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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
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<title>Zend_Db Performance - Zend Framework Manual</title>
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<div id="performance.database" class="section"><div class="info"><h1 class="title">Zend_Db Performance</h1></div>
<p class="para">
<span class="classname">Zend_Db</span> is a database abstraction layer, and is intended to
provide a common <acronym class="acronym">API</acronym> for <acronym class="acronym">SQL</acronym> operations.
<span class="classname">Zend_Db_Table</span> is a
Table Data Gateway, intended to abstract common table-level database
operations. Due to their abstract nature and the "magic" they do under
the hood to perform their operations, they can sometimes introduce
performance overhead.
</p>
<div class="section" id="performance.database.tableMetadata" name="performance.database.tableMetadata"><div class="info"><h1 class="title">How can I reduce overhead introduced by Zend_Db_Table for
retrieving table metadata?</h1></div>
<p class="para">
In order to keep usage as simple as possible, and also to support
constantly changing schemas during development,
<span class="classname">Zend_Db_Table</span> does some magic under the hood: on
first use, it fetches the table schema and stores it within object
members. This operation is typically expensive, regardless of the
database -- which can contribute to bottlenecks in production.
</p>
<p class="para">
Fortunately, there are techniques for improving the situation.
</p>
<div class="section" id="performance.database.tableMetadata.cache" name="performance.database.tableMetadata.cache"><div class="info"><h1 class="title">Use the metadata cache</h1></div>
<p class="para">
<span class="classname">Zend_Db_Table</span> can optionally utilize
<span class="classname">Zend_Cache</span> to cache table metadata. This is
typically faster to access and less expensive than fetching the
metadata from the database itself.
</p>
<p class="para">
The <a href="" class="link"><span class="classname">Zend_Db_Table
</span> documentation includes information on metadata caching</a>.
</p>
</div>
<div class="section" id="performance.database.tableMetadata.hardcoding" name="performance.database.tableMetadata.hardcoding"><div class="info"><h1 class="title">Hardcode your metadata in the table definition</h1></div>
<p class="para">
As of 1.7.0, <span class="classname">Zend_Db_Table</span> also provides <a href="" class="link">support
for hardcoding metadata in the table definition</a>. This is
an advanced use case, and should only be used when you know the
table schema is unlikely to change, or that you're able to keep
the definitions up-to-date.
</p>
</div>
</div>
<div class="section" id="performance.database.select" name="performance.database.select"><div class="info"><h1 class="title">
SQL generated with Zend_Db_Select s not hitting my indexes; how can I make it better?
</h1></div>
<p class="para">
<span class="classname">Zend_Db_Select</span> is relatively good at its job. However,
if you are performing complex queries requiring joins or
sub-selects, it can often be fairly naive.
</p>
<div class="section" id="performance.database.select.writeyourown" name="performance.database.select.writeyourown"><div class="info"><h1 class="title">Write your own tuned SQL</h1></div>
<p class="para">
The only real answer is to write your own <acronym class="acronym">SQL</acronym>;
<span class="classname">Zend_Db</span> does not require the usage of
<span class="classname">Zend_Db_Select</span>, so providing your own, tuned
<acronym class="acronym">SQL</acronym> select statements is a perfectly legitimate approach,
</p>
<p class="para">
Run <b><tt>EXPLAIN</tt></b> on your queries, and test a variety of
approaches until you can reliably hit your indices in the most
performant way -- and then hardcode the <acronym class="acronym">SQL</acronym> as a class property
or constant.
</p>
<p class="para">
If the <acronym class="acronym">SQL</acronym> requires variable arguments, provide placeholders in
the <acronym class="acronym">SQL</acronym>, and utilize a combination of
<span class="methodname">vsprintf()</span> and <span class="methodname">array_map()</span> to
inject the values into the <acronym class="acronym">SQL</acronym>:
</p>
<div class="programlisting php"><div class="phpcode"><div class="php" style="font-family: monospace;"><ol><li style="font-family: 'Courier New', Courier, monospace; color: black; font-weight: normal; font-style: normal;"><div style="font-family: 'Courier New', Courier, monospace; font-weight: normal;"><span style="color: #808080; font-style: italic;">// $adapter is the DB adapter. In Zend_Db_Table, retrieve</span></div></li>
<li style="font-family: 'Courier New', Courier, monospace; color: black; font-weight: normal; font-style: normal;"><div style="font-family: 'Courier New', Courier, monospace; font-weight: normal;"><span style="color: #808080; font-style: italic;">// it using $this->getAdapter().</span></div></li>
<li style="font-family: 'Courier New', Courier, monospace; color: black; font-weight: normal; font-style: normal;"><div style="font-family: 'Courier New', Courier, monospace; font-weight: normal;"><span style="color: #0000ff;">$sql</span> = <a href="http://www.php.net/vsprintf"><span style="color: #000066;">vsprintf</span></a><span style="color: #66cc66;">(</span></div></li>
<li style="font-family: 'Courier New', Courier, monospace; color: black; font-weight: normal; font-style: normal;"><div style="font-family: 'Courier New', Courier, monospace; font-weight: normal;"> self::<span style="color: #006600;">SELECT_FOO</span>,</div></li>
<li style="font-family: 'Courier New', Courier, monospace; color: black; font-weight: normal; font-style: normal;"><div style="font-family: 'Courier New', Courier, monospace; font-weight: normal;"> <a href="http://www.php.net/array_map"><span style="color: #000066;">array_map</span></a><span style="color: #66cc66;">(</span><a href="http://www.php.net/array"><span style="color: #000066;">array</span></a><span style="color: #66cc66;">(</span><span style="color: #0000ff;">$adapter</span>, <span style="color: #ff0000;">'quoteInto'</span><span style="color: #66cc66;">)</span>, <span style="color: #0000ff;">$values</span><span style="color: #66cc66;">)</span></div></li>
<li style="font-family: 'Courier New', Courier, monospace; color: black; font-weight: normal; font-style: normal;"><div style="font-family: 'Courier New', Courier, monospace; font-weight: normal;"><span style="color: #66cc66;">)</span>;</div></li></ol></div></div></div>
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