mirror of
https://github.com/yasuhirokimura/db18
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Yasuhiro KIMURA
222 lines
8.0 KiB
HTML
222 lines
8.0 KiB
HTML
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>DB->set_ext_file_threshold()</title>
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<link rel="stylesheet" href="apiReference.css" type="text/css" />
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<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
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<link rel="start" href="index.html" title="Berkeley DB C API Reference" />
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<link rel="up" href="blob.html" title="Chapter 13. External Files" />
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<link rel="prev" href="set_blob_dir.html" title="DB->set_ext_file_dir()" />
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</head>
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<body>
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<div xmlns="" class="navheader">
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<div class="libver">
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<p>Library Version 18.1.40</p>
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</div>
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">
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<span xmlns="http://www.w3.org/1999/xhtml">DB->set_ext_file_threshold()</span>
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</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="set_blob_dir.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 13.
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External Files
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="dbstream.html">Next</a></td>
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</tr>
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</table>
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<hr />
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</div>
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<div class="sect1" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h2 class="title" style="clear: both"><a id="set_blob_threshold"></a>
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<span>DB->set_ext_file_threshold()</span>
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</h2>
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</div>
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</div>
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</div>
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<pre class="programlisting">#include <db.h>
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int
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DB->set_ext_file_threshold(DB *db, u_int32_t bytes, u_int32_t flags); </pre>
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<p>
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The <code class="methodname">DB->set_ext_file_threshold()</code> method sets
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a size which is used to determine when a data item will be
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stored as an external file. Data items sized less than this threshold
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are stored as normal data within the database. Data items larger than
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this size are stored on-disk in a subdirectory set aside for the
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purpose.
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</p>
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<p>
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If this threshold value is set to <code class="literal">0</code>, then external
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files will never be used by the database.
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</p>
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<p>
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It is illegal to set an external file threshold if any of the
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following flags were specified for the database:
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<a class="link" href="dbset_flags.html#dbset_flags_DB_DUP">DB_DUP</a>, and
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<a class="link" href="dbset_flags.html#dbset_flags_DB_DUPSORT">DB_DUPSORT</a>.
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</p>
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<p>
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It is also illegal to set an external file threshold if compression is
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turned on for the database. That is, if <a class="xref" href="dbset_bt_compress.html" title="DB->set_bt_compress()">
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<span>DB->set_bt_compress()</span>
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</a> has
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been called for the database handle.
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</p>
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<p>
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This method configures the underlying database. The external file
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threshold is stored in the database at database creation time. Any
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external file threshold set after creating the database is ignored.
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</p>
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<p>
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This method may not be called after <a class="xref" href="dbopen.html" title="DB->open()">
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<span>DB->open()</span>
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</a> is called.
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</p>
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<p>
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Unless otherwise specified, the
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<code class="methodname">DB->set_ext_file_threshold()</code> <span>
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<span>
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method returns a non-zero error value on failure and 0 on success.
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</span>
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</span>
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</p>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h3 class="title"><a id="idm139753795538400"></a>Parameters</h3>
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</div>
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</div>
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</div>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h4 class="title"><a id="idm139753795537120"></a>bytes</h4>
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</div>
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</div>
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</div>
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<p>
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The <span class="bold"><strong>bytes</strong></span> parameter
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identifies the threshold size, in bytes, beyond which a
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data item is stored as an external file.
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</p>
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</div>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h4 class="title"><a id="idm139753795557552"></a>flags</h4>
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</div>
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</div>
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</div>
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<p>
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The <span class="bold"><strong>flags</strong></span> parameter must be set to 0.
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</p>
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</div>
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</div>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h3 class="title"><a id="idm139753795540352"></a>Errors</h3>
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</div>
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</div>
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</div>
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<p>
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The <code class="methodname">DB->set_ext_file_threshold()</code> <span>
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<span>
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method may fail and return one of the following non-zero errors:
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</span>
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</span>
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</p>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h4 class="title"><a id="idm139753795556224"></a>EINVAL</h4>
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</div>
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</div>
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</div>
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<p>
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If the method was called after <a class="xref" href="dbopen.html" title="DB->open()">
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<span>DB->open()</span>
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</a> was called; or if
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an invalid flag or parameter was specified; or if
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compression is turned on for the database; or if the
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database is configured with one or more of the following
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flags:
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<a class="link" href="dbset_flags.html#dbset_flags_DB_DUP">DB_DUP</a>, and
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<a class="link" href="dbset_flags.html#dbset_flags_DB_DUPSORT">DB_DUPSORT</a>.
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</p>
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</div>
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</div>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h3 class="title"><a id="idm139753795520688"></a>Class</h3>
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</div>
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</div>
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</div>
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<p>
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<a class="link" href="db.html" title="Chapter 2. The DB Handle">DB</a>
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</p>
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</div>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h3 class="title"><a id="idm139753795528464"></a>See Also</h3>
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</div>
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</div>
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</div>
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<p>
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<a class="xref" href="blob.html#bloblist" title="External Files and Related Methods">External Files and Related Methods</a>
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</p>
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</div>
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</div>
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<div class="navfooter">
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<hr />
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<table width="100%" summary="Navigation footer">
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<tr>
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<td width="40%" align="left"><a accesskey="p" href="set_blob_dir.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="blob.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="dbstream.html">Next</a></td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">
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<span>DB->set_ext_file_dir()</span>
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</td>
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<td width="20%" align="center">
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<a accesskey="h" href="index.html">Home</a>
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</td>
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<td width="40%" align="right" valign="top">
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<span>DBC->db_stream()</span>
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</td>
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</tr>
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</table>
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</div>
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</body>
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</html>
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