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https://github.com/sigmasternchen/php-doc-en
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git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@301137 c90b9560-bf6c-de11-be94-00142212c4b1
257 lines
7 KiB
XML
257 lines
7 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<!-- Membership: pecl -->
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<book xml:id="book.mysqlnd-qc" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
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<title>Mysqlnd query result cache plugin</title>
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<titleabbrev>mysqlnd_qc</titleabbrev>
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<preface xml:id="intro.mysqlnd-qc">
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&reftitle.intro;
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<para>
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The mysqlnd query result cache plugin adds easy to use client-side query
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caching to all PHP MySQL extensions using
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<link linkend="book.mysqlnd">mysqlnd</link>.
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</para>
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<para>
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As of version PHP 5.3.3 the MySQL native driver for PHP (
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<literal>mysqlnd</literal>)
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features an internal plugin C API. C plugins, such as the query cache
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plugin, can extend the functionality of
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<link linkend="book.mysqlnd">mysqlnd</link>.
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</para>
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<para>
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The MySQL native driver for PHP is a C library which ships together with
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PHP as of PHP 5.3.0. It serves as a drop-in replacement for the
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MySQL Client Library (AKA libmysql/libmysqlclient). Using mysqlnd has
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several advantages: no extra downloads because it comes with PHP,
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PHP license, lower memory consumption in certain cases,
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new functionality such as asynchronous queries.
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</para>
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<para>
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Mysqlnd plugins such as the query cache plugin operate transparent
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from a user perspective. The cache plugin supports all PHP applications
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and all PHP MySQL extensions (
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<link linkend="ref.mysqli">mysqli</link>,
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<link linkend="ref.mysql">mysql</link>,
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<link linkend="ref.pdo-mysql">PDO_MYSQL</link>).
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It does not change existing APIs.
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</para>
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<para>
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No significant application changes are required to cache a query.
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The cache has two operation modes. It will either cache all
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queries (not recommended) or only those queries marked with a
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certain SQL hint (recommended).
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</para>
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<section xml:id="mysqlnd-qc.key_features">
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<title>Key Features</title>
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<para>
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<itemizedlist>
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<listitem>
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<para>
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Transparent and therefore easy to use
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</para>
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<para>
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<itemizedlist>
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<listitem>
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<para>
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supports all PHP MySQL extensions
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</para>
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</listitem>
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<listitem>
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<para>
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no API changes
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</para>
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</listitem>
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<listitem>
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<para>
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very little application changes required
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</para>
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</listitem>
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</itemizedlist>
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</para>
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</listitem>
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<listitem>
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<para>
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Flexible invalidation strategy
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</para>
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<para>
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<itemizedlist>
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<listitem>
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<para>
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Time-to-Live (TTL)
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</para>
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</listitem>
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<listitem>
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<para>
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user-defined
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</para>
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</listitem>
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</itemizedlist>
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</para>
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</listitem>
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<listitem>
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<para>
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Storage with different scope and life-span
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</para>
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<para>
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<itemizedlist>
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<listitem>
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<para>
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Default (Hash)
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</para>
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</listitem>
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<listitem>
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<para>
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<link linkend="ref.apc">APC</link>
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</para>
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</listitem>
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<listitem>
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<para>
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MEMCACHE
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</para>
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</listitem>
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<listitem>
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<para>
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sqlite
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</para>
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</listitem>
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<listitem>
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<para>
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user-defined
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</para>
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</listitem>
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</itemizedlist>
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</para>
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</listitem>
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</itemizedlist>
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</para>
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</section>
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<section xml:id="mysqlnd-qc.limitations">
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<title>Limitations</title>
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<para>
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The query cache plugin prototype will not cache unbuffered
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queries or results from prepared statements. This limitation
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is likely to be lifted soon.
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</para>
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<para>
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The following popular user API calls use buffered queries which
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can be cached:
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</para>
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<para>
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<itemizedlist>
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<listitem>
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<para>
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<link linkend="ref.mysqli">mysqli</link>
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<itemizedlist>
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<listitem>
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<para>
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<function>mysqli_query</function>
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</para>
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</listitem>
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<listitem>
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<para>
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<function>mysqli_real_query</function> +
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<function>mysqli_store_result</function>
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</para>
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</listitem>
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</itemizedlist>
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</para>
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</listitem>
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<listitem>
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<para>
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<link linkend="ref.pdo-mysql">PDO_MYSQL</link>
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<itemizedlist>
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<listitem>
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<para>
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<function>PDO::query</function> if
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<literal>PDO::ATTR_EMULATE_PREPARES = 1</literal> (default setting)
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</para>
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</listitem>
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</itemizedlist>
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</para>
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</listitem>
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<listitem>
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<para>
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<link linkend="ref.mysql">mysql</link>
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<itemizedlist>
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<listitem>
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<para>
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<function>mysql_query</function>
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</para>
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</listitem>
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</itemizedlist>
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</para>
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</listitem>
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</itemizedlist>
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</para>
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</section>
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<section xml:id="mysqlnd-qc.architecture">
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<title>Architecture</title>
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<para>
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The query cache is implemented as a PHP extension.
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It is written in C and operates under the hood of PHP. During the
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startup of the PHP interpreter it gets registered as a
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<link linkend="book.mysqlnd">mysqlnd</link> plugin to replace selected
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mysqlnd C methods.
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</para>
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<para>
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At PHP run time it proxies queries send from
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mysqlnd (PHP) to the MySQL server. If a query string starts with the SQL hint
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(
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<literal>/*qc=on*/</literal>) to enable caching of it and the query
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is not cached (cache miss), the query cache plugin will record the
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raw wire protocol data send from MySQL to PHP to answer the query.
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The query cache records the wire protocol data in its cache
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and replays it, if still valid, on a cache hit.
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</para>
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<para>
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Note that the query cache does not hold decoded result sets consisting
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of
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<literal>zvals</literal> (C struct representing a PHP variable).
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It stores the raw wire data of the MySQL client server protocol.
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In case of a cache hits,
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<link linkend="book.mysqlnd">mysqlnd</link> still needs
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to decode the cached raw wire data into PHP variables before passing
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the result to the user space.
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This approach has one major advantage: simplicity. Furthermore this
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approach eliminates the need for serializing data for cache storage.
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</para>
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</section>
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</preface>
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&reference.mysqlnd-qc.setup;
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&reference.mysqlnd-qc.constants;
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&reference.mysqlnd-qc.usage;
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&reference.mysqlnd-qc.reference;
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</book>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"~/.phpdoc/manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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