2011-09-13 17:44:24 +00:00
|
|
|
|
<?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>DB->set_bt_compress()</title>
|
|
|
|
|
|
<link rel="stylesheet" href="apiReference.css" type="text/css" />
|
|
|
|
|
|
<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
|
|
|
|
|
|
<link rel="start" href="index.html" title="Berkeley DB C API Reference" />
|
|
|
|
|
|
<link rel="up" href="db.html" title="Chapter 2. The DB Handle" />
|
|
|
|
|
|
<link rel="prev" href="dbset_bt_compare.html" title="DB->set_bt_compare()" />
|
|
|
|
|
|
<link rel="next" href="dbset_bt_minkey.html" title="DB->set_bt_minkey()" />
|
|
|
|
|
|
</head>
|
|
|
|
|
|
<body>
|
|
|
|
|
|
<div xmlns="" class="navheader">
|
|
|
|
|
|
<div class="libver">
|
2012-11-14 21:35:20 +00:00
|
|
|
|
<p>Library Version 11.2.5.3</p>
|
2011-09-13 17:44:24 +00:00
|
|
|
|
</div>
|
|
|
|
|
|
<table width="100%" summary="Navigation header">
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<th colspan="3" align="center">DB->set_bt_compress()</th>
|
|
|
|
|
|
</tr>
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<td width="20%" align="left"><a accesskey="p" href="dbset_bt_compare.html">Prev</a> </td>
|
|
|
|
|
|
<th width="60%" align="center">Chapter 2.
|
|
|
|
|
|
The DB Handle
|
|
|
|
|
|
</th>
|
|
|
|
|
|
<td width="20%" align="right"> <a accesskey="n" href="dbset_bt_minkey.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="dbset_bt_compress"></a>DB->set_bt_compress()</h2>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
<pre class="programlisting">#include <db.h>
|
|
|
|
|
|
|
|
|
|
|
|
int
|
|
|
|
|
|
DB->set_bt_compress(DB *db,
|
|
|
|
|
|
int (*bt_compress_fcn)(DB *db, const DBT *prevKey,
|
|
|
|
|
|
const DBT *prevData, const DBT *key, const DBT *data, DBT *dest),
|
|
|
|
|
|
int (*bt_decompress_fcn)(DB *db, const DBT *prevKey,
|
|
|
|
|
|
const DBT *prevData, DBT *compressed, DBT *destKey,
|
|
|
|
|
|
DBT *destData)); </pre>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
Set the Btree compression and decompression functions. The
|
|
|
|
|
|
compression function is called whenever a key/data pair is added to
|
|
|
|
|
|
the tree and the decompression function is called whenever data is
|
|
|
|
|
|
requested from the tree.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
This method is only compatible with prefix-based compression
|
|
|
|
|
|
routines. This callback is mostly intended for compressing keys.
|
|
|
|
|
|
From a performance perspective, it is better to perform compression
|
|
|
|
|
|
of the data portion of your records outside of the Berkeley DB
|
|
|
|
|
|
library.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
If NULL function pointers are specified, then default compression
|
|
|
|
|
|
and decompression functions are used. Berkeley DB's default
|
|
|
|
|
|
compression function performs prefix compression on all keys and
|
|
|
|
|
|
prefix compression on data values for duplicate keys. If using
|
|
|
|
|
|
default compression, both the default compression and decompression
|
|
|
|
|
|
functions must be used.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
The <code class="methodname">DB->set_bt_compress()</code> method
|
|
|
|
|
|
configures operations performed using the specified <a class="link" href="db.html" title="Chapter 2. The DB Handle">DB</a> handle, not all operations
|
|
|
|
|
|
performed on the underlying database.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
The <code class="methodname">DB->set_bt_compress()</code> method may not be called after the
|
|
|
|
|
|
<a class="xref" href="dbopen.html" title="DB->open()">DB->open()</a> method is called. If
|
|
|
|
|
|
the database already exists when <a class="xref" href="dbopen.html" title="DB->open()">DB->open()</a>
|
|
|
|
|
|
is called, the information specified to <code class="methodname">DB->set_bt_compress()</code> must be the same as
|
|
|
|
|
|
that historically used to create the database or corruption can occur.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
The <code class="methodname">DB->set_bt_compress()</code> <span>
|
|
|
|
|
|
<span>
|
|
|
|
|
|
method returns a non-zero error value on failure and 0 on success.
|
|
|
|
|
|
</span>
|
|
|
|
|
|
|
|
|
|
|
|
</span>
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<div class="sect2" lang="en" xml:lang="en">
|
|
|
|
|
|
<div class="titlepage">
|
|
|
|
|
|
<div>
|
|
|
|
|
|
<div>
|
2012-11-14 21:35:20 +00:00
|
|
|
|
<h3 class="title"><a id="idp58062024"></a>Parameters</h3>
|
2011-09-13 17:44:24 +00:00
|
|
|
|
</div>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
<div class="sect3" lang="en" xml:lang="en">
|
|
|
|
|
|
<div class="titlepage">
|
|
|
|
|
|
<div>
|
|
|
|
|
|
<div>
|
2012-11-14 21:35:20 +00:00
|
|
|
|
<h4 class="title"><a id="idp58082824"></a>bt_compress_fcn</h4>
|
2011-09-13 17:44:24 +00:00
|
|
|
|
</div>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
The <span class="bold"><strong>bt_compress_fcn</strong></span> function is the
|
|
|
|
|
|
application-specified Btree compression function. The compression
|
|
|
|
|
|
function takes six parameters:
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<div class="itemizedlist">
|
|
|
|
|
|
<ul type="disc">
|
|
|
|
|
|
<li>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
<code class="literal">db</code>
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
The <span class="bold"><strong>db</strong></span> parameter is the enclosing
|
|
|
|
|
|
database handle.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
<li>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
<code class="literal">prevKey</code>
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
The <span class="bold"><strong>prevKey</strong></span>
|
|
|
|
|
|
parameter is the <a class="link" href="dbt.html" title="Chapter 4. The DBT Handle">DBT</a>
|
|
|
|
|
|
representing the key immediately preceding
|
|
|
|
|
|
the application supplied key.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
<li>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
<code class="literal">prevData</code>
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
The <span class="bold"><strong>prevData</strong></span>
|
|
|
|
|
|
parameter is the <a class="link" href="dbt.html" title="Chapter 4. The DBT Handle">DBT</a>
|
|
|
|
|
|
representing the data associated with
|
|
|
|
|
|
<span class="bold"><strong>prevKey</strong></span>.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
<li>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
<code class="literal">key</code>
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
The <span class="bold"><strong>key</strong></span>
|
|
|
|
|
|
parameter is the
|
|
|
|
|
|
<a class="link" href="dbt.html" title="Chapter 4. The DBT Handle">DBT</a>
|
|
|
|
|
|
representing the application supplied key.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
<li>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
<code class="literal">data</code>
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
The <span class="bold"><strong>data</strong></span> parameter is the
|
|
|
|
|
|
<a class="link" href="dbt.html" title="Chapter 4. The DBT Handle">DBT</a> representing the application
|
|
|
|
|
|
supplied data.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
<li>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
<code class="literal">dest</code>
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
The <span class="bold"><strong>dest</strong></span>
|
|
|
|
|
|
parameter is the
|
|
|
|
|
|
<a class="link" href="dbt.html" title="Chapter 4. The DBT Handle">DBT</a>
|
|
|
|
|
|
representing the data stored in the tree,
|
|
|
|
|
|
where the function should write the
|
|
|
|
|
|
compressed data.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
</ul>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
The <span class="bold"><strong>bt_compress_fcn</strong></span>
|
|
|
|
|
|
function must return 0 on success and a non-zero value
|
|
|
|
|
|
on failure. If the compressed data cannot fit in
|
|
|
|
|
|
<span class="bold"><strong>dest->data</strong></span>
|
|
|
|
|
|
|
|
|
|
|
|
(the size of which is
|
|
|
|
|
|
<span>
|
|
|
|
|
|
stored in
|
|
|
|
|
|
<span class="bold"><strong>dest->ulen</strong></span>),
|
|
|
|
|
|
</span>
|
|
|
|
|
|
|
|
|
|
|
|
the function should identify the required buffer size in
|
|
|
|
|
|
<span class="bold"><strong>dest->size</strong></span>
|
|
|
|
|
|
|
|
|
|
|
|
and return <code class="literal">DB_BUFFER_SMALL</code>.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
<div class="sect3" lang="en" xml:lang="en">
|
|
|
|
|
|
<div class="titlepage">
|
|
|
|
|
|
<div>
|
|
|
|
|
|
<div>
|
2012-11-14 21:35:20 +00:00
|
|
|
|
<h4 class="title"><a id="idp58105048"></a>bt_decompress_fcn</h4>
|
2011-09-13 17:44:24 +00:00
|
|
|
|
</div>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
The <span class="bold"><strong>bt_decompress_fcn</strong></span> function is the
|
|
|
|
|
|
application-specified Btree decompression function. The decompression
|
|
|
|
|
|
function takes six parameters:
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<div class="itemizedlist">
|
|
|
|
|
|
<ul type="disc">
|
|
|
|
|
|
<li>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
<code class="literal">db</code>
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
The <span class="bold"><strong>db</strong></span> parameter is the enclosing
|
|
|
|
|
|
database handle.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
<li>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
<code class="literal">prevKey</code>
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
The <span class="bold"><strong>prevKey</strong></span>
|
|
|
|
|
|
parameter is the
|
|
|
|
|
|
<a class="link" href="dbt.html" title="Chapter 4. The DBT Handle">DBT</a>
|
|
|
|
|
|
representing the key immediately preceding
|
|
|
|
|
|
the key being decompressed.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
<li>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
<code class="literal">prevData</code>
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
The <span class="bold"><strong>prevData</strong></span>
|
|
|
|
|
|
parameter is the
|
|
|
|
|
|
<a class="link" href="dbt.html" title="Chapter 4. The DBT Handle">DBT</a>
|
|
|
|
|
|
representing the data associated with
|
|
|
|
|
|
<span class="bold"><strong>prevKey</strong></span>.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
<li>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
<code class="literal">compressed</code>
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
The
|
|
|
|
|
|
<span class="bold"><strong>compressed</strong></span>
|
|
|
|
|
|
parameter is the
|
|
|
|
|
|
<a class="link" href="dbt.html" title="Chapter 4. The DBT Handle">DBT</a>
|
|
|
|
|
|
representing the data stored in the tree,
|
|
|
|
|
|
that is, the compressed data.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
<li>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
<code class="literal">destKey</code>
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
The <span class="bold"><strong>key</strong></span>
|
|
|
|
|
|
parameter is the <a class="link" href="dbt.html" title="Chapter 4. The DBT Handle">DBT</a> where
|
|
|
|
|
|
the decompression function should store the
|
|
|
|
|
|
decompressed key.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
<li>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
<code class="literal">destData</code>
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
The <span class="bold"><strong>data</strong></span>
|
|
|
|
|
|
parameter is the
|
|
|
|
|
|
<a class="link" href="dbt.html" title="Chapter 4. The DBT Handle">DBT</a> where
|
|
|
|
|
|
the decompression function should store the
|
|
|
|
|
|
decompressed key.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
</li>
|
|
|
|
|
|
</ul>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
The <span class="bold"><strong>bt_decompress_fcn</strong></span>
|
|
|
|
|
|
function must return 0 on success and a non-zero value
|
|
|
|
|
|
on failure.
|
|
|
|
|
|
If the decompressed data cannot fit in
|
|
|
|
|
|
<span class="bold"><strong>key->data</strong></span>
|
|
|
|
|
|
|
|
|
|
|
|
or
|
|
|
|
|
|
<span class="bold"><strong>data->data</strong></span>
|
|
|
|
|
|
|
|
|
|
|
|
(the size of which is
|
|
|
|
|
|
<span>
|
|
|
|
|
|
available in the <a class="link" href="dbt.html" title="Chapter 4. The DBT Handle">DBT</a>'s
|
|
|
|
|
|
<span class="bold"><strong>ulen</strong></span> field),
|
|
|
|
|
|
</span>
|
|
|
|
|
|
|
|
|
|
|
|
the function should identify the required buffer size
|
|
|
|
|
|
<span>
|
|
|
|
|
|
using the <a class="link" href="dbt.html" title="Chapter 4. The DBT Handle">DBT</a>'s
|
|
|
|
|
|
<span class="bold"><strong>size</strong></span>
|
|
|
|
|
|
field
|
|
|
|
|
|
</span>
|
|
|
|
|
|
|
|
|
|
|
|
and return <code class="literal">DB_BUFFER_SMALL</code>.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
<div class="sect2" lang="en" xml:lang="en">
|
|
|
|
|
|
<div class="titlepage">
|
|
|
|
|
|
<div>
|
|
|
|
|
|
<div>
|
2012-11-14 21:35:20 +00:00
|
|
|
|
<h3 class="title"><a id="idp58119576"></a>Errors</h3>
|
2011-09-13 17:44:24 +00:00
|
|
|
|
</div>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
The <code class="methodname">DB->set_bt_compress()</code> <span>
|
|
|
|
|
|
<span>
|
|
|
|
|
|
method may fail and return one of the following non-zero errors:
|
|
|
|
|
|
</span>
|
|
|
|
|
|
|
|
|
|
|
|
</span>
|
|
|
|
|
|
</p>
|
|
|
|
|
|
<div class="sect3" lang="en" xml:lang="en">
|
|
|
|
|
|
<div class="titlepage">
|
|
|
|
|
|
<div>
|
|
|
|
|
|
<div>
|
2012-11-14 21:35:20 +00:00
|
|
|
|
<h4 class="title"><a id="idp58105152"></a>EINVAL</h4>
|
2011-09-13 17:44:24 +00:00
|
|
|
|
</div>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
If the method was called after <a class="xref" href="dbopen.html" title="DB->open()">DB->open()</a>
|
|
|
|
|
|
was called; or if an invalid flag value or parameter was specified.
|
|
|
|
|
|
</p>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
<div class="sect2" lang="en" xml:lang="en">
|
|
|
|
|
|
<div class="titlepage">
|
|
|
|
|
|
<div>
|
|
|
|
|
|
<div>
|
2012-11-14 21:35:20 +00:00
|
|
|
|
<h3 class="title"><a id="idp58092920"></a>Class</h3>
|
2011-09-13 17:44:24 +00:00
|
|
|
|
</div>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
<a class="link" href="db.html" title="Chapter 2. The DB Handle">DB</a>
|
|
|
|
|
|
</p>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
<div class="sect2" lang="en" xml:lang="en">
|
|
|
|
|
|
<div class="titlepage">
|
|
|
|
|
|
<div>
|
|
|
|
|
|
<div>
|
2012-11-14 21:35:20 +00:00
|
|
|
|
<h3 class="title"><a id="idp58053440"></a>See Also</h3>
|
2011-09-13 17:44:24 +00:00
|
|
|
|
</div>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
<p>
|
|
|
|
|
|
<a class="xref" href="db.html#dblist" title="Database and Related Methods">Database and Related Methods</a>
|
|
|
|
|
|
</p>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
<div class="navfooter">
|
|
|
|
|
|
<hr />
|
|
|
|
|
|
<table width="100%" summary="Navigation footer">
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<td width="40%" align="left"><a accesskey="p" href="dbset_bt_compare.html">Prev</a> </td>
|
|
|
|
|
|
<td width="20%" align="center">
|
|
|
|
|
|
<a accesskey="u" href="db.html">Up</a>
|
|
|
|
|
|
</td>
|
|
|
|
|
|
<td width="40%" align="right"> <a accesskey="n" href="dbset_bt_minkey.html">Next</a></td>
|
|
|
|
|
|
</tr>
|
|
|
|
|
|
<tr>
|
|
|
|
|
|
<td width="40%" align="left" valign="top">DB->set_bt_compare() </td>
|
|
|
|
|
|
<td width="20%" align="center">
|
|
|
|
|
|
<a accesskey="h" href="index.html">Home</a>
|
|
|
|
|
|
</td>
|
|
|
|
|
|
<td width="40%" align="right" valign="top"> DB->set_bt_minkey()</td>
|
|
|
|
|
|
</tr>
|
|
|
|
|
|
</table>
|
|
|
|
|
|
</div>
|
|
|
|
|
|
</body>
|
|
|
|
|
|
</html>
|
