrading Berkeley DB 1.85 or 1.86 applications to Berkeley DB 2.0</th> 23 <td width="20%" align="right">��<a accesskey="n" href="upgrade_2_0_disk.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="upgrade_2_0_convert"></a>Release 2.0: converting applications</h2> 33 </div> 34 </div> 35 </div> 36 <p>Mapping the Berkeley DB 1.85 functionality into Berkeley DB version 2 is almost always 37simple. The manual page <a href="../api_reference/C/dbopen.html" class="olink">DB->open()</a> replaces the Berkeley DB 1.85 manual 38pages <code class="literal">dbopen</code>(3), <code class="literal">btree</code>(3), <code class="literal">hash</code>(3) and 39<code class="literal">recno</code>(3). You should be able to convert each 1.85 function 40call into a Berkeley DB version 2 function call using just the <a href="../api_reference/C/dbopen.html" class="olink">DB->open()</a> 41documentation.</p> 42 <p>Some guidelines and things to watch out for:</p> 43 <div class="orderedlist"> 44 <ol type="1"> 45 <li>Most access method functions have exactly the same semantics as in Berkeley DB 461.85, although the arguments to the functions have changed in some cases. 47To get your code to compile, the most common change is to add the 48transaction ID as an argument (NULL, since Berkeley DB 1.85 did not support 49transactions.)</li> 50 <li>You must always initialize DBT structures to zero before using them with 51any Berkeley DB version 2 function. (They do not normally have to be 52reinitialized each time, only when they are first allocated. Do this by 53declaring the DBT structure external or static, or by calling the C 54library routine <code class="literal">bzero</code>(3) or <code class="literal">memset</code>(3).)</li> 55 <li>The error returns are completely different in the two versions. In Berkeley DB 561.85, < 0 meant an error, and > 0 meant a minor Berkeley DB exception. 57In Berkeley DB 2.0, > 0 means an error (the Berkeley DB version 2 functions 58return <code class="literal">errno</code> on error) and < 0 means a Berkeley DB exception. 59See <a class="xref" href="program_errorret.html" title="Error returns to applications">Error returns to applications</a> 60for more information.</li> 61 <li>The Berkeley DB 1.85 DB->seq function has been replaced by cursors in Berkeley DB 62version 2. The semantics are approximately the same, but cursors require 63the creation of an extra object (the DBC object), which is then used to 64access the database. 65<p>Specifically, the partial key match and range search functionality of the 66R_CURSOR flag in DB->seq has been replaced by the <a href="../api_reference/C/dbcget.html#dbcget_DB_SET_RANGE" class="olink">DB_SET_RANGE</a> flag in 67<a href="../api_reference/C/dbcget.html" class="olink">DBC->get()</a>.</p></li> 68 <li>In version 2 of the Berkeley DB library, additions or deletions into Recno 69(fixed and variable-length record) databases no longer automatically 70logically renumber all records after the add/delete point, by default. 71The default behavior is that deleting records does not cause subsequent 72records to be renumbered, and it is an error to attempt to add new records 73between records already in the database. Applications wanting the 74historic Recno access method semantics should call the 75<a href="../api_reference/C/dbset_flags.html" class="olink">DB->set_flags()</a> method with the <a href="../api_reference/C/dbset_flags.html#dbset_flags_DB_RENUMBER" class="olink">DB_RENUMBER</a> flag.</li> 76 <li>Opening a database in Berkeley DB version 2 is a much heavier-weight operation 77than it was in Berkeley DB 1.85. Therefore, if your historic applications were 78written to open a database, perform a single operation, and close the 79database, you may observe performance degradation. In most cases, this 80is due to the expense of creating the environment upon each open. While 81we encourage restructuring your application to avoid repeated opens and 82closes, you can probably recover most of the lost performance by simply 83using a persistent environment across invocations.</li> 84 </ol> 85 </div> 86 <p>While simply converting Berkeley DB 1.85 function calls to Berkeley DB version 2 87function calls will work, we recommend that you eventually reconsider your 88application's interface to the Berkeley DB database library in light of the 89additional functionality supplied by Berkeley DB version 2, as it is likely to 90result in enhanced application performance.</p> 91 </div> 92 <div class="navfooter"> 93 <hr /> 94 <table width="100%" summary="Navigation footer"> 95 <tr> 96 <td width="40%" align="left"><a accesskey="p" href="upgrade_2_0_system.html">Prev</a>��</td> 97 <td width="20%" align="center"> 98 <a accesskey="u" href="upgrade_2_0_toc.html">Up</a> 99 </td> 100 <td width="40%" align="right">��<a accesskey="n" href="upgrade_2_0_disk.html">Next</a></td> 101 </tr> 102 <tr> 103 <td width="40%" align="left" valign="top">Release 2.0: system integration��</td> 104 <td width="20%" align="center"> 105 <a accesskey="h" href="index.html">Home</a> 106 </td> 107 <td width="40%" align="right" valign="top">��Release 2.0: Upgrade Requirements</td> 108 </tr> 109 </table> 110 </div> 111 </body> 112</html> 113