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<div class="body" >
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<div class="section" id="eager-cursors">
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<h1>Eager Cursors<a class="headerlink" href="#eager-cursors" title="Permalink to this headline">¶</a></h1>
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<p>With a typical MongoDB cursor, it stays open during iteration and fetches
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batches of documents as you iterate over the cursor. This isn't bad,
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but sometimes you want to fetch all of the data eagerly. For example
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when dealing with web applications, and you want to only show 50
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documents from a collection you should fetch all the data in your
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controller first before going on to the view.</p>
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<p>Benefits:</p>
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<ul class="simple">
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<li>The cursor stays open for a much shorter period of time.</li>
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<li>Data retrieval and hydration are consolidated operations.</li>
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<li>Doctrine has the ability to retry the cursor when exceptions during interaction with mongodb are encountered.</li>
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</ul>
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<p>Example:</p>
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<div class="highlight-php"><div class="highlight"><pre><span class="cp"><?php</span>
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<span class="nv">$qb</span> <span class="o">=</span> <span class="nv">$dm</span><span class="o">-></span><span class="na">createQueryBuilder</span><span class="p">(</span><span class="s1">'User'</span><span class="p">)</span>
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<span class="o">-></span><span class="na">eagerCursor</span><span class="p">(</span><span class="k">true</span><span class="p">);</span>
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<span class="nv">$query</span> <span class="o">=</span> <span class="nv">$qb</span><span class="o">-></span><span class="na">getQuery</span><span class="p">();</span>
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<span class="nv">$users</span> <span class="o">=</span> <span class="nv">$query</span><span class="o">-></span><span class="na">execute</span><span class="p">();</span> <span class="c1">// returns instance of Doctrine\MongoDB\ODM\EagerCursor</span>
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</pre></div>
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</div>
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<p>At this point all data is loaded from the database and cursors to MongoDB
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have been closed but hydration of the data in to objects has not begun. Once
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insertion starts the data will be hydrated in to PHP objects.</p>
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<p>Example:</p>
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<div class="highlight-php"><div class="highlight"><pre><span class="cp"><?php</span>
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<span class="k">foreach</span> <span class="p">(</span><span class="nv">$users</span> <span class="k">as</span> <span class="nv">$user</span><span class="p">)</span> <span class="p">{</span>
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<span class="k">echo</span> <span class="nv">$user</span><span class="o">-></span><span class="na">getUsername</span><span class="p">()</span><span class="o">.</span><span class="s2">"</span><span class="se">\n</span><span class="s2">"</span><span class="p">;</span>
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<span class="p">}</span>
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</pre></div>
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</div>
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<p>Not all documents are converted to objects at once, the hydration is still done
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one document at a time during iteration. The only change is that all data is retrieved
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first.</p>
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