Merge pull request #238

Author: jmikola

Resources/doc/index.rst

@@ -738,6 +738,17 @@ same than the `entity` provider described in :doc:`the cookbook</cookbook/securi
             </provider>
         </config>
 
+Validation
+----------
+
+This bundle provides a ``Unique`` constraint, which extends the `UniqueEntity`_
+constraint provided by Symfony's Doctrine bridge. This constraint allows you to
+validate the uniqueness of an document field against the database.
+
+The ``Unique`` constraint shares the same options as `UniqueEntity`_, which
+means that the ``em`` option should be used if you wish to specify the document
+manager explicitly instead of having it be inferred from the document class.
+
 Using the Abstraction Layer
 ---------------------------
 
@@ -792,3 +803,4 @@ Learn more from the Cookbook
 .. _`Conditional Operators`: http://www.doctrine-project.org/docs/mongodb_odm/1.0/en/reference/query-builder-api.html#conditional-operators
 .. _`Event Documentation`: http://www.doctrine-project.org/docs/mongodb_odm/1.0/en/reference/events.html
 .. _`PHP Documentation`: http://www.php.net/manual/en/mongo.tutorial.php
+.. _`UniqueEntity`: http://symfony.com/doc/current/reference/constraints/UniqueEntity.html