php-doc-en/reference/mysqlnd_qc/book.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<!-- Membership: pecl -->

<book xml:id="book.mysqlnd-qc" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 <title>Mysqlnd query result cache plugin</title>
 <titleabbrev>mysqlnd_qc</titleabbrev>

 <preface xml:id="intro.mysqlnd-qc">
  &reftitle.intro;
  <para>
   The mysqlnd query result cache plugin adds easy to use client-side query
   caching to all PHP MySQL extensions using
   <link linkend="book.mysqlnd">mysqlnd</link>.
  </para>
  <para>
   As of version PHP 5.3.3 the MySQL native driver for PHP (
   <literal>mysqlnd</literal>)
   features an internal plugin C API. C plugins, such as the query cache
   plugin, can extend the functionality of
   <link linkend="book.mysqlnd">mysqlnd</link>.
  </para>
  <para>
   Mysqlnd plugins such as the query cache plugin operate transparent
   from a user perspective. The cache plugin supports all PHP applications
   and all PHP MySQL extensions (
   <link linkend="ref.mysqli">mysqli</link>,
   <link linkend="ref.mysql">mysql</link>,
   <link linkend="ref.pdo-mysql">PDO_MYSQL</link>).
   It does not change existing APIs.
  </para>
  <para>
   No significant application changes are required to cache a query.
   The cache has two operation modes. It will either cache all
   queries (not recommended) or only those queries marked with a
   certain SQL hint (recommended).
  </para>

  <section xml:id="mysqlnd-qc.key_features">
   <title>Key Features</title>
   <para>
    <itemizedlist>
     <listitem>
      <para>
       Transparent and therefore easy to use
      </para>
      <para>
       <itemizedlist>
        <listitem>
         <para>
          supports all PHP MySQL extensions
         </para>
        </listitem>
        <listitem>
         <para>
          no API changes
         </para>
        </listitem>
        <listitem>
         <para>
          very little application changes required
         </para>
        </listitem>
       </itemizedlist>
      </para>
     </listitem>

     <listitem>
      <para>
       Flexible invalidation strategy
      </para>
      <para>
       <itemizedlist>
        <listitem>
         <para>
          Time-to-Live (TTL)
         </para>
        </listitem>
        <listitem>
         <para>
          user-defined
         </para>
        </listitem>
       </itemizedlist>
      </para>
     </listitem>

     <listitem>
      <para>
       Storage with different scope and life-span
      </para>
      <para>
       <itemizedlist>
        <listitem>
         <para>
          Default (Hash, process memory)
         </para>
        </listitem>
        <listitem>
         <para>
          <link linkend="ref.apc">APC</link>
         </para>
        </listitem>
        <listitem>
         <para>
          MEMCACHE
         </para>
        </listitem>
        <listitem>
         <para>
          sqlite
         </para>
        </listitem>
        <listitem>
         <para>
          user-defined
         </para>
        </listitem>
       </itemizedlist>
      </para>
     </listitem>
    </itemizedlist>
   </para>
  </section>

  <section xml:id="mysqlnd-qc.limitations">
   <title>Limitations</title>
   <para>
    The current 1.0.1 release of PECL mysqlnd_qc does
    not support PHP 5.4.
   </para>
   <para>
    Prepared statements and unbuffered queries are fully supported.
    Thus, the plugin is capable of caching all statements issued
    with <literal>mysqli</literal> or <literal>PDO_MySQL</literal>, which are
    the only two PHP MySQL APIs to offer prepared statement support.
   </para>
  </section>

  <section xml:id="mysqlnd-qc.architecture">
   <title>Architecture</title>
   <para>
    The query cache is implemented as a PHP extension.
    It is written in C and operates under the hood of PHP. During the
    startup of the PHP interpreter it gets registered as a
    <link linkend="book.mysqlnd">mysqlnd</link> plugin to replace selected
    mysqlnd C methods.
   </para>
   <para>
    At PHP run time it proxies queries send from
    mysqlnd (PHP) to the MySQL server. If a query string starts with the SQL hint
    (<literal>/*qc=on*/</literal>) to enable caching of it and the query
    is not cached (cache miss), the query cache plugin will record the
    raw wire protocol data send from MySQL to PHP to answer the query.
    The query cache records the wire protocol data in its cache
    and replays it, if still valid, on a cache hit.
   </para>
   <para>
    Note that the query cache does not hold decoded result sets consisting
    of
    <literal>zvals</literal> (C struct representing a PHP variable).
    It stores the raw wire data of the MySQL client server protocol.
    In case of a cache hits,
    <link linkend="book.mysqlnd">mysqlnd</link> still needs
    to decode the cached raw wire data into PHP variables before passing
    the result to the user space.
    This approach has one major advantage: simplicity. Furthermore this
    approach eliminates the need for serializing data for cache storage.
   </para>
  </section>

 </preface>


 &reference.mysqlnd-qc.setup;
 &reference.mysqlnd-qc.constants;
 &reference.mysqlnd-qc.usage;
 &reference.mysqlnd-qc.reference;
 &reference.mysqlnd-qc.changes;

</book>

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