php-doc-en/reference/mongo/mongocollection/createindex.xml

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<refentry xml:id="mongocollection.createindex" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 <refnamediv>
  <refname>MongoCollection::createIndex</refname>
  <refpurpose>
   Creates an index on the specified field(s) if it does not already exist
  </refpurpose>
 </refnamediv>

 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <modifier>public</modifier> <type>bool</type><methodname>MongoCollection::createIndex</methodname>
   <methodparam><type>array</type><parameter>keys</parameter></methodparam>
   <methodparam choice="opt"><type>array</type><parameter>options</parameter><initializer>array()</initializer></methodparam>
  </methodsynopsis>
  <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).
  </para>
  <note>
   <para>
    This method will use the
    <link xlink:href="&url.mongodb.docs.command;createIndexes">createIndexes</link>
    database command when communicating with MongoDB 2.6+. For previous database
    versions, the method will perform an insert operation on the
    special <literal>system.indexes</literal> collection.
   </para>
  </note>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term>
      <parameter>keys</parameter>
     </term>
     <listitem>
      <para>
       An array specifying the index's fields as its keys. For each field, the
       value is either the index direction or
       <link xlink:href="&url.mongodb.dochub.indexes.types;">index type</link>.
       If specifying direction, specify <literal>1</literal> for ascending or
       <literal>-1</literal> for descending.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term>
      <parameter>options</parameter>
     </term>
     <listitem>
      <para>
       An array of options for the index creation. We pass all given options
       straight to the server, but a non-exhaustive list of currently
       available options include:
       <itemizedlist>
        &mongo.index.parameters.unique;
        &mongo.index.parameters.sparse;
        &mongo.index.parameters.expireafterseconds;
        &mongo.index.parameters.name;
        &mongo.index.parameters.background;
        &mongo.writes.parameters.sockettimeoutms;
       </itemizedlist>
      </para>
      <para>
       The following option may be used with MongoDB 2.6+:
       <itemizedlist>
        &mongo.command.parameters.maxtimems;
       </itemizedlist>
      </para>
      <para>
       The following options may be used with MongoDB versions before 2.8:
       <itemizedlist>
        &mongo.index.parameters.dropdups;
       </itemizedlist>
      </para>
      <para>
       The following options may be used with MongoDB versions before 2.6:
       <itemizedlist>
        &mongo.writes.parameters.writeconcern;
        &mongo.writes.parameters.writeconcerntimeoutms;
       </itemizedlist>
      </para>
      <para>
       The following options are deprecated and should no longer be used:
       <itemizedlist>
        &mongo.writes.parameters.safe;
        &mongo.writes.parameters.timeout;
        &mongo.writes.parameters.writeconcerntimeout;
       </itemizedlist>
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns an array containing the status of the index creation. The array
   contains whether the operation succeeded (<literal>"ok"</literal>), the
   number of indexes before and after the operation
   (<literal>"numIndexesBefore"</literal> and
   <literal>"numIndexesAfter"</literal>), and whether the collection that the
   index belongs to has been created
   (<literal>"createdCollectionAutomatically"</literal>). If the index already
   existed and did not need to be created, a <literal>"note"</literal> field may
   be present in lieu of <literal>"numIndexesAfter"</literal>.
  </para>
  <para>
   With MongoDB 2.4 and earlier, a status document is only returned if the
   <link linkend="mongo.writeconcerns">write concern</link> is at least
   <literal>1</literal>. Otherwise, &true; is returned. The fields in the status
   document are different, except for the <literal>"ok"</literal> field, which
   signals whether the index creation was successful. Additional fields are
   described in the documentation for
   <function>MongoCollection::insert</function>.
  </para>
 </refsect1>

 <refsect1 role="errors">
  &reftitle.errors;
  <para>
   Throws <classname>MongoException</classname> if the index name is longer
   than 128 bytes, or if the index specification is not an array.
  </para>
  <para>
   Throws <classname>MongoDuplicateKeyException</classname> if the server could not
   create the unique index due to conflicting documents.
  </para>
  <para>
   Throws <classname>MongoResultException</classname> if the server could not
   create the index due to an error.
  </para>
  &mongo.errors.exceptions.writeconcern;
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <example>
   <title><function>MongoCollection::createIndex</function> example</title>
   <programlisting role="php">
<![CDATA[
<?php

$c = new MongoCollection($db, 'foo');

// create an index on 'x' ascending
$c->createIndex(array('x' => 1));

// create a unique index on 'y'
$c->createIndex(array('y' => 1), array('unique' => true));

// create a compound index on 'za' ascending and 'zb' descending
$c->createIndex(array('za' => 1, 'zb' => -1));

?>
]]>
   </programlisting>
  </example>
  <example>
   <title>Geospatial Indexing</title>
   <para>
    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 <literal>"loc"</literal> field:
   </para>
   <programlisting role="php">
<![CDATA[
<?php

$collection->createIndex(array('loc' => '2dsphere'));

?>
]]>
   </programlisting>
  </example>
  <example>
   <title>Drop duplicates example</title>
   <programlisting role="php">
<![CDATA[
<?php

$collection->insert(array('username' => 'joeschmoe'));
$collection->insert(array('username' => 'joeschmoe'));

/* Index creation fails, since you cannot create a unique index on a field when
 * duplicates exist.
 */
$collection->createIndex(array('username' => 1), array('unique' => 1));

/* MongoDB will one of the conflicting documents and allow the unique index to
 * be created.
 */
$collection->createIndex(array('username' => 1), array('unique' => 1, 'dropDups' => 1));

/* We now have a unique index and subsequent inserts with the same username will
 * fail.
 */
$collection->insert(array('username' => 'joeschmoe'));

?>
]]>
   </programlisting>
  </example>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <simplelist>
   <member><methodname>MongoCollection::deleteIndex</methodname></member>
   <member><methodname>MongoCollection::deleteIndexes</methodname></member>
   <member>
    The MongoDB
    <link xlink:href="&url.mongodb.dochub.indexes;">index</link> and
    <link xlink:href="&url.mongodb.dochub.indexes.types;">index type</link>
    documentation.
   </member>
  </simplelist>
 </refsect1>

</refentry>
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