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  <div class="section" id="trees">
<h1>Trees<a class="headerlink" href="#trees" title="Permalink to this headline">¶</a></h1>
<p>MongoDB lends itself quite well to storing hierarchical data. This
chapter will demonstrate some examples!</p>
<div class="section" id="full-tree-in-single-document">
<h2>Full Tree in Single Document<a class="headerlink" href="#full-tree-in-single-document" title="Permalink to this headline">¶</a></h2>
<div class="highlight-php"><div class="highlight"><pre><span class="cp">&lt;?php</span>

<span class="sd">/** @Document */</span>
<span class="k">class</span> <span class="nc">BlogPost</span>
<span class="p">{</span>
    <span class="sd">/** @Id */</span>
    <span class="k">private</span> <span class="nv">$id</span><span class="p">;</span>

    <span class="sd">/** @Field(type=&quot;string&quot;) */</span>
    <span class="k">private</span> <span class="nv">$title</span><span class="p">;</span>

    <span class="sd">/** @Field(type=&quot;string&quot;) */</span>
    <span class="k">private</span> <span class="nv">$body</span><span class="p">;</span>

    <span class="sd">/** @EmbedMany(targetDocument=&quot;Comment&quot;) */</span>
    <span class="k">private</span> <span class="nv">$comments</span> <span class="o">=</span> <span class="k">array</span><span class="p">();</span>

    <span class="c1">// ...</span>
<span class="p">}</span>

<span class="sd">/** @EmbeddedDocument */</span>
<span class="k">class</span> <span class="nc">Comment</span>
<span class="p">{</span>
    <span class="sd">/** @Field(type=&quot;string&quot;) */</span>
    <span class="k">private</span> <span class="nv">$by</span><span class="p">;</span>

    <span class="sd">/** @Field(type=&quot;string&quot;) */</span>
    <span class="k">private</span> <span class="nv">$text</span><span class="p">;</span>

    <span class="sd">/** @EmbedMany(targetDocument=&quot;Comment&quot;) */</span>
    <span class="k">private</span> <span class="nv">$replies</span> <span class="o">=</span> <span class="k">array</span><span class="p">();</span>

    <span class="c1">// ...</span>
<span class="p">}</span>
</pre></div>
</div>
<p>Retrieve a blog post and only select the first 10 comments:</p>
<div class="highlight-php"><div class="highlight"><pre><span class="cp">&lt;?php</span>

<span class="nv">$post</span> <span class="o">=</span> <span class="nv">$dm</span><span class="o">-&gt;</span><span class="na">createQueryBuilder</span><span class="p">(</span><span class="s1">&#39;BlogPost&#39;</span><span class="p">)</span>
    <span class="o">-&gt;</span><span class="na">selectSlice</span><span class="p">(</span><span class="s1">&#39;replies&#39;</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">10</span><span class="p">)</span>
    <span class="o">-&gt;</span><span class="na">getQuery</span><span class="p">()</span>
    <span class="o">-&gt;</span><span class="na">getSingleResult</span><span class="p">();</span>

<span class="nv">$replies</span> <span class="o">=</span> <span class="nv">$post</span><span class="o">-&gt;</span><span class="na">getReplies</span><span class="p">();</span>
</pre></div>
</div>
<p>You can read more about this pattern on the MongoDB documentation page &quot;Trees in MongoDB&quot; in the
<a class="reference external" href="http://www.mongodb.org/display/DOCS/Trees+in+MongoDB#TreesinMongoDB-FullTreeinSingleDocument">Full Tree in Single Document</a> section.</p>
</div>
<div class="section" id="parent-reference">
<h2>Parent Reference<a class="headerlink" href="#parent-reference" title="Permalink to this headline">¶</a></h2>
<div class="highlight-php"><div class="highlight"><pre><span class="cp">&lt;?php</span>

<span class="sd">/** @Document */</span>
<span class="k">class</span> <span class="nc">Category</span>
<span class="p">{</span>
    <span class="sd">/** @Id */</span>
    <span class="k">private</span> <span class="nv">$id</span><span class="p">;</span>

    <span class="sd">/** @Field(type=&quot;string&quot;) */</span>
    <span class="k">private</span> <span class="nv">$name</span><span class="p">;</span>

    <span class="sd">/**</span>
<span class="sd">     * @ReferenceOne(targetDocument=&quot;Category&quot;)</span>
<span class="sd">     * @Index</span>
<span class="sd">     */</span>
    <span class="k">private</span> <span class="nv">$parent</span><span class="p">;</span>

    <span class="c1">// ...</span>
<span class="p">}</span>
</pre></div>
</div>
<p>Query for children by a specific parent id:</p>
<div class="highlight-php"><div class="highlight"><pre><span class="cp">&lt;?php</span>

<span class="nv">$children</span> <span class="o">=</span> <span class="nv">$dm</span><span class="o">-&gt;</span><span class="na">createQueryBuilder</span><span class="p">(</span><span class="s1">&#39;Category&#39;</span><span class="p">)</span>
    <span class="o">-&gt;</span><span class="na">field</span><span class="p">(</span><span class="s1">&#39;parent.id&#39;</span><span class="p">)</span><span class="o">-&gt;</span><span class="na">equals</span><span class="p">(</span><span class="s1">&#39;theid&#39;</span><span class="p">)</span>
    <span class="o">-&gt;</span><span class="na">getQuery</span><span class="p">()</span>
    <span class="o">-&gt;</span><span class="na">execute</span><span class="p">();</span>
</pre></div>
</div>
<p>You can read more about this pattern on the MongoDB documentation page &quot;Trees in MongoDB&quot; in the
<a class="reference external" href="https://docs.mongodb.com/manual/tutorial/model-tree-structures/#model-tree-structures-with-parent-references">Parent Links</a> section.</p>
</div>
<div class="section" id="child-reference">
<h2>Child Reference<a class="headerlink" href="#child-reference" title="Permalink to this headline">¶</a></h2>
<div class="highlight-php"><div class="highlight"><pre><span class="cp">&lt;?php</span>

<span class="sd">/** @Document */</span>
<span class="k">class</span> <span class="nc">Category</span>
<span class="p">{</span>
    <span class="sd">/** @Id */</span>
    <span class="k">private</span> <span class="nv">$id</span><span class="p">;</span>

    <span class="sd">/** @Field(type=&quot;string&quot;) */</span>
    <span class="k">private</span> <span class="nv">$name</span><span class="p">;</span>

    <span class="sd">/**</span>
<span class="sd">     * @ReferenceMany(targetDocument=&quot;Category&quot;)</span>
<span class="sd">     * @Index</span>
<span class="sd">     */</span>
    <span class="k">private</span> <span class="nv">$children</span> <span class="o">=</span> <span class="k">array</span><span class="p">();</span>

    <span class="c1">// ...</span>
<span class="p">}</span>
</pre></div>
</div>
<p>Query for immediate children of a category:</p>
<div class="highlight-php"><div class="highlight"><pre><span class="cp">&lt;?php</span>

<span class="nv">$category</span> <span class="o">=</span> <span class="nv">$dm</span><span class="o">-&gt;</span><span class="na">createQueryBuilder</span><span class="p">(</span><span class="s1">&#39;Category&#39;</span><span class="p">)</span>
    <span class="o">-&gt;</span><span class="na">field</span><span class="p">(</span><span class="s1">&#39;id&#39;</span><span class="p">)</span><span class="o">-&gt;</span><span class="na">equals</span><span class="p">(</span><span class="s1">&#39;theid&#39;</span><span class="p">)</span>
    <span class="o">-&gt;</span><span class="na">getQuery</span><span class="p">()</span>
    <span class="o">-&gt;</span><span class="na">getSingleResult</span><span class="p">();</span>

<span class="nv">$children</span> <span class="o">=</span> <span class="nv">$category</span><span class="o">-&gt;</span><span class="na">getChildren</span><span class="p">();</span>
</pre></div>
</div>
<p>Query for immediate parent of a category:</p>
<div class="highlight-php"><div class="highlight"><pre><span class="cp">&lt;?php</span>

<span class="nv">$parent</span> <span class="o">=</span> <span class="nv">$dm</span><span class="o">-&gt;</span><span class="na">createQueryBuilder</span><span class="p">(</span><span class="s1">&#39;Category&#39;</span><span class="p">)</span>
    <span class="o">-&gt;</span><span class="na">field</span><span class="p">(</span><span class="s1">&#39;children.id&#39;</span><span class="p">)</span><span class="o">-&gt;</span><span class="na">equals</span><span class="p">(</span><span class="s1">&#39;theid&#39;</span><span class="p">)</span>
    <span class="o">-&gt;</span><span class="na">getQuery</span><span class="p">()</span>
    <span class="o">-&gt;</span><span class="na">getSingleResult</span><span class="p">();</span>
</pre></div>
</div>
<p>You can read more about this pattern on the MongoDB documentation page &quot;Trees in MongoDB&quot; in the
<a class="reference external" href="https://docs.mongodb.com/manual/tutorial/model-tree-structures/#model-tree-structures-with-child-references">Child Links</a> section.</p>
</div>
<div class="section" id="array-of-ancestors">
<h2>Array of Ancestors<a class="headerlink" href="#array-of-ancestors" title="Permalink to this headline">¶</a></h2>
<div class="highlight-php"><div class="highlight"><pre><span class="cp">&lt;?php</span>

<span class="sd">/** @MappedSuperclass */</span>
<span class="k">class</span> <span class="nc">BaseCategory</span>
<span class="p">{</span>
    <span class="sd">/** @Field(type=&quot;string&quot;) */</span>
    <span class="k">private</span> <span class="nv">$name</span><span class="p">;</span>

    <span class="c1">// ...</span>
<span class="p">}</span>

<span class="sd">/** @Document */</span>
<span class="k">class</span> <span class="nc">Category</span> <span class="k">extends</span> <span class="nx">BaseCategory</span>
<span class="p">{</span>
    <span class="sd">/** @Id */</span>
    <span class="k">private</span> <span class="nv">$id</span><span class="p">;</span>

    <span class="sd">/**</span>
<span class="sd">     * @ReferenceMany(targetDocument=&quot;Category&quot;)</span>
<span class="sd">     * @Index</span>
<span class="sd">     */</span>
    <span class="k">private</span> <span class="nv">$ancestors</span> <span class="o">=</span> <span class="k">array</span><span class="p">();</span>

    <span class="sd">/**</span>
<span class="sd">     * @ReferenceOne(targetDocument=&quot;Category&quot;)</span>
<span class="sd">     * @Index</span>
<span class="sd">     */</span>
    <span class="k">private</span> <span class="nv">$parent</span><span class="p">;</span>

    <span class="c1">// ...</span>
<span class="p">}</span>

<span class="sd">/** @EmbeddedDocument */</span>
<span class="k">class</span> <span class="nc">SubCategory</span> <span class="k">extends</span> <span class="nx">BaseCategory</span>
<span class="p">{</span>
<span class="p">}</span>
</pre></div>
</div>
<p>Query for all descendants of a category:</p>
<div class="highlight-php"><div class="highlight"><pre><span class="cp">&lt;?php</span>

<span class="nv">$categories</span> <span class="o">=</span> <span class="nv">$dm</span><span class="o">-&gt;</span><span class="na">createQueryBuilder</span><span class="p">(</span><span class="s1">&#39;Category&#39;</span><span class="p">)</span>
    <span class="o">-&gt;</span><span class="na">field</span><span class="p">(</span><span class="s1">&#39;ancestors.id&#39;</span><span class="p">)</span><span class="o">-&gt;</span><span class="na">equals</span><span class="p">(</span><span class="s1">&#39;theid&#39;</span><span class="p">)</span>
    <span class="o">-&gt;</span><span class="na">getQuery</span><span class="p">()</span>
    <span class="o">-&gt;</span><span class="na">execute</span><span class="p">();</span>
</pre></div>
</div>
<p>Query for all ancestors of a category:</p>
<div class="highlight-php"><div class="highlight"><pre><span class="cp">&lt;?php</span>

<span class="nv">$category</span> <span class="o">=</span> <span class="nv">$dm</span><span class="o">-&gt;</span><span class="na">createQuery</span><span class="p">(</span><span class="s1">&#39;Category&#39;</span><span class="p">)</span>
    <span class="o">-&gt;</span><span class="na">field</span><span class="p">(</span><span class="s1">&#39;id&#39;</span><span class="p">)</span><span class="o">-&gt;</span><span class="na">equals</span><span class="p">(</span><span class="s1">&#39;theid&#39;</span><span class="p">)</span>
    <span class="o">-&gt;</span><span class="na">getQuery</span><span class="p">()</span>
    <span class="o">-&gt;</span><span class="na">getSingleResult</span><span class="p">();</span>

<span class="nv">$ancestors</span> <span class="o">=</span> <span class="nv">$category</span><span class="o">-&gt;</span><span class="na">getAncestors</span><span class="p">();</span>
</pre></div>
</div>
<p>You can read more about this pattern on the MongoDB documentation page &quot;Trees in MongoDB&quot; in the
<a class="reference external" href="https://docs.mongodb.com/manual/tutorial/model-tree-structures/#model-tree-structures-with-an-array-of-ancestors">Array of Ancestors</a> section.</p>
</div>
<div class="section" id="materialized-paths">
<h2>Materialized Paths<a class="headerlink" href="#materialized-paths" title="Permalink to this headline">¶</a></h2>
<div class="highlight-php"><div class="highlight"><pre><span class="cp">&lt;?php</span>

<span class="sd">/** @Document */</span>
<span class="k">class</span> <span class="nc">Category</span>
<span class="p">{</span>
    <span class="sd">/** @Id */</span>
    <span class="k">private</span> <span class="nv">$id</span><span class="p">;</span>

    <span class="sd">/** @Field(type=&quot;string&quot;) */</span>
    <span class="k">private</span> <span class="nv">$name</span><span class="p">;</span>

    <span class="sd">/** @Field(type=&quot;string&quot;) */</span>
    <span class="k">private</span> <span class="nv">$path</span><span class="p">;</span>

    <span class="c1">// ...</span>
<span class="p">}</span>
</pre></div>
</div>
<p>Query for the entire tree:</p>
<div class="highlight-php"><div class="highlight"><pre><span class="cp">&lt;?php</span>

<span class="nv">$categories</span> <span class="o">=</span> <span class="nv">$dm</span><span class="o">-&gt;</span><span class="na">createQuery</span><span class="p">(</span><span class="s1">&#39;Category&#39;</span><span class="p">)</span>
    <span class="o">-&gt;</span><span class="na">sort</span><span class="p">(</span><span class="s1">&#39;path&#39;</span><span class="p">,</span> <span class="s1">&#39;asc&#39;</span><span class="p">)</span>
    <span class="o">-&gt;</span><span class="na">getQuery</span><span class="p">()</span>
    <span class="o">-&gt;</span><span class="na">execute</span><span class="p">();</span>
</pre></div>
</div>
<p>Query for the node 'b' and all its descendants:</p>
<div class="highlight-php"><div class="highlight"><pre><span class="cp">&lt;?php</span>
<span class="nv">$categories</span> <span class="o">=</span> <span class="nv">$dm</span><span class="o">-&gt;</span><span class="na">createQuery</span><span class="p">(</span><span class="s1">&#39;Category&#39;</span><span class="p">)</span>
    <span class="o">-&gt;</span><span class="na">field</span><span class="p">(</span><span class="s1">&#39;path&#39;</span><span class="p">)</span><span class="o">-&gt;</span><span class="na">equals</span><span class="p">(</span><span class="s1">&#39;/^a,b,/&#39;</span><span class="p">)</span>
    <span class="o">-&gt;</span><span class="na">getQuery</span><span class="p">()</span>
    <span class="o">-&gt;</span><span class="na">execute</span><span class="p">();</span>
</pre></div>
</div>
<p>You can read more about this pattern on the MongoDB documentation page &quot;Trees in MongoDB&quot; in the
<a class="reference external" href="https://docs.mongodb.com/manual/tutorial/model-tree-structures/#model-tree-structures-with-materialized-paths">Materialized Paths (Full Path in Each Node)</a> section.</p>
</div>
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            <h3><a href="../index.html">Table Of Contents</a></h3>
            <ul>
<li><a class="reference internal" href="#">Trees</a><ul>
<li><a class="reference internal" href="#full-tree-in-single-document">Full Tree in Single Document</a></li>
<li><a class="reference internal" href="#parent-reference">Parent Reference</a></li>
<li><a class="reference internal" href="#child-reference">Child Reference</a></li>
<li><a class="reference internal" href="#array-of-ancestors">Array of Ancestors</a></li>
<li><a class="reference internal" href="#materialized-paths">Materialized Paths</a></li>
</ul>
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</ul>

            <h3>This Page</h3>
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              <li><a href="../_sources/reference/trees.rst.txt"
                     rel="nofollow">Show Source</a></li>
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