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<title>Creates an index on the specified field(s) if it does not already exist</title>
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<h1 class="refname">MongoCollection::ensureIndex</h1>
<p class="verinfo">(PECL mongo >=0.9.0)</p><p class="refpurpose"><span class="refname">MongoCollection::ensureIndex</span> — <span class="dc-title">
Creates an index on the specified field(s) if it does not already exist
</span></p>
</div>
<div class="refsect1 description" id="refsect1-mongocollection.ensureindex-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="modifier">public</span> <span class="type">bool</span> <span class="methodname"><strong>MongoCollection::ensureIndex</strong></span>
( <span class="methodparam"><span class="type"><span class="type string|array">string|array</span></span> <code class="parameter">$key|keys</code></span>
[, <span class="methodparam"><span class="type">array</span> <code class="parameter">$options</code><span class="initializer"> = array()</span></span>
] )</div>
<div class="warning"><strong class="warning">Warning</strong>
<p class="para">
This method is deprecated since version 1.5.0. Please use
<span class="methodname"><a href="mongocollection.createindex.html" class="methodname">MongoCollection::createIndex()</a></span> instead.
</p>
</div>
<p class="para">
Creates an index on the specified field(s) if it does not already exist.
Fields may be indexed with a direction (e.g. ascending or descending) or a
special type (e.g. text, geospatial, hashed).
</p>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
This method will use the
<a href="https://docs.mongodb.com/manual/reference/command/createIndexes" class="link external">» createIndexes</a>
database command when communicating with MongoDB 2.6+. For previous database
versions, the method will perform an insert operation on the
special <em>system.indexes</em> collection.
</p>
</p></blockquote>
</div>
<div class="refsect1 parameters" id="refsect1-mongocollection.ensureindex-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<code class="parameter">keys</code>
</dt>
<dd>
<p class="para">
An array specifying the index's fields as its keys. For each field, the
value is either the index direction or
<a href="https://docs.mongodb.com/manual/core/index-types/" class="link external">» index type</a>.
If specifying direction, specify <em>1</em> for ascending or
<em>-1</em> for descending.
</p>
</dd>
<dt>
<code class="parameter">options</code>
</dt>
<dd>
<p class="para">
An array of options for the index creation. Currently available options
include:
<ul class="itemizedlist">
<li class="listitem"><p class="para"><em>"unique"</em></p><p class="para">Specify <strong><code>TRUE</code></strong> to create a unique index. The default value is <strong><code>FALSE</code></strong>. This option applies only to ascending/descending indexes.</p><blockquote class="note"><p><strong class="note">Note</strong>: <p class="para">When MongoDB indexes a field, if a document does not have a value for the field, a <strong><code>NULL</code></strong> value is indexed. If multiple documents do not contain a field, a unique index will reject all but the first of those documents. The <em>"sparse"</em> option may be used to overcome this, since it will prevent documents without the field from being indexed.</p></p></blockquote></li>
<li class="listitem"><p class="para"><em>"sparse"</em></p><p class="para">Specify <strong><code>TRUE</code></strong> to create a sparse index, which only indexes documents containing a specified field. The default value is <strong><code>FALSE</code></strong>.</p></li>
<li class="listitem"><p class="para"><em>"expireAfterSeconds"</em></p><p class="para">The value of this option should specify the number of seconds after which a document should be considered expired and automatically removed from the collection. This option is only compatible with single-field indexes where the field will contain <a href="class.mongodate.html" class="classname">MongoDate</a> values.</p><blockquote class="note"><p><strong class="note">Note</strong>: <p class="para">This feature is available in MongoDB 2.2+. See <a href="https://docs.mongodb.com/manual/tutorial/expire-data/" class="link external">» Expire Data from Collections by Setting TTL</a> for more information.</p></p></blockquote></li>
<li class="listitem"><p class="para"><em>"name"</em></p><p class="para">A optional name that uniquely identifies the index.</p><blockquote class="note"><p><strong class="note">Note</strong>: <p class="para">By default, the driver will generate an index name based on the index's field(s) and ordering or type. For example, a compound index <em>array("x" => 1, "y" => -1)</em> would be named <em>"x_1_y_-1"</em> and a geospatial index <em>array("loc" => "2dsphere")</em> would be named <em>"loc_2dsphere"</em>. For indexes with many fields, it is possible that the generated name might exceed MongoDB's <a href="https://docs.mongodb.com/manual/reference/limits/#Index-Name-Length" class="link external">» limit for index names</a>. The <em>"name"</em> option may be used in that case to supply a shorter name.</p></p></blockquote></li>
<li class="listitem"><p class="para"><em>"background"</em></p><p class="para">Builds the index in the background so that building an index does <em class="emphasis">not</em> block other database activities. Specify <strong><code>TRUE</code></strong> to build in the background. The default value is <strong><code>FALSE</code></strong>.</p><div class="warning"><strong class="warning">Warning</strong><p class="para">Prior to MongoDB 2.6.0, index builds on secondaries were executed as foreground operations, irrespective of this option. See <a href="https://docs.mongodb.com/manual/tutorial/build-indexes-on-replica-sets/" class="link external">» Building Indexes with Replica Sets</a> for more information.</p></div></li>
<li class="listitem"><p class="para"><em>"socketTimeoutMS"</em></p><p class="para">This option specifies the time limit, in milliseconds, for socket communication. If the server does not respond within the timeout period, a <a href="class.mongocursortimeoutexception.html" class="classname">MongoCursorTimeoutException</a> will be thrown and there will be no way to determine if the server actually handled the write or not. A value of <em>-1</em> may be specified to block indefinitely. The default value for <a href="class.mongoclient.html" class="classname">MongoClient</a> is <em>30000</em> (30 seconds).</p></li>
</ul>
</p>
<p class="para">
The following option may be used with MongoDB 2.6+:
<ul class="itemizedlist">
<li class="listitem"><p class="para"><em>"maxTimeMS"</em></p><p class="para">Specifies a cumulative time limit in milliseconds for processing the operation on the server (does not include idle time). If the operation is not completed by the server within the timeout period, a <a href="class.mongoexecutiontimeoutexception.html" class="classname">MongoExecutionTimeoutException</a> will be thrown.</p></li>
</ul>
</p>
<p class="para">
The following options may be used with MongoDB versions before 2.8:
<ul class="itemizedlist">
<li class="listitem"><p class="para"><em>"dropDups"</em></p><p class="para">Specify <strong><code>TRUE</code></strong> to force creation of a unique index where the collection may contain duplicate values for a key. MongoDB will index the first occurrence of a key and delete all subsequent documents from the collection that contain a duplicate value for that key. The default value is <strong><code>FALSE</code></strong>.</p><div class="warning"><strong class="warning">Warning</strong><p class="para"><em>"dropDups"</em> may delete data from your database. Use with extreme caution.</p></div><blockquote class="note"><p><strong class="note">Note</strong>: <p class="para">This option is not supported on MongoDB 2.8+. Index creation will fail if the collection contains duplicate values.</p></p></blockquote></li>
</ul>
</p>
<p class="para">
The following options may be used with MongoDB versions before 2.6:
<ul class="itemizedlist">
<li class="listitem"><p class="para"><em>"w"</em></p><p class="para">See <a href="mongo.writeconcerns.html" class="link">Write Concerns</a>. The default value for <a href="class.mongoclient.html" class="classname">MongoClient</a> is <em>1</em>.</p></li>
<li class="listitem"><p class="para"><em>"wTimeoutMS"</em></p><p class="para">This option specifies the time limit, in milliseconds, for <a href="mongo.writeconcerns.html" class="link">write concern</a> acknowledgement. It is only applicable when <em>"w"</em> is greater than <em>1</em>, as the timeout pertains to replication. If the write concern is not satisfied within the time limit, a <a href="class.mongocursorexception.html" class="classname">MongoCursorException</a> will be thrown. A value of <em>0</em> may be specified to block indefinitely. The default value for <a href="class.mongoclient.html" class="classname">MongoClient</a> is <em>10000</em> (ten seconds).</p></li>
</ul>
</p>
<p class="para">
The following options are deprecated and should no longer be used:
<ul class="itemizedlist">
<li class="listitem"><p class="para"><em>"safe"</em></p><p class="para">Deprecated. Please use the <a href="mongo.writeconcerns.html" class="link">write concern</a> <em>"w"</em> option.</p></li>
<li class="listitem"><p class="para"><em>"timeout"</em></p><p class="para">Deprecated alias for <em>"socketTimeoutMS"</em>.</p></li>
<li class="listitem"><p class="para"><em>"wtimeout"</em></p><p class="para">Deprecated alias for <em>"wTimeoutMS"</em>.</p></li>
</ul>
</p>
</dd>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-mongocollection.ensureindex-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns an array containing the status of the index creation. The array
contains whether the operation succeeded (<em>"ok"</em>), the
number of indexes before and after the operation
(<em>"numIndexesBefore"</em> and
<em>"numIndexesAfter"</em>), and whether the collection that the
index belongs to has been created
(<em>"createdCollectionAutomatically"</em>). If the index already
existed and did not need to be created, a <em>"note"</em> field may
be present in lieu of <em>"numIndexesAfter"</em>.
</p>
<p class="para">
With MongoDB 2.4 and earlier, a status document is only returned if the
<a href="mongo.writeconcerns.html" class="link">write concern</a> is at least
<em>1</em>. Otherwise, <strong><code>TRUE</code></strong> is returned. The fields in the status
document are different, except for the <em>"ok"</em> field, which
signals whether the index creation was successful. Additional fields are
described in the documentation for
<span class="function"><a href="mongocollection.insert.html" class="function">MongoCollection::insert()</a></span>.
</p>
</div>
<div class="refsect1 changelog" id="refsect1-mongocollection.ensureindex-changelog">
<h3 class="title">Changelog</h3>
<p class="para">
<table class="doctable informaltable">
<thead>
<tr>
<th>Version</th>
<th>Description</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td>1.5.0</td>
<td>
<p class="para">
Renamed the <em>"wtimeout"</em> option to
<em>"wTimeoutMS"</em>. Emits
<strong><code>E_DEPRECATED</code></strong> when <em>"wtimeout"</em> is
used.
</p>
<p class="para">
Renamed the <em>"timeout"</em> option to
<em>"socketTimeoutMS"</em>. Emits
<strong><code>E_DEPRECATED</code></strong> when <em>"timeout"</em> is
used.
</p>
<p class="para">
Emits <strong><code>E_DEPRECATED</code></strong> when <em>"safe"</em>
is used.
</p>
</td>
</tr>
<tr>
<td>1.3.4</td>
<td>Added <em>"wtimeout"</em> option.</td>
</tr>
<tr>
<td>1.3.0</td>
<td>
<p class="para">Added <em>"w"</em> option.</p>
<p class="para">
The <code class="parameter">options</code> parameter no longer accepts a
boolean to signify a unique index. Instead, this now has to be done
with <em>array('unique' => true)</em>.
</p>
</td>
</tr>
<tr>
<td>1.2.11</td>
<td>
Emits <strong><code>E_DEPRECATED</code></strong> when
<code class="parameter">options</code> is <span class="type"><span class="type scalar">scalar</span></span>.
</td>
</tr>
<tr>
<td>1.2.0</td>
<td>Added <em>"timeout"</em> option.</td>
</tr>
<tr>
<td>1.0.11</td>
<td>
<p class="para">
The <em>"safe"</em> option will trigger a primary failover,
if necessary.
</p>
<p class="para">
<a href="class.mongoexception.html" class="classname">MongoException</a> will be thrown if the index name
(either generated or set) is longer than 128 bytes.
</p>
</td>
</tr>
<tr>
<td>1.0.5</td>
<td>
Added the <em>"name"</em> option to override index name
creation.
</td>
</tr>
<tr>
<td>1.0.2</td>
<td>
Changed <code class="parameter">options</code> parameter from boolean to array.
Pre-1.0.2, the second parameter was an optional boolean value specifying
a unique index.
</td>
</tr>
</tbody>
</table>
</p>
</div>
<div class="refsect1 errors" id="refsect1-mongocollection.ensureindex-errors">
<h3 class="title">Errors/Exceptions</h3>
<p class="para">
Throws <a href="class.mongoexception.html" class="classname">MongoException</a> if the index name is longer
than 128 bytes, or if the index specification is not an array.
</p>
<p class="para">
Throws <a href="class.mongoduplicatekeyexception.html" class="classname">MongoDuplicateKeyException</a> if the server could not
create the unique index due to conflicting documents.
</p>
<p class="para">
Throws <a href="class.mongoresultexception.html" class="classname">MongoResultException</a> if the server could not
create the index due to an error.
</p>
<p class="para">Throws <a href="class.mongocursorexception.html" class="classname">MongoCursorException</a> if the <em>"w"</em> option is set and the write fails.</p><p class="para">Throws <a href="class.mongocursortimeoutexception.html" class="classname">MongoCursorTimeoutException</a> if the <em>"w"</em> option is set to a value greater than one and the operation takes longer than <var class="varname"><var class="varname">MongoCursor::$timeout</var></var> milliseconds to complete. This does not kill the operation on the server, it is a client-side timeout. The operation in <var class="varname"><var class="varname">MongoCollection::$wtimeout</var></var> is milliseconds.</p>
</div>
<div class="refsect1 examples" id="refsect1-mongocollection.ensureindex-examples">
<h3 class="title">Examples</h3>
<div class="example" id="mongocollection.aggregate.example.zipcode.explain">
<p><strong>Example #1 <span class="function"><strong>MongoCollection::ensureIndex()</strong></span> example</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br />$c </span><span style="color: #007700">= new </span><span style="color: #0000BB">MongoCollection</span><span style="color: #007700">(</span><span style="color: #0000BB">$db</span><span style="color: #007700">, </span><span style="color: #DD0000">'foo'</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// create an index on 'x' ascending<br /></span><span style="color: #0000BB">$c</span><span style="color: #007700">-></span><span style="color: #0000BB">ensureIndex</span><span style="color: #007700">(array(</span><span style="color: #DD0000">'x' </span><span style="color: #007700">=> </span><span style="color: #0000BB">1</span><span style="color: #007700">));<br /><br /></span><span style="color: #FF8000">// create a unique index on 'y'<br /></span><span style="color: #0000BB">$c</span><span style="color: #007700">-></span><span style="color: #0000BB">ensureIndex</span><span style="color: #007700">(array(</span><span style="color: #DD0000">'y' </span><span style="color: #007700">=> </span><span style="color: #0000BB">1</span><span style="color: #007700">), array(</span><span style="color: #DD0000">'unique' </span><span style="color: #007700">=> </span><span style="color: #0000BB">true</span><span style="color: #007700">));<br /><br /></span><span style="color: #FF8000">// create a compound index on 'za' ascending and 'zb' descending<br /></span><span style="color: #0000BB">$c</span><span style="color: #007700">-></span><span style="color: #0000BB">ensureIndex</span><span style="color: #007700">(array(</span><span style="color: #DD0000">'za' </span><span style="color: #007700">=> </span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #DD0000">'zb' </span><span style="color: #007700">=> -</span><span style="color: #0000BB">1</span><span style="color: #007700">));<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<div class="example" id="example-1582">
<p><strong>Example #2 Geospatial Indexing</strong></p>
<div class="example-contents"><p>
Mongo supports geospatial indexes, which allow you to search for documents
near a given location or within a shape. The following example creates a
geospatial index on the <em>"loc"</em> field:
</p></div>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br />$collection</span><span style="color: #007700">-></span><span style="color: #0000BB">ensureIndex</span><span style="color: #007700">(array(</span><span style="color: #DD0000">'loc' </span><span style="color: #007700">=> </span><span style="color: #DD0000">'2dsphere'</span><span style="color: #007700">));<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<div class="example" id="example-1583">
<p><strong>Example #3 Drop duplicates example</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br />$collection</span><span style="color: #007700">-></span><span style="color: #0000BB">insert</span><span style="color: #007700">(array(</span><span style="color: #DD0000">'username' </span><span style="color: #007700">=> </span><span style="color: #DD0000">'joeschmoe'</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">$collection</span><span style="color: #007700">-></span><span style="color: #0000BB">insert</span><span style="color: #007700">(array(</span><span style="color: #DD0000">'username' </span><span style="color: #007700">=> </span><span style="color: #DD0000">'joeschmoe'</span><span style="color: #007700">));<br /><br /></span><span style="color: #FF8000">/* Index creation fails, since you cannot create a unique index on a field when<br /> * duplicates exist.<br /> */<br /></span><span style="color: #0000BB">$collection</span><span style="color: #007700">-></span><span style="color: #0000BB">ensureIndex</span><span style="color: #007700">(array(</span><span style="color: #DD0000">'username' </span><span style="color: #007700">=> </span><span style="color: #0000BB">1</span><span style="color: #007700">), array(</span><span style="color: #DD0000">'unique' </span><span style="color: #007700">=> </span><span style="color: #0000BB">1</span><span style="color: #007700">));<br /><br /></span><span style="color: #FF8000">/* MongoDB will one of the conflicting documents and allow the unique index to<br /> * be created.<br /> */<br /></span><span style="color: #0000BB">$collection</span><span style="color: #007700">-></span><span style="color: #0000BB">ensureIndex</span><span style="color: #007700">(array(</span><span style="color: #DD0000">'username' </span><span style="color: #007700">=> </span><span style="color: #0000BB">1</span><span style="color: #007700">), array(</span><span style="color: #DD0000">'unique' </span><span style="color: #007700">=> </span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #DD0000">'dropDups' </span><span style="color: #007700">=> </span><span style="color: #0000BB">1</span><span style="color: #007700">));<br /><br /></span><span style="color: #FF8000">/* We now have a unique index and subsequent inserts with the same username will<br /> * fail.<br /> */<br /></span><span style="color: #0000BB">$collection</span><span style="color: #007700">-></span><span style="color: #0000BB">insert</span><span style="color: #007700">(array(</span><span style="color: #DD0000">'username' </span><span style="color: #007700">=> </span><span style="color: #DD0000">'joeschmoe'</span><span style="color: #007700">));<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</div>
<div class="refsect1 seealso" id="refsect1-mongocollection.ensureindex-seealso">
<h3 class="title">See Also</h3>
<ul class="simplelist">
<li class="member"><span class="methodname"><a href="mongocollection.createindex.html" class="methodname" rel="rdfs-seeAlso">MongoCollection::createIndex()</a> - Creates an index on the specified field(s) if it does not already exist</span></li>
<li class="member"><span class="methodname"><a href="mongocollection.deleteindex.html" class="methodname" rel="rdfs-seeAlso">MongoCollection::deleteIndex()</a> - Deletes an index from this collection</span></li>
<li class="member"><span class="methodname"><a href="mongocollection.deleteindexes.html" class="methodname" rel="rdfs-seeAlso">MongoCollection::deleteIndexes()</a> - Delete all indices for this collection</span></li>
<li class="member">
The MongoDB
<a href="https://docs.mongodb.com/manual/indexes/" class="link external">» index</a> and
<a href="https://docs.mongodb.com/manual/core/index-types/" class="link external">» index type</a>
documentation.
</li>
</ul>
</div>
</div><hr /><div class="manualnavbar" style="text-align: center;">
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