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<title>Creating An Index</title>
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<h2 class="title">Creating An Index</h2>
<p class="para">
MongoDB supports indexes, and they are very easy to add on a collection. To
create an index, you specify the field name and direction: ascending (1) or
descending (-1). The following creates an ascending index on the "i" field:
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<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$connection </span><span style="color: #007700">= new </span><span style="color: #0000BB">MongoClient</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">$collection </span><span style="color: #007700">= </span><span style="color: #0000BB">$connection</span><span style="color: #007700">-></span><span style="color: #0000BB">database</span><span style="color: #007700">-></span><span style="color: #0000BB">collectionName</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">$coll</span><span style="color: #007700">-></span><span style="color: #0000BB">ensureIndex</span><span style="color: #007700">( array( </span><span style="color: #DD0000">"i" </span><span style="color: #007700">=> </span><span style="color: #0000BB">1 </span><span style="color: #007700">) ); </span><span style="color: #FF8000">// create index on "i"<br /></span><span style="color: #0000BB">$coll</span><span style="color: #007700">-></span><span style="color: #0000BB">ensureIndex</span><span style="color: #007700">( array( </span><span style="color: #DD0000">"i" </span><span style="color: #007700">=> -</span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #DD0000">"j" </span><span style="color: #007700">=> </span><span style="color: #0000BB">1 </span><span style="color: #007700">) ); </span><span style="color: #FF8000">// index on "i" descending, "j" ascending<br /></span><span style="color: #0000BB">?></span>
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<p class="para">
Indexing is critical for good read performance as your data grows. If you
are not familiar with indexing, check out the
<span class="function"><a href="mongocollection.ensureindex.html" class="function">MongoCollection::ensureIndex()</a></span> documentation and the core
<a href="http://docs.mongodb.org/manual/indexes/" class="link external">» MongoDB indexing documentation</a>.
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