diff --git a/extensions/mongo/ActiveQuery.php b/extensions/mongo/ActiveQuery.php
new file mode 100644
index 00000000000..fc02df93632
--- /dev/null
+++ b/extensions/mongo/ActiveQuery.php
@@ -0,0 +1,107 @@
+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\mongo;
+
+use yii\db\ActiveQueryInterface;
+use yii\db\ActiveQueryTrait;
+
+/**
+ * ActiveQuery represents a Mongo query associated with an Active Record class.
+ *
+ * ActiveQuery instances are usually created by [[ActiveRecord::find()]].
+ *
+ * Because ActiveQuery extends from [[Query]], one can use query methods, such as [[where()]],
+ * [[orderBy()]] to customize the query options.
+ *
+ * ActiveQuery also provides the following additional query options:
+ *
+ * - [[with()]]: list of relations that this query should be performed with.
+ * - [[asArray()]]: whether to return each record as an array.
+ *
+ * These options can be configured using methods of the same name. For example:
+ *
+ * ~~~
+ * $customers = Customer::find()->with('orders')->asArray()->all();
+ * ~~~
+ *
+ * @author Paul Klimov <klimov.paul@gmail.com>
+ * @since 2.0
+ */
+class ActiveQuery extends Query implements ActiveQueryInterface
+{
+	use ActiveQueryTrait;
+
+	/**
+	 * Executes query and returns all results as an array.
+	 * @param Connection $db the Mongo connection used to execute the query.
+	 * If null, the Mongo connection returned by [[modelClass]] will be used.
+	 * @return array the query results. If the query results in nothing, an empty array will be returned.
+	 */
+	public function all($db = null)
+	{
+		$cursor = $this->buildCursor($db);
+		$rows = $this->fetchRows($cursor);
+		if (!empty($rows)) {
+			$models = $this->createModels($rows);
+			if (!empty($this->with)) {
+				$this->findWith($this->with, $models);
+			}
+			return $models;
+		} else {
+			return [];
+		}
+	}
+
+	/**
+	 * Executes query and returns a single row of result.
+	 * @param Connection $db the Mongo connection used to execute the query.
+	 * If null, the Mongo connection returned by [[modelClass]] will be used.
+	 * @return ActiveRecord|array|null a single row of query result. Depending on the setting of [[asArray]],
+	 * the query result may be either an array or an ActiveRecord object. Null will be returned
+	 * if the query results in nothing.
+	 */
+	public function one($db = null)
+	{
+		$row = parent::one($db);
+		if ($row !== false) {
+			if ($this->asArray) {
+				$model = $row;
+			} else {
+				/** @var ActiveRecord $class */
+				$class = $this->modelClass;
+				$model = $class::create($row);
+			}
+			if (!empty($this->with)) {
+				$models = [$model];
+				$this->findWith($this->with, $models);
+				$model = $models[0];
+			}
+			return $model;
+		} else {
+			return null;
+		}
+	}
+
+	/**
+	 * Returns the Mongo collection for this query.
+	 * @param Connection $db Mongo connection.
+	 * @return Collection collection instance.
+	 */
+	public function getCollection($db = null)
+	{
+		/** @var ActiveRecord $modelClass */
+		$modelClass = $this->modelClass;
+		if ($db === null) {
+			$db = $modelClass::getDb();
+		}
+		if ($this->from === null) {
+			$this->from = $modelClass::collectionName();
+		}
+		return $db->getCollection($this->from);
+	}
+}
\ No newline at end of file
diff --git a/extensions/mongo/ActiveRecord.php b/extensions/mongo/ActiveRecord.php
new file mode 100644
index 00000000000..b0a360e9bf4
--- /dev/null
+++ b/extensions/mongo/ActiveRecord.php
@@ -0,0 +1,353 @@
+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\mongo;
+
+use yii\base\InvalidConfigException;
+use yii\base\InvalidParamException;
+use yii\db\BaseActiveRecord;
+use yii\base\UnknownMethodException;
+use yii\db\StaleObjectException;
+use yii\helpers\Inflector;
+use yii\helpers\StringHelper;
+
+/**
+ * ActiveRecord is the base class for classes representing Mongo documents in terms of objects.
+ *
+ * @author Paul Klimov <klimov.paul@gmail.com>
+ * @since 2.0
+ */
+abstract class ActiveRecord extends BaseActiveRecord
+{
+	/**
+	 * Returns the Mongo connection used by this AR class.
+	 * By default, the "mongo" application component is used as the Mongo connection.
+	 * You may override this method if you want to use a different database connection.
+	 * @return Connection the database connection used by this AR class.
+	 */
+	public static function getDb()
+	{
+		return \Yii::$app->getComponent('mongo');
+	}
+
+	/**
+	 * Updates all documents in the collection using the provided attribute values and conditions.
+	 * For example, to change the status to be 1 for all customers whose status is 2:
+	 *
+	 * ~~~
+	 * Customer::updateAll(['status' => 1], ['status' = 2]);
+	 * ~~~
+	 *
+	 * @param array $attributes attribute values (name-value pairs) to be saved into the collection
+	 * @param array $condition description of the objects to update.
+	 * Please refer to [[Query::where()]] on how to specify this parameter.
+	 * @param array $options list of options in format: optionName => optionValue.
+	 * @return integer the number of documents updated.
+	 */
+	public static function updateAll($attributes, $condition = [], $options = [])
+	{
+		return static::getCollection()->update($condition, $attributes, $options);
+	}
+
+	/**
+	 * Updates all documents in the collection using the provided counter changes and conditions.
+	 * For example, to increment all customers' age by 1,
+	 *
+	 * ~~~
+	 * Customer::updateAllCounters(['age' => 1]);
+	 * ~~~
+	 *
+	 * @param array $counters the counters to be updated (attribute name => increment value).
+	 * Use negative values if you want to decrement the counters.
+	 * @param array $condition description of the objects to update.
+	 * Please refer to [[Query::where()]] on how to specify this parameter.
+	 * @param array $options list of options in format: optionName => optionValue.
+	 * @return integer the number of documents updated.
+	 */
+	public static function updateAllCounters($counters, $condition = [], $options = [])
+	{
+		return static::getCollection()->update($condition, ['$inc' => $counters], $options);
+	}
+
+	/**
+	 * Deletes documents in the collection using the provided conditions.
+	 * WARNING: If you do not specify any condition, this method will delete documents rows in the collection.
+	 *
+	 * For example, to delete all customers whose status is 3:
+	 *
+	 * ~~~
+	 * Customer::deleteAll('status = 3');
+	 * ~~~
+	 *
+	 * @param array $condition description of the objects to delete.
+	 * Please refer to [[Query::where()]] on how to specify this parameter.
+	 * @param array $options list of options in format: optionName => optionValue.
+	 * @return integer the number of documents deleted.
+	 */
+	public static function deleteAll($condition = [], $options = [])
+	{
+		$options['w'] = 1;
+		if (!array_key_exists('multiple', $options)) {
+			$options['multiple'] = true;
+		}
+		return static::getCollection()->remove($condition, $options);
+	}
+
+	/**
+	 * Creates an [[ActiveQuery]] instance.
+	 * This method is called by [[find()]] to start a "find" command.
+	 * You may override this method to return a customized query (e.g. `CustomerQuery` specified
+	 * written for querying `Customer` purpose.)
+	 * @return ActiveQuery the newly created [[ActiveQuery]] instance.
+	 */
+	public static function createQuery()
+	{
+		return new ActiveQuery(['modelClass' => get_called_class()]);
+	}
+
+	/**
+	 * Declares the name of the Mongo collection associated with this AR class.
+	 * Collection name can be either a string or array:
+	 *  - if string considered as the name of the collection inside the default database.
+	 *  - if array - first element considered as the name of the database, second - as
+	 * name of collection inside that database
+	 * By default this method returns the class name as the collection name by calling [[Inflector::camel2id()]].
+	 * For example, 'Customer' becomes 'customer', and 'OrderItem' becomes
+	 * 'order_item'. You may override this method if the table is not named after this convention.
+	 * @return string|array the collection name
+	 */
+	public static function collectionName()
+	{
+		return Inflector::camel2id(StringHelper::basename(get_called_class()), '_');
+	}
+
+	/**
+	 * Return the Mongo collection instance for this AR class.
+	 * @return Collection collection instance.
+	 */
+	public static function getCollection()
+	{
+		return static::getDb()->getCollection(static::collectionName());
+	}
+
+	/**
+	 * Returns the primary key name(s) for this AR class.
+	 * The default implementation will return ['_id'].
+	 *
+	 * Note that an array should be returned even for a collection with single primary key.
+	 *
+	 * @return string[] the primary keys of the associated Mongo collection.
+	 */
+	public static function primaryKey()
+	{
+		return ['_id'];
+	}
+
+	/**
+	 * Creates an [[ActiveRelation]] instance.
+	 * This method is called by [[hasOne()]] and [[hasMany()]] to create a relation instance.
+	 * You may override this method to return a customized relation.
+	 * @param array $config the configuration passed to the ActiveRelation class.
+	 * @return ActiveRelation the newly created [[ActiveRelation]] instance.
+	 */
+	public static function createActiveRelation($config = [])
+	{
+		return new ActiveRelation($config);
+	}
+
+	/**
+	 * Returns the list of all attribute names of the model.
+	 * This method must be overridden by child classes to define available attributes.
+	 * Note: primary key attribute "_id" should be always present in returned array.
+	 * For example:
+	 * ~~~
+	 * public function attributes()
+	 * {
+	 *     return ['_id', 'name', 'address', 'status'];
+	 * }
+	 * ~~~
+	 * @return array list of attribute names.
+	 */
+	public function attributes()
+	{
+		throw new InvalidConfigException('The attributes() method of mongo ActiveRecord has to be implemented by child classes.');
+	}
+
+	/**
+	 * Inserts a row into the associated Mongo collection using the attribute values of this record.
+	 *
+	 * This method performs the following steps in order:
+	 *
+	 * 1. call [[beforeValidate()]] when `$runValidation` is true. If validation
+	 *    fails, it will skip the rest of the steps;
+	 * 2. call [[afterValidate()]] when `$runValidation` is true.
+	 * 3. call [[beforeSave()]]. If the method returns false, it will skip the
+	 *    rest of the steps;
+	 * 4. insert the record into collection. If this fails, it will skip the rest of the steps;
+	 * 5. call [[afterSave()]];
+	 *
+	 * In the above step 1, 2, 3 and 5, events [[EVENT_BEFORE_VALIDATE]],
+	 * [[EVENT_BEFORE_INSERT]], [[EVENT_AFTER_INSERT]] and [[EVENT_AFTER_VALIDATE]]
+	 * will be raised by the corresponding methods.
+	 *
+	 * Only the [[dirtyAttributes|changed attribute values]] will be inserted into database.
+	 *
+	 * If the primary key  is null during insertion, it will be populated with the actual
+	 * value after insertion.
+	 *
+	 * For example, to insert a customer record:
+	 *
+	 * ~~~
+	 * $customer = new Customer;
+	 * $customer->name = $name;
+	 * $customer->email = $email;
+	 * $customer->insert();
+	 * ~~~
+	 *
+	 * @param boolean $runValidation whether to perform validation before saving the record.
+	 * If the validation fails, the record will not be inserted into the collection.
+	 * @param array $attributes list of attributes that need to be saved. Defaults to null,
+	 * meaning all attributes that are loaded will be saved.
+	 * @return boolean whether the attributes are valid and the record is inserted successfully.
+	 * @throws \Exception in case insert failed.
+	 */
+	public function insert($runValidation = true, $attributes = null)
+	{
+		if ($runValidation && !$this->validate($attributes)) {
+			return false;
+		}
+		$result = $this->insertInternal($attributes);
+		return $result;
+	}
+
+	/**
+	 * @see ActiveRecord::insert()
+	 */
+	protected function insertInternal($attributes = null)
+	{
+		if (!$this->beforeSave(true)) {
+			return false;
+		}
+		$values = $this->getDirtyAttributes($attributes);
+		if (empty($values)) {
+			$currentAttributes = $this->getAttributes();
+			foreach ($this->primaryKey() as $key) {
+				$values[$key] = isset($currentAttributes[$key]) ? $currentAttributes[$key] : null;
+			}
+		}
+		$collection = static::getCollection();
+		$newId = $collection->insert($values);
+		$this->setAttribute('_id', $newId);
+		foreach ($values as $name => $value) {
+			$this->setOldAttribute($name, $value);
+		}
+		$this->afterSave(true);
+		return true;
+	}
+
+	/**
+	 * @see ActiveRecord::update()
+	 * @throws StaleObjectException
+	 */
+	protected function updateInternal($attributes = null)
+	{
+		if (!$this->beforeSave(false)) {
+			return false;
+		}
+		$values = $this->getDirtyAttributes($attributes);
+		if (empty($values)) {
+			$this->afterSave(false);
+			return 0;
+		}
+		$condition = $this->getOldPrimaryKey(true);
+		$lock = $this->optimisticLock();
+		if ($lock !== null) {
+			if (!isset($values[$lock])) {
+				$values[$lock] = $this->$lock + 1;
+			}
+			$condition[$lock] = $this->$lock;
+		}
+		// We do not check the return value of update() because it's possible
+		// that it doesn't change anything and thus returns 0.
+		$rows = static::getCollection()->update($condition, $values);
+
+		if ($lock !== null && !$rows) {
+			throw new StaleObjectException('The object being updated is outdated.');
+		}
+
+		foreach ($values as $name => $value) {
+			$this->setOldAttribute($name, $this->getAttribute($name));
+		}
+		$this->afterSave(false);
+		return $rows;
+	}
+
+	/**
+	 * Deletes the document corresponding to this active record from the collection.
+	 *
+	 * This method performs the following steps in order:
+	 *
+	 * 1. call [[beforeDelete()]]. If the method returns false, it will skip the
+	 *    rest of the steps;
+	 * 2. delete the document from the collection;
+	 * 3. call [[afterDelete()]].
+	 *
+	 * In the above step 1 and 3, events named [[EVENT_BEFORE_DELETE]] and [[EVENT_AFTER_DELETE]]
+	 * will be raised by the corresponding methods.
+	 *
+	 * @return integer|boolean the number of documents deleted, or false if the deletion is unsuccessful for some reason.
+	 * Note that it is possible the number of documents deleted is 0, even though the deletion execution is successful.
+	 * @throws StaleObjectException if [[optimisticLock|optimistic locking]] is enabled and the data
+	 * being deleted is outdated.
+	 * @throws \Exception in case delete failed.
+	 */
+	public function delete()
+	{
+		$result = false;
+		if ($this->beforeDelete()) {
+			$result = $this->deleteInternal();
+			$this->afterDelete();
+		}
+		return $result;
+	}
+
+	/**
+	 * @see ActiveRecord::delete()
+	 * @throws StaleObjectException
+	 */
+	protected function deleteInternal()
+	{
+		// we do not check the return value of deleteAll() because it's possible
+		// the record is already deleted in the database and thus the method will return 0
+		$condition = $this->getOldPrimaryKey(true);
+		$lock = $this->optimisticLock();
+		if ($lock !== null) {
+			$condition[$lock] = $this->$lock;
+		}
+		$result = static::getCollection()->remove($condition);
+		if ($lock !== null && !$result) {
+			throw new StaleObjectException('The object being deleted is outdated.');
+		}
+		$this->setOldAttributes(null);
+		return $result;
+	}
+
+	/**
+	 * Returns a value indicating whether the given active record is the same as the current one.
+	 * The comparison is made by comparing the table names and the primary key values of the two active records.
+	 * If one of the records [[isNewRecord|is new]] they are also considered not equal.
+	 * @param ActiveRecord $record record to compare to
+	 * @return boolean whether the two active records refer to the same row in the same Mongo collection.
+	 */
+	public function equals($record)
+	{
+		if ($this->isNewRecord || $record->isNewRecord) {
+			return false;
+		}
+		return $this->collectionName() === $record->collectionName() && $this->getPrimaryKey() === $record->getPrimaryKey();
+	}
+}
\ No newline at end of file
diff --git a/extensions/mongo/ActiveRelation.php b/extensions/mongo/ActiveRelation.php
new file mode 100644
index 00000000000..539dc7b186f
--- /dev/null
+++ b/extensions/mongo/ActiveRelation.php
@@ -0,0 +1,22 @@
+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\mongo;
+
+use yii\db\ActiveRelationInterface;
+use yii\db\ActiveRelationTrait;
+
+/**
+ * ActiveRelation represents a relation to Mongo Active Record class.
+ *
+ * @author Paul Klimov <klimov.paul@gmail.com>
+ * @since 2.0
+ */
+class ActiveRelation extends ActiveQuery implements ActiveRelationInterface
+{
+	use ActiveRelationTrait;
+}
\ No newline at end of file
diff --git a/extensions/mongo/Collection.php b/extensions/mongo/Collection.php
new file mode 100644
index 00000000000..e9c37b8e0b8
--- /dev/null
+++ b/extensions/mongo/Collection.php
@@ -0,0 +1,899 @@
+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\mongo;
+
+use yii\base\InvalidParamException;
+use yii\base\Object;
+use Yii;
+use yii\helpers\Json;
+
+/**
+ * Collection represents the Mongo collection information.
+ *
+ * A collection object is usually created by calling [[Database::getCollection()]] or [[Connection::getCollection()]].
+ *
+ * Collection provides the basic interface for the Mongo queries, mostly: insert, update, delete operations.
+ * For example:
+ *
+ * ~~~
+ * $collection = Yii::$app->mongo->getCollection('customer');
+ * $collection->insert(['name' => 'John Smith', 'status' => 1]);
+ * ~~~
+ *
+ * To perform "find" queries, please use [[Query]] instead.
+ *
+ * Mongo uses JSON format to specify query conditions with quite specific syntax.
+ * However Collection class provides the ability of "translating" common condition format used "yii\db\*"
+ * into Mongo condition.
+ * For example:
+ * ~~~
+ * $condition = [
+ *     [
+ *         'OR',
+ *         ['AND', ['first_name' => 'John'], ['last_name' => 'Smith']],
+ *         ['status' => [1, 2, 3]]
+ *     ],
+ * ];
+ * print_r($collection->buildCondition($condition));
+ * // outputs :
+ * [
+ *     '$or' => [
+ *         [
+ *             'first_name' => 'John',
+ *             'last_name' => 'John',
+ *         ],
+ *         [
+ *             'status' => ['$in' => [1, 2, 3]],
+ *         ]
+ *     ]
+ * ]
+ * ~~~
+ *
+ * Note: condition values for the key '_id' will be automatically cast to [[\MongoId]] instance,
+ * even if they are plain strings. However if you have other columns, containing [[\MongoId]], you
+ * should take care of possible typecast on your own.
+ *
+ * @property string $name name of this collection. This property is read-only.
+ * @property string $fullName full name of this collection, including database name. This property is read-only.
+ * @property array $lastError last error information. This property is read-only.
+ *
+ * @author Paul Klimov <klimov.paul@gmail.com>
+ * @since 2.0
+ */
+class Collection extends Object
+{
+	/**
+	 * @var \MongoCollection Mongo collection instance.
+	 */
+	public $mongoCollection;
+
+	/**
+	 * @return string name of this collection.
+	 */
+	public function getName()
+	{
+		return $this->mongoCollection->getName();
+	}
+
+	/**
+	 * @return string full name of this collection, including database name.
+	 */
+	public function getFullName()
+	{
+		return $this->mongoCollection->__toString();
+	}
+
+	/**
+	 * @return array last error information.
+	 */
+	public function getLastError()
+	{
+		return $this->mongoCollection->db->lastError();
+	}
+
+	/**
+	 * Composes log/profile token.
+	 * @param string $command command name
+	 * @param array $arguments command arguments.
+	 * @return string token.
+	 */
+	protected function composeLogToken($command, $arguments = [])
+	{
+		$parts = [];
+		foreach ($arguments as $argument) {
+			$parts[] = is_scalar($argument) ? $argument : Json::encode($argument);
+		}
+		return $this->getFullName() . '.' . $command . '(' . implode(', ', $parts) . ')';
+	}
+
+	/**
+	 * Drops this collection.
+	 * @throws Exception on failure.
+	 * @return boolean whether the operation successful.
+	 */
+	public function drop()
+	{
+		$token = $this->composeLogToken('drop');
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			$result = $this->mongoCollection->drop();
+			$this->tryResultError($result);
+			Yii::endProfile($token, __METHOD__);
+			return true;
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Creates an index on the collection and the specified fields.
+	 * @param array|string $columns column name or list of column names.
+	 * If array is given, each element in the array has as key the field name, and as
+	 * value either 1 for ascending sort, or -1 for descending sort.
+	 * You can specify field using native numeric key with the field name as a value,
+	 * in this case ascending sort will be used.
+	 * For example:
+	 * ~~~
+	 * [
+	 *     'name',
+	 *     'status' => -1,
+	 * ]
+	 * ~~~
+	 * @param array $options list of options in format: optionName => optionValue.
+	 * @throws Exception on failure.
+	 * @return boolean whether the operation successful.
+	 */
+	public function createIndex($columns, $options = [])
+	{
+		if (!is_array($columns)) {
+			$columns = [$columns];
+		}
+		$keys = $this->normalizeIndexKeys($columns);
+		$token = $this->composeLogToken('createIndex', [$keys, $options]);
+		$options = array_merge(['w' => 1], $options);
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			$result = $this->mongoCollection->ensureIndex($keys, $options);
+			$this->tryResultError($result);
+			Yii::endProfile($token, __METHOD__);
+			return true;
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Drop indexes for specified column(s).
+	 * @param string|array $columns column name or list of column names.
+	 * If array is given, each element in the array has as key the field name, and as
+	 * value either 1 for ascending sort, or -1 for descending sort.
+	 * Use value 'text' to specify text index.
+	 * You can specify field using native numeric key with the field name as a value,
+	 * in this case ascending sort will be used.
+	 * For example:
+	 * ~~~
+	 * [
+	 *     'name',
+	 *     'status' => -1,
+	 *     'description' => 'text',
+	 * ]
+	 * ~~~
+	 * @throws Exception on failure.
+	 * @return boolean whether the operation successful.
+	 */
+	public function dropIndex($columns)
+	{
+		if (!is_array($columns)) {
+			$columns = [$columns];
+		}
+		$keys = $this->normalizeIndexKeys($columns);
+		$token = $this->composeLogToken('dropIndex', [$keys]);
+		Yii::info($token, __METHOD__);
+		try {
+			$result = $this->mongoCollection->deleteIndex($keys);
+			$this->tryResultError($result);
+			return true;
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Compose index keys from given columns/keys list.
+	 * @param array $columns raw columns/keys list.
+	 * @return array normalizes index keys array.
+	 */
+	protected function normalizeIndexKeys($columns)
+	{
+		$keys = [];
+		foreach ($columns as $key => $value) {
+			if (is_numeric($key)) {
+				$keys[$value] = \MongoCollection::ASCENDING;
+			} else {
+				$keys[$key] = $value;
+			}
+		}
+		return $keys;
+	}
+
+	/**
+	 * Drops all indexes for this collection.
+	 * @throws Exception on failure.
+	 * @return integer count of dropped indexes.
+	 */
+	public function dropAllIndexes()
+	{
+		$token = $this->composeLogToken('dropIndexes');
+		Yii::info($token, __METHOD__);
+		try {
+			$result = $this->mongoCollection->deleteIndexes();
+			$this->tryResultError($result);
+			return $result['nIndexesWas'];
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Returns a cursor for the search results.
+	 * In order to perform "find" queries use [[Query]] class.
+	 * @param array $condition query condition
+	 * @param array $fields fields to be selected
+	 * @return \MongoCursor cursor for the search results
+	 * @see Query
+	 */
+	public function find($condition = [], $fields = [])
+	{
+		return $this->mongoCollection->find($this->buildCondition($condition), $fields);
+	}
+
+	/**
+	 * Inserts new data into collection.
+	 * @param array|object $data data to be inserted.
+	 * @param array $options list of options in format: optionName => optionValue.
+	 * @return \MongoId new record id instance.
+	 * @throws Exception on failure.
+	 */
+	public function insert($data, $options = [])
+	{
+		$token = $this->composeLogToken('insert', [$data]);
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			$options = array_merge(['w' => 1], $options);
+			$this->tryResultError($this->mongoCollection->insert($data, $options));
+			Yii::endProfile($token, __METHOD__);
+			return is_array($data) ? $data['_id'] : $data->_id;
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Inserts several new rows into collection.
+	 * @param array $rows array of arrays or objects to be inserted.
+	 * @param array $options list of options in format: optionName => optionValue.
+	 * @return array inserted data, each row will have "_id" key assigned to it.
+	 * @throws Exception on failure.
+	 */
+	public function batchInsert($rows, $options = [])
+	{
+		$token = $this->composeLogToken('batchInsert', [$rows]);
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			$options = array_merge(['w' => 1], $options);
+			$this->tryResultError($this->mongoCollection->batchInsert($rows, $options));
+			Yii::endProfile($token, __METHOD__);
+			return $rows;
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Updates the rows, which matches given criteria by given data.
+	 * Note: for "multiple" mode Mongo requires explicit strategy "$set" or "$inc"
+	 * to be specified for the "newData". If no strategy is passed "$set" will be used.
+	 * @param array $condition description of the objects to update.
+	 * @param array $newData the object with which to update the matching records.
+	 * @param array $options list of options in format: optionName => optionValue.
+	 * @return integer|boolean number of updated documents or whether operation was successful.
+	 * @throws Exception on failure.
+	 */
+	public function update($condition, $newData, $options = [])
+	{
+		$condition = $this->buildCondition($condition);
+		$options = array_merge(['w' => 1, 'multiple' => true], $options);
+		if ($options['multiple']) {
+			$keys = array_keys($newData);
+			if (!empty($keys) && strncmp('$', $keys[0], 1) !== 0) {
+				$newData = ['$set' => $newData];
+			}
+		}
+		$token = $this->composeLogToken('update', [$condition, $newData, $options]);
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			$result = $this->mongoCollection->update($condition, $newData, $options);
+			$this->tryResultError($result);
+			Yii::endProfile($token, __METHOD__);
+			if (is_array($result) && array_key_exists('n', $result)) {
+				return $result['n'];
+			} else {
+				return true;
+			}
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Update the existing database data, otherwise insert this data
+	 * @param array|object $data data to be updated/inserted.
+	 * @param array $options list of options in format: optionName => optionValue.
+	 * @return \MongoId updated/new record id instance.
+	 * @throws Exception on failure.
+	 */
+	public function save($data, $options = [])
+	{
+		$token = $this->composeLogToken('save', [$data]);
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			$options = array_merge(['w' => 1], $options);
+			$this->tryResultError($this->mongoCollection->save($data, $options));
+			Yii::endProfile($token, __METHOD__);
+			return is_array($data) ? $data['_id'] : $data->_id;
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Removes data from the collection.
+	 * @param array $condition description of records to remove.
+	 * @param array $options list of options in format: optionName => optionValue.
+	 * @return integer|boolean number of updated documents or whether operation was successful.
+	 * @throws Exception on failure.
+	 */
+	public function remove($condition = [], $options = [])
+	{
+		$condition = $this->buildCondition($condition);
+		$options = array_merge(['w' => 1, 'multiple' => true], $options);
+		$token = $this->composeLogToken('remove', [$condition, $options]);
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			$result = $this->mongoCollection->remove($condition, $options);
+			$this->tryResultError($result);
+			Yii::endProfile($token, __METHOD__);
+			if (is_array($result) && array_key_exists('n', $result)) {
+				return $result['n'];
+			} else {
+				return true;
+			}
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Returns a list of distinct values for the given column across a collection.
+	 * @param string $column column to use.
+	 * @param array $condition query parameters.
+	 * @return array|boolean array of distinct values, or "false" on failure.
+	 * @throws Exception on failure.
+	 */
+	public function distinct($column, $condition = [])
+	{
+		$condition = $this->buildCondition($condition);
+		$token = $this->composeLogToken('distinct', [$column, $condition]);
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			$result = $this->mongoCollection->distinct($column, $condition);
+			Yii::endProfile($token, __METHOD__);
+			return $result;
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Performs aggregation using Mongo Aggregation Framework.
+	 * @param array $pipeline list of pipeline operators, or just the first operator
+	 * @param array $pipelineOperator additional pipeline operator. You can specify additional
+	 * pipelines via third argument, fourth argument etc.
+	 * @return array the result of the aggregation.
+	 * @throws Exception on failure.
+	 * @see http://docs.mongodb.org/manual/applications/aggregation/
+	 */
+	public function aggregate($pipeline, $pipelineOperator = [])
+	{
+		$args = func_get_args();
+		$token = $this->composeLogToken('aggregate', $args);
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			$result = call_user_func_array([$this->mongoCollection, 'aggregate'], $args);
+			$this->tryResultError($result);
+			Yii::endProfile($token, __METHOD__);
+			return $result['result'];
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Performs aggregation using Mongo "group" command.
+	 * @param mixed $keys fields to group by. If an array or non-code object is passed,
+	 * it will be the key used to group results. If instance of [[\MongoCode]] passed,
+	 * it will be treated as a function that returns the key to group by.
+	 * @param array $initial Initial value of the aggregation counter object.
+	 * @param \MongoCode|string $reduce function that takes two arguments (the current
+	 * document and the aggregation to this point) and does the aggregation.
+	 * Argument will be automatically cast to [[\MongoCode]].
+	 * @param array $options optional parameters to the group command. Valid options include:
+	 *  - condition - criteria for including a document in the aggregation.
+	 *  - finalize - function called once per unique key that takes the final output of the reduce function.
+	 * @return array the result of the aggregation.
+	 * @throws Exception on failure.
+	 * @see http://docs.mongodb.org/manual/reference/command/group/
+	 */
+	public function group($keys, $initial, $reduce, $options = [])
+	{
+		if (!($reduce instanceof \MongoCode)) {
+			$reduce = new \MongoCode((string)$reduce);
+		}
+		if (array_key_exists('condition', $options)) {
+			$options['condition'] = $this->buildCondition($options['condition']);
+		}
+		if (array_key_exists('finalize', $options)) {
+			if (!($options['finalize'] instanceof \MongoCode)) {
+				$options['finalize'] = new \MongoCode((string)$options['finalize']);
+			}
+		}
+		$token = $this->composeLogToken('group', [$keys, $initial, $reduce, $options]);
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			// Avoid possible E_DEPRECATED for $options:
+			if (empty($options)) {
+				$result = $this->mongoCollection->group($keys, $initial, $reduce);
+			} else {
+				$result = $this->mongoCollection->group($keys, $initial, $reduce, $options);
+			}
+			$this->tryResultError($result);
+
+			Yii::endProfile($token, __METHOD__);
+			if (array_key_exists('retval', $result)) {
+				return $result['retval'];
+			} else {
+				return [];
+			}
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Performs aggregation using Mongo "map reduce" mechanism.
+	 * Note: this function will not return the aggregation result, instead it will
+	 * write it inside the another Mongo collection specified by "out" parameter.
+	 * For example:
+	 *
+	 * ~~~
+	 * $customerCollection = Yii::$app->mongo->getCollection('customer');
+	 * $resultCollectionName = $customerCollection->mapReduce(
+	 *     'function () {emit(this.status, this.amount)}',
+	 *     'function (key, values) {return Array.sum(values)}',
+	 *     'mapReduceOut',
+	 *     ['status' => 3]
+	 * );
+	 * $query = new Query();
+	 * $results = $query->from($resultCollectionName)->all();
+	 * ~~~
+	 *
+	 * @param \MongoCode|string $map function, which emits map data from collection.
+	 * Argument will be automatically cast to [[\MongoCode]].
+	 * @param \MongoCode|string $reduce function that takes two arguments (the map key
+	 * and the map values) and does the aggregation.
+	 * Argument will be automatically cast to [[\MongoCode]].
+	 * @param string|array $out output collection name. It could be a string for simple output
+	 * ('outputCollection'), or an array for parametrized output (['merge' => 'outputCollection'])
+	 * @param array $condition criteria for including a document in the aggregation.
+	 * @return string the map reduce output collection name.
+	 * @throws Exception on failure.
+	 */
+	public function mapReduce($map, $reduce, $out, $condition = [])
+	{
+		if (!($map instanceof \MongoCode)) {
+			$map = new \MongoCode((string)$map);
+		}
+		if (!($reduce instanceof \MongoCode)) {
+			$reduce = new \MongoCode((string)$reduce);
+		}
+		$command = [
+			'mapReduce' => $this->getName(),
+			'map' => $map,
+			'reduce' => $reduce,
+			'out' => $out
+		];
+		if (!empty($condition)) {
+			$command['query'] = $this->buildCondition($condition);
+		}
+		$token = $this->composeLogToken('mapReduce', [$map, $reduce, $out]);
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			$command = array_merge(['mapReduce' => $this->getName()], $command);
+			$result = $this->mongoCollection->db->command($command);
+			$this->tryResultError($result);
+			Yii::endProfile($token, __METHOD__);
+			return $result['result'];
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Performs full text search.
+	 * @param string $search string of terms that MongoDB parses and uses to query the text index.
+	 * @param array $condition criteria for filtering a results list.
+	 * @param array $fields list of fields to be returned in result.
+	 * @param integer $limit the maximum number of documents to include in the response (by default 100).
+	 * @param string $language he language that determines the list of stop words for the search
+	 * and the rules for the stemmer and tokenizer. If not specified, the search uses the default
+	 * language of the index.
+	 * @return array the highest scoring documents, in descending order by score.
+	 * @throws Exception on failure.
+	 */
+	public function fullTextSearch($search, $condition = [], $fields = [], $limit = null, $language = null) {
+		$command = [
+			'search' => $search
+		];
+		if (!empty($condition)) {
+			$command['filter'] = $this->buildCondition($condition);
+		}
+		if (!empty($fields)) {
+			$command['project'] = $fields;
+		}
+		if ($limit !== null) {
+			$command['limit'] = $limit;
+		}
+		if ($language !== null) {
+			$command['language'] = $language;
+		}
+		$token = $this->composeLogToken('text', $command);
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			$command = array_merge(['text' => $this->getName()], $command);
+			$result = $this->mongoCollection->db->command($command);
+			$this->tryResultError($result);
+			Yii::endProfile($token, __METHOD__);
+			return $result['results'];
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Checks if command execution result ended with an error.
+	 * @param mixed $result raw command execution result.
+	 * @throws Exception if an error occurred.
+	 */
+	protected function tryResultError($result)
+	{
+		if (is_array($result)) {
+			if (!empty($result['errmsg'])) {
+				$errorMessage = $result['errmsg'];
+			} elseif (!empty($result['err'])) {
+				$errorMessage = $result['err'];
+			}
+			if (isset($errorMessage)) {
+				if (array_key_exists('code', $result)) {
+					$errorCode = (int)$result['code'];
+				} elseif (array_key_exists('ok', $result)) {
+					$errorCode = (int)$result['ok'];
+				} else {
+					$errorCode = 0;
+				}
+				throw new Exception($errorMessage, $errorCode);
+			}
+		} elseif (!$result) {
+			throw new Exception('Unknown error, use "w=1" option to enable error tracking');
+		}
+	}
+
+	/**
+	 * Throws an exception if there was an error on the last operation.
+	 * @throws Exception if an error occurred.
+	 */
+	protected function tryLastError()
+	{
+		$this->tryResultError($this->getLastError());
+	}
+
+	/**
+	 * Converts user friendly condition keyword into actual Mongo condition keyword.
+	 * @param string $key raw condition key.
+	 * @return string actual key.
+	 */
+	protected function normalizeConditionKeyword($key)
+	{
+		static $map = [
+			'OR' => '$or',
+			'>' => '$gt',
+			'>=' => '$gte',
+			'<' => '$lt',
+			'<=' => '$lte',
+			'!=' => '$ne',
+			'<>' => '$ne',
+			'IN' => '$in',
+			'NOT IN' => '$nin',
+			'ALL' => '$all',
+			'SIZE' => '$size',
+			'TYPE' => '$type',
+			'EXISTS' => '$exists',
+			'NOTEXISTS' => '$exists',
+			'ELEMMATCH' => '$elemMatch',
+			'MOD' => '$mod',
+			'%' => '$mod',
+			'=' => '$$eq',
+			'==' => '$$eq',
+			'WHERE' => '$where'
+		];
+		$matchKey = strtoupper($key);
+		if (array_key_exists($matchKey, $map)) {
+			return $map[$matchKey];
+		} else {
+			return $key;
+		}
+	}
+
+	/**
+	 * Converts given value into [[MongoId]] instance.
+	 * If array given, each element of it will be processed.
+	 * @param mixed $rawId raw id(s).
+	 * @return array|\MongoId normalized id(s).
+	 */
+	protected function ensureMongoId($rawId)
+	{
+		if (is_array($rawId)) {
+			$result = [];
+			foreach ($rawId as $key => $value) {
+				$result[$key] = $this->ensureMongoId($value);
+			}
+			return $result;
+		} elseif (is_object($rawId)) {
+			if ($rawId instanceof \MongoId) {
+				return $rawId;
+			} else {
+				$rawId = (string)$rawId;
+			}
+		}
+		return new \MongoId($rawId);
+	}
+
+	/**
+	 * Parses the condition specification and generates the corresponding Mongo condition.
+	 * @param array $condition the condition specification. Please refer to [[Query::where()]]
+	 * on how to specify a condition.
+	 * @return array the generated Mongo condition
+	 * @throws InvalidParamException if the condition is in bad format
+	 */
+	public function buildCondition($condition)
+	{
+		static $builders = [
+			'AND' => 'buildAndCondition',
+			'OR' => 'buildOrCondition',
+			'BETWEEN' => 'buildBetweenCondition',
+			'NOT BETWEEN' => 'buildBetweenCondition',
+			'IN' => 'buildInCondition',
+			'NOT IN' => 'buildInCondition',
+			'LIKE' => 'buildLikeCondition',
+		];
+
+		if (!is_array($condition)) {
+			throw new InvalidParamException('Condition should be an array.');
+		} elseif (empty($condition)) {
+			return [];
+		}
+		if (isset($condition[0])) { // operator format: operator, operand 1, operand 2, ...
+			$operator = strtoupper($condition[0]);
+			if (isset($builders[$operator])) {
+				$method = $builders[$operator];
+				array_shift($condition);
+				return $this->$method($operator, $condition);
+			} else {
+				throw new InvalidParamException('Found unknown operator in query: ' . $operator);
+			}
+		} else {
+			// hash format: 'column1' => 'value1', 'column2' => 'value2', ...
+			return $this->buildHashCondition($condition);
+		}
+	}
+
+	/**
+	 * Creates a condition based on column-value pairs.
+	 * @param array $condition the condition specification.
+	 * @return array the generated Mongo condition.
+	 */
+	public function buildHashCondition($condition)
+	{
+		$result = [];
+		foreach ($condition as $name => $value) {
+			$name = $this->normalizeConditionKeyword($name);
+			if (strncmp('$', $name, 1) === 0) {
+				// Native Mongo condition:
+				$result[$name] = $value;
+			} else {
+				if (is_array($value)) {
+					if (array_key_exists(0, $value)) {
+						// Quick IN condition:
+						$result = array_merge($result, $this->buildInCondition('IN', [$name, $value]));
+					} else {
+						// Normalize possible verbose condition:
+						$actualValue = [];
+						foreach ($value as $k => $v) {
+							$actualValue[$this->normalizeConditionKeyword($k)] = $v;
+						}
+						$result[$name] = $actualValue;
+					}
+				} else {
+					// Direct match:
+					if ($name == '_id') {
+						$value = $this->ensureMongoId($value);
+					}
+					$result[$name] = $value;
+				}
+			}
+		}
+		return $result;
+	}
+
+	/**
+	 * Connects two or more conditions with the `AND` operator.
+	 * @param string $operator the operator to use for connecting the given operands
+	 * @param array $operands the Mongo conditions to connect.
+	 * @return array the generated Mongo condition.
+	 */
+	public function buildAndCondition($operator, $operands)
+	{
+		$result = [];
+		foreach ($operands as $operand) {
+			$condition = $this->buildCondition($operand);
+			$result = array_merge_recursive($result, $condition);
+		}
+		return $result;
+	}
+
+	/**
+	 * Connects two or more conditions with the `OR` operator.
+	 * @param string $operator the operator to use for connecting the given operands
+	 * @param array $operands the Mongo conditions to connect.
+	 * @return array the generated Mongo condition.
+	 */
+	public function buildOrCondition($operator, $operands)
+	{
+		$operator = $this->normalizeConditionKeyword($operator);
+		$parts = [];
+		foreach ($operands as $operand) {
+			$parts[] = $this->buildCondition($operand);
+		}
+		return [$operator => $parts];
+	}
+
+	/**
+	 * Creates an Mongo condition, which emulates the `BETWEEN` operator.
+	 * @param string $operator the operator to use
+	 * @param array $operands the first operand is the column name. The second and third operands
+	 * describe the interval that column value should be in.
+	 * @return array the generated Mongo condition.
+	 * @throws InvalidParamException if wrong number of operands have been given.
+	 */
+	public function buildBetweenCondition($operator, $operands)
+	{
+		if (!isset($operands[0], $operands[1], $operands[2])) {
+			throw new InvalidParamException("Operator '$operator' requires three operands.");
+		}
+		list($column, $value1, $value2) = $operands;
+		if (strncmp('NOT', $operator, 3) === 0) {
+			return [
+				$column => [
+					'$lt' => $value1,
+					'$gt' => $value2,
+				]
+			];
+		} else {
+			return [
+				$column => [
+					'$gte' => $value1,
+					'$lte' => $value2,
+				]
+			];
+		}
+	}
+
+	/**
+	 * Creates an Mongo condition with the `IN` operator.
+	 * @param string $operator the operator to use (e.g. `IN` or `NOT IN`)
+	 * @param array $operands the first operand is the column name. If it is an array
+	 * a composite IN condition will be generated.
+	 * The second operand is an array of values that column value should be among.
+	 * @return array the generated Mongo condition.
+	 * @throws InvalidParamException if wrong number of operands have been given.
+	 */
+	public function buildInCondition($operator, $operands)
+	{
+		if (!isset($operands[0], $operands[1])) {
+			throw new InvalidParamException("Operator '$operator' requires two operands.");
+		}
+
+		list($column, $values) = $operands;
+
+		$values = (array)$values;
+
+		if (!is_array($column)) {
+			$columns = [$column];
+			$values = [$column => $values];
+		} elseif (count($column) < 2) {
+			$columns = $column;
+			$values = [$column[0] => $values];
+		} else {
+			$columns = $column;
+		}
+
+		$operator = $this->normalizeConditionKeyword($operator);
+		$result = [];
+		foreach ($columns as $column) {
+			if ($column == '_id') {
+				$inValues = $this->ensureMongoId($values[$column]);
+			} else {
+				$inValues = $values[$column];
+			}
+			$result[$column][$operator] = $inValues;
+		}
+		return $result;
+	}
+
+	/**
+	 * Creates a Mongo condition, which emulates the `LIKE` operator.
+	 * @param string $operator the operator to use
+	 * @param array $operands the first operand is the column name.
+	 * The second operand is a single value that column value should be compared with.
+	 * @return array the generated Mongo condition.
+	 * @throws InvalidParamException if wrong number of operands have been given.
+	 */
+	public function buildLikeCondition($operator, $operands)
+	{
+		if (!isset($operands[0], $operands[1])) {
+			throw new InvalidParamException("Operator '$operator' requires two operands.");
+		}
+		list($column, $value) = $operands;
+		return [$column => '/' . $value . '/'];
+	}
+}
\ No newline at end of file
diff --git a/extensions/mongo/Connection.php b/extensions/mongo/Connection.php
new file mode 100644
index 00000000000..8c19cb484cc
--- /dev/null
+++ b/extensions/mongo/Connection.php
@@ -0,0 +1,253 @@
+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\mongo;
+
+use yii\base\Component;
+use yii\base\InvalidConfigException;
+use Yii;
+
+/**
+ * Connection represents a connection to a MongoDb server.
+ *
+ * Connection works together with [[Database]] and [[Collection]] to provide data access
+ * to the Mongo database. They are wrappers of the [[MongoDB PHP extension]](http://us1.php.net/manual/en/book.mongo.php).
+ *
+ * To establish a DB connection, set [[dsn]] and then call [[open()]] to be true.
+ *
+ * The following example shows how to create a Connection instance and establish
+ * the DB connection:
+ *
+ * ~~~
+ * $connection = new \yii\mongo\Connection([
+ *     'dsn' => $dsn,
+ * ]);
+ * $connection->open();
+ * ~~~
+ *
+ * After the Mongo connection is established, one can access Mongo databases and collections:
+ *
+ * ~~~
+ * $database = $connection->getDatabase('my_mongo_db');
+ * $collection = $database->getCollection('customer');
+ * $collection->insert(['name' => 'John Smith', 'status' => 1]);
+ * ~~~
+ *
+ * You can work with several different databases at the same server using this class.
+ * However, while it is unlikely your application will actually need it, the Connection class
+ * provides ability to use [[defaultDatabaseName]] as well as a shortcut method [[getCollection()]]
+ * to retrieve a particular collection instance:
+ *
+ * ~~~
+ * // get collection 'customer' from default database:
+ * $collection = $connection->getCollection('customer');
+ * // get collection 'customer' from database 'mydatabase':
+ * $collection = $connection->getCollection(['mydatabase', 'customer']);
+ * ~~~
+ *
+ * Connection is often used as an application component and configured in the application
+ * configuration like the following:
+ *
+ * ~~~
+ * [
+ *	 'components' => [
+ *		 'mongo' => [
+ *			 'class' => '\yii\mongo\Connection',
+ *			 'dsn' => 'mongodb://developer:password@localhost:27017/mydatabase',
+ *		 ],
+ *	 ],
+ * ]
+ * ~~~
+ *
+ * @property boolean $isActive Whether the Mongo connection is established. This property is read-only.
+ * is read-only.
+ *
+ * @author Paul Klimov <klimov.paul@gmail.com>
+ * @since 2.0
+ */
+class Connection extends Component
+{
+	/**
+	 * @var string host:port
+	 *
+	 * Correct syntax is:
+	 * mongodb://[username:password@]host1[:port1][,host2[:port2:],...][/dbname]
+	 * For example:
+	 * mongodb://localhost:27017
+	 * mongodb://developer:password@localhost:27017
+	 * mongodb://developer:password@localhost:27017/mydatabase
+	 */
+	public $dsn;
+	/**
+	 * @var array connection options.
+	 * for example:
+	 * ~~~
+	 * [
+	 *     'persist' => true, // use persistent connection
+	 *     'socketTimeoutMS' => 1000, // how long a send or receive on a socket can take before timing out
+	 *     'journal' => true // block write operations until the journal be flushed the to disk
+	 * ]
+	 * ~~~
+	 */
+	public $options = [];
+	/**
+	 * @var string name of the Mongo database to use by default.
+	 * If this field left blank, connection instance will attempt to determine it from
+	 * [[options]] and [[dsn]] automatically, if needed.
+	 */
+	public $defaultDatabaseName;
+	/**
+	 * @var \MongoClient mongo client instance.
+	 */
+	public $mongoClient;
+	/**
+	 * @var Database[] list of Mongo databases
+	 */
+	private $_databases = [];
+
+	/**
+	 * Returns the Mongo collection with the given name.
+	 * @param string|null $name collection name, if null default one will be used.
+	 * @param boolean $refresh whether to reload the table schema even if it is found in the cache.
+	 * @return Database database instance.
+	 */
+	public function getDatabase($name = null, $refresh = false)
+	{
+		if ($name === null) {
+			$name = $this->fetchDefaultDatabaseName();
+		}
+		if ($refresh || !array_key_exists($name, $this->_databases)) {
+			$this->_databases[$name] = $this->selectDatabase($name);
+		}
+		return $this->_databases[$name];
+	}
+
+	/**
+	 * Returns [[defaultDatabaseName]] value, if it is not set,
+	 * attempts to determine it from [[dsn]] value.
+	 * @return string default database name
+	 * @throws \yii\base\InvalidConfigException if unable to determine default database name.
+	 */
+	protected function fetchDefaultDatabaseName()
+	{
+		if ($this->defaultDatabaseName === null) {
+			if (isset($this->options['db'])) {
+				$this->defaultDatabaseName = $this->options['db'];
+			} elseif (preg_match('/^mongodb:\\/\\/.+\\/(.+)$/s', $this->dsn, $matches)) {
+				$this->defaultDatabaseName = $matches[1];
+			} else {
+				throw new InvalidConfigException("Unable to determine default database name from dsn.");
+			}
+		}
+		return $this->defaultDatabaseName;
+	}
+
+	/**
+	 * Selects the database with given name.
+	 * @param string $name database name.
+	 * @return Database database instance.
+	 */
+	protected function selectDatabase($name)
+	{
+		$this->open();
+		return Yii::createObject([
+			'class' => 'yii\mongo\Database',
+			'mongoDb' => $this->mongoClient->selectDB($name)
+		]);
+	}
+
+	/**
+	 * Returns the Mongo collection with the given name.
+	 * @param string|array $name collection name. If string considered as the name of the collection
+	 * inside the default database. If array - first element considered as the name of the database,
+	 * second - as name of collection inside that database
+	 * @param boolean $refresh whether to reload the collection instance even if it is found in the cache.
+	 * @return Collection Mongo collection instance.
+	 */
+	public function getCollection($name, $refresh = false)
+	{
+		if (is_array($name)) {
+			list ($dbName, $collectionName) = $name;
+			return $this->getDatabase($dbName)->getCollection($collectionName, $refresh);
+		} else {
+			return $this->getDatabase()->getCollection($name, $refresh);
+		}
+	}
+
+	/**
+	 * Returns the Mongo GridFS collection.
+	 * @param string|array $prefix collection prefix. If string considered as the prefix of the GridFS
+	 * collection inside the default database. If array - first element considered as the name of the database,
+	 * second - as prefix of the GridFS collection inside that database, if no second element present
+	 * default "fs" prefix will be used.
+	 * @param boolean $refresh whether to reload the collection instance even if it is found in the cache.
+	 * @return file\Collection Mongo GridFS collection instance.
+	 */
+	public function getFileCollection($prefix = 'fs', $refresh = false)
+	{
+		if (is_array($prefix)) {
+			list ($dbName, $collectionPrefix) = $prefix;
+			if (!isset($collectionPrefix)) {
+				$collectionPrefix = 'fs';
+			}
+			return $this->getDatabase($dbName)->getFileCollection($collectionPrefix, $refresh);
+		} else {
+			return $this->getDatabase()->getFileCollection($prefix, $refresh);
+		}
+	}
+
+	/**
+	 * Returns a value indicating whether the Mongo connection is established.
+	 * @return boolean whether the Mongo connection is established
+	 */
+	public function getIsActive()
+	{
+		return is_object($this->mongoClient) && $this->mongoClient->connected;
+	}
+
+	/**
+	 * Establishes a Mongo connection.
+	 * It does nothing if a Mongo connection has already been established.
+	 * @throws Exception if connection fails
+	 */
+	public function open()
+	{
+		if ($this->mongoClient === null) {
+			if (empty($this->dsn)) {
+				throw new InvalidConfigException($this->className() . '::dsn cannot be empty.');
+			}
+			$token = 'Opening Mongo connection: ' . $this->dsn;
+			try {
+				Yii::trace($token, __METHOD__);
+				Yii::beginProfile($token, __METHOD__);
+				$options = $this->options;
+				$options['connect'] = true;
+				if ($this->defaultDatabaseName !== null) {
+					$options['db'] = $this->defaultDatabaseName;
+				}
+				$this->mongoClient = new \MongoClient($this->dsn, $options);
+				Yii::endProfile($token, __METHOD__);
+			} catch (\Exception $e) {
+				Yii::endProfile($token, __METHOD__);
+				throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+			}
+		}
+	}
+
+	/**
+	 * Closes the currently active DB connection.
+	 * It does nothing if the connection is already closed.
+	 */
+	public function close()
+	{
+		if ($this->mongoClient !== null) {
+			Yii::trace('Closing Mongo connection: ' . $this->dsn, __METHOD__);
+			$this->mongoClient = null;
+			$this->_databases = [];
+		}
+	}
+}
\ No newline at end of file
diff --git a/extensions/mongo/Database.php b/extensions/mongo/Database.php
new file mode 100644
index 00000000000..bb919b545a8
--- /dev/null
+++ b/extensions/mongo/Database.php
@@ -0,0 +1,172 @@
+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\mongo;
+
+use yii\base\Object;
+use Yii;
+use yii\helpers\Json;
+
+/**
+ * Database represents the Mongo database information.
+ *
+ * @property string $name name of this database. This property is read-only.
+ *
+ * @author Paul Klimov <klimov.paul@gmail.com>
+ * @since 2.0
+ */
+class Database extends Object
+{
+	/**
+	 * @var \MongoDB Mongo database instance.
+	 */
+	public $mongoDb;
+	/**
+	 * @var Collection[] list of collections.
+	 */
+	private $_collections = [];
+	/**
+	 * @var file\Collection[] list of GridFS collections.
+	 */
+	private $_fileCollections = [];
+
+	/**
+	 * @return string name of this database.
+	 */
+	public function getName()
+	{
+		return $this->mongoDb->__toString();
+	}
+
+	/**
+	 * Returns the Mongo collection with the given name.
+	 * @param string $name collection name
+	 * @param boolean $refresh whether to reload the collection instance even if it is found in the cache.
+	 * @return Collection mongo collection instance.
+	 */
+	public function getCollection($name, $refresh = false)
+	{
+		if ($refresh || !array_key_exists($name, $this->_collections)) {
+			$this->_collections[$name] = $this->selectCollection($name);
+		}
+		return $this->_collections[$name];
+	}
+
+	/**
+	 * Returns Mongo GridFS collection with given prefix.
+	 * @param string $prefix collection prefix.
+	 * @param boolean $refresh whether to reload the collection instance even if it is found in the cache.
+	 * @return file\Collection mongo GridFS collection.
+	 */
+	public function getFileCollection($prefix = 'fs', $refresh = false)
+	{
+		if ($refresh || !array_key_exists($prefix, $this->_fileCollections)) {
+			$this->_fileCollections[$prefix] = $this->selectFileCollection($prefix);
+		}
+		return $this->_fileCollections[$prefix];
+	}
+
+	/**
+	 * Selects collection with given name.
+	 * @param string $name collection name.
+	 * @return Collection collection instance.
+	 */
+	protected function selectCollection($name)
+	{
+		return Yii::createObject([
+			'class' => 'yii\mongo\Collection',
+			'mongoCollection' => $this->mongoDb->selectCollection($name)
+		]);
+	}
+
+	/**
+	 * Selects GridFS collection with given prefix.
+	 * @param string $prefix file collection prefix.
+	 * @return file\Collection file collection instance.
+	 */
+	protected function selectFileCollection($prefix)
+	{
+		return Yii::createObject([
+			'class' => 'yii\mongo\file\Collection',
+			'mongoCollection' => $this->mongoDb->getGridFS($prefix)
+		]);
+	}
+
+	/**
+	 * Creates new collection.
+	 * Note: Mongo creates new collections automatically on the first demand,
+	 * this method makes sense only for the migration script or for the case
+	 * you need to create collection with the specific options.
+	 * @param string $name name of the collection
+	 * @param array $options collection options in format: "name" => "value"
+	 * @return \MongoCollection new mongo collection instance.
+	 * @throws Exception on failure.
+	 */
+	public function createCollection($name, $options = [])
+	{
+		$token = $this->getName() . '.create(' . $name . ', ' . Json::encode($options) . ')';
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			$result = $this->mongoDb->createCollection($name, $options);
+			Yii::endProfile($token, __METHOD__);
+			return $result;
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Executes Mongo command.
+	 * @param array $command command specification.
+	 * @param array $options options in format: "name" => "value"
+	 * @return array database response.
+	 * @throws Exception on failure.
+	 */
+	public function executeCommand($command, $options = [])
+	{
+		$token = $this->getName() . '.$cmd(' . Json::encode($command) . ', ' . Json::encode($options) . ')';
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			$result = $this->mongoDb->command($command, $options);
+			$this->tryResultError($result);
+			Yii::endProfile($token, __METHOD__);
+			return $result;
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Checks if command execution result ended with an error.
+	 * @param mixed $result raw command execution result.
+	 * @throws Exception if an error occurred.
+	 */
+	protected function tryResultError($result)
+	{
+		if (is_array($result)) {
+			if (!empty($result['errmsg'])) {
+				$errorMessage = $result['errmsg'];
+			} elseif (!empty($result['err'])) {
+				$errorMessage = $result['err'];
+			}
+			if (isset($errorMessage)) {
+				if (array_key_exists('ok', $result)) {
+					$errorCode = (int)$result['ok'];
+				} else {
+					$errorCode = 0;
+				}
+				throw new Exception($errorMessage, $errorCode);
+			}
+		} elseif (!$result) {
+			throw new Exception('Unknown error, use "w=1" option to enable error tracking');
+		}
+	}
+}
\ No newline at end of file
diff --git a/extensions/mongo/Exception.php b/extensions/mongo/Exception.php
new file mode 100644
index 00000000000..0687e4893c3
--- /dev/null
+++ b/extensions/mongo/Exception.php
@@ -0,0 +1,25 @@
+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\mongo;
+
+/**
+ * Exception represents an exception that is caused by some Mongo-related operations.
+ *
+ * @author Paul Klimov <klimov.paul@gmail.com>
+ * @since 2.0
+ */
+class Exception extends \yii\base\Exception
+{
+	/**
+	 * @return string the user-friendly name of this exception
+	 */
+	public function getName()
+	{
+		return \Yii::t('yii', 'Mongo Exception');
+	}
+}
\ No newline at end of file
diff --git a/extensions/mongo/LICENSE.md b/extensions/mongo/LICENSE.md
new file mode 100644
index 00000000000..0bb1a8dca88
--- /dev/null
+++ b/extensions/mongo/LICENSE.md
@@ -0,0 +1,32 @@
+The Yii framework is free software. It is released under the terms of
+the following BSD License.
+
+Copyright © 2008-2013 by Yii Software LLC (http://www.yiisoft.com)
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+
+ * Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+ * Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions and the following disclaimer in
+   the documentation and/or other materials provided with the
+   distribution.
+ * Neither the name of Yii Software LLC nor the names of its
+   contributors may be used to endorse or promote products derived
+   from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
diff --git a/extensions/mongo/Query.php b/extensions/mongo/Query.php
new file mode 100644
index 00000000000..cce6645beeb
--- /dev/null
+++ b/extensions/mongo/Query.php
@@ -0,0 +1,344 @@
+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\mongo;
+
+use yii\base\Component;
+use yii\db\QueryInterface;
+use yii\db\QueryTrait;
+use yii\helpers\Json;
+use Yii;
+
+/**
+ * Query represents Mongo "find" operation.
+ *
+ * Query provides a set of methods to facilitate the specification of "find" command.
+ * These methods can be chained together.
+ *
+ * For example,
+ *
+ * ~~~
+ * $query = new Query;
+ * // compose the query
+ * $query->select(['name', 'status'])
+ *     ->from('customer')
+ *     ->limit(10);
+ * // execute the query
+ * $rows = $query->all();
+ * ~~~
+ *
+ * @author Paul Klimov <klimov.paul@gmail.com>
+ * @since 2.0
+ */
+class Query extends Component implements QueryInterface
+{
+	use QueryTrait;
+
+	/**
+	 * @var array the fields of the results to return. For example, `['name', 'group_id']`.
+	 * The "_id" field is always returned. If not set, if means selecting all columns.
+	 * @see select()
+	 */
+	public $select = [];
+	/**
+	 * @var string|array the collection to be selected from. If string considered as  the name of the collection
+	 * inside the default database. If array - first element considered as the name of the database,
+	 * second - as name of collection inside that database
+	 * @see from()
+	 */
+	public $from;
+
+	/**
+	 * Returns the Mongo collection for this query.
+	 * @param Connection $db Mongo connection.
+	 * @return Collection collection instance.
+	 */
+	public function getCollection($db = null)
+	{
+		if ($db === null) {
+			$db = Yii::$app->getComponent('mongo');
+		}
+		return $db->getCollection($this->from);
+	}
+
+	/**
+	 * Sets the list of fields of the results to return.
+	 * @param array $fields fields of the results to return.
+	 * @return static the query object itself.
+	 */
+	public function select(array $fields)
+	{
+		$this->select = $fields;
+		return $this;
+	}
+
+	/**
+	 * Sets the collection to be selected from.
+	 * @param string|array the collection to be selected from. If string considered as  the name of the collection
+	 * inside the default database. If array - first element considered as the name of the database,
+	 * second - as name of collection inside that database
+	 * @return static the query object itself.
+	 */
+	public function from($collection)
+	{
+		$this->from = $collection;
+		return $this;
+	}
+
+	/**
+	 * Builds the Mongo cursor for this query.
+	 * @param Connection $db the database connection used to execute the query.
+	 * @return \MongoCursor mongo cursor instance.
+	 */
+	protected function buildCursor($db = null)
+	{
+		if ($this->where === null) {
+			$where = [];
+		} else {
+			$where = $this->where;
+		}
+		$selectFields = [];
+		if (!empty($this->select)) {
+			foreach ($this->select as $fieldName) {
+				$selectFields[$fieldName] = true;
+			}
+		}
+		$cursor = $this->getCollection($db)->find($where, $selectFields);
+		if (!empty($this->orderBy)) {
+			$sort = [];
+			foreach ($this->orderBy as $fieldName => $sortOrder) {
+				$sort[$fieldName] = $sortOrder === SORT_DESC ? \MongoCollection::DESCENDING : \MongoCollection::ASCENDING;
+			}
+			$cursor->sort($sort);
+		}
+		$cursor->limit($this->limit);
+		$cursor->skip($this->offset);
+		return $cursor;
+	}
+
+	/**
+	 * Fetches rows from the given Mongo cursor.
+	 * @param \MongoCursor $cursor Mongo cursor instance to fetch data from.
+	 * @param boolean $all whether to fetch all rows or only first one.
+	 * @param string|callable $indexBy the column name or PHP callback,
+	 * by which the query results should be indexed by.
+	 * @throws Exception on failure.
+	 * @return array|boolean result.
+	 */
+	protected function fetchRows($cursor, $all = true, $indexBy = null)
+	{
+		$token = 'find(' . Json::encode($cursor->info()) . ')';
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			$result = $this->fetchRowsInternal($cursor, $all, $indexBy);
+			Yii::endProfile($token, __METHOD__);
+			return $result;
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * @param \MongoCursor $cursor Mongo cursor instance to fetch data from.
+	 * @param boolean $all whether to fetch all rows or only first one.
+	 * @param string|callable $indexBy value to index by.
+	 * @return array|boolean result.
+	 * @see Query::fetchRows()
+	 */
+	protected function fetchRowsInternal($cursor, $all, $indexBy)
+	{
+		$result = [];
+		if ($all) {
+			foreach ($cursor as $row) {
+				if ($indexBy !== null) {
+					if (is_string($indexBy)) {
+						$key = $row[$indexBy];
+					} else {
+						$key = call_user_func($indexBy, $row);
+					}
+					$result[$key] = $row;
+				} else {
+					$result[] = $row;
+				}
+			}
+		} else {
+			if ($cursor->hasNext()) {
+				$result = $cursor->getNext();
+			} else {
+				$result = false;
+			}
+		}
+		return $result;
+	}
+
+	/**
+	 * Executes the query and returns all results as an array.
+	 * @param Connection $db the Mongo connection used to execute the query.
+	 * If this parameter is not given, the `mongo` application component will be used.
+	 * @return array the query results. If the query results in nothing, an empty array will be returned.
+	 */
+	public function all($db = null)
+	{
+		$cursor = $this->buildCursor($db);
+		return $this->fetchRows($cursor, true, $this->indexBy);
+	}
+
+	/**
+	 * Executes the query and returns a single row of result.
+	 * @param Connection $db the Mongo connection used to execute the query.
+	 * If this parameter is not given, the `mongo` application component will be used.
+	 * @return array|boolean the first row (in terms of an array) of the query result. False is returned if the query
+	 * results in nothing.
+	 */
+	public function one($db = null)
+	{
+		$cursor = $this->buildCursor($db);
+		return $this->fetchRows($cursor, false);
+	}
+
+	/**
+	 * Returns the number of records.
+	 * @param string $q kept to match [[QueryInterface]], its value is ignored.
+	 * @param Connection $db the Mongo connection used to execute the query.
+	 * If this parameter is not given, the `mongo` application component will be used.
+	 * @return integer number of records
+	 * @throws Exception on failure.
+	 */
+	public function count($q = '*', $db = null)
+	{
+		$cursor = $this->buildCursor($db);
+		$token = 'find.count(' . Json::encode($cursor->info()) . ')';
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			$result = $cursor->count();
+			Yii::endProfile($token, __METHOD__);
+			return $result;
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Returns a value indicating whether the query result contains any row of data.
+	 * @param Connection $db the Mongo connection used to execute the query.
+	 * If this parameter is not given, the `mongo` application component will be used.
+	 * @return boolean whether the query result contains any row of data.
+	 */
+	public function exists($db = null)
+	{
+		return $this->one($db) !== null;
+	}
+
+	/**
+	 * Returns the sum of the specified column values.
+	 * @param string $q the column name.
+	 * Make sure you properly quote column names in the expression.
+	 * @param Connection $db the Mongo connection used to execute the query.
+	 * If this parameter is not given, the `mongo` application component will be used.
+	 * @return integer the sum of the specified column values
+	 */
+	public function sum($q, $db = null)
+	{
+		return $this->aggregate($q, 'sum', $db);
+	}
+
+	/**
+	 * Returns the average of the specified column values.
+	 * @param string $q the column name.
+	 * Make sure you properly quote column names in the expression.
+	 * @param Connection $db the Mongo connection used to execute the query.
+	 * If this parameter is not given, the `mongo` application component will be used.
+	 * @return integer the average of the specified column values.
+	 */
+	public function average($q, $db = null)
+	{
+		return $this->aggregate($q, 'avg', $db);
+	}
+
+	/**
+	 * Returns the minimum of the specified column values.
+	 * @param string $q the column name.
+	 * Make sure you properly quote column names in the expression.
+	 * @param Connection $db the database connection used to generate the SQL statement.
+	 * If this parameter is not given, the `db` application component will be used.
+	 * @return integer the minimum of the specified column values.
+	 */
+	public function min($q, $db = null)
+	{
+		return $this->aggregate($q, 'min', $db);
+	}
+
+	/**
+	 * Returns the maximum of the specified column values.
+	 * @param string $q the column name.
+	 * Make sure you properly quote column names in the expression.
+	 * @param Connection $db the Mongo connection used to execute the query.
+	 * If this parameter is not given, the `mongo` application component will be used.
+	 * @return integer the maximum of the specified column values.
+	 */
+	public function max($q, $db = null)
+	{
+		return $this->aggregate($q, 'max', $db);
+	}
+
+	/**
+	 * Performs the aggregation for the given column.
+	 * @param string $column column name.
+	 * @param string $operator aggregation operator.
+	 * @param Connection $db the database connection used to execute the query.
+	 * @return integer aggregation result.
+	 */
+	protected function aggregate($column, $operator, $db)
+	{
+		$collection = $this->getCollection($db);
+		$pipelines = [];
+		if ($this->where !== null) {
+			$pipelines[] = ['$match' => $collection->buildCondition($this->where)];
+		}
+		$pipelines[] = [
+			'$group' => [
+				'_id' => '1',
+				'total' => [
+					'$' . $operator => '$' . $column
+				],
+			]
+		];
+		$result = $collection->aggregate($pipelines);
+		if (array_key_exists(0, $result)) {
+			return $result[0]['total'];
+		} else {
+			return 0;
+		}
+	}
+
+	/**
+	 * Returns a list of distinct values for the given column across a collection.
+	 * @param string $q column to use.
+	 * @param Connection $db the Mongo connection used to execute the query.
+	 * If this parameter is not given, the `mongo` application component will be used.
+	 * @return array array of distinct values
+	 */
+	public function distinct($q, $db = null)
+	{
+		$collection = $this->getCollection($db);
+		if ($this->where !== null) {
+			$condition = $this->where;
+		} else {
+			$condition = [];
+		}
+		$result = $collection->distinct($q, $condition);
+		if ($result === false) {
+			return [];
+		} else {
+			return $result;
+		}
+	}
+}
\ No newline at end of file
diff --git a/extensions/mongo/README.md b/extensions/mongo/README.md
new file mode 100644
index 00000000000..7f5ef709f65
--- /dev/null
+++ b/extensions/mongo/README.md
@@ -0,0 +1,116 @@
+Yii 2.0 Public Preview - MongoDb Extension
+==========================================
+
+Thank you for choosing Yii - a high-performance component-based PHP framework.
+
+If you are looking for a production-ready PHP framework, please use
+[Yii v1.1](https://github.com/yiisoft/yii).
+
+Yii 2.0 is still under heavy development. We may make significant changes
+without prior notices. **Yii 2.0 is not ready for production use yet.**
+
+[![Build Status](https://secure.travis-ci.org/yiisoft/yii2.png)](http://travis-ci.org/yiisoft/yii2)
+
+This is the yii2-sphinx extension.
+
+
+Installation
+------------
+
+The preferred way to install this extension is through [composer](http://getcomposer.org/download/).
+
+Either run
+```
+php composer.phar require yiisoft/yii2-mongo "*"
+```
+
+or add
+```
+"yiisoft/yii2-mongo": "*"
+```
+to the require section of your composer.json.
+
+
+*Note: You might have to run `php composer.phar selfupdate`*
+
+
+Usage & Documentation
+---------------------
+
+This extension adds [MongoDB](http://www.mongodb.org/) data storage support for the Yii2 framework.
+
+Note: extension requires [MongoDB PHP Extension](http://us1.php.net/manual/en/book.mongo.php) version 1.3.0 or higher.
+
+To use this extension, simply add the following code in your application configuration:
+
+```php
+return [
+	//....
+	'components' => [
+		'mongo' => [
+			'class' => '\yii\mongo\Connection',
+			'dsn' => 'mongodb://developer:password@localhost:27017/mydatabase',
+		],
+	],
+];
+```
+
+This extension provides ActiveRecord solution similar ot the [[\yii\db\ActiveRecord]].
+To declare an ActiveRecord class you need to extend [[\yii\mongo\ActiveRecord]] and
+implement the `collectionName` and 'attributes' methods:
+
+```php
+use yii\mongo\ActiveRecord;
+
+class Customer extends ActiveRecord
+{
+	/**
+	 * @return string the name of the index associated with this ActiveRecord class.
+	 */
+	public static function collectionName()
+	{
+		return 'customer';
+	}
+
+	/**
+	 * @return array list of attribute names.
+	 */
+	public function attributes()
+	{
+		return ['name', 'email', 'address', 'status'];
+	}
+}
+```
+
+You can use [[\yii\data\ActiveDataProvider]] with the [[\yii\mongo\Query]] and [[\yii\mongo\ActiveQuery]]:
+
+```php
+use yii\data\ActiveDataProvider;
+use yii\mongo\Query;
+
+$query = new Query;
+$query->from('customer')->where(['status' => 2]);
+$provider = new ActiveDataProvider([
+	'query' => $query,
+	'pagination' => [
+		'pageSize' => 10,
+	]
+]);
+$models = $provider->getModels();
+```
+
+```php
+use yii\data\ActiveDataProvider;
+use app\models\Customer;
+
+$provider = new ActiveDataProvider([
+	'query' => Customer::find(),
+	'pagination' => [
+		'pageSize' => 10,
+	]
+]);
+$models = $provider->getModels();
+```
+
+This extension supports [MongoGridFS](http://docs.mongodb.org/manual/core/gridfs/) via
+classes at namespace "\yii\mongo\file".
\ No newline at end of file
diff --git a/extensions/mongo/composer.json b/extensions/mongo/composer.json
new file mode 100644
index 00000000000..a9dd06e1da4
--- /dev/null
+++ b/extensions/mongo/composer.json
@@ -0,0 +1,28 @@
+{
+	"name": "yiisoft/yii2-mongo",
+	"description": "MongoDb extension for the Yii framework",
+	"keywords": ["yii", "mongo", "mongodb", "active-record"],
+	"type": "yii2-extension",
+	"license": "BSD-3-Clause",
+	"support": {
+		"issues": "https://github.com/yiisoft/yii2/issues?state=open",
+		"forum": "http://www.yiiframework.com/forum/",
+		"wiki": "http://www.yiiframework.com/wiki/",
+		"irc": "irc://irc.freenode.net/yii",
+		"source": "https://github.com/yiisoft/yii2"
+	},
+	"authors": [
+		{
+			"name": "Paul Klimov",
+			"email": "klimov.paul@gmail.com"
+		}
+	],
+	"minimum-stability": "dev",
+	"require": {
+		"yiisoft/yii2": "*",
+		"ext-mongo": ">=1.3.0"
+	},
+	"autoload": {
+		"psr-0": { "yii\\mongo\\": "" }
+	}
+}
diff --git a/extensions/mongo/file/ActiveQuery.php b/extensions/mongo/file/ActiveQuery.php
new file mode 100644
index 00000000000..91661d69c31
--- /dev/null
+++ b/extensions/mongo/file/ActiveQuery.php
@@ -0,0 +1,107 @@
+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\mongo\file;
+
+use yii\db\ActiveQueryInterface;
+use yii\db\ActiveQueryTrait;
+
+/**
+ * ActiveQuery represents a Mongo query associated with an file Active Record class.
+ *
+ * ActiveQuery instances are usually created by [[ActiveRecord::find()]].
+ *
+ * Because ActiveQuery extends from [[Query]], one can use query methods, such as [[where()]],
+ * [[orderBy()]] to customize the query options.
+ *
+ * ActiveQuery also provides the following additional query options:
+ *
+ * - [[with()]]: list of relations that this query should be performed with.
+ * - [[asArray()]]: whether to return each record as an array.
+ *
+ * These options can be configured using methods of the same name. For example:
+ *
+ * ~~~
+ * $images = ImageFile::find()->with('tags')->asArray()->all();
+ * ~~~
+ *
+ * @author Paul Klimov <klimov.paul@gmail.com>
+ * @since 2.0
+ */
+class ActiveQuery extends Query implements ActiveQueryInterface
+{
+	use ActiveQueryTrait;
+
+	/**
+	 * Executes query and returns all results as an array.
+	 * @param \yii\mongo\Connection $db the Mongo connection used to execute the query.
+	 * If null, the Mongo connection returned by [[modelClass]] will be used.
+	 * @return array the query results. If the query results in nothing, an empty array will be returned.
+	 */
+	public function all($db = null)
+	{
+		$cursor = $this->buildCursor($db);
+		$rows = $this->fetchRows($cursor);
+		if (!empty($rows)) {
+			$models = $this->createModels($rows);
+			if (!empty($this->with)) {
+				$this->findWith($this->with, $models);
+			}
+			return $models;
+		} else {
+			return [];
+		}
+	}
+
+	/**
+	 * Executes query and returns a single row of result.
+	 * @param \yii\mongo\Connection $db the Mongo connection used to execute the query.
+	 * If null, the Mongo connection returned by [[modelClass]] will be used.
+	 * @return ActiveRecord|array|null a single row of query result. Depending on the setting of [[asArray]],
+	 * the query result may be either an array or an ActiveRecord object. Null will be returned
+	 * if the query results in nothing.
+	 */
+	public function one($db = null)
+	{
+		$row = parent::one($db);
+		if ($row !== false) {
+			if ($this->asArray) {
+				$model = $row;
+			} else {
+				/** @var ActiveRecord $class */
+				$class = $this->modelClass;
+				$model = $class::create($row);
+			}
+			if (!empty($this->with)) {
+				$models = [$model];
+				$this->findWith($this->with, $models);
+				$model = $models[0];
+			}
+			return $model;
+		} else {
+			return null;
+		}
+	}
+
+	/**
+	 * Returns the Mongo collection for this query.
+	 * @param \yii\mongo\Connection $db Mongo connection.
+	 * @return Collection collection instance.
+	 */
+	public function getCollection($db = null)
+	{
+		/** @var ActiveRecord $modelClass */
+		$modelClass = $this->modelClass;
+		if ($db === null) {
+			$db = $modelClass::getDb();
+		}
+		if ($this->from === null) {
+			$this->from = $modelClass::collectionName();
+		}
+		return $db->getFileCollection($this->from);
+	}
+}
\ No newline at end of file
diff --git a/extensions/mongo/file/ActiveRecord.php b/extensions/mongo/file/ActiveRecord.php
new file mode 100644
index 00000000000..c7ca7525a05
--- /dev/null
+++ b/extensions/mongo/file/ActiveRecord.php
@@ -0,0 +1,340 @@
+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\mongo\file;
+
+use yii\base\InvalidParamException;
+use yii\db\StaleObjectException;
+use yii\web\UploadedFile;
+
+/**
+ * ActiveRecord is the base class for classes representing Mongo GridFS files in terms of objects.
+ *
+ * To specify source file use the [[file]] attribute. It can be specified in one of the following ways:
+ *  - string - full name of the file, which content should be stored in GridFS
+ *  - \yii\web\UploadedFile - uploaded file instance, which content should be stored in GridFS
+ *
+ * For example:
+ *
+ * ~~~
+ * $record = new ImageFile();
+ * $record->file = '/path/to/some/file.jpg';
+ * $record->save();
+ * ~~~
+ *
+ * You can also specify file content via [[newFileContent]] attribute:
+ *
+ * ~~~
+ * $record = new ImageFile();
+ * $record->newFileContent = 'New file content';
+ * $record->save();
+ * ~~~
+ *
+ * Note: [[newFileContent]] always takes precedence over [[file]].
+ *
+ * @property \MongoId|string $_id primary key.
+ * @property string $filename name of stored file.
+ * @property \MongoDate $uploadDate file upload date.
+ * @property integer $length file size.
+ * @property integer $chunkSize file chunk size.
+ * @property string $md5 file md5 hash.
+ * @property \MongoGridFSFile|\yii\web\UploadedFile|string $file associated file.
+ * @property string $newFileContent new file content.
+ *
+ * @author Paul Klimov <klimov.paul@gmail.com>
+ * @since 2.0
+ */
+abstract class ActiveRecord extends \yii\mongo\ActiveRecord
+{
+	/**
+	 * Creates an [[ActiveQuery]] instance.
+	 * This method is called by [[find()]] to start a "find" command.
+	 * You may override this method to return a customized query (e.g. `ImageFileQuery` specified
+	 * written for querying `ImageFile` purpose.)
+	 * @return ActiveQuery the newly created [[ActiveQuery]] instance.
+	 */
+	public static function createQuery()
+	{
+		return new ActiveQuery(['modelClass' => get_called_class()]);
+	}
+
+	/**
+	 * Return the Mongo GridFS collection instance for this AR class.
+	 * @return Collection collection instance.
+	 */
+	public static function getCollection()
+	{
+		return static::getDb()->getFileCollection(static::collectionName());
+	}
+
+	/**
+	 * Creates an [[ActiveRelation]] instance.
+	 * This method is called by [[hasOne()]] and [[hasMany()]] to create a relation instance.
+	 * You may override this method to return a customized relation.
+	 * @param array $config the configuration passed to the ActiveRelation class.
+	 * @return ActiveRelation the newly created [[ActiveRelation]] instance.
+	 */
+	public static function createActiveRelation($config = [])
+	{
+		return new ActiveRelation($config);
+	}
+
+	/**
+	 * Returns the list of all attribute names of the model.
+	 * This method could be overridden by child classes to define available attributes.
+	 * Note: all attributes defined in base Active Record class should be always present
+	 * in returned array.
+	 * For example:
+	 * ~~~
+	 * public function attributes()
+	 * {
+	 *     return array_merge(
+	 *         parent::attributes(),
+	 *         ['tags', 'status']
+	 *     );
+	 * }
+	 * ~~~
+	 * @return array list of attribute names.
+	 */
+	public function attributes()
+	{
+		return [
+			'_id',
+			'filename',
+			'uploadDate',
+			'length',
+			'chunkSize',
+			'md5',
+			'file',
+			'newFileContent'
+		];
+	}
+
+	/**
+	 * @see ActiveRecord::insert()
+	 */
+	protected function insertInternal($attributes = null)
+	{
+		if (!$this->beforeSave(true)) {
+			return false;
+		}
+		$values = $this->getDirtyAttributes($attributes);
+		if (empty($values)) {
+			$currentAttributes = $this->getAttributes();
+			foreach ($this->primaryKey() as $key) {
+				$values[$key] = isset($currentAttributes[$key]) ? $currentAttributes[$key] : null;
+			}
+		}
+		$collection = static::getCollection();
+		if (isset($values['newFileContent'])) {
+			$newFileContent = $values['newFileContent'];
+			unset($values['newFileContent']);
+		}
+		if (isset($values['file'])) {
+			$newFile = $values['file'];
+			unset($values['file']);
+		}
+		if (isset($newFileContent)) {
+			$newId = $collection->insertFileContent($newFileContent, $values);
+		} elseif (isset($newFile)) {
+			$fileName = $this->extractFileName($newFile);
+			$newId = $collection->insertFile($fileName, $values);
+		} else {
+			$newId = $collection->insert($values);
+		}
+		$this->setAttribute('_id', $newId);
+		foreach ($values as $name => $value) {
+			$this->setOldAttribute($name, $value);
+		}
+		$this->afterSave(true);
+		return true;
+	}
+
+	/**
+	 * @see ActiveRecord::update()
+	 * @throws StaleObjectException
+	 */
+	protected function updateInternal($attributes = null)
+	{
+		if (!$this->beforeSave(false)) {
+			return false;
+		}
+		$values = $this->getDirtyAttributes($attributes);
+		if (empty($values)) {
+			$this->afterSave(false);
+			return 0;
+		}
+
+		$collection = static::getCollection();
+		if (isset($values['newFileContent'])) {
+			$newFileContent = $values['newFileContent'];
+			unset($values['newFileContent']);
+		}
+		if (isset($values['file'])) {
+			$newFile = $values['file'];
+			unset($values['file']);
+		}
+		if (isset($newFileContent) || isset($newFile)) {
+			$rows = $this->deleteInternal();
+			$insertValues = $values;
+			$insertValues['_id'] = $this->getAttribute('_id');
+			if (isset($newFileContent)) {
+				$collection->insertFileContent($newFileContent, $insertValues);
+			} else {
+				$fileName = $this->extractFileName($newFile);
+				$collection->insertFile($fileName, $insertValues);
+			}
+			$this->setAttribute('newFileContent', null);
+			$this->setAttribute('file', null);
+		} else {
+			$condition = $this->getOldPrimaryKey(true);
+			$lock = $this->optimisticLock();
+			if ($lock !== null) {
+				if (!isset($values[$lock])) {
+					$values[$lock] = $this->$lock + 1;
+				}
+				$condition[$lock] = $this->$lock;
+			}
+			// We do not check the return value of update() because it's possible
+			// that it doesn't change anything and thus returns 0.
+			$rows = $collection->update($condition, $values);
+			if ($lock !== null && !$rows) {
+				throw new StaleObjectException('The object being updated is outdated.');
+			}
+		}
+
+		foreach ($values as $name => $value) {
+			$this->setOldAttribute($name, $this->getAttribute($name));
+		}
+		$this->afterSave(false);
+		return $rows;
+	}
+
+	/**
+	 * Extracts filename from given raw file value.
+	 * @param mixed $file raw file value.
+	 * @return string file name.
+	 * @throws \yii\base\InvalidParamException on invalid file value.
+	 */
+	protected function extractFileName($file)
+	{
+		if ($file instanceof UploadedFile) {
+			return $file->tempName;
+		} elseif (is_string($file)) {
+			if (file_exists($file)) {
+				return $file;
+			} else {
+				throw new InvalidParamException("File '{$file}' does not exist.");
+			}
+		} else {
+			throw new InvalidParamException('Unsupported type of "file" attribute.');
+		}
+	}
+
+	/**
+	 * Refreshes the [[file]] attribute from file collection, using current primary key.
+	 * @return \MongoGridFSFile|null refreshed file value.
+	 */
+	public function refreshFile()
+	{
+		$mongoFile = $this->getCollection()->get($this->getPrimaryKey());
+		$this->setAttribute('file', $mongoFile);
+		return $mongoFile;
+	}
+
+	/**
+	 * Returns the associated file content.
+	 * @return null|string file content.
+	 * @throws \yii\base\InvalidParamException on invalid file attribute value.
+	 */
+	public function getFileContent()
+	{
+		$file = $this->getAttribute('file');
+		if (empty($file) && !$this->getIsNewRecord()) {
+			$file = $this->refreshFile();
+		}
+		if (empty($file)) {
+			return null;
+		} elseif ($file instanceof \MongoGridFSFile) {
+			$fileSize = $file->getSize();
+			if (empty($fileSize)) {
+				return null;
+			} else {
+				return $file->getBytes();
+			}
+		} elseif ($file instanceof UploadedFile) {
+			return file_get_contents($file->tempName);
+		} elseif (is_string($file)) {
+			if (file_exists($file)) {
+				return file_get_contents($file);
+			} else {
+				throw new InvalidParamException("File '{$file}' does not exist.");
+			}
+		} else {
+			throw new InvalidParamException('Unsupported type of "file" attribute.');
+		}
+	}
+
+	/**
+	 * Writes the the internal file content into the given filename.
+	 * @param string $filename full filename to be written.
+	 * @return boolean whether the operation was successful.
+	 * @throws \yii\base\InvalidParamException on invalid file attribute value.
+	 */
+	public function writeFile($filename)
+	{
+		$file = $this->getAttribute('file');
+		if (empty($file) && !$this->getIsNewRecord()) {
+			$file = $this->refreshFile();
+		}
+		if (empty($file)) {
+			throw new InvalidParamException('There is no file associated with this object.');
+		} elseif ($file instanceof \MongoGridFSFile) {
+			return ($file->write($filename) == $file->getSize());
+		} elseif ($file instanceof UploadedFile) {
+			return copy($file->tempName, $filename);
+		} elseif (is_string($file)) {
+			if (file_exists($file)) {
+				return copy($file, $filename);
+			} else {
+				throw new InvalidParamException("File '{$file}' does not exist.");
+			}
+		} else {
+			throw new InvalidParamException('Unsupported type of "file" attribute.');
+		}
+	}
+
+	/**
+	 * This method returns a stream resource that can be used with all file functions in PHP,
+	 * which deal with reading files. The contents of the file are pulled out of MongoDB on the fly,
+	 * so that the whole file does not have to be loaded into memory first.
+	 * @return resource file stream resource.
+	 * @throws \yii\base\InvalidParamException on invalid file attribute value.
+	 */
+	public function getFileResource()
+	{
+		$file = $this->getAttribute('file');
+		if (empty($file) && !$this->getIsNewRecord()) {
+			$file = $this->refreshFile();
+		}
+		if (empty($file)) {
+			throw new InvalidParamException('There is no file associated with this object.');
+		} elseif ($file instanceof \MongoGridFSFile) {
+			return $file->getResource();
+		} elseif ($file instanceof UploadedFile) {
+			return fopen($file->tempName, 'r');
+		} elseif (is_string($file)) {
+			if (file_exists($file)) {
+				return fopen($file, 'r');
+			} else {
+				throw new InvalidParamException("File '{$file}' does not exist.");
+			}
+		} else {
+			throw new InvalidParamException('Unsupported type of "file" attribute.');
+		}
+	}
+}
\ No newline at end of file
diff --git a/extensions/mongo/file/ActiveRelation.php b/extensions/mongo/file/ActiveRelation.php
new file mode 100644
index 00000000000..6ea0831cc9b
--- /dev/null
+++ b/extensions/mongo/file/ActiveRelation.php
@@ -0,0 +1,22 @@
+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\mongo\file;
+
+use yii\db\ActiveRelationInterface;
+use yii\db\ActiveRelationTrait;
+
+/**
+ * ActiveRelation represents a relation to Mongo GridFS Active Record class.
+ *
+ * @author Paul Klimov <klimov.paul@gmail.com>
+ * @since 2.0
+ */
+class ActiveRelation extends ActiveQuery implements ActiveRelationInterface
+{
+	use ActiveRelationTrait;
+}
\ No newline at end of file
diff --git a/extensions/mongo/file/Collection.php b/extensions/mongo/file/Collection.php
new file mode 100644
index 00000000000..b3c722b4c06
--- /dev/null
+++ b/extensions/mongo/file/Collection.php
@@ -0,0 +1,186 @@
+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\mongo\file;
+
+use yii\mongo\Exception;
+use Yii;
+
+/**
+ * Collection represents the Mongo GridFS collection information.
+ *
+ * A file collection object is usually created by calling [[Database::getFileCollection()]] or [[Connection::getFileCollection()]].
+ *
+ * File collection inherits all interface from regular [[\yii\mongo\Collection]], adding methods to store files.
+ *
+ * @property \yii\mongo\Collection $chunkCollection file chunks Mongo collection. This property is read-only.
+ * @method \MongoGridFSCursor find() returns a cursor for the search results.
+ *
+ * @author Paul Klimov <klimov.paul@gmail.com>
+ * @since 2.0
+ */
+class Collection extends \yii\mongo\Collection
+{
+	/**
+	 * @var \MongoGridFS Mongo GridFS collection instance.
+	 */
+	public $mongoCollection;
+	/**
+	 * @var \yii\mongo\Collection file chunks Mongo collection.
+	 */
+	private $_chunkCollection;
+
+	/**
+	 * Returns the Mongo collection for the file chunks.
+	 * @param boolean $refresh whether to reload the collection instance even if it is found in the cache.
+	 * @return \yii\mongo\Collection mongo collection instance.
+	 */
+	public function getChunkCollection($refresh = false)
+	{
+		if ($refresh || !is_object($this->_chunkCollection)) {
+			$this->_chunkCollection = Yii::createObject([
+				'class' => 'yii\mongo\Collection',
+				'mongoCollection' => $this->mongoCollection->chunks
+			]);
+		}
+		return $this->_chunkCollection;
+	}
+
+	/**
+	 * Removes data from the collection.
+	 * @param array $condition description of records to remove.
+	 * @param array $options list of options in format: optionName => optionValue.
+	 * @return integer|boolean number of updated documents or whether operation was successful.
+	 * @throws Exception on failure.
+	 */
+	public function remove($condition = [], $options = [])
+	{
+		$result = parent::remove($condition, $options);
+		$this->tryLastError(); // MongoGridFS::remove will return even if the remove failed
+		return $result;
+	}
+
+	/**
+	 * Creates new file in GridFS collection from given local filesystem file.
+	 * Additional attributes can be added file document using $metadata.
+	 * @param string $filename name of the file to store.
+	 * @param array $metadata other metadata fields to include in the file document.
+	 * @param array $options list of options in format: optionName => optionValue
+	 * @return mixed the "_id" of the saved file document. This will be a generated [[\MongoId]]
+	 * unless an "_id" was explicitly specified in the metadata.
+	 * @throws Exception on failure.
+	 */
+	public function insertFile($filename, $metadata = [], $options = [])
+	{
+		$token = 'Inserting file into ' . $this->getFullName();
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			$options = array_merge(['w' => 1], $options);
+			$result = $this->mongoCollection->storeFile($filename, $metadata, $options);
+			Yii::endProfile($token, __METHOD__);
+			return $result;
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Creates new file in GridFS collection with specified content.
+	 * Additional attributes can be added file document using $metadata.
+	 * @param string $bytes string of bytes to store.
+	 * @param array $metadata other metadata fields to include in the file document.
+	 * @param array $options list of options in format: optionName => optionValue
+	 * @return mixed the "_id" of the saved file document. This will be a generated [[\MongoId]]
+	 * unless an "_id" was explicitly specified in the metadata.
+	 * @throws Exception on failure.
+	 */
+	public function insertFileContent($bytes, $metadata = [], $options = [])
+	{
+		$token = 'Inserting file content into ' . $this->getFullName();
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			$options = array_merge(['w' => 1], $options);
+			$result = $this->mongoCollection->storeBytes($bytes, $metadata, $options);
+			Yii::endProfile($token, __METHOD__);
+			return $result;
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Creates new file in GridFS collection from uploaded file.
+	 * Additional attributes can be added file document using $metadata.
+	 * @param string $name name of the uploaded file to store. This should correspond to
+	 * the file field's name attribute in the HTML form.
+	 * @param array $metadata other metadata fields to include in the file document.
+	 * @return mixed the "_id" of the saved file document. This will be a generated [[\MongoId]]
+	 * unless an "_id" was explicitly specified in the metadata.
+	 * @throws Exception on failure.
+	 */
+	public function insertUploads($name, $metadata = [])
+	{
+		$token = 'Inserting file uploads into ' . $this->getFullName();
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			$result = $this->mongoCollection->storeUpload($name, $metadata);
+			Yii::endProfile($token, __METHOD__);
+			return $result;
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Retrieves the file with given _id.
+	 * @param mixed $id _id of the file to find.
+	 * @return \MongoGridFSFile|null found file, or null if file does not exist
+	 * @throws Exception on failure.
+	 */
+	public function get($id)
+	{
+		$token = 'Inserting file uploads into ' . $this->getFullName();
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			$result = $this->mongoCollection->get($id);
+			Yii::endProfile($token, __METHOD__);
+			return $result;
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+
+	/**
+	 * Deletes the file with given _id.
+	 * @param mixed $id _id of the file to find.
+	 * @return boolean whether the operation was successful.
+	 * @throws Exception on failure.
+	 */
+	public function delete($id)
+	{
+		$token = 'Inserting file uploads into ' . $this->getFullName();
+		Yii::info($token, __METHOD__);
+		try {
+			Yii::beginProfile($token, __METHOD__);
+			$result = $this->mongoCollection->delete($id);
+			$this->tryResultError($result);
+			Yii::endProfile($token, __METHOD__);
+			return true;
+		} catch (\Exception $e) {
+			Yii::endProfile($token, __METHOD__);
+			throw new Exception($e->getMessage(), (int)$e->getCode(), $e);
+		}
+	}
+}
\ No newline at end of file
diff --git a/extensions/mongo/file/Query.php b/extensions/mongo/file/Query.php
new file mode 100644
index 00000000000..c15d4f1b4b5
--- /dev/null
+++ b/extensions/mongo/file/Query.php
@@ -0,0 +1,75 @@
+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\mongo\file;
+
+use Yii;
+use yii\helpers\Json;
+use yii\mongo\Exception;
+
+/**
+ * Query represents Mongo "find" operation for GridFS collection.
+ *
+ * Query behaves exactly as regular [[\yii\mongo\Query]].
+ * Found files will be represented as arrays of file document attributes with
+ * additional 'file' key, which stores [[\MongoGridFSFile]] instance.
+ *
+ * @author Paul Klimov <klimov.paul@gmail.com>
+ * @since 2.0
+ */
+class Query extends \yii\mongo\Query
+{
+	/**
+	 * Returns the Mongo collection for this query.
+	 * @param \yii\mongo\Connection $db Mongo connection.
+	 * @return Collection collection instance.
+	 */
+	public function getCollection($db = null)
+	{
+		if ($db === null) {
+			$db = Yii::$app->getComponent('mongo');
+		}
+		return $db->getFileCollection($this->from);
+	}
+
+	/**
+	 * @param \MongoGridFSCursor $cursor Mongo cursor instance to fetch data from.
+	 * @param boolean $all whether to fetch all rows or only first one.
+	 * @param string|callable $indexBy value to index by.
+	 * @return array|boolean result.
+	 * @see Query::fetchRows()
+	 */
+	protected function fetchRowsInternal($cursor, $all, $indexBy)
+	{
+		$result = [];
+		if ($all) {
+			foreach ($cursor as $file) {
+				$row = $file->file;
+				$row['file'] = $file;
+				if ($indexBy !== null) {
+					if (is_string($indexBy)) {
+						$key = $row[$indexBy];
+					} else {
+						$key = call_user_func($indexBy, $row);
+					}
+					$result[$key] = $row;
+				} else {
+					$result[] = $row;
+				}
+			}
+		} else {
+			if ($cursor->hasNext()) {
+				$file = $cursor->getNext();
+				$result = $file->file;
+				$result['file'] = $file;
+			} else {
+				$result = false;
+			}
+		}
+		return $result;
+	}
+}
\ No newline at end of file
diff --git a/framework/yii/db/ActiveRelationTrait.php b/framework/yii/db/ActiveRelationTrait.php
index 832bb62d2e1..c477df9e97b 100644
--- a/framework/yii/db/ActiveRelationTrait.php
+++ b/framework/yii/db/ActiveRelationTrait.php
@@ -203,7 +203,8 @@ private function getModelKey($model, $attributes)
 			return serialize($key);
 		} else {
 			$attribute = reset($attributes);
-			return $model[$attribute];
+			$key = $model[$attribute];
+			return is_scalar($key) ? $key : serialize($key);
 		}
 	}
 
diff --git a/tests/unit/data/ar/mongo/ActiveRecord.php b/tests/unit/data/ar/mongo/ActiveRecord.php
new file mode 100644
index 00000000000..6f5bc49ac98
--- /dev/null
+++ b/tests/unit/data/ar/mongo/ActiveRecord.php
@@ -0,0 +1,16 @@
+<?php
+
+namespace yiiunit\data\ar\mongo;
+
+/**
+ * Test Mongo ActiveRecord
+ */
+class ActiveRecord extends \yii\mongo\ActiveRecord
+{
+	public static $db;
+
+	public static function getDb()
+	{
+		return self::$db;
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/data/ar/mongo/Customer.php b/tests/unit/data/ar/mongo/Customer.php
new file mode 100644
index 00000000000..f90e5cd81a6
--- /dev/null
+++ b/tests/unit/data/ar/mongo/Customer.php
@@ -0,0 +1,32 @@
+<?php
+
+namespace yiiunit\data\ar\mongo;
+
+class Customer extends ActiveRecord
+{
+	public static function collectionName()
+	{
+		return 'customer';
+	}
+
+	public function attributes()
+	{
+		return [
+			'_id',
+			'name',
+			'email',
+			'address',
+			'status',
+		];
+	}
+
+	public static function activeOnly($query)
+	{
+		$query->andWhere(['status' => 2]);
+	}
+
+	public function getOrders()
+	{
+		return $this->hasMany(CustomerOrder::className(), ['customer_id' => '_id']);
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/data/ar/mongo/CustomerOrder.php b/tests/unit/data/ar/mongo/CustomerOrder.php
new file mode 100644
index 00000000000..a01e47fe5e2
--- /dev/null
+++ b/tests/unit/data/ar/mongo/CustomerOrder.php
@@ -0,0 +1,27 @@
+<?php
+
+namespace yiiunit\data\ar\mongo;
+
+
+class CustomerOrder extends ActiveRecord
+{
+	public static function collectionName()
+	{
+		return 'customer_order';
+	}
+
+	public function attributes()
+	{
+		return [
+			'_id',
+			'number',
+			'customer_id',
+			'items',
+		];
+	}
+
+	public function getCustomer()
+	{
+		return $this->hasOne(Customer::className(), ['_id' => 'customer_id']);
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/data/ar/mongo/file/ActiveRecord.php b/tests/unit/data/ar/mongo/file/ActiveRecord.php
new file mode 100644
index 00000000000..70ebeb23ac4
--- /dev/null
+++ b/tests/unit/data/ar/mongo/file/ActiveRecord.php
@@ -0,0 +1,16 @@
+<?php
+
+namespace yiiunit\data\ar\mongo\file;
+
+/**
+ * Test Mongo ActiveRecord
+ */
+class ActiveRecord extends \yii\mongo\file\ActiveRecord
+{
+	public static $db;
+
+	public static function getDb()
+	{
+		return self::$db;
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/data/ar/mongo/file/CustomerFile.php b/tests/unit/data/ar/mongo/file/CustomerFile.php
new file mode 100644
index 00000000000..f5d16b9d7a8
--- /dev/null
+++ b/tests/unit/data/ar/mongo/file/CustomerFile.php
@@ -0,0 +1,27 @@
+<?php
+
+namespace yiiunit\data\ar\mongo\file;
+
+class CustomerFile extends ActiveRecord
+{
+	public static function collectionName()
+	{
+		return 'customer_fs';
+	}
+
+	public function attributes()
+	{
+		return array_merge(
+			parent::attributes(),
+			[
+				'tag',
+				'status',
+			]
+		);
+	}
+
+	public static function activeOnly($query)
+	{
+		$query->andWhere(['status' => 2]);
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/data/config.php b/tests/unit/data/config.php
index 0bd5e474820..7b23a8dd806 100644
--- a/tests/unit/data/config.php
+++ b/tests/unit/data/config.php
@@ -51,5 +51,10 @@
 			'password' => '',
 			'fixture' => __DIR__ . '/sphinx/source.sql',
 		],
+	],
+	'mongo' => [
+		'dsn' => 'mongodb://travis:test@localhost:27017',
+		'defaultDatabaseName' => 'yii2test',
+		'options' => [],
 	]
 ];
diff --git a/tests/unit/extensions/mongo/ActiveDataProviderTest.php b/tests/unit/extensions/mongo/ActiveDataProviderTest.php
new file mode 100644
index 00000000000..366051613c1
--- /dev/null
+++ b/tests/unit/extensions/mongo/ActiveDataProviderTest.php
@@ -0,0 +1,91 @@
+<?php
+
+namespace yiiunit\extensions\mongo;
+
+use yii\data\ActiveDataProvider;
+use yii\mongo\Query;
+use yiiunit\data\ar\mongo\ActiveRecord;
+use yiiunit\data\ar\mongo\Customer;
+
+/**
+ * @group mongo
+ */
+class ActiveDataProviderTest extends MongoTestCase
+{
+	protected function setUp()
+	{
+		parent::setUp();
+		ActiveRecord::$db = $this->getConnection();
+		$this->setUpTestRows();
+	}
+
+	protected function tearDown()
+	{
+		$this->dropCollection(Customer::collectionName());
+		parent::tearDown();
+	}
+
+	/**
+	 * Sets up test rows.
+	 */
+	protected function setUpTestRows()
+	{
+		$collection = $this->getConnection()->getCollection('customer');
+		$rows = [];
+		for ($i = 1; $i <= 10; $i++) {
+			$rows[] = [
+				'name' => 'name' . $i,
+				'email' => 'email' . $i,
+				'address' => 'address' . $i,
+				'status' => $i,
+			];
+		}
+		$collection->batchInsert($rows);
+	}
+
+	// Tests :
+
+	public function testQuery()
+	{
+		$query = new Query;
+		$query->from('customer');
+
+		$provider = new ActiveDataProvider([
+			'query' => $query,
+			'db' => $this->getConnection(),
+		]);
+		$models = $provider->getModels();
+		$this->assertEquals(10, count($models));
+
+		$provider = new ActiveDataProvider([
+			'query' => $query,
+			'db' => $this->getConnection(),
+			'pagination' => [
+				'pageSize' => 5,
+			]
+		]);
+		$models = $provider->getModels();
+		$this->assertEquals(5, count($models));
+	}
+
+	public function testActiveQuery()
+	{
+		$provider = new ActiveDataProvider([
+			'query' => Customer::find()->orderBy('id ASC'),
+		]);
+		$models = $provider->getModels();
+		$this->assertEquals(10, count($models));
+		$this->assertTrue($models[0] instanceof Customer);
+		$keys = $provider->getKeys();
+		$this->assertTrue($keys[0] instanceof \MongoId);
+
+		$provider = new ActiveDataProvider([
+			'query' => Customer::find(),
+			'pagination' => [
+				'pageSize' => 5,
+			]
+		]);
+		$models = $provider->getModels();
+		$this->assertEquals(5, count($models));
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/extensions/mongo/ActiveRecordTest.php b/tests/unit/extensions/mongo/ActiveRecordTest.php
new file mode 100644
index 00000000000..8467ba0b6e8
--- /dev/null
+++ b/tests/unit/extensions/mongo/ActiveRecordTest.php
@@ -0,0 +1,246 @@
+<?php
+
+namespace yiiunit\extensions\mongo;
+
+use yii\mongo\ActiveQuery;
+use yiiunit\data\ar\mongo\ActiveRecord;
+use yiiunit\data\ar\mongo\Customer;
+
+/**
+ * @group mongo
+ */
+class ActiveRecordTest extends MongoTestCase
+{
+	/**
+	 * @var array[] list of test rows.
+	 */
+	protected $testRows = [];
+
+	protected function setUp()
+	{
+		parent::setUp();
+		ActiveRecord::$db = $this->getConnection();
+		$this->setUpTestRows();
+	}
+
+	protected function tearDown()
+	{
+		$this->dropCollection(Customer::collectionName());
+		parent::tearDown();
+	}
+
+	/**
+	 * Sets up test rows.
+	 */
+	protected function setUpTestRows()
+	{
+		$collection = $this->getConnection()->getCollection('customer');
+		$rows = [];
+		for ($i = 1; $i <= 10; $i++) {
+			$rows[] = [
+				'name' => 'name' . $i,
+				'email' => 'email' . $i,
+				'address' => 'address' . $i,
+				'status' => $i,
+			];
+		}
+		$collection->batchInsert($rows);
+		$this->testRows = $rows;
+	}
+
+	// Tests :
+
+	public function testFind()
+	{
+		// find one
+		$result = Customer::find();
+		$this->assertTrue($result instanceof ActiveQuery);
+		$customer = $result->one();
+		$this->assertTrue($customer instanceof Customer);
+
+		// find all
+		$customers = Customer::find()->all();
+		$this->assertEquals(10, count($customers));
+		$this->assertTrue($customers[0] instanceof Customer);
+		$this->assertTrue($customers[1] instanceof Customer);
+
+		// find by _id
+		$testId = $this->testRows[0]['_id'];
+		$customer = Customer::find($testId);
+		$this->assertTrue($customer instanceof Customer);
+		$this->assertEquals($testId, $customer->_id);
+
+		// find by column values
+		$customer = Customer::find(['name' => 'name5']);
+		$this->assertTrue($customer instanceof Customer);
+		$this->assertEquals($this->testRows[4]['_id'], $customer->_id);
+		$this->assertEquals('name5', $customer->name);
+		$customer = Customer::find(['name' => 'unexisting name']);
+		$this->assertNull($customer);
+
+		// find by attributes
+		$customer = Customer::find()->where(['status' => 4])->one();
+		$this->assertTrue($customer instanceof Customer);
+		$this->assertEquals(4, $customer->status);
+
+		// find count, sum, average, min, max, distinct
+		$this->assertEquals(10, Customer::find()->count());
+		$this->assertEquals(1, Customer::find()->where(['status' => 2])->count());
+		$this->assertEquals((1+10)/2*10, Customer::find()->sum('status'));
+		$this->assertEquals((1+10)/2, Customer::find()->average('status'));
+		$this->assertEquals(1, Customer::find()->min('status'));
+		$this->assertEquals(10, Customer::find()->max('status'));
+		$this->assertEquals(range(1, 10), Customer::find()->distinct('status'));
+
+		// scope
+		$this->assertEquals(1, Customer::find()->activeOnly()->count());
+
+		// asArray
+		$testRow = $this->testRows[2];
+		$customer = Customer::find()->where(['_id' => $testRow['_id']])->asArray()->one();
+		$this->assertEquals($testRow, $customer);
+
+		// indexBy
+		$customers = Customer::find()->indexBy('name')->all();
+		$this->assertTrue($customers['name1'] instanceof Customer);
+		$this->assertTrue($customers['name2'] instanceof Customer);
+
+		// indexBy callable
+		$customers = Customer::find()->indexBy(function ($customer) {
+			return $customer->status . '-' . $customer->status;
+		})->all();
+		$this->assertTrue($customers['1-1'] instanceof Customer);
+		$this->assertTrue($customers['2-2'] instanceof Customer);
+	}
+
+	public function testInsert()
+	{
+		$record = new Customer;
+		$record->name = 'new name';
+		$record->email = 'new email';
+		$record->address = 'new address';
+		$record->status = 7;
+
+		$this->assertTrue($record->isNewRecord);
+
+		$record->save();
+
+		$this->assertTrue($record->_id instanceof \MongoId);
+		$this->assertFalse($record->isNewRecord);
+	}
+
+	/**
+	 * @depends testInsert
+	 */
+	public function testUpdate()
+	{
+		$record = new Customer;
+		$record->name = 'new name';
+		$record->email = 'new email';
+		$record->address = 'new address';
+		$record->status = 7;
+		$record->save();
+
+		// save
+		$record = Customer::find($record->_id);
+		$this->assertTrue($record instanceof Customer);
+		$this->assertEquals(7, $record->status);
+		$this->assertFalse($record->isNewRecord);
+
+		$record->status = 9;
+		$record->save();
+		$this->assertEquals(9, $record->status);
+		$this->assertFalse($record->isNewRecord);
+		$record2 = Customer::find($record->_id);
+		$this->assertEquals(9, $record2->status);
+
+		// updateAll
+		$pk = ['_id' => $record->_id];
+		$ret = Customer::updateAll(['status' => 55], $pk);
+		$this->assertEquals(1, $ret);
+		$record = Customer::find($pk);
+		$this->assertEquals(55, $record->status);
+	}
+
+	/**
+	 * @depends testInsert
+	 */
+	public function testDelete()
+	{
+		// delete
+		$record = new Customer;
+		$record->name = 'new name';
+		$record->email = 'new email';
+		$record->address = 'new address';
+		$record->status = 7;
+		$record->save();
+
+		$record = Customer::find($record->_id);
+		$record->delete();
+		$record = Customer::find($record->_id);
+		$this->assertNull($record);
+
+		// deleteAll
+		$record = new Customer;
+		$record->name = 'new name';
+		$record->email = 'new email';
+		$record->address = 'new address';
+		$record->status = 7;
+		$record->save();
+
+		$ret = Customer::deleteAll(['name' => 'new name']);
+		$this->assertEquals(1, $ret);
+		$records = Customer::find()->where(['name' => 'new name'])->all();
+		$this->assertEquals(0, count($records));
+	}
+
+	public function testUpdateAllCounters()
+	{
+		$this->assertEquals(1, Customer::updateAllCounters(['status' => 10], ['status' => 10]));
+
+		$record = Customer::find(['status' => 10]);
+		$this->assertNull($record);
+	}
+
+	/**
+	 * @depends testUpdateAllCounters
+	 */
+	public function testUpdateCounters()
+	{
+		$record = Customer::find($this->testRows[9]);
+
+		$originalCounter = $record->status;
+		$counterIncrement = 20;
+		$record->updateCounters(['status' => $counterIncrement]);
+		$this->assertEquals($originalCounter + $counterIncrement, $record->status);
+
+		$refreshedRecord = Customer::find($record->_id);
+		$this->assertEquals($originalCounter + $counterIncrement, $refreshedRecord->status);
+	}
+
+	/**
+	 * @depends testUpdate
+	 */
+	public function testUpdateNestedAttribute()
+	{
+		$record = new Customer;
+		$record->name = 'new name';
+		$record->email = 'new email';
+		$record->address = [
+			'city' => 'SomeCity',
+			'street' => 'SomeStreet',
+		];
+		$record->status = 7;
+		$record->save();
+
+		// save
+		$record = Customer::find($record->_id);
+		$newAddress = [
+			'city' => 'AnotherCity'
+		];
+		$record->address = $newAddress;
+		$record->save();
+		$record2 = Customer::find($record->_id);
+		$this->assertEquals($newAddress, $record2->address);
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/extensions/mongo/ActiveRelationTest.php b/tests/unit/extensions/mongo/ActiveRelationTest.php
new file mode 100644
index 00000000000..26cf63e534e
--- /dev/null
+++ b/tests/unit/extensions/mongo/ActiveRelationTest.php
@@ -0,0 +1,83 @@
+<?php
+
+namespace yiiunit\extensions\mongo;
+
+use yiiunit\data\ar\mongo\ActiveRecord;
+use yiiunit\data\ar\mongo\Customer;
+use yiiunit\data\ar\mongo\CustomerOrder;
+
+/**
+ * @group mongo
+ */
+class ActiveRelationTest extends MongoTestCase
+{
+	protected function setUp()
+	{
+		parent::setUp();
+		ActiveRecord::$db = $this->getConnection();
+		$this->setUpTestRows();
+	}
+
+	protected function tearDown()
+	{
+		$this->dropCollection(Customer::collectionName());
+		$this->dropCollection(CustomerOrder::collectionName());
+		parent::tearDown();
+	}
+
+	/**
+	 * Sets up test rows.
+	 */
+	protected function setUpTestRows()
+	{
+		$customerCollection = $this->getConnection()->getCollection('customer');
+
+		$customers = [];
+		for ($i = 1; $i <= 5; $i++) {
+			$customers[] = [
+				'name' => 'name' . $i,
+				'email' => 'email' . $i,
+				'address' => 'address' . $i,
+				'status' => $i,
+			];
+		}
+		$customerCollection->batchInsert($customers);
+
+		$customerOrderCollection = $this->getConnection()->getCollection('customer_order');
+		$customerOrders = [];
+		foreach ($customers as $customer) {
+			$customerOrders[] = [
+				'customer_id' => $customer['_id'],
+				'number' => $customer['status'],
+			];
+			$customerOrders[] = [
+				'customer_id' => $customer['_id'],
+				'number' => $customer['status'] + 1,
+			];
+		}
+		$customerOrderCollection->batchInsert($customerOrders);
+	}
+
+	// Tests :
+
+	public function testFindLazy()
+	{
+		/** @var CustomerOrder $order */
+		$order = CustomerOrder::find(['number' => 2]);
+		$this->assertFalse($order->isRelationPopulated('customer'));
+		$index = $order->customer;
+		$this->assertTrue($order->isRelationPopulated('customer'));
+		$this->assertTrue($index instanceof Customer);
+		$this->assertEquals(1, count($order->populatedRelations));
+	}
+
+	public function testFindEager()
+	{
+		$orders = CustomerOrder::find()->with('customer')->all();
+		$this->assertEquals(10, count($orders));
+		$this->assertTrue($orders[0]->isRelationPopulated('customer'));
+		$this->assertTrue($orders[1]->isRelationPopulated('customer'));
+		$this->assertTrue($orders[0]->customer instanceof Customer);
+		$this->assertTrue($orders[1]->customer instanceof Customer);
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/extensions/mongo/CollectionTest.php b/tests/unit/extensions/mongo/CollectionTest.php
new file mode 100644
index 00000000000..153ffa9033b
--- /dev/null
+++ b/tests/unit/extensions/mongo/CollectionTest.php
@@ -0,0 +1,313 @@
+<?php
+
+namespace yiiunit\extensions\mongo;
+
+/**
+ * @group mongo
+ */
+class CollectionTest extends MongoTestCase
+{
+	protected function tearDown()
+	{
+		$this->dropCollection('customer');
+		$this->dropCollection('mapReduceOut');
+		parent::tearDown();
+	}
+
+	// Tests :
+
+	public function testGetName()
+	{
+		$collectionName = 'customer';
+		$collection = $this->getConnection()->getCollection($collectionName);
+		$this->assertEquals($collectionName, $collection->getName());
+		$this->assertEquals($this->mongoConfig['defaultDatabaseName'] . '.' . $collectionName, $collection->getFullName());
+	}
+
+	public function testFind()
+	{
+		$collection = $this->getConnection()->getCollection('customer');
+		$cursor = $collection->find();
+		$this->assertTrue($cursor instanceof \MongoCursor);
+	}
+
+	public function testInsert()
+	{
+		$collection = $this->getConnection()->getCollection('customer');
+		$data = [
+			'name' => 'customer 1',
+			'address' => 'customer 1 address',
+		];
+		$id = $collection->insert($data);
+		$this->assertTrue($id instanceof \MongoId);
+		$this->assertNotEmpty($id->__toString());
+	}
+
+	/**
+	 * @depends testInsert
+	 * @depends testFind
+	 */
+	public function testFindAll()
+	{
+		$collection = $this->getConnection()->getCollection('customer');
+		$data = [
+			'name' => 'customer 1',
+			'address' => 'customer 1 address',
+		];
+		$id = $collection->insert($data);
+
+		$cursor = $collection->find();
+		$rows = [];
+		foreach ($cursor as $row) {
+			$rows[] = $row;
+		}
+		$this->assertEquals(1, count($rows));
+		$this->assertEquals($id, $rows[0]['_id']);
+	}
+
+	/**
+	 * @depends testFind
+	 */
+	public function testBatchInsert()
+	{
+		$collection = $this->getConnection()->getCollection('customer');
+		$rows = [
+			[
+				'name' => 'customer 1',
+				'address' => 'customer 1 address',
+			],
+			[
+				'name' => 'customer 2',
+				'address' => 'customer 2 address',
+			],
+		];
+		$insertedRows = $collection->batchInsert($rows);
+		$this->assertTrue($insertedRows[0]['_id'] instanceof \MongoId);
+		$this->assertTrue($insertedRows[1]['_id'] instanceof \MongoId);
+		$this->assertEquals(count($rows), $collection->find()->count());
+	}
+
+	public function testSave()
+	{
+		$collection = $this->getConnection()->getCollection('customer');
+		$data = [
+			'name' => 'customer 1',
+			'address' => 'customer 1 address',
+		];
+		$id = $collection->save($data);
+		$this->assertTrue($id instanceof \MongoId);
+		$this->assertNotEmpty($id->__toString());
+	}
+
+	/**
+	 * @depends testSave
+	 */
+	public function testUpdateBySave()
+	{
+		$collection = $this->getConnection()->getCollection('customer');
+		$data = [
+			'name' => 'customer 1',
+			'address' => 'customer 1 address',
+		];
+		$newId = $collection->save($data);
+
+		$updatedId = $collection->save($data);
+		$this->assertEquals($newId, $updatedId, 'Unable to update data!');
+
+		$data['_id'] = $newId->__toString();
+		$updatedId = $collection->save($data);
+		$this->assertEquals($newId, $updatedId, 'Unable to updated data by string id!');
+	}
+
+	/**
+	 * @depends testFindAll
+	 */
+	public function testRemove()
+	{
+		$collection = $this->getConnection()->getCollection('customer');
+		$data = [
+			'name' => 'customer 1',
+			'address' => 'customer 1 address',
+		];
+		$id = $collection->insert($data);
+
+		$count = $collection->remove(['_id' => $id]);
+		$this->assertEquals(1, $count);
+
+		$rows = $this->findAll($collection);
+		$this->assertEquals(0, count($rows));
+	}
+
+	/**
+	 * @depends testFindAll
+	 */
+	public function testUpdate()
+	{
+		$collection = $this->getConnection()->getCollection('customer');
+		$data = [
+			'name' => 'customer 1',
+			'address' => 'customer 1 address',
+		];
+		$id = $collection->insert($data);
+
+		$newData = [
+			'name' => 'new name'
+		];
+		$count = $collection->update(['_id' => $id], $newData);
+		$this->assertEquals(1, $count);
+
+		list($row) = $this->findAll($collection);
+		$this->assertEquals($newData['name'], $row['name']);
+	}
+
+	/**
+	 * @depends testBatchInsert
+	 */
+	public function testGroup()
+	{
+		$collection = $this->getConnection()->getCollection('customer');
+		$rows = [
+			[
+				'name' => 'customer 1',
+				'address' => 'customer 1 address',
+			],
+			[
+				'name' => 'customer 2',
+				'address' => 'customer 2 address',
+			],
+		];
+		$collection->batchInsert($rows);
+
+		$keys = ['address' => 1];
+		$initial = ['items' => []];
+		$reduce = "function (obj, prev) { prev.items.push(obj.name); }";
+		$result = $collection->group($keys, $initial, $reduce);
+		$this->assertEquals(2, count($result));
+		$this->assertNotEmpty($result[0]['address']);
+		$this->assertNotEmpty($result[0]['items']);
+	}
+
+	/**
+	 * @depends testBatchInsert
+	 */
+	public function testMapReduce()
+	{
+		$collection = $this->getConnection()->getCollection('customer');
+		$rows = [
+			[
+				'name' => 'customer 1',
+				'status' => 1,
+				'amount' => 100,
+			],
+			[
+				'name' => 'customer 2',
+				'status' => 1,
+				'amount' => 200,
+			],
+			[
+				'name' => 'customer 2',
+				'status' => 2,
+				'amount' => 400,
+			],
+			[
+				'name' => 'customer 2',
+				'status' => 3,
+				'amount' => 500,
+			],
+		];
+		$collection->batchInsert($rows);
+
+		$result = $collection->mapReduce(
+			'function () {emit(this.status, this.amount)}',
+			'function (key, values) {return Array.sum(values)}',
+			'mapReduceOut',
+			['status' => ['$lt' => 3]]
+		);
+		$this->assertEquals('mapReduceOut', $result);
+
+		$outputCollection = $this->getConnection()->getCollection($result);
+		$rows = $this->findAll($outputCollection);
+		$expectedRows = [
+			[
+				'_id' => 1,
+				'value' => 300,
+			],
+			[
+				'_id' => 2,
+				'value' => 400,
+			],
+		];
+		$this->assertEquals($expectedRows, $rows);
+	}
+
+	public function testCreateIndex()
+	{
+		$collection = $this->getConnection()->getCollection('customer');
+		$columns = [
+			'name',
+			'status' => \MongoCollection::DESCENDING,
+		];
+		$this->assertTrue($collection->createIndex($columns));
+		$indexInfo = $collection->mongoCollection->getIndexInfo();
+		$this->assertEquals(2, count($indexInfo));
+	}
+
+	/**
+	 * @depends testCreateIndex
+	 */
+	public function testDropIndex()
+	{
+		$collection = $this->getConnection()->getCollection('customer');
+
+		$collection->createIndex('name');
+		$this->assertTrue($collection->dropIndex('name'));
+		$indexInfo = $collection->mongoCollection->getIndexInfo();
+		$this->assertEquals(1, count($indexInfo));
+
+		$this->setExpectedException('\yii\mongo\Exception');
+		$collection->dropIndex('name');
+	}
+
+	/**
+	 * @depends testCreateIndex
+	 */
+	public function testDropAllIndexes()
+	{
+		$collection = $this->getConnection()->getCollection('customer');
+		$collection->createIndex('name');
+		$this->assertEquals(2, $collection->dropAllIndexes());
+		$indexInfo = $collection->mongoCollection->getIndexInfo();
+		$this->assertEquals(1, count($indexInfo));
+	}
+
+	/**
+	 * @depends testBatchInsert
+	 * @depends testCreateIndex
+	 */
+	public function testFullTextSearch()
+	{
+		if (version_compare('2.4', $this->getServerVersion(), '>')) {
+			$this->markTestSkipped("Mongo Server 2.4 required.");
+		}
+
+		$collection = $this->getConnection()->getCollection('customer');
+
+		$rows = [
+			[
+				'name' => 'customer 1',
+				'status' => 1,
+				'amount' => 100,
+			],
+			[
+				'name' => 'some customer',
+				'status' => 1,
+				'amount' => 200,
+			],
+		];
+		$collection->batchInsert($rows);
+		$collection->createIndex(['name' => 'text']);
+
+		$result = $collection->fullTextSearch('some');
+		$this->assertNotEmpty($result);
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/extensions/mongo/ConnectionTest.php b/tests/unit/extensions/mongo/ConnectionTest.php
new file mode 100644
index 00000000000..04d5351e01e
--- /dev/null
+++ b/tests/unit/extensions/mongo/ConnectionTest.php
@@ -0,0 +1,119 @@
+<?php
+
+namespace yiiunit\extensions\mongo;
+
+use yii\mongo\Collection;
+use yii\mongo\file\Collection as FileCollection;
+use yii\mongo\Connection;
+use yii\mongo\Database;
+
+/**
+ * @group mongo
+ */
+class ConnectionTest extends MongoTestCase
+{
+	public function testConstruct()
+	{
+		$connection = $this->getConnection(false);
+		$params = $this->mongoConfig;
+
+		$connection->open();
+
+		$this->assertEquals($params['dsn'], $connection->dsn);
+		$this->assertEquals($params['defaultDatabaseName'], $connection->defaultDatabaseName);
+		$this->assertEquals($params['options'], $connection->options);
+	}
+
+	public function testOpenClose()
+	{
+		$connection = $this->getConnection(false, false);
+
+		$this->assertFalse($connection->isActive);
+		$this->assertEquals(null, $connection->mongoClient);
+
+		$connection->open();
+		$this->assertTrue($connection->isActive);
+		$this->assertTrue(is_object($connection->mongoClient));
+
+		$connection->close();
+		$this->assertFalse($connection->isActive);
+		$this->assertEquals(null, $connection->mongoClient);
+
+		$connection = new Connection;
+		$connection->dsn = 'unknown::memory:';
+		$this->setExpectedException('yii\mongo\Exception');
+		$connection->open();
+	}
+
+	public function testGetDatabase()
+	{
+		$connection = $this->getConnection();
+
+		$database = $connection->getDatabase($connection->defaultDatabaseName);
+		$this->assertTrue($database instanceof Database);
+		$this->assertTrue($database->mongoDb instanceof \MongoDB);
+
+		$database2 = $connection->getDatabase($connection->defaultDatabaseName);
+		$this->assertTrue($database === $database2);
+
+		$databaseRefreshed = $connection->getDatabase($connection->defaultDatabaseName, true);
+		$this->assertFalse($database === $databaseRefreshed);
+	}
+
+	/**
+	 * @depends testGetDatabase
+	 */
+	public function testGetDefaultDatabase()
+	{
+		$connection = new Connection();
+		$connection->dsn = $this->mongoConfig['dsn'];
+		$connection->defaultDatabaseName = $this->mongoConfig['defaultDatabaseName'];
+		$database = $connection->getDatabase();
+		$this->assertTrue($database instanceof Database, 'Unable to get default database!');
+
+		$connection = new Connection();
+		$connection->dsn = $this->mongoConfig['dsn'];
+		$connection->options = ['db' => $this->mongoConfig['defaultDatabaseName']];
+		$database = $connection->getDatabase();
+		$this->assertTrue($database instanceof Database, 'Unable to determine default database from options!');
+
+		$connection = new Connection();
+		$connection->dsn = $this->mongoConfig['dsn'] . '/' . $this->mongoConfig['defaultDatabaseName'];
+		$database = $connection->getDatabase();
+		$this->assertTrue($database instanceof Database, 'Unable to determine default database from dsn!');
+	}
+
+	/**
+	 * @depends testGetDefaultDatabase
+	 */
+	public function testGetCollection()
+	{
+		$connection = $this->getConnection();
+
+		$collection = $connection->getCollection('customer');
+		$this->assertTrue($collection instanceof Collection);
+
+		$collection2 = $connection->getCollection('customer');
+		$this->assertTrue($collection === $collection2);
+
+		$collection2 = $connection->getCollection('customer', true);
+		$this->assertFalse($collection === $collection2);
+	}
+
+	/**
+	 * @depends testGetDefaultDatabase
+	 */
+	public function testGetFileCollection()
+	{
+		$connection = $this->getConnection();
+
+		$collection = $connection->getFileCollection('testfs');
+		$this->assertTrue($collection instanceof FileCollection);
+
+		$collection2 = $connection->getFileCollection('testfs');
+		$this->assertTrue($collection === $collection2);
+
+		$collection2 = $connection->getFileCollection('testfs', true);
+		$this->assertFalse($collection === $collection2);
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/extensions/mongo/DatabaseTest.php b/tests/unit/extensions/mongo/DatabaseTest.php
new file mode 100644
index 00000000000..6847d2e6a18
--- /dev/null
+++ b/tests/unit/extensions/mongo/DatabaseTest.php
@@ -0,0 +1,70 @@
+<?php
+
+namespace yiiunit\extensions\mongo;
+
+use yii\mongo\Collection;
+use yii\mongo\file\Collection as FileCollection;
+
+/**
+ * @group mongo
+ */
+class DatabaseTest extends MongoTestCase
+{
+	protected function tearDown()
+	{
+		$this->dropCollection('customer');
+		$this->dropFileCollection('testfs');
+		parent::tearDown();
+	}
+
+	// Tests :
+
+	public function testGetCollection()
+	{
+		$database = $connection = $this->getConnection()->getDatabase();
+
+		$collection = $database->getCollection('customer');
+		$this->assertTrue($collection instanceof Collection);
+		$this->assertTrue($collection->mongoCollection instanceof \MongoCollection);
+
+		$collection2 = $database->getCollection('customer');
+		$this->assertTrue($collection === $collection2);
+
+		$collectionRefreshed = $database->getCollection('customer', true);
+		$this->assertFalse($collection === $collectionRefreshed);
+	}
+
+	public function testGetFileCollection()
+	{
+		$database = $connection = $this->getConnection()->getDatabase();
+
+		$collection = $database->getFileCollection('testfs');
+		$this->assertTrue($collection instanceof FileCollection);
+		$this->assertTrue($collection->mongoCollection instanceof \MongoGridFS);
+
+		$collection2 = $database->getFileCollection('testfs');
+		$this->assertTrue($collection === $collection2);
+
+		$collectionRefreshed = $database->getFileCollection('testfs', true);
+		$this->assertFalse($collection === $collectionRefreshed);
+	}
+
+	public function testExecuteCommand()
+	{
+		$database = $connection = $this->getConnection()->getDatabase();
+
+		$result = $database->executeCommand([
+			'distinct' => 'customer',
+			'key' => 'name'
+		]);
+		$this->assertTrue(array_key_exists('ok', $result));
+		$this->assertTrue(array_key_exists('values', $result));
+	}
+
+	public function testCreateCollection()
+	{
+		$database = $connection = $this->getConnection()->getDatabase();
+		$collection = $database->createCollection('customer');
+		$this->assertTrue($collection instanceof \MongoCollection);
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/extensions/mongo/MongoTestCase.php b/tests/unit/extensions/mongo/MongoTestCase.php
new file mode 100644
index 00000000000..291debdee57
--- /dev/null
+++ b/tests/unit/extensions/mongo/MongoTestCase.php
@@ -0,0 +1,149 @@
+<?php
+
+namespace yiiunit\extensions\mongo;
+
+use yii\helpers\FileHelper;
+use yii\mongo\Connection;
+use Yii;
+use yii\mongo\Exception;
+use yiiunit\TestCase;
+
+class MongoTestCase extends TestCase
+{
+	/**
+	 * @var array Mongo connection configuration.
+	 */
+	protected $mongoConfig = [
+		'dsn' => 'mongodb://localhost:27017',
+		'defaultDatabaseName' => 'yii2test',
+		'options' => [],
+	];
+	/**
+	 * @var Connection Mongo connection instance.
+	 */
+	protected $mongo;
+
+	public static function setUpBeforeClass()
+	{
+		static::loadClassMap();
+	}
+
+	protected function setUp()
+	{
+		parent::setUp();
+		if (!extension_loaded('mongo')) {
+			$this->markTestSkipped('mongo extension required.');
+		}
+		$config = $this->getParam('mongo');
+		if (!empty($config)) {
+			$this->mongoConfig = $config;
+		}
+		$this->mockApplication();
+		static::loadClassMap();
+	}
+
+	protected function tearDown()
+	{
+		if ($this->mongo) {
+			$this->mongo->close();
+		}
+		$this->destroyApplication();
+	}
+
+	/**
+	 * Adds sphinx extension files to [[Yii::$classPath]],
+	 * avoiding the necessity of usage Composer autoloader.
+	 */
+	protected static function loadClassMap()
+	{
+		$baseNameSpace = 'yii/mongo';
+		$basePath = realpath(__DIR__. '/../../../../extensions/mongo');
+		$files = FileHelper::findFiles($basePath);
+		foreach ($files as $file) {
+			$classRelativePath = str_replace($basePath, '', $file);
+			$classFullName = str_replace(['/', '.php'], ['\\', ''], $baseNameSpace . $classRelativePath);
+			Yii::$classMap[$classFullName] = $file;
+		}
+	}
+
+	/**
+	 * @param boolean $reset whether to clean up the test database
+	 * @param boolean $open whether to open test database
+	 * @return \yii\mongo\Connection
+	 */
+	public function getConnection($reset = false, $open = true)
+	{
+		if (!$reset && $this->mongo) {
+			return $this->mongo;
+		}
+		$db = new Connection;
+		$db->dsn = $this->mongoConfig['dsn'];
+		$db->defaultDatabaseName = $this->mongoConfig['defaultDatabaseName'];
+		if (isset($this->mongoConfig['options'])) {
+			$db->options = $this->mongoConfig['options'];
+		}
+		if ($open) {
+			$db->open();
+		}
+		$this->mongo = $db;
+		return $db;
+	}
+
+	/**
+	 * Drops the specified collection.
+	 * @param string $name collection name.
+	 */
+	protected function dropCollection($name)
+	{
+		if ($this->mongo) {
+			try {
+				$this->mongo->getCollection($name)->drop();
+			} catch (Exception $e) {
+				// shut down exception
+			}
+		}
+	}
+
+	/**
+	 * Drops the specified file collection.
+	 * @param string $name file collection name.
+	 */
+	protected function dropFileCollection($name = 'fs')
+	{
+		if ($this->mongo) {
+			try {
+				$this->mongo->getFileCollection($name)->drop();
+			} catch (Exception $e) {
+				// shut down exception
+			}
+		}
+	}
+
+	/**
+	 * Finds all records in collection.
+	 * @param \yii\mongo\Collection $collection
+	 * @param array $condition
+	 * @param array $fields
+	 * @return array rows
+	 */
+	protected function findAll($collection, $condition = [], $fields = [])
+	{
+		$cursor = $collection->find($condition, $fields);
+		$result = [];
+		foreach ($cursor as $data) {
+			$result[] = $data;
+		}
+		return $result;
+	}
+
+	/**
+	 * Returns the Mongo server version.
+	 * @return string Mongo server version.
+	 */
+	protected function getServerVersion()
+	{
+		$connection = $this->getConnection();
+		$buildInfo = $connection->getDatabase()->executeCommand(['buildinfo' => true]);
+		return $buildInfo['version'];
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/extensions/mongo/QueryRunTest.php b/tests/unit/extensions/mongo/QueryRunTest.php
new file mode 100644
index 00000000000..7fe481235df
--- /dev/null
+++ b/tests/unit/extensions/mongo/QueryRunTest.php
@@ -0,0 +1,132 @@
+<?php
+
+namespace yiiunit\extensions\mongo;
+
+use yii\mongo\Query;
+
+/**
+ * @group mongo
+ */
+class QueryRunTest extends MongoTestCase
+{
+	protected function setUp()
+	{
+		parent::setUp();
+		$this->setUpTestRows();
+	}
+
+	protected function tearDown()
+	{
+		$this->dropCollection('customer');
+		parent::tearDown();
+	}
+
+	/**
+	 * Sets up test rows.
+	 */
+	protected function setUpTestRows()
+	{
+		$collection = $this->getConnection()->getCollection('customer');
+		$rows = [];
+		for ($i = 1; $i <= 10; $i++) {
+			$rows[] = [
+				'name' => 'name' . $i,
+				'address' => 'address' . $i,
+				'avatar' => [
+					'width' => 50 + $i,
+					'height' => 100 + $i,
+					'url' => 'http://some.url/' . $i,
+				],
+			];
+		}
+		$collection->batchInsert($rows);
+	}
+
+	// Tests :
+
+	public function testAll()
+	{
+		$connection = $this->getConnection();
+		$query = new Query;
+		$rows = $query->from('customer')->all($connection);
+		$this->assertEquals(10, count($rows));
+	}
+
+	public function testDirectMatch()
+	{
+		$connection = $this->getConnection();
+		$query = new Query;
+		$rows = $query->from('customer')
+			->where(['name' => 'name1'])
+			->all($connection);
+		$this->assertEquals(1, count($rows));
+		$this->assertEquals('name1', $rows[0]['name']);
+	}
+
+	public function testIndexBy()
+	{
+		$connection = $this->getConnection();
+		$query = new Query;
+		$rows = $query->from('customer')
+			->indexBy('name')
+			->all($connection);
+		$this->assertEquals(10, count($rows));
+		$this->assertNotEmpty($rows['name1']);
+	}
+
+	public function testInCondition()
+	{
+		$connection = $this->getConnection();
+		$query = new Query;
+		$rows = $query->from('customer')
+			->where([
+				'name' => ['name1', 'name5']
+			])
+			->all($connection);
+		$this->assertEquals(2, count($rows));
+		$this->assertEquals('name1', $rows[0]['name']);
+		$this->assertEquals('name5', $rows[1]['name']);
+	}
+
+	public function testOrCondition()
+	{
+		$connection = $this->getConnection();
+		$query = new Query;
+		$rows = $query->from('customer')
+			->where(['name' => 'name1'])
+			->orWhere(['address' => 'address5'])
+			->all($connection);
+		$this->assertEquals(2, count($rows));
+		$this->assertEquals('name1', $rows[0]['name']);
+		$this->assertEquals('address5', $rows[1]['address']);
+	}
+
+	public function testOrder()
+	{
+		$connection = $this->getConnection();
+
+		$query = new Query;
+		$rows = $query->from('customer')
+			->orderBy(['name' => SORT_DESC])
+			->all($connection);
+		$this->assertEquals('name9', $rows[0]['name']);
+
+		$query = new Query;
+		$rows = $query->from('customer')
+			->orderBy(['avatar.height' => SORT_DESC])
+			->all($connection);
+		$this->assertEquals('name10', $rows[0]['name']);
+	}
+
+	public function testMatchPlainId()
+	{
+		$connection = $this->getConnection();
+		$query = new Query;
+		$row = $query->from('customer')->one($connection);
+		$query = new Query;
+		$rows = $query->from('customer')
+			->where(['_id' => $row['_id']->__toString()])
+			->all($connection);
+		$this->assertEquals(1, count($rows));
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/extensions/mongo/QueryTest.php b/tests/unit/extensions/mongo/QueryTest.php
new file mode 100644
index 00000000000..35d45e01098
--- /dev/null
+++ b/tests/unit/extensions/mongo/QueryTest.php
@@ -0,0 +1,97 @@
+<?php
+
+namespace yiiunit\extensions\mongo;
+
+use yii\mongo\Query;
+
+/**
+ * @group mongo
+ */
+class QueryTest extends MongoTestCase
+{
+	public function testSelect()
+	{
+		// default
+		$query = new Query;
+		$select = [];
+		$query->select($select);
+		$this->assertEquals($select, $query->select);
+
+		$query = new Query;
+		$select = ['name', 'something'];
+		$query->select($select);
+		$this->assertEquals($select, $query->select);
+	}
+
+	public function testFrom()
+	{
+		$query = new Query;
+		$from = 'customer';
+		$query->from($from);
+		$this->assertEquals($from, $query->from);
+
+		$query = new Query;
+		$from = ['', 'customer'];
+		$query->from($from);
+		$this->assertEquals($from, $query->from);
+	}
+
+	public function testWhere()
+	{
+		$query = new Query;
+		$query->where(['name' => 'name1']);
+		$this->assertEquals(['name' => 'name1'], $query->where);
+
+		$query->andWhere(['address' => 'address1']);
+		$this->assertEquals(
+			[
+				'and',
+				['name' => 'name1'],
+				['address' => 'address1']
+			],
+			$query->where
+		);
+
+		$query->orWhere(['name' => 'name2']);
+		$this->assertEquals(
+			[
+				'or',
+				[
+					'and',
+					['name' => 'name1'],
+					['address' => 'address1']
+				],
+				['name' => 'name2']
+
+			],
+			$query->where
+		);
+	}
+
+	public function testOrder()
+	{
+		$query = new Query;
+		$query->orderBy('team');
+		$this->assertEquals(['team' => SORT_ASC], $query->orderBy);
+
+		$query->addOrderBy('company');
+		$this->assertEquals(['team' => SORT_ASC, 'company' => SORT_ASC], $query->orderBy);
+
+		$query->addOrderBy('age');
+		$this->assertEquals(['team' => SORT_ASC, 'company' => SORT_ASC, 'age' => SORT_ASC], $query->orderBy);
+
+		$query->addOrderBy(['age' => SORT_DESC]);
+		$this->assertEquals(['team' => SORT_ASC, 'company' => SORT_ASC, 'age' => SORT_DESC], $query->orderBy);
+
+		$query->addOrderBy('age ASC, company DESC');
+		$this->assertEquals(['team' => SORT_ASC, 'company' => SORT_DESC, 'age' => SORT_ASC], $query->orderBy);
+	}
+
+	public function testLimitOffset()
+	{
+		$query = new Query;
+		$query->limit(10)->offset(5);
+		$this->assertEquals(10, $query->limit);
+		$this->assertEquals(5, $query->offset);
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/extensions/mongo/file/ActiveRecordTest.php b/tests/unit/extensions/mongo/file/ActiveRecordTest.php
new file mode 100644
index 00000000000..93fb5520bcf
--- /dev/null
+++ b/tests/unit/extensions/mongo/file/ActiveRecordTest.php
@@ -0,0 +1,323 @@
+<?php
+
+namespace yiiunit\extensions\mongo\file;
+
+use Yii;
+use yii\helpers\FileHelper;
+use yiiunit\extensions\mongo\MongoTestCase;
+use yii\mongo\file\ActiveQuery;
+use yiiunit\data\ar\mongo\file\ActiveRecord;
+use yiiunit\data\ar\mongo\file\CustomerFile;
+
+/**
+ * @group mongo
+ */
+class ActiveRecordTest extends MongoTestCase
+{
+	/**
+	 * @var array[] list of test rows.
+	 */
+	protected $testRows = [];
+
+	protected function setUp()
+	{
+		parent::setUp();
+		ActiveRecord::$db = $this->getConnection();
+		$this->setUpTestRows();
+		$filePath = $this->getTestFilePath();
+		if (!file_exists($filePath)) {
+			FileHelper::createDirectory($filePath);
+		}
+	}
+
+	protected function tearDown()
+	{
+		$filePath = $this->getTestFilePath();
+		if (file_exists($filePath)) {
+			FileHelper::removeDirectory($filePath);
+		}
+		$this->dropFileCollection(CustomerFile::collectionName());
+		parent::tearDown();
+	}
+
+	/**
+	 * @return string test file path.
+	 */
+	protected function getTestFilePath()
+	{
+		return Yii::getAlias('@yiiunit/runtime') . DIRECTORY_SEPARATOR . basename(get_class($this)) . '_' . getmypid();
+	}
+
+	/**
+	 * Sets up test rows.
+	 */
+	protected function setUpTestRows()
+	{
+		$collection = $this->getConnection()->getFileCollection(CustomerFile::collectionName());
+		$rows = [];
+		for ($i = 1; $i <= 10; $i++) {
+			$record = [
+				'tag' => 'tag' . $i,
+				'status' => $i,
+			];
+			$content = 'content' . $i;
+			$record['_id'] = $collection->insertFileContent($content, $record);
+			$record['content'] = $content;
+			$rows[] = $record;
+		}
+		$this->testRows = $rows;
+	}
+
+	// Tests :
+
+	public function testFind()
+	{
+		// find one
+		$result = CustomerFile::find();
+		$this->assertTrue($result instanceof ActiveQuery);
+		$customer = $result->one();
+		$this->assertTrue($customer instanceof CustomerFile);
+
+		// find all
+		$customers = CustomerFile::find()->all();
+		$this->assertEquals(10, count($customers));
+		$this->assertTrue($customers[0] instanceof CustomerFile);
+		$this->assertTrue($customers[1] instanceof CustomerFile);
+
+		// find by _id
+		$testId = $this->testRows[0]['_id'];
+		$customer = CustomerFile::find($testId);
+		$this->assertTrue($customer instanceof CustomerFile);
+		$this->assertEquals($testId, $customer->_id);
+
+		// find by column values
+		$customer = CustomerFile::find(['tag' => 'tag5']);
+		$this->assertTrue($customer instanceof CustomerFile);
+		$this->assertEquals($this->testRows[4]['_id'], $customer->_id);
+		$this->assertEquals('tag5', $customer->tag);
+		$customer = CustomerFile::find(['tag' => 'unexisting tag']);
+		$this->assertNull($customer);
+
+		// find by attributes
+		$customer = CustomerFile::find()->where(['status' => 4])->one();
+		$this->assertTrue($customer instanceof CustomerFile);
+		$this->assertEquals(4, $customer->status);
+
+		// find count, sum, average, min, max, distinct
+		$this->assertEquals(10, CustomerFile::find()->count());
+		$this->assertEquals(1, CustomerFile::find()->where(['status' => 2])->count());
+		$this->assertEquals((1+10)/2*10, CustomerFile::find()->sum('status'));
+		$this->assertEquals((1+10)/2, CustomerFile::find()->average('status'));
+		$this->assertEquals(1, CustomerFile::find()->min('status'));
+		$this->assertEquals(10, CustomerFile::find()->max('status'));
+		$this->assertEquals(range(1, 10), CustomerFile::find()->distinct('status'));
+
+		// scope
+		$this->assertEquals(1, CustomerFile::find()->activeOnly()->count());
+
+		// asArray
+		$testRow = $this->testRows[2];
+		$customer = CustomerFile::find()->where(['_id' => $testRow['_id']])->asArray()->one();
+		$this->assertEquals($testRow['_id'], $customer['_id']);
+		$this->assertEquals($testRow['tag'], $customer['tag']);
+		$this->assertEquals($testRow['status'], $customer['status']);
+
+		// indexBy
+		$customers = CustomerFile::find()->indexBy('tag')->all();
+		$this->assertTrue($customers['tag1'] instanceof CustomerFile);
+		$this->assertTrue($customers['tag2'] instanceof CustomerFile);
+
+		// indexBy callable
+		$customers = CustomerFile::find()->indexBy(function ($customer) {
+			return $customer->status . '-' . $customer->status;
+		})->all();
+		$this->assertTrue($customers['1-1'] instanceof CustomerFile);
+		$this->assertTrue($customers['2-2'] instanceof CustomerFile);
+	}
+
+	public function testInsert()
+	{
+		$record = new CustomerFile;
+		$record->tag = 'new new';
+		$record->status = 7;
+
+		$this->assertTrue($record->isNewRecord);
+
+		$record->save();
+
+		$this->assertTrue($record->_id instanceof \MongoId);
+		$this->assertFalse($record->isNewRecord);
+
+		$fileContent = $record->getFileContent();
+		$this->assertEmpty($fileContent);
+	}
+
+	/**
+	 * @depends testInsert
+	 */
+	public function testInsertFile()
+	{
+		$record = new CustomerFile;
+		$record->tag = 'new new';
+		$record->status = 7;
+
+		$fileName = __FILE__;
+		$record->setAttribute('file', $fileName);
+
+		$record->save();
+
+		$this->assertTrue($record->_id instanceof \MongoId);
+		$this->assertFalse($record->isNewRecord);
+
+		$fileContent = $record->getFileContent();
+		$this->assertEquals(file_get_contents($fileName), $fileContent);
+	}
+
+	/**
+	 * @depends testInsert
+	 */
+	public function testInsertFileContent()
+	{
+		$record = new CustomerFile;
+		$record->tag = 'new new';
+		$record->status = 7;
+
+		$newFileContent = 'Test new file content';
+		$record->setAttribute('newFileContent', $newFileContent);
+
+		$record->save();
+
+		$this->assertTrue($record->_id instanceof \MongoId);
+		$this->assertFalse($record->isNewRecord);
+
+		$fileContent = $record->getFileContent();
+		$this->assertEquals($newFileContent, $fileContent);
+	}
+
+	/**
+	 * @depends testInsert
+	 */
+	public function testUpdate()
+	{
+		$record = new CustomerFile;
+		$record->tag = 'new new';
+		$record->status = 7;
+		$record->save();
+
+		// save
+		$record = CustomerFile::find($record->_id);
+		$this->assertTrue($record instanceof CustomerFile);
+		$this->assertEquals(7, $record->status);
+		$this->assertFalse($record->isNewRecord);
+
+		$record->status = 9;
+		$record->save();
+		$this->assertEquals(9, $record->status);
+		$this->assertFalse($record->isNewRecord);
+		$record2 = CustomerFile::find($record->_id);
+		$this->assertEquals(9, $record2->status);
+
+		// updateAll
+		$pk = ['_id' => $record->_id];
+		$ret = CustomerFile::updateAll(['status' => 55], $pk);
+		$this->assertEquals(1, $ret);
+		$record = CustomerFile::find($pk);
+		$this->assertEquals(55, $record->status);
+	}
+
+	/**
+	 * @depends testUpdate
+	 * @depends testInsertFileContent
+	 */
+	public function testUpdateFile()
+	{
+		$record = new CustomerFile;
+		$record->tag = 'new new';
+		$record->status = 7;
+		$newFileContent = 'Test new file content';
+		$record->setAttribute('newFileContent', $newFileContent);
+		$record->save();
+
+		$updateFileName = __FILE__;
+		$record = CustomerFile::find($record->_id);
+		$record->setAttribute('file', $updateFileName);
+		$record->status = 55;
+		$record->save();
+		$this->assertEquals(file_get_contents($updateFileName), $record->getFileContent());
+
+		$record2 = CustomerFile::find($record->_id);
+		$this->assertEquals($record->status, $record2->status);
+		$this->assertEquals(file_get_contents($updateFileName), $record2->getFileContent());
+	}
+
+	/**
+	 * @depends testUpdate
+	 * @depends testInsertFileContent
+	 */
+	public function testUpdateFileContent()
+	{
+		$record = new CustomerFile;
+		$record->tag = 'new new';
+		$record->status = 7;
+		$newFileContent = 'Test new file content';
+		$record->setAttribute('newFileContent', $newFileContent);
+		$record->save();
+
+		$updateFileContent = 'New updated file content';
+		$record = CustomerFile::find($record->_id);
+		$record->setAttribute('newFileContent', $updateFileContent);
+		$record->status = 55;
+		$record->save();
+		$this->assertEquals($updateFileContent, $record->getFileContent());
+
+		$record2 = CustomerFile::find($record->_id);
+		$this->assertEquals($record->status, $record2->status);
+		$this->assertEquals($updateFileContent, $record2->getFileContent());
+	}
+
+	/**
+	 * @depends testInsertFileContent
+	 */
+	public function testWriteFile()
+	{
+		$record = new CustomerFile;
+		$record->tag = 'new new';
+		$record->status = 7;
+		$newFileContent = 'Test new file content';
+		$record->setAttribute('newFileContent', $newFileContent);
+		$record->save();
+
+		$outputFileName = $this->getTestFilePath() . DIRECTORY_SEPARATOR . 'out.txt';
+		$this->assertTrue($record->writeFile($outputFileName));
+		$this->assertEquals($newFileContent, file_get_contents($outputFileName));
+
+		$record2 = CustomerFile::find($record->_id);
+		$outputFileName = $this->getTestFilePath() . DIRECTORY_SEPARATOR . 'out_refreshed.txt';
+		$this->assertTrue($record2->writeFile($outputFileName));
+		$this->assertEquals($newFileContent, file_get_contents($outputFileName));
+	}
+
+	/**
+	 * @depends testInsertFileContent
+	 */
+	public function testGetFileResource()
+	{
+		$record = new CustomerFile;
+		$record->tag = 'new new';
+		$record->status = 7;
+		$newFileContent = 'Test new file content';
+		$record->setAttribute('newFileContent', $newFileContent);
+		$record->save();
+
+		$fileResource = $record->getFileResource();
+		$contents = stream_get_contents($fileResource);
+		fclose($fileResource);
+		$this->assertEquals($newFileContent, $contents);
+
+		$record2 = CustomerFile::find($record->_id);
+		$fileResource = $record2->getFileResource();
+		$contents = stream_get_contents($fileResource);
+		fclose($fileResource);
+		$this->assertEquals($newFileContent, $contents);
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/extensions/mongo/file/CollectionTest.php b/tests/unit/extensions/mongo/file/CollectionTest.php
new file mode 100644
index 00000000000..58a5864defa
--- /dev/null
+++ b/tests/unit/extensions/mongo/file/CollectionTest.php
@@ -0,0 +1,98 @@
+<?php
+
+namespace yiiunit\extensions\mongo\file;
+
+use yiiunit\extensions\mongo\MongoTestCase;
+
+/**
+ * @group mongo
+ */
+class CollectionTest extends MongoTestCase
+{
+	protected function tearDown()
+	{
+		$this->dropFileCollection('fs');
+		parent::tearDown();
+	}
+
+	// Tests :
+
+	public function testGetChunkCollection()
+	{
+		$collection = $this->getConnection()->getFileCollection();
+		$chunkCollection = $collection->getChunkCollection();
+		$this->assertTrue($chunkCollection instanceof \yii\mongo\Collection);
+		$this->assertTrue($chunkCollection->mongoCollection instanceof \MongoCollection);
+	}
+
+	public function testFind()
+	{
+		$collection = $this->getConnection()->getFileCollection();
+		$cursor = $collection->find();
+		$this->assertTrue($cursor instanceof \MongoGridFSCursor);
+	}
+
+	public function testInsertFile()
+	{
+		$collection = $this->getConnection()->getFileCollection();
+
+		$filename = __FILE__;
+		$id = $collection->insertFile($filename);
+		$this->assertTrue($id instanceof \MongoId);
+
+		$files = $this->findAll($collection);
+		$this->assertEquals(1, count($files));
+
+		/** @var $file \MongoGridFSFile */
+		$file = $files[0];
+		$this->assertEquals($filename, $file->getFilename());
+		$this->assertEquals(file_get_contents($filename), $file->getBytes());
+	}
+
+	public function testInsertFileContent()
+	{
+		$collection = $this->getConnection()->getFileCollection();
+
+		$bytes = 'Test file content';
+		$id = $collection->insertFileContent($bytes);
+		$this->assertTrue($id instanceof \MongoId);
+
+		$files = $this->findAll($collection);
+		$this->assertEquals(1, count($files));
+
+		/** @var $file \MongoGridFSFile */
+		$file = $files[0];
+		$this->assertEquals($bytes, $file->getBytes());
+	}
+
+	/**
+	 * @depends testInsertFileContent
+	 */
+	public function testGet()
+	{
+		$collection = $this->getConnection()->getFileCollection();
+
+		$bytes = 'Test file content';
+		$id = $collection->insertFileContent($bytes);
+
+		$file = $collection->get($id);
+		$this->assertTrue($file instanceof \MongoGridFSFile);
+		$this->assertEquals($bytes, $file->getBytes());
+	}
+
+	/**
+	 * @depends testGet
+	 */
+	public function testDelete()
+	{
+		$collection = $this->getConnection()->getFileCollection();
+
+		$bytes = 'Test file content';
+		$id = $collection->insertFileContent($bytes);
+
+		$this->assertTrue($collection->delete($id));
+
+		$file = $collection->get($id);
+		$this->assertNull($file);
+	}
+}
\ No newline at end of file
diff --git a/tests/unit/extensions/mongo/file/QueryTest.php b/tests/unit/extensions/mongo/file/QueryTest.php
new file mode 100644
index 00000000000..2f9ec67db61
--- /dev/null
+++ b/tests/unit/extensions/mongo/file/QueryTest.php
@@ -0,0 +1,70 @@
+<?php
+
+namespace yiiunit\extensions\mongo\file;
+
+use yii\mongo\file\Query;
+use yiiunit\extensions\mongo\MongoTestCase;
+
+/**
+ * @group mongo
+ */
+class QueryTest extends MongoTestCase
+{
+	protected function setUp()
+	{
+		parent::setUp();
+		$this->setUpTestRows();
+	}
+
+	protected function tearDown()
+	{
+		$this->dropFileCollection();
+		parent::tearDown();
+	}
+
+	/**
+	 * Sets up test rows.
+	 */
+	protected function setUpTestRows()
+	{
+		$collection = $this->getConnection()->getFileCollection();
+		for ($i = 1; $i <= 10; $i++) {
+			$collection->insertFileContent('content' . $i, [
+				'filename' => 'name' . $i,
+				'file_index' => $i,
+			]);
+		}
+	}
+
+	// Tests :
+
+	public function testAll()
+	{
+		$connection = $this->getConnection();
+		$query = new Query;
+		$rows = $query->from('fs')->all($connection);
+		$this->assertEquals(10, count($rows));
+	}
+
+	public function testOne()
+	{
+		$connection = $this->getConnection();
+		$query = new Query;
+		$row = $query->from('fs')->one($connection);
+		$this->assertTrue(is_array($row));
+		$this->assertTrue($row['file'] instanceof \MongoGridFSFile);
+	}
+
+	public function testDirectMatch()
+	{
+		$connection = $this->getConnection();
+		$query = new Query;
+		$rows = $query->from('fs')
+			->where(['file_index' => 5])
+			->all($connection);
+		$this->assertEquals(1, count($rows));
+		/** @var $file \MongoGridFSFile */
+		$file = $rows[0];
+		$this->assertEquals('name5', $file['filename']);
+	}
+}
\ No newline at end of file