php-doc-en/reference/mysqlnd_qc/functions/mysqlnd-qc-set-is-select.xml

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<refentry xml:id="function.mysqlnd-qc-set-is-select" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 <refnamediv>
  <refname>mysqlnd_qc_set_is_select</refname>
  <refpurpose>Installs a callback which decides whether a statement is cached</refpurpose>
 </refnamediv>

 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>mixed</type>
   <methodname>mysqlnd_qc_set_is_select</methodname>
   <methodparam>
    <type>string</type>
    <parameter>callback</parameter>
   </methodparam>
  </methodsynopsis>
  <para>
   Installs a callback which decides whether a statement is cached.
  </para>
  <para>
   There are several ways of hinting PELC/mysqlnd_qc to cache a query.
   By default, PECL/mysqlnd_qc attempts to cache a if caching of all statements
   is enabled or the query string begins with a certain SQL hint.
   The plugin internally calls a function named <literal>is_select()</literal>
   to find out. This internal function can be replaced with a user-defined callback.
   Then, the user-defined callback is responsible to decide whether the plugin
   attempts to cache a statement. Because the internal function is replaced
   with the callback, the callback gains full control. The callback is free
   to ignore the configuration setting <literal>mysqlnd_qc.cache_by_default</literal>
   and SQL hints.
  </para>
  <para>
   The callback is invoked for every statement inspected by the plugin.
   It is given the statements string as a parameter. The callback returns
   &false; if the statement shall not be cached. It returns &true; to
   make the plugin attempt to cache the statements result set, if any.
   A so-created cache entry is given the default TTL set with the
   PHP configuration directive <literal>mysqlnd_qc.ttl</literal>.
   If a different TTL shall be used, the callback returns a numeric
   value to be used as the TTL.
  </para>
  <para>
   The internal <literal>is_select</literal> function is part of the internal
   cache storage handler interface. Thus, a user-defined storage handler
   offers the same capabilities.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  &no.function.parameters;
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   &return.success;
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <example>
   <title><function>mysqlnd_qc_set_is_select</function> example</title>
   <programlisting role="php">
<![CDATA[
<?php
/* callback which decides if query is cached */
function is_select($query) {
  static $patterns = array(
   /* true - use default from mysqlnd_qc.ttl */
   "@SELECT\s+.*\s+FROM\s+test@ismU" => true,
   /* 3 - use TTL = 3 seconds */
   "@SELECT\s+.*\s+FROM\s+news@ismU" => 3
  );
  /* check if query does match pattern */
  foreach ($patterns as $pattern => $ttl) {
    if (preg_match($pattern, $query)) {
      printf("is_select(%45s): cache\n", $query);
      return $ttl;
    }
  }
  printf("is_select(%45s): do not cache\n", $query);
  return false;
}
mysqlnd_qc_set_is_select("is_select");

/* Connect, create and populate test table */
$mysqli = new mysqli("host", "user", "password", "schema");
$mysqli->query("DROP TABLE IF EXISTS test");
$mysqli->query("CREATE TABLE test(id INT)");
$mysqli->query("INSERT INTO test(id) VALUES (1), (2), (3)");

/* cache put */
$mysqli->query("SELECT id FROM test WHERE id = 1");
/* cache hit */
$mysqli->query("SELECT id FROM test WHERE id = 1");
/* cache put */
$mysqli->query("SELECT * FROM test");
?>
]]>
   </programlisting>
   &examples.outputs;
   <screen>
<![CDATA[
is_select(                    DROP TABLE IF EXISTS test): do not cache
is_select(                    CREATE TABLE test(id INT)): do not cache
is_select(    INSERT INTO test(id) VALUES (1), (2), (3)): do not cache
is_select(             SELECT id FROM test WHERE id = 1): cache
is_select(             SELECT id FROM test WHERE id = 1): cache
is_select(                           SELECT * FROM test): cache
]]>
   </screen>
  </example>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member>
     <link linkend="mysqlnd-qc.configuration">Runtime configuration</link>
    </member>
    <member>
     <link linkend="ini.mysqlnd-qc.ttl">mysqlnd_qc.ttl</link>
    </member>
    <member>
     <link linkend="ini.mysqlnd-qc.cache-by-default">mysqlnd_qc.cache_by_default</link>
    </member>
    <member>
     <function>mysqlnd_qc_set_user_handlers</function>
    </member>
   </simplelist>
  </para>
 </refsect1>

</refentry>

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