=======
Indexes
=======
.. default-domain:: mongodb
Indexes support the efficient execution of queries in MongoDB. Without indexes,
MongoDB must perform a *collection scan*, i.e. scan every document in a
collection, to select those documents that match the query statement. If an
appropriate index exists for a query, MongoDB can use the index to limit the
number of documents it must inspect.
The PHP driver supports managing indexes through the
:phpclass:`MongoDB\\Collection` class, which implements MongoDB's
cross-driver `Index Management
<https://github.com/mongodb/specifications/blob/master/source/index-management.rst>`_
and `Enumerating Indexes
<https://github.com/mongodb/specifications/blob/master/source/enumerate-indexes.rst>`_
specifications.
This document provides an introduction to creating, listing, and dropping
indexes using the |php-library|. The MongoDB Manual's :manual:`Indexes
</indexes>` reference provides more thorough information about indexing in
MongoDB.
Create Indexes
--------------
Create indexes with the :phpmethod:`MongoDB\\Collection::createIndex()` or
:phpmethod:`MongoDB\\Collection::createIndexes()` methods. Refer to the method
reference for more details about each method.
The following example creates an ascending index on the ``state`` field using
the :phpmethod:`createIndex() <MongoDB\\Collection::createIndex>` method:
.. code-block:: php
<?php
$collection = (new MongoDB\Client)->test->zips;
$result = $collection->createIndex(['state' => 1]);
var_dump($result);
When you create an index, the method returns its name, which is automatically
generated from its specification. The above example would output something
similar to::
string(7) "state_1"
List Indexes
------------
The :phpmethod:`MongoDB\\Collection::listIndexes()` method provides information
about the indexes in a collection. The
:phpmethod:`MongoDB\\Collection::listIndexes()` method returns an iterator of
:phpclass:`MongoDB\\Model\\IndexInfo` objects, which you can use to view
information about each index. Refer to the method reference for more details.
The following example lists all indexes in the ``zips`` collection in the
``test`` database:
.. code-block:: php
<?php
$collection = (new MongoDB\Client)->test->zips;
foreach ($collection->listIndexes() as $indexInfo) {
var_dump($indexInfo);
}
The output would resemble::
object(MongoDB\Model\IndexInfo)#10 (4) {
["v"]=>
int(1)
["key"]=>
array(1) {
["_id"]=>
int(1)
}
["name"]=>
string(4) "_id_"
["ns"]=>
string(9) "test.zips"
}
object(MongoDB\Model\IndexInfo)#13 (4) {
["v"]=>
int(1)
["key"]=>
array(1) {
["state"]=>
int(1)
}
["name"]=>
string(7) "state_1"
["ns"]=>
string(9) "test.zips"
}
Drop Indexes
------------
The :phpmethod:`MongoDB\\Collection::dropIndex()` method lets you drop a single
index while :phpmethod:`MongoDB\\Collection::dropIndexes()` drops all of the
indexes on a collection. Refer to the method reference for more details about
each method.
The following example drops a single index by its name, ``state_1``:
.. code-block:: php
<?php
$collection = (new MongoDB\Client)->test->zips;
$result = $collection->dropIndex('state_1');
var_dump($result);
The operation's output would resemble::
object(MongoDB\Model\BSONDocument)#11 (1) {
["storage":"ArrayObject":private]=>
array(2) {
["nIndexesWas"]=>
int(2)
["ok"]=>
float(1)
}
}
|
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