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HTML
83 lines
3.8 KiB
HTML
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<?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>Minor Change in Behavior of DB_MPOOLFILE->get</title>
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<link rel="stylesheet" href="gettingStarted.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 Installation and Build Guide" />
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<link rel="up" href="upgrade_4_8_toc.html" title="Chapter 12. Upgrading Berkeley DB 4.7 applications to Berkeley DB 4.8" />
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<link rel="prev" href="upgrade_4_8_dpl.html" title="Registering DPL Secondary Keys" />
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<div xmlns="" class="navheader">
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<div class="libver">
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<p>Library Version 11.2.5.2</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">Minor Change in Behavior of DB_MPOOLFILE->get</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="upgrade_4_8_dpl.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 12. Upgrading Berkeley DB 4.7 applications to Berkeley DB 4.8</th>
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<td width="20%" align="right"> <a accesskey="n" href="upgrade_4_8_fcntl.html">Next</a></td>
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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="upgrade_4_8_mpool"></a>Minor Change in Behavior of DB_MPOOLFILE->get</h2>
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</div>
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</div>
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</div>
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<p>
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DB 4.8 introduces some performance enhancements, based on the use
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of shared/exclusive latches instead of locks in some areas of the
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internal buffer management code. This change will affect how the
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<code class="classname">DB_MPOOL</code> interface handles dirty buffers.
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</p>
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<p> Because of these
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changes, <code class="methodname">DB_MPOOLFILE->get</code> will now
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acquire an exclusive latch on the buffer if
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the <code class="literal">DB_MPOOL_DIRTY</code>
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or <code class="literal">DB_MPOOL_EDIT</code> flags are specified. This
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could lead to an application deadlock if the application tries to
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fetch the buffer again, without an
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intervening <code class="methodname">DB_MPOOLFILE->put</code> call.
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</p>
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<p>
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If your application uses the <code class="literal">DB_MPOOL</code>
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interface, and especially the <code class="literal">DB_MPOOL_DIRTY</code>
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and <code class="literal">DB_MPOOL_EDIT</code> flags, you should review your
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code to ensure that this behavior change does not cause your
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application to deadlock.
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</p>
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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="upgrade_4_8_dpl.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="upgrade_4_8_toc.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="upgrade_4_8_fcntl.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">Registering DPL Secondary Keys </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"> Dropped Support for fcntl System Calls</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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