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<title>Installs a callback which decides whether a statement is cached</title>
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</div><hr /><div id="function.mysqlnd-qc-set-is-select" class="refentry">
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<h1 class="refname">mysqlnd_qc_set_is_select</h1>
<p class="verinfo">(PECL mysqlnd_qc >= 1.0.0)</p><p class="refpurpose"><span class="refname">mysqlnd_qc_set_is_select</span> — <span class="dc-title">Installs a callback which decides whether a statement is cached</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.mysqlnd-qc-set-is-select-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span>
<span class="methodname"><strong>mysqlnd_qc_set_is_select</strong></span>
( <span class="methodparam">
<span class="type">string</span>
<code class="parameter">$callback</code>
</span>
)</div>
<p class="para rdfs-comment">
Installs a callback which decides whether a statement is cached.
</p>
<p class="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 <em>is_select()</em>
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 <em>mysqlnd_qc.cache_by_default</em>
and SQL hints.
</p>
<p class="para">
The callback is invoked for every statement inspected by the plugin.
It is given the statements string as a parameter. The callback returns
<strong><code>FALSE</code></strong> if the statement shall not be cached. It returns <strong><code>TRUE</code></strong> 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 <em>mysqlnd_qc.ttl</em>.
If a different TTL shall be used, the callback returns a numeric
value to be used as the TTL.
</p>
<p class="para">
The internal <em>is_select</em> function is part of the internal
cache storage handler interface. Thus, a user-defined storage handler
offers the same capabilities.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.mysqlnd-qc-set-is-select-parameters">
<h3 class="title">Parameters</h3>
<p class="para">This function has no parameters.</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.mysqlnd-qc-set-is-select-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns <strong><code>TRUE</code></strong> on success or <strong><code>FALSE</code></strong> on failure.
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.mysqlnd-qc-set-is-select-examples">
<h3 class="title">Examples</h3>
<div class="example" id="example-1868">
<p><strong>Example #1 <span class="function"><strong>mysqlnd_qc_set_is_select()</strong></span> example</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">/* callback which decides if query is cached */<br /></span><span style="color: #007700">function </span><span style="color: #0000BB">is_select</span><span style="color: #007700">(</span><span style="color: #0000BB">$query</span><span style="color: #007700">) {<br /> static </span><span style="color: #0000BB">$patterns </span><span style="color: #007700">= array(<br /> </span><span style="color: #FF8000">/* true - use default from mysqlnd_qc.ttl */<br /> </span><span style="color: #DD0000">"@SELECT\s+.*\s+FROM\s+test@ismU" </span><span style="color: #007700">=> </span><span style="color: #0000BB">true</span><span style="color: #007700">,<br /> </span><span style="color: #FF8000">/* 3 - use TTL = 3 seconds */<br /> </span><span style="color: #DD0000">"@SELECT\s+.*\s+FROM\s+news@ismU" </span><span style="color: #007700">=> </span><span style="color: #0000BB">3<br /> </span><span style="color: #007700">);<br /> </span><span style="color: #FF8000">/* check if query does match pattern */<br /> </span><span style="color: #007700">foreach (</span><span style="color: #0000BB">$patterns </span><span style="color: #007700">as </span><span style="color: #0000BB">$pattern </span><span style="color: #007700">=> </span><span style="color: #0000BB">$ttl</span><span style="color: #007700">) {<br /> if (</span><span style="color: #0000BB">preg_match</span><span style="color: #007700">(</span><span style="color: #0000BB">$pattern</span><span style="color: #007700">, </span><span style="color: #0000BB">$query</span><span style="color: #007700">)) {<br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"is_select(%45s): cache\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">$query</span><span style="color: #007700">);<br /> return </span><span style="color: #0000BB">$ttl</span><span style="color: #007700">;<br /> }<br /> }<br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"is_select(%45s): do not cache\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">$query</span><span style="color: #007700">);<br /> return </span><span style="color: #0000BB">false</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">mysqlnd_qc_set_is_select</span><span style="color: #007700">(</span><span style="color: #DD0000">"is_select"</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">/* Connect, create and populate test table */<br /></span><span style="color: #0000BB">$mysqli </span><span style="color: #007700">= new </span><span style="color: #0000BB">mysqli</span><span style="color: #007700">(</span><span style="color: #DD0000">"host"</span><span style="color: #007700">, </span><span style="color: #DD0000">"user"</span><span style="color: #007700">, </span><span style="color: #DD0000">"password"</span><span style="color: #007700">, </span><span style="color: #DD0000">"schema"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">query</span><span style="color: #007700">(</span><span style="color: #DD0000">"DROP TABLE IF EXISTS test"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">query</span><span style="color: #007700">(</span><span style="color: #DD0000">"CREATE TABLE test(id INT)"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">query</span><span style="color: #007700">(</span><span style="color: #DD0000">"INSERT INTO test(id) VALUES (1), (2), (3)"</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">/* cache put */<br /></span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">query</span><span style="color: #007700">(</span><span style="color: #DD0000">"SELECT id FROM test WHERE id = 1"</span><span style="color: #007700">);<br /></span><span style="color: #FF8000">/* cache hit */<br /></span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">query</span><span style="color: #007700">(</span><span style="color: #DD0000">"SELECT id FROM test WHERE id = 1"</span><span style="color: #007700">);<br /></span><span style="color: #FF8000">/* cache put */<br /></span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">query</span><span style="color: #007700">(</span><span style="color: #DD0000">"SELECT * FROM test"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above examples will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
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
</pre></div>
</div>
</div>
</div>
<div class="refsect1 seealso" id="refsect1-function.mysqlnd-qc-set-is-select-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member">
<a href="mysqlnd-qc.configuration.html" class="link">Runtime configuration</a>
</li>
<li class="member">
<a href="mysqlnd-qc.configuration.html#ini.mysqlnd-qc.ttl" class="link">mysqlnd_qc.ttl</a>
</li>
<li class="member">
<a href="mysqlnd-qc.configuration.html#ini.mysqlnd-qc.cache-by-default" class="link">mysqlnd_qc.cache_by_default</a>
</li>
<li class="member">
<span class="function"><a href="function.mysqlnd-qc-set-user-handlers.html" class="function" rel="rdfs-seeAlso">mysqlnd_qc_set_user_handlers()</a> - Sets the callback functions for a user-defined procedural storage handler</span>
</li>
</ul>
</p>
</div>
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