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<title>Find whether to send the query to the master, the slave or the last used MySQL server</title>
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</div><hr /><div id="function.mysqlnd-ms-query-is-select" class="refentry">
<div class="refnamediv">
<h1 class="refname">mysqlnd_ms_query_is_select</h1>
<p class="verinfo">(PECL mysqlnd_ms >= 1.0.0)</p><p class="refpurpose"><span class="refname">mysqlnd_ms_query_is_select</span> — <span class="dc-title">Find whether to send the query to the master, the slave or the last used MySQL server</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.mysqlnd-ms-query-is-select-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">int</span>
<span class="methodname"><strong>mysqlnd_ms_query_is_select</strong></span>
( <span class="methodparam"><span class="type">string</span> <code class="parameter">$query</code></span>
)</div>
<p class="para rdfs-comment">
Finds whether to send the query to the master, the slave or the
last used MySQL server.
</p>
<p class="para">
The plugins built-in read/write split mechanism
will be used to analyze the query string to make a recommendation where
to send the query. The built-in read/write split mechanism is very
basic and simple. The plugin will recommend sending all queries to the
MySQL replication master server but those which begin with
<em>SELECT</em>, or begin with a SQL hint which
enforces sending the query to a slave server. Due to the basic
but fast algorithm the plugin may propose to run some read-only
statements such as <em>SHOW TABLES</em> on the replication master.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.mysqlnd-ms-query-is-select-parameters">
<h3 class="title">Parameters</h3>
<dl>
<dt>
<span class="term"><em><code class="parameter">query</code></em></span>
<dd>
<p class="para">
Query string to test.
</p>
</dd>
</dt>
</dl>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.mysqlnd-ms-query-is-select-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
A return value of <strong><code>MYSQLND_MS_QUERY_USE_MASTER</code></strong>
indicates that the query should be send to the MySQL replication
master server. The function returns a value of
<strong><code>MYSQLND_MS_QUERY_USE_SLAVE</code></strong> if the query can be run
on a slave because it is considered read-only. A value of
<strong><code>MYSQLND_MS_QUERY_USE_LAST_USED</code></strong> is returned to recommend
running the query on the last used server. This can either be a MySQL
replication master server or a MySQL replication slave server.
</p>
<p class="para">
If read write splitting has been disabled by setting
<em>mysqlnd_ms.disable_rw_split</em>, the function will
always return <strong><code>MYSQLND_MS_QUERY_USE_MASTER</code></strong> or
<strong><code>MYSQLND_MS_QUERY_USE_LAST_USED</code></strong>.
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.mysqlnd-ms-query-is-select-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-1842">
<p><strong>Example #1 <span class="function"><strong>mysqlnd_ms_query_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: #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 />{<br /> switch (</span><span style="color: #0000BB">mysqlnd_ms_query_is_select</span><span style="color: #007700">(</span><span style="color: #0000BB">$query</span><span style="color: #007700">))<br /> {<br /> case </span><span style="color: #0000BB">MYSQLND_MS_QUERY_USE_MASTER</span><span style="color: #007700">:<br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"'%s' should be run on the master.\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">$query</span><span style="color: #007700">);<br /> break;<br /> case </span><span style="color: #0000BB">MYSQLND_MS_QUERY_USE_SLAVE</span><span style="color: #007700">:<br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"'%s' should be run on a slave.\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">$query</span><span style="color: #007700">);<br /> break;<br /> case </span><span style="color: #0000BB">MYSQLND_MS_QUERY_USE_LAST_USED</span><span style="color: #007700">:<br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"'%s' should be run on the server that has run the previous query\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">$query</span><span style="color: #007700">);<br /> break;<br /> default:<br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"No suggestion where to run the '%s', fallback to master recommended\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">$query</span><span style="color: #007700">);<br /> break;<br /> }<br />}<br /><br /></span><span style="color: #0000BB">is_select</span><span style="color: #007700">(</span><span style="color: #DD0000">"INSERT INTO test(id) VALUES (1)"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">is_select</span><span style="color: #007700">(</span><span style="color: #DD0000">"SELECT 1 FROM DUAL"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">is_select</span><span style="color: #007700">(</span><span style="color: #DD0000">"/*" </span><span style="color: #007700">. </span><span style="color: #0000BB">MYSQLND_MS_LAST_USED_SWITCH </span><span style="color: #007700">. </span><span style="color: #DD0000">"*/SELECT 2 FROM DUAL"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
INSERT INTO test(id) VALUES (1) should be run on the master.
SELECT 1 FROM DUAL should be run on a slave.
/*ms=last_used*/SELECT 2 FROM DUAL should be run on the server that has run the previous query
</pre></div>
</div>
</div>
</p>
</div>
<div class="refsect1 seealso" id="refsect1-function.mysqlnd-ms-query-is-select-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member">
<a href="mysqlnd-ms.constants.html" class="link">Predefined Constants</a>
</li>
<li class="member">
<a href="mysqlnd-ms.plugin-ini-json.html#ini.mysqlnd-ms-plugin-config-v2.filter-user" class="link"><em>user</em></a> filter
</li>
</ul>
<ul class="simplelist">
<li class="member">
<a href="mysqlnd-ms.configuration.html" class="link">Runtime configuration</a>
</li>
<li class="member">
<a href="mysqlnd-ms.configuration.html#ini.mysqlnd-ms.disable-rw-split" class="link">mysqlnd_ms.disable_rw_split</a>
</li>
<li class="member">
<a href="mysqlnd-ms.configuration.html#ini.mysqlnd-ms.enable" class="link">mysqlnd_ms.enable</a>
</li>
</ul>
</p>
</div>
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