1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
|
<! "@(#)keydata.so 10.7 (Sleepycat) 11/1/98">
<!Copyright 1997, 1998 by Sleepycat Software, Inc. All rights reserved.>
<html>
<body bgcolor=white>
<head>
<title>Berkeley DB Reference Guide: Simple Tutorial</title>
<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
<meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btr
ee,hash,hashing,transaction,transactions,locking,logging,access method,access me
thods,java,C,C++">
</head>
<h3>Berkeley DB Reference Guide: Simple Tutorial</h3>
<p>
<h1 align=center>Key/data pairs</h1>
<p>
Berkeley DB uses key/data pairs to identify elements in the database.
That is, in the general case, whenever you call a Berkeley DB interface,
you present a key to identify the key/data pair on which you intend
to operate.
<p>
For example, you might store the key/data pairs:
<p><ul><pre>
<b>Key:</b> <b>Data:</b>
fruit apple
sport cricket
drink water
</pre></ul><p>
In each case, the first element of the pair is the key, and the second
is the data.
<p>
To store the first of these key data pairs into the database, you would
call the Berkeley DB interface to store items, with <b>fruit</b> as the key,
and <b>apple</b> as the data. At some future time, you could then
retrieve the data item associated with <b>fruit</b>, and the Berkeley DB
retrieval interface would return <b>apple</b> to you.
<p>
While there are many variations and some subtleties, <b>all</b> accesses
to data in Berkeley DB come down to key/data pairs.
<p>
Both key and data items are stored in simple structures
(called DBTs) that contain
a reference to memory and a length, counted in bytes. The key and
data items can be arbitrary binary data of practically any length.
<p>
<a href="../../ref/simple_tut/intro.html"><img src="../../images/prev.gif"></a>
<a href="../../ref/toc.html"><img src="../../images/toc.gif"></a>
<a href="../../ref/simple_tut/errors.html"><img src="../../images/next.gif"></a>
</tt>
</body>
</html>
|
