2
<!--Copyright 1997-2002 by Sleepycat Software, Inc.-->
3
<!--All rights reserved.-->
4
<!--See the file LICENSE for redistribution information.-->
7
<title>Berkeley DB Reference Guide: Release 2.0: converting applications</title>
8
<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
9
<meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++">
12
<table width="100%"><tr valign=top>
13
<td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Upgrading Berkeley DB Applications</dl></h3></td>
14
<td align=right><a href="../../ref/upgrade.2.0/system.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../../reftoc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../../ref/upgrade.2.0/disk.html"><img src="../../images/next.gif" alt="Next"></a>
17
<h1 align=center>Release 2.0: converting applications</h1>
18
<p>Mapping the Berkeley DB 1.85 functionality into Berkeley DB version 2 is almost always
19
simple. The manual page <a href="../../api_c/db_open.html">DB->open</a> replaces the Berkeley DB 1.85 manual
20
pages <b>dbopen</b>(3), <b>btree</b>(3), <b>hash</b>(3) and
21
<b>recno</b>(3). You should be able to convert each 1.85 function
22
call into a Berkeley DB version 2 function call using just the <a href="../../api_c/db_open.html">DB->open</a>
24
<p>Some guidelines and things to watch out for:
26
<p><li>Most access method functions have exactly the same semantics as in Berkeley DB
27
1.85, although the arguments to the functions have changed in some cases.
28
To get your code to compile, the most common change is to add the
29
transaction ID as an argument (NULL, since Berkeley DB 1.85 did not support
31
<p><li>You must always initialize DBT structures to zero before using them with
32
any Berkeley DB version 2 function. (They do not normally have to be
33
reinitialized each time, only when they are first allocated. Do this by
34
declaring the DBT structure external or static, or by calling the C
35
library routine <b>bzero</b>(3) or <b>memset</b>(3).)
36
<p><li>The error returns are completely different in the two versions. In Berkeley DB
37
1.85, < 0 meant an error, and > 0 meant a minor Berkeley DB exception.
38
In Berkeley DB 2.0, > 0 means an error (the Berkeley DB version 2 functions
39
return <b>errno</b> on error) and < 0 means a Berkeley DB exception.
40
See <a href="../../ref/program/errorret.html">Error Returns to Applications</a>
42
<p><li>The Berkeley DB 1.85 DB->seq function has been replaced by cursors in Berkeley DB
43
version 2. The semantics are approximately the same, but cursors require
44
the creation of an extra object (the DBC object), which is then used to
46
<p>Specifically, the partial key match and range search functionality of the
47
R_CURSOR flag in DB->seq has been replaced by the
48
<a href="../../api_c/dbc_get.html#DB_SET_RANGE">DB_SET_RANGE</a> flag in <a href="../../api_c/dbc_get.html">DBcursor->c_get</a>.
49
<p><li>In version 2 of the Berkeley DB library, additions or deletions into Recno
50
(fixed and variable-length record) databases no longer automatically
51
logically renumber all records after the add/delete point, by default.
52
The default behavior is that deleting records does not cause subsequent
53
records to be renumbered, and it is an error to attempt to add new records
54
between records already in the database. Applications wanting the
55
historic Recno access method semantics should call the
56
<a href="../../api_c/db_set_flags.html">DB->set_flags</a> method with the <a href="../../api_c/db_set_flags.html#DB_RENUMBER">DB_RENUMBER</a> flag.
57
<p><li>Opening a database in Berkeley DB version 2 is a much heavier-weight operation
58
than it was in Berkeley DB 1.85. Therefore, if your historic applications were
59
written to open a database, perform a single operation, and close the
60
database, you may observe performance degradation. In most cases, this
61
is due to the expense of creating the environment upon each open. While
62
we encourage restructuring your application to avoid repeated opens and
63
closes, you can probably recover most of the lost performance by simply
64
using a persistent environment across invocations.
66
<p>While simply converting Berkeley DB 1.85 function calls to Berkeley DB version 2
67
function calls will work, we recommend that you eventually reconsider your
68
application's interface to the Berkeley DB database library in light of the
69
additional functionality supplied by Berkeley DB version 2, as it is likely to
70
result in enhanced application performance.
71
<table width="100%"><tr><td><br></td><td align=right><a href="../../ref/upgrade.2.0/system.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../../reftoc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../../ref/upgrade.2.0/disk.html"><img src="../../images/next.gif" alt="Next"></a>
73
<p><font size=1><a href="http://www.sleepycat.com">Copyright Sleepycat Software</a></font>