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<div class="section" id="extra-lazy-associations">
<h1>Extra Lazy Associations<a class="headerlink" href="#extra-lazy-associations" title="Permalink to this headline">¶</a></h1>
<div class="versionadded">
<p><span class="versionmodified">New in version 2.1.</span></p>
</div>
<p>In many cases associations between entities can get pretty large. Even in a simple scenario like a blog.
where posts can be commented, you always have to assume that a post draws hundreds of comments.
In Doctrine 2.0 if you accessed an association it would always get loaded completely into memory. This
can lead to pretty serious performance problems, if your associations contain several hundreds or thousands
of entities.</p>
<p>With Doctrine 2.1 a feature called <strong>Extra Lazy</strong> is introduced for associations. Associations
are marked as <strong>Lazy</strong> by default, which means the whole collection object for an association is populated
the first time its accessed. If you mark an association as extra lazy the following methods on collections
can be called without triggering a full load of the collection:</p>
<ul class="simple">
<li><tt class="docutils literal"><span class="pre">Collection#contains($entity)</span></tt></li>
<li><tt class="docutils literal"><span class="pre">Collection#count()</span></tt></li>
<li><tt class="docutils literal"><span class="pre">Collection#slice($offset,</span> <span class="pre">$length</span> <span class="pre">=</span> <span class="pre">null)</span></tt></li>
</ul>
<p>For each of this three methods the following semantics apply:</p>
<ul class="simple">
<li>For each call, if the Collection is not yet loaded, issue a straight SELECT statement against the database.</li>
<li>For each call, if the collection is already loaded, fallback to the default functionality for lazy collections. No additional SELECT statements are executed.</li>
</ul>
<p>Additionally even with Doctrine 2.0 the following methods do not trigger the collection load:</p>
<ul class="simple">
<li><tt class="docutils literal"><span class="pre">Collection#add($entity)</span></tt></li>
<li><tt class="docutils literal"><span class="pre">Collection#offsetSet($key,</span> <span class="pre">$entity)</span></tt> - ArrayAccess with no specific key <tt class="docutils literal"><span class="pre">$coll[]</span> <span class="pre">=</span> <span class="pre">$entity</span></tt>, it does
not work when setting specific keys like <tt class="docutils literal"><span class="pre">$coll[0]</span> <span class="pre">=</span> <span class="pre">$entity</span></tt>.</li>
</ul>
<p>With extra lazy collections you can now not only add entities to large collections but also paginate them
easily using a combination of <tt class="docutils literal"><span class="pre">count</span></tt> and <tt class="docutils literal"><span class="pre">slice</span></tt>.</p>
<div class="section" id="enabling-extra-lazy-associations">
<h2>Enabling Extra-Lazy Associations<a class="headerlink" href="#enabling-extra-lazy-associations" title="Permalink to this headline">¶</a></h2>
<p>The mapping configuration is simple. Instead of using the default value of <tt class="docutils literal"><span class="pre">fetch="LAZY"</span></tt> you have to
switch to extra lazy as shown in these examples:</p>
<div class="configuration-block">
<ul class="simple">
<li><em>PHP</em><div class="highlight-php"><div class="highlight"><pre><span class="cp"><?php</span>
<span class="k">namespace</span> <span class="nx">Doctrine\Tests\Models\CMS</span><span class="p">;</span>
<span class="sd">/**</span>
<span class="sd"> * @Entity</span>
<span class="sd"> */</span>
<span class="k">class</span> <span class="nc">CmsGroup</span>
<span class="p">{</span>
<span class="sd">/**</span>
<span class="sd"> * @ManyToMany(targetEntity="CmsUser", mappedBy="groups", fetch="EXTRA_LAZY")</span>
<span class="sd"> */</span>
<span class="k">public</span> <span class="nv">$users</span><span class="p">;</span>
<span class="p">}</span>
</pre></div>
</div>
</li>
<li><em>XML</em><div class="highlight-xml"><div class="highlight"><pre><span class="cp"><?xml version="1.0" encoding="UTF-8"?></span>
<span class="nt"><doctrine-mapping</span> <span class="na">xmlns=</span><span class="s">"http://doctrine-project.org/schemas/orm/doctrine-mapping"</span>
<span class="na">xmlns:xsi=</span><span class="s">"http://www.w3.org/2001/XMLSchema-instance"</span>
<span class="na">xsi:schemaLocation=</span><span class="s">"http://doctrine-project.org/schemas/orm/doctrine-mapping</span>
<span class="s"> http://www.doctrine-project.org/schemas/orm/doctrine-mapping.xsd"</span><span class="nt">></span>
<span class="nt"><entity</span> <span class="na">name=</span><span class="s">"Doctrine\Tests\Models\CMS\CmsGroup"</span><span class="nt">></span>
<span class="c"><!-- ... --></span>
<span class="nt"><many-to-many</span> <span class="na">field=</span><span class="s">"users"</span> <span class="na">target-entity=</span><span class="s">"CmsUser"</span> <span class="na">mapped-by=</span><span class="s">"groups"</span> <span class="na">fetch=</span><span class="s">"EXTRA_LAZY"</span> <span class="nt">/></span>
<span class="nt"></entity></span>
<span class="nt"></doctrine-mapping></span>
</pre></div>
</div>
</li>
<li><em>YAML</em><div class="highlight-yaml"><div class="highlight"><pre><span class="l-Scalar-Plain">Doctrine\Tests\Models\CMS\CmsGroup</span><span class="p-Indicator">:</span>
<span class="l-Scalar-Plain">type</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">entity</span>
<span class="c1"># ...</span>
<span class="l-Scalar-Plain">manyToMany</span><span class="p-Indicator">:</span>
<span class="l-Scalar-Plain">users</span><span class="p-Indicator">:</span>
<span class="l-Scalar-Plain">targetEntity</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">CmsUser</span>
<span class="l-Scalar-Plain">mappedBy</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">groups</span>
<span class="l-Scalar-Plain">fetch</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">EXTRA_LAZY</span>
</pre></div>
</div>
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<h3><a href="../index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">Extra Lazy Associations</a><ul>
<li><a class="reference internal" href="#enabling-extra-lazy-associations">Enabling Extra-Lazy Associations</a></li>
</ul>
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