ActiveRecord.php

<?php
/**
 * ActiveRecord class file.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @link http://www.yiiframework.com/
 * @copyright Copyright &copy; 2008-2012 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */

namespace yii\db\ar;

use yii\base\Model;
use yii\base\Event;
use yii\base\ModelEvent;
use yii\db\Exception;
use yii\db\dao\Connection;
use yii\db\dao\TableSchema;
use yii\db\dao\Query;
use yii\db\dao\Expression;
use yii\util\StringHelper;

/**
 * ActiveRecord is the base class for classes representing relational data.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @since 2.0
 *
 * @property array $attributes attribute values indexed by attribute names
 *
 * ActiveRecord provides a set of events for further customization:
 *
 * - `beforeInsert`. Raised before the record is saved.
 *   By setting [[\yii\base\ModelEvent::isValid]] to be false, the normal [[save()]] will be stopped.
 * - `afterInsert`. Raised after the record is saved.
 * - `beforeUpdate`. Raised before the record is saved.
 *   By setting [[\yii\base\ModelEvent::isValid]] to be false, the normal [[save()]] will be stopped.
 * - `afterUpdate`. Raised after the record is saved.
 * - `beforeDelete`. Raised before the record is deleted.
 *   By setting [[\yii\base\ModelEvent::isValid]] to be false, the normal [[delete()]] process will be stopped.
 * - `afterDelete`. Raised after the record is deleted.
 *
 */
abstract class ActiveRecord extends Model
{
	/**
	 * @var array attribute values indexed by attribute names
	 */
	private $_attributes = array();
	/**
	 * @var array old attribute values indexed by attribute names.
	 */
	private $_oldAttributes;
	/**
	 * @var array related records indexed by relation names.
	 */
	private $_related;

	/**
	 * Returns the metadata for this AR class.
	 * @param boolean $refresh whether to rebuild the metadata.
	 * @return ActiveMetaData the meta for this AR class.
	 */
	public static function getMetaData($refresh = false)
	{
		return ActiveMetaData::getInstance(get_called_class(), $refresh);
	}

	/**
	 * Returns the database connection used by this AR class.
	 * By default, the "db" application component is used as the database 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 getDbConnection()
	{
		return \Yii::$application->getDb();
	}

	/**
	 * Creates an [[ActiveQuery]] instance for query purpose.
	 *
	 * Because [[ActiveQuery]] implements a set of query building methods,
	 * additional query conditions can be specified by calling the methods of [[ActiveQuery]].
	 *
	 * Below are some usage examples:
	 *
	 * ~~~
	 * // find all customers
	 * $customers = Customer::find()->all();
	 * // find a single customer whose primary key value is 10
	 * $customer = Customer::find(10);
	 * // the above is equivalent to:
	 * Customer::find()->where(array('id' => 10))->one();
	 * // find all active customers and order them by their age:
	 * $customers = Customer::find()
	 *     ->where(array('status' => 1))
	 *     ->order('age')
	 *     ->all();
	 * // or alternatively:
	 * $customers = Customer::find(array(
	 *     'where' => array('status' => 1),
	 *     'order' => 'age',
	 * ))->all();
	 * ~~~
	 *
	 * @param mixed $q the query parameter. This can be one of the followings:
	 *
	 *  - a scalar value (integer or string): query by a single primary key value.
	 *  - an array of name-value pairs: it will be used to configure the [[ActiveQuery]] object.
	 *
	 * @return ActiveQuery|ActiveRecord|null the [[ActiveQuery]] instance for query purpose, or
	 * the ActiveRecord object when a scalar is passed to this method which is considered to be a
	 * primary key value (null will be returned if no record is found in this case.)
	 */
	public static function find($q = null)
	{
		$query = static::createActiveQuery();
		if (is_array($q)) {
			foreach ($q as $name => $value) {
				$query->$name = $value;
			}
		} elseif ($q !== null) {
			// query by primary key
			$primaryKey = static::getMetaData()->table->primaryKey;
			return $query->where(array($primaryKey[0] => $q))->one();
		}
		return $query;
	}

	/**
	 * Creates an [[ActiveQuery]] instance and query by a given SQL statement.
	 * Note that because the SQL statement is already specified, calling further
	 * query methods (such as `where()`, `order()`) on [[ActiveQuery]] will have no effect.
	 * Methods such as `with()`, `asArray()` can still be called though.
	 * @param string $sql the SQL statement to be executed
	 * @param array $params parameters to be bound to the SQL statement during execution.
	 * @return ActiveQuery the [[ActiveQuery]] instance
	 */
	public static function findBySql($sql, $params = array())
	{
		$query = static::createActiveQuery();
		$query->sql = $sql;
		return $query->params($params);
	}

	/**
	 * Performs a COUNT query for this AR class.
	 *
	 * Below are some usage examples:
	 *
	 * ~~~
	 * // count the total number of customers
	 * echo Customer::count()->value();
	 * // count the number of active customers:
	 * echo Customer::count(array(
	 *     'where' => array('status' => 1),
	 * ))->value();
	 * // equivalent usage:
	 * echo Customer::count()
	 *     ->where(array('status' => 1))
	 *     ->value();
	 * // customize the count option
	 * echo Customer::count('COUNT(DISTINCT age)')->value();
	 * ~~~
	 *
	 * @param array $q the query configuration. This should be an array of name-value pairs.
	 * It will be used to configure the [[ActiveQuery]] object for query purpose.
	 *
	 * @return integer the counting result
	 */
	public static function count($q = null)
	{
		$query = static::createActiveQuery();
		if (is_array($q)) {
			foreach ($q as $name => $value) {
				$query->$name = $value;
			}
		}
		if ($query->select === null) {
			$query->select = array('COUNT(*)');
		}
		return $query->value();
	}

	/**
	 * Updates the whole table using the provided attribute values and conditions.
	 * @param array $attributes attribute values to be saved into the table
	 * @param string|array $condition the conditions that will be put in the WHERE part.
	 * Please refer to [[Query::where()]] on how to specify this parameter.
	 * @param array $params the parameters (name=>value) to be bound to the query.
	 * @return integer the number of rows updated
	 */
	public static function updateAll($attributes, $condition = '', $params = array())
	{
		$query = new Query;
		$query->update(static::tableName(), $attributes, $condition, $params);
		return $query->createCommand(static::getDbConnection())->execute();
	}

	/**
	 * Updates the whole table using the provided counter values and conditions.
	 * @param array $counters the counters to be updated (attribute name => increment value).
	 * @param string|array $condition the conditions that will be put in the WHERE part.
	 * Please refer to [[Query::where()]] on how to specify this parameter.
	 * @param array $params the parameters (name=>value) to be bound to the query.
	 * @return integer the number of rows updated
	 */
	public static function updateAllCounters($counters, $condition = '', $params = array())
	{
		$db = static::getDbConnection();
		foreach ($counters as $name => $value) {
			$value = (int)$value;
			$quotedName = $db->quoteColumnName($name, true);
			$counters[$name] = new Expression($value >= 0 ? "$quotedName+$value" : "$quotedName$value");
		}
		$query = new Query;
		$query->update(static::tableName(), $counters, $condition, $params);
		return $query->createCommand($db)->execute();
	}

	/**
	 * Deletes rows in the table using the provided conditions.
	 * @param string|array $condition the conditions that will be put in the WHERE part.
	 * Please refer to [[Query::where()]] on how to specify this parameter.
	 * @param array $params the parameters (name=>value) to be bound to the query.
	 * @return integer the number of rows updated
	 */
	public static function deleteAll($condition = '', $params = array())
	{
		$query = new Query;
		$query->delete(static::tableName(), $condition, $params);
		return $query->createCommand(static::getDbConnection())->execute();
	}

	/**
	 * Creates a [[ActiveQuery]] instance.
	 * This method is called by [[find()]] and [[findBySql()]] to start a SELECT query.
	 * @return ActiveQuery the newly created [[ActiveQuery]] instance.
	 */
	public static function createActiveQuery()
	{
		return new ActiveQuery(get_called_class());
	}

	/**
	 * Declares the name of the database table associated with this AR class.
	 * By default this method returns the class name as the table name by calling [[StringHelper::camel2id()]].
	 * For example, 'Customer' becomes 'customer', and 'OrderDetail' becomes 'order_detail'.
	 * You may override this method if the table is not named after this convention.
	 * @return string the table name
	 */
	public static function tableName()
	{
		return StringHelper::camel2id(basename(get_called_class()), '_');
	}

	/**
	 * Declares the primary key name for this AR class.
	 * This method is meant to be overridden in case when the table has no primary key defined
	 * (for some legacy database). If the table already has a primary key,
	 * you do not need to override this method. The default implementation simply returns null,
	 * meaning using the primary key defined in the database table.
	 * @return string|array the primary key of the associated database table.
	 * If the key is a single column, it should return the column name;
	 * If the key is a composite one consisting of several columns, it should
	 * return the array of the key column names.
	 */
	public static function primaryKey()
	{
	}

	/**
	 * Declares the relations for this AR class.
	 *
	 * Child classes may override this method to specify their relations.
	 *
	 * The following code shows how to declare relations for a `Programmer` AR class:
	 *
	 * ~~~
	 * return array(
	 *	 'manager:Manager' => '@.id = ?.manager_id',
	 *	 'assignments:Assignment[]' => array(
	 *		 'on' => '@.owner_id = ?.id AND @.status = 1',
	 *		 'order' => '@.create_time DESC',
	 *	 ),
	 *	 'projects:Project[]' => array(
	 *		 'via' => 'assignments',
	 *		 'on' => '@.id = ?.project_id',
	 *	 ),
	 * );
	 * ~~~
	 *
	 * This method should be overridden to declare related objects.
	 *
	 * There are four types of relations that may exist between two active record objects:
	 * <ul>
	 * <li>BELONGS_TO: e.g. a member belongs to a team;</li>
	 * <li>HAS_ONE: e.g. a member has at most one profile;</li>
	 * <li>HAS_MANY: e.g. a team has many members;</li>
	 * <li>MANY_MANY: e.g. a member has many skills and a skill belongs to a member.</li>
	 * </ul>
	 *
	 * Besides the above relation types, a special relation called STAT is also supported
	 * that can be used to perform statistical query (or aggregational query).
	 * It retrieves the aggregational information about the related objects, such as the number
	 * of comments for each post, the average rating for each product, etc.
	 *
	 * Each kind of related objects is defined in this method as an array with the following elements:
	 * <pre>
	 * 'varName'=>array('relationType', 'className', 'foreign_key', ...additional options)
	 * </pre>
	 * where 'varName' refers to the name of the variable/property that the related object(s) can
	 * be accessed through; 'relationType' refers to the type of the relation, which can be one of the
	 * following four constants: self::BELONGS_TO, self::HAS_ONE, self::HAS_MANY and self::MANY_MANY;
	 * 'className' refers to the name of the active record class that the related object(s) is of;
	 * and 'foreign_key' states the foreign key that relates the two kinds of active record.
	 * Note, for composite foreign keys, they must be listed together, separated by commas;
	 * and for foreign keys used in MANY_MANY relation, the joining table must be declared as well
	 * (e.g. 'join_table(fk1, fk2)').
	 *
	 * Additional options may be specified as name-value pairs in the rest array elements:
	 * <ul>
	 * <li>'select': string|array, a list of columns to be selected. Defaults to '*', meaning all columns.
	 *   Column names should be disambiguated if they appear in an expression (e.g. COUNT(relationName.name) AS name_count).</li>
	 * <li>'condition': string, the WHERE clause. Defaults to empty. Note, column references need to
	 *   be disambiguated with prefix 'relationName.' (e.g. relationName.age&gt;20)</li>
	 * <li>'order': string, the ORDER BY clause. Defaults to empty. Note, column references need to
	 *   be disambiguated with prefix 'relationName.' (e.g. relationName.age DESC)</li>
	 * <li>'with': string|array, a list of child related objects that should be loaded together with this object.
	 *   Note, this is only honored by lazy loading, not eager loading.</li>
	 * <li>'joinType': type of join. Defaults to 'LEFT OUTER JOIN'.</li>
	 * <li>'alias': the alias for the table associated with this relationship.
	 *   This option has been available since version 1.0.1. It defaults to null,
	 *   meaning the table alias is the same as the relation name.</li>
	 * <li>'params': the parameters to be bound to the generated SQL statement.
	 *   This should be given as an array of name-value pairs. This option has been
	 *   available since version 1.0.3.</li>
	 * <li>'on': the ON clause. The condition specified here will be appended
	 *   to the joining condition using the AND operator. This option has been
	 *   available since version 1.0.2.</li>
	 * <li>'index': the name of the column whose values should be used as keys
	 *   of the array that stores related objects. This option is only available to
	 *   HAS_MANY and MANY_MANY relations. This option has been available since version 1.0.7.</li>
	 * <li>'scopes': scopes to apply. In case of a single scope can be used like 'scopes'=>'scopeName',
	 *   in case of multiple scopes can be used like 'scopes'=>array('scopeName1','scopeName2').
	 *   This option has been available since version 1.1.9.</li>
	 * </ul>
	 *
	 * The following options are available for certain relations when lazy loading:
	 * <ul>
	 * <li>'group': string, the GROUP BY clause. Defaults to empty. Note, column references need to
	 *   be disambiguated with prefix 'relationName.' (e.g. relationName.age). This option only applies to HAS_MANY and MANY_MANY relations.</li>
	 * <li>'having': string, the HAVING clause. Defaults to empty. Note, column references need to
	 *   be disambiguated with prefix 'relationName.' (e.g. relationName.age). This option only applies to HAS_MANY and MANY_MANY relations.</li>
	 * <li>'limit': limit of the rows to be selected. This option does not apply to BELONGS_TO relation.</li>
	 * <li>'offset': offset of the rows to be selected. This option does not apply to BELONGS_TO relation.</li>
	 * <li>'through': name of the model's relation that will be used as a bridge when getting related data. Can be set only for HAS_ONE and HAS_MANY. This option has been available since version 1.1.7.</li>
	 * </ul>
	 *
	 * Below is an example declaring related objects for 'Post' active record class:
	 * <pre>
	 * return array(
	 *	 'author'=>array(self::BELONGS_TO, 'User', 'author_id'),
	 *	 'comments'=>array(self::HAS_MANY, 'Comment', 'post_id', 'with'=>'author', 'order'=>'create_time DESC'),
	 *	 'tags'=>array(self::MANY_MANY, 'Tag', 'post_tag(post_id, tag_id)', 'order'=>'name'),
	 * );
	 * </pre>
	 *
	 * @return array list of related object declarations. Defaults to empty array.
	 */
	public static function relations()
	{
		return array();
	}

	/**
	 * Returns the default named scope that should be implicitly applied to all queries for this model.
	 * Note, default scope only applies to SELECT queries. It is ignored for INSERT, UPDATE and DELETE queries.
	 * The default implementation simply returns an empty array. You may override this method
	 * if the model needs to be queried with some default criteria (e.g. only active records should be returned).
	 * @param BaseActiveQuery
	 * @return BaseActiveQuery the query criteria. This will be used as the parameter to the constructor
	 * of {@link CDbCriteria}.
	 */
	public static function defaultScope($query)
	{
		return $query;
	}

	/**
	 * Returns the declaration of named scopes.
	 * A named scope represents a query criteria that can be chained together with
	 * other named scopes and applied to a query. This method should be overridden
	 * by child classes to declare named scopes for the particular AR classes.
	 * For example, the following code declares two named scopes: 'recently' and
	 * 'published'.
	 * <pre>
	 * return array(
	 *	 'published'=>array(
	 *		   'condition'=>'status=1',
	 *	 ),
	 *	 'recently'=>array(
	 *		   'order'=>'create_time DESC',
	 *		   'limit'=>5,
	 *	 ),
	 * );
	 * </pre>
	 * If the above scopes are declared in a 'Post' model, we can perform the following
	 * queries:
	 * <pre>
	 * $posts=Post::model()->published()->findAll();
	 * $posts=Post::model()->published()->recently()->findAll();
	 * $posts=Post::model()->published()->with('comments')->findAll();
	 * </pre>
	 * Note that the last query is a relational query.
	 *
	 * @return array the scope definition. The array keys are scope names; the array
	 * values are the corresponding scope definitions. Each scope definition is represented
	 * as an array whose keys must be properties of {@link CDbCriteria}.
	 */
	public static function scopes()
	{
		return array();
	}

	/**
	 * PHP getter magic method.
	 * This method is overridden so that attributes and related objects can be accessed like properties.
	 * @param string $name property name
	 * @return mixed property value
	 * @see getAttribute
	 */
	public function __get($name)
	{
		if (isset($this->_attributes[$name])) {
			return $this->_attributes[$name];
		}
		$md = $this->getMetaData();
		if (isset($md->table->columns[$name])) {
			return null;
		} elseif (isset($md->relations[$name])) {
			if (isset($this->_related[$name]) || $this->_related !== null && array_key_exists($name, $this->_related)) {
				return $this->_related[$name];
			} else {
				return $this->_related[$name] = $this->findByRelation($md->relations[$name]);
			}
		}
		return parent::__get($name);
	}

	/**
	 * PHP setter magic method.
	 * This method is overridden so that AR attributes can be accessed like properties.
	 * @param string $name property name
	 * @param mixed $value property value
	 */
	public function __set($name, $value)
	{
		$md = $this->getMetaData();
		if (isset($md->table->columns[$name])) {
			$this->_attributes[$name] = $value;
		} elseif (isset($md->relations[$name])) {
			$this->_related[$name] = $value;
		} else {
			parent::__set($name, $value);
		}
	}

	/**
	 * Checks if a property value is null.
	 * This method overrides the parent implementation by checking
	 * if the named attribute is null or not.
	 * @param string $name the property name or the event name
	 * @return boolean whether the property value is null
	 */
	public function __isset($name)
	{
		if (isset($this->_attributes[$name]) || isset($this->_related[$name])) {
			return true;
		}
		$md = $this->getMetaData();
		if (isset($md->table->columns[$name]) || isset($md->relations[$name])) {
			return false;
		} else {
			return parent::__isset($name);
		}
	}

	/**
	 * Sets a component property to be null.
	 * This method overrides the parent implementation by clearing
	 * the specified attribute value.
	 * @param string $name the property name or the event name
	 */
	public function __unset($name)
	{
		$md = $this->getMetaData();
		if (isset($md->table->columns[$name])) {
			unset($this->_attributes[$name]);
		} elseif (isset($md->relations[$name])) {
			unset($this->_related[$name]);
		} else {
			parent::__unset($name);
		}
	}

	/**
	 * Calls the named method which is not a class method.
	 * Do not call this method. This is a PHP magic method that we override
	 * to implement the named scope feature.
	 * @param string $name the method name
	 * @param array $params method parameters
	 * @return mixed the method return value
	 */
	public function __call($name, $params)
	{
		$md = $this->getMetaData();
		if (isset($md->relations[$name])) {
			return $this->findByRelation($md->relations[$name], isset($params[0]) ? $params[0] : array());
		}
		return parent::__call($name, $params);
	}

	/**
	 * Initializes the internal storage for the relation.
	 * This method is internally used by [[ActiveQuery]] when populating relation data.
	 * @param ActiveRelation $relation the relation object
	 */
	public function initRelation($relation)
	{
		$this->_related[$relation->name] = $relation->hasMany ? array() : null;
	}

	/**
	 * @param ActiveRelation $relation
	 * @param ActiveRecord $record
	 */
	public function addRelatedRecord($relation, $record)
	{
		if ($relation->hasMany) {
			if ($relation->index !== null) {
				$this->_related[$relation->name][$record->{$relation->index}] = $record;
			} else {
				$this->_related[$relation->name][] = $record;
			}
		} else {
			$this->_related[$relation->name] = $record;
		}
	}

	/**
	 * Returns the related record(s).
	 * This method will return the related record(s) of the current record.
	 * If the relation is HAS_ONE or BELONGS_TO, it will return a single object
	 * or null if the object does not exist.
	 * If the relation is HAS_MANY or MANY_MANY, it will return an array of objects
	 * or an empty array.
	 * @param ActiveRelation|string $relation the relation object or the name of the relation
	 * @param array|\Closure $params additional parameters that customize the query conditions as specified in the relation declaration.
	 * @return mixed the related object(s).
	 * @throws Exception if the relation is not specified in [[relations()]].
	 */
	public function findByRelation($relation, $params = array())
	{
		if (is_string($relation)) {
			$md = $this->getMetaData();
			if (!isset($md->relations[$relation])) {
				throw new Exception(get_class($this) . ' has no relation named "' . $relation . '".');
			}
			$relation = $md->relations[$relation];
		}
		$relation = clone $relation;
		if ($params instanceof \Closure) {
			$params($relation);
		} else {
			foreach ($params as $name => $value) {
				$relation->$name = $value;
			}
		}

		$finder = new ActiveFinder($this->getDbConnection());
		return $finder->findWithRecord($this, $relation);
	}

	/**
	 * Returns the list of all attribute names of the model.
	 * This would return all column names of the table associated with this AR class.
	 * @return array list of attribute names.
	 */
	public function attributes()
	{
		return array_keys($this->getMetaData()->table->columns);
	}

	/**
	 * Returns the named attribute value.
	 * If this is a new record and the attribute is not set before,
	 * the default column value will be returned.
	 * If this record is the result of a query and the attribute is not loaded,
	 * null will be returned.
	 * You may also use $this->AttributeName to obtain the attribute value.
	 * @param string $name the attribute name
	 * @return mixed the attribute value. Null if the attribute is not set or does not exist.
	 * @see hasAttribute
	 */
	public function getAttribute($name)
	{
		return isset($this->_attributes[$name]) ? $this->_attributes[$name] : null;
	}

	/**
	 * Sets the named attribute value.
	 * You may also use $this->AttributeName to set the attribute value.
	 * @param string $name the attribute name
	 * @param mixed $value the attribute value.
	 * @see hasAttribute
	 */
	public function setAttribute($name, $value)
	{
		$this->_attributes[$name] = $value;
	}

	/**
	 * Returns all column attribute values.
	 * Note, related objects are not returned.
	 * @param null|array $names names of attributes whose value needs to be returned.
	 * If this is true (default), then all attribute values will be returned, including
	 * those that are not loaded from DB (null will be returned for those attributes).
	 * If this is null, all attributes except those that are not loaded from DB will be returned.
	 * @return array attribute values indexed by attribute names.
	 */
	public function getAttributes($names = null)
	{
		if ($names === null) {
			$names = $this->attributes();
		}
		$values = array();
		foreach ($names as $name) {
			$values[$name] = isset($this->_attributes[$name]) ? $this->_attributes[$name] : null;
		}
		return $values;
	}

	public function getChangedAttributes($names = null)
	{
		if ($names === null) {
			$names = $this->attributes();
		}
		$names = array_flip($names);
		$attributes = array();
		if ($this->_oldAttributes === null) {
			foreach ($this->_attributes as $name => $value) {
				if (isset($names[$name])) {
					$attributes[$name] = $value;
				}
			}
		} else {
			foreach ($this->_attributes as $name => $value) {
				if (isset($names[$name]) && (!array_key_exists($name, $this->_oldAttributes) || $value !== $this->_oldAttributes[$name])) {
					$attributes[$name] = $value;
				}
			}
		}
		return $attributes;
	}

	/**
	 * Saves the current record.
	 *
	 * The record is inserted as a row into the database table if its {@link isNewRecord}
	 * property is true (usually the case when the record is created using the 'new'
	 * operator). Otherwise, it will be used to update the corresponding row in the table
	 * (usually the case if the record is obtained using one of those 'find' methods.)
	 *
	 * Validation will be performed before saving the record. If the validation fails,
	 * the record will not be saved. You can call {@link getErrors()} to retrieve the
	 * validation errors.
	 *
	 * If the record is saved via insertion, its {@link isNewRecord} property will be
	 * set false, and its {@link scenario} property will be set to be 'update'.
	 * And if its primary key is auto-incremental and is not set before insertion,
	 * the primary key will be populated with the automatically generated key value.
	 *
	 * @param boolean $runValidation whether to perform validation before saving the record.
	 * If the validation fails, the record will not be saved to database.
	 * @param array $attributes list of attributes that need to be saved. Defaults to null,
	 * meaning all attributes that are loaded from DB will be saved.
	 * @return boolean whether the saving succeeds
	 */
	public function save($runValidation = true, $attributes = null)
	{
		if (!$runValidation || $this->validate($attributes)) {
			return $this->getIsNewRecord() ? $this->insert($attributes) : $this->update($attributes);
		}
		return false;
	}

	/**
	 * Inserts a row into the table based on this active record attributes.
	 * If the table's primary key is auto-incremental and is null before insertion,
	 * it will be populated with the actual value after insertion.
	 * Note, validation is not performed in this method. You may call {@link validate} to perform the validation.
	 * After the record is inserted to DB successfully, its {@link isNewRecord} property will be set false,
	 * and its {@link scenario} property will be set to be 'update'.
	 * @param array $attributes list of attributes that need to be saved. Defaults to null,
	 * meaning all attributes that are loaded from DB will be saved.
	 * @return boolean whether the attributes are valid and the record is inserted successfully.
	 * @throws Exception if the record is not new
	 */
	public function insert($attributes = null)
	{
		if ($this->beforeInsert()) {
			$query = new Query;
			$values = $this->getChangedAttributes($attributes);
			$db = $this->getDbConnection();
			$command = $query->insert($this->tableName(), $values)->createCommand($db);
			if ($command->execute()) {
				$table = $this->getMetaData()->table;
				if ($table->sequenceName !== null) {
					foreach ($table->primaryKey as $name) {
						if (!isset($this->_attributes[$name])) {
							$this->_oldAttributes[$name] = $this->_attributes[$name] = $db->getLastInsertID($table->sequenceName);
							break;
						}
					}
				}
				foreach ($values as $name => $value) {
					$this->_oldAttributes[$name] = $value;
				}
				$this->afterInsert();
				return true;
			}
		}
		return false;
	}

	/**
	 * Updates the row represented by this active record.
	 * All loaded attributes will be saved to the database.
	 * Note, validation is not performed in this method. You may call {@link validate} to perform the validation.
	 * @param array $attributes list of attributes that need to be saved. Defaults to null,
	 * meaning all attributes that are loaded from DB will be saved.
	 * @return boolean whether the update is successful
	 * @throws Exception if the record is new
	 */
	public function update($attributes = null)
	{
		if ($this->getIsNewRecord()) {
			throw new Exception('The active record cannot be updated because it is new.');
		}
		if ($this->beforeUpdate()) {
			$values = $this->getChangedAttributes($attributes);
			if ($values !== array()) {
				$this->updateAll($values, $this->getOldPrimaryKey(true));
				foreach ($values as $name => $value) {
					$this->_oldAttributes[$name] = $this->_attributes[$name];
				}
				$this->afterUpdate();
			}
			return true;
		} else {
			return false;
		}
	}

	/**
	 * Saves one or several counter columns for the current AR object.
	 * Note that this method differs from [[updateAllCounters()]] in that it only
	 * saves counters for the current AR object.
	 *
	 * An example usage is as follows:
	 *
	 * ~~~
	 * $post = Post::find($id)->one();
	 * $post->updateCounters(array('view_count' => 1));
	 * ~~~
	 *
	 * Use negative values if you want to decrease the counters.
	 * @param array $counters the counters to be updated (attribute name => increment value)
	 * @return boolean whether the saving is successful
	 * @throws Exception if the record is new or any database error
	 * @see updateAllCounters()
	 */
	public function updateCounters($counters)
	{
		if ($this->getIsNewRecord()) {
			throw new Exception('The active record cannot be updated because it is new.');
		}
		$this->updateAllCounters($counters, $this->getOldPrimaryKey(true));
		foreach ($counters as $name => $value) {
			$this->_attributes[$name] += $value;
			$this->_oldAttributes[$name] = $this->_attributes[$name];
		}
		return true;
	}

	/**
	 * Deletes the row corresponding to this active record.
	 * @return boolean whether the deletion is successful.
	 * @throws Exception if the record is new or any database error
	 */
	public function delete()
	{
		if ($this->getIsNewRecord()) {
			throw new Exception('The active record cannot be deleted because it is new.');
		}
		if ($this->beforeDelete()) {
			$result = $this->deleteAll($this->getPrimaryKey(true)) > 0;
			$this->_oldAttributes = null;
			$this->afterDelete();
			return $result;
		} else {
			return false;
		}
	}

	/**
	 * Returns if the current record is new.
	 * @return boolean whether the record is new and should be inserted when calling {@link save}.
	 * This property is automatically set in constructor and {@link populateRecord}.
	 * Defaults to false, but it will be set to true if the instance is created using
	 * the new operator.
	 */
	public function getIsNewRecord()
	{
		return $this->_oldAttributes === null;
	}

	/**
	 * Sets if the record is new.
	 * @param boolean $value whether the record is new and should be inserted when calling {@link save}.
	 * @see getIsNewRecord
	 */
	public function setIsNewRecord($value)
	{
		$this->_oldAttributes = $value ? null : $this->_attributes;
	}

	/**
	 * This method is invoked before saving a record (after validation, if any).
	 * The default implementation raises the `beforeSave` event.
	 * You may override this method to do any preparation work for record saving.
	 * Use {@link isNewRecord} to determine whether the saving is
	 * for inserting or updating record.
	 * Make sure you call the parent implementation so that the event is raised properly.
	 * @return boolean whether the saving should be executed. Defaults to true.
	 */
	public function beforeInsert()
	{
		$event = new ModelEvent($this);
		$this->trigger('beforeInsert', $event);
		return $event->isValid;
	}

	/**
	 * This method is invoked after saving a record successfully.
	 * The default implementation raises the `afterSave` event.
	 * You may override this method to do postprocessing after record saving.
	 * Make sure you call the parent implementation so that the event is raised properly.
	 */
	public function afterInsert()
	{
		$this->trigger('afterInsert', new Event($this));
	}

	/**
	 * This method is invoked before saving a record (after validation, if any).
	 * The default implementation raises the `beforeSave` event.
	 * You may override this method to do any preparation work for record saving.
	 * Use {@link isNewRecord} to determine whether the saving is
	 * for inserting or updating record.
	 * Make sure you call the parent implementation so that the event is raised properly.
	 * @return boolean whether the saving should be executed. Defaults to true.
	 */
	public function beforeUpdate()
	{
		$event = new ModelEvent($this);
		$this->trigger('beforeUpdate', $event);
		return $event->isValid;
	}

	/**
	 * This method is invoked after saving a record successfully.
	 * The default implementation raises the `afterSave` event.
	 * You may override this method to do postprocessing after record saving.
	 * Make sure you call the parent implementation so that the event is raised properly.
	 */
	public function afterUpdate()
	{
		$this->trigger('afterUpdate', new Event($this));
	}

	/**
	 * This method is invoked before deleting a record.
	 * The default implementation raises the `beforeDelete` event.
	 * You may override this method to do any preparation work for record deletion.
	 * Make sure you call the parent implementation so that the event is raised properly.
	 * @return boolean whether the record should be deleted. Defaults to true.
	 */
	public function beforeDelete()
	{
		$event = new ModelEvent($this);
		$this->trigger('beforeDelete', $event);
		return $event->isValid;
	}

	/**
	 * This method is invoked after deleting a record.
	 * The default implementation raises the `afterDelete` event.
	 * You may override this method to do postprocessing after the record is deleted.
	 * Make sure you call the parent implementation so that the event is raised properly.
	 */
	public function afterDelete()
	{
		$this->trigger('afterDelete', new Event($this));
	}

	/**
	 * Repopulates this active record with the latest data.
	 * @param array $attributes
	 * @return boolean whether the row still exists in the database. If true, the latest data will be populated to this active record.
	 */
	public function refresh($attributes = null)
	{
		if ($this->getIsNewRecord()) {
			return false;
		}
		$record = $this->find()->where($this->getPrimaryKey(true))->one();
		if ($record === null) {
			return false;
		}
		if ($attributes === null) {
			foreach ($this->attributes() as $name) {
				$this->_attributes[$name] = $record->_attributes[$name];
			}
			$this->_oldAttributes = $this->_attributes;
		} else {
			foreach ($attributes as $name) {
				$this->_oldAttributes[$name] = $this->_attributes[$name] = $record->_attributes[$name];
			}
		}
		return true;
	}

	/**
	 * Compares current active record with another one.
	 * The comparison is made by comparing table name and the primary key values of the two active records.
	 * @param ActiveRecord $record record to compare to
	 * @return boolean whether the two active records refer to the same row in the database table.
	 */
	public function equals($record)
	{
		return $this->tableName() === $record->tableName() && $this->getPrimaryKey() === $record->getPrimaryKey();
	}

	/**
	 * Returns the primary key value.
	 * @param boolean $asArray whether to return the primary key value as an array. If true,
	 * the return value will be an array with column name as key and column value as value.
	 * @return mixed the primary key value. An array (column name=>column value) is returned if the primary key is composite.
	 * If primary key is not defined, null will be returned.
	 */
	public function getPrimaryKey($asArray = false)
	{
		$table = static::getMetaData()->table;
		if (count($table->primaryKey) === 1 && !$asArray) {
			return isset($this->_attributes[$table->primaryKey[0]]) ? $this->_attributes[$table->primaryKey[0]] : null;
		} else {
			$values = array();
			foreach ($table->primaryKey as $name) {
				$values[$name] = isset($this->_attributes[$name]) ? $this->_attributes[$name] : null;
			}
			return $values;
		}
	}

	/**
	 * Returns the old primary key value.
	 * This refers to the primary key value that is populated into the record
	 * after executing a find method (e.g. find(), findAll()).
	 * The value remains unchanged even if the primary key attribute is manually assigned with a different value.
	 * @param boolean $asArray whether to return the primary key value as an array. If true,
	 * the return value will be an array with column name as key and column value as value.
	 * If this is false (default), a scalar value will be returned for non-composite primary key.
	 * @return string|array the old primary key value. An array (column name=>column value) is returned if the primary key is composite.
	 * If primary key is not defined, null will be returned.
	 */
	public function getOldPrimaryKey($asArray = false)
	{
		$table = static::getMetaData()->table;
		if (count($table->primaryKey) === 1 && !$asArray) {
			return isset($this->_oldAttributes[$table->primaryKey[0]]) ? $this->_oldAttributes[$table->primaryKey[0]] : null;
		} else {
			$values = array();
			foreach ($table->primaryKey as $name) {
				$values[$name] = isset($this->_oldAttributes[$name]) ? $this->_oldAttributes[$name] : null;
			}
			return $values;
		}
	}

	/**
	 * Creates an active record with the given attributes.
	 * @param array $row attribute values (name => value)
	 * @return ActiveRecord the newly created active record.
	 */
	public static function create($row)
	{
		$record = static::instantiate($row);
		$columns = static::getMetaData()->table->columns;
		foreach ($row as $name => $value) {
			if (isset($columns[$name])) {
				$record->_attributes[$name] = $value;
			} else {
				$record->$name = $value;
			}
		}
		$record->_oldAttributes = $record->_attributes;
		return $record;
	}

	/**
	 * Creates an active record instance.
	 * This method is called by [[createRecord()]].
	 * You may override this method if the instance being created
	 * depends the attributes that are to be populated to the record.
	 * For example, by creating a record based on the value of a column,
	 * you may implement the so-called single-table inheritance mapping.
	 * @param array $row list of attribute values for the active records.
	 * @return ActiveRecord the active record
	 */
	public static function instantiate($row)
	{
		$class = get_called_class();
		return new $class;
	}

	/**
	 * Returns whether there is an element at the specified offset.
	 * This method is required by the interface ArrayAccess.
	 * @param mixed $offset the offset to check on
	 * @return boolean
	 */
	public function offsetExists($offset)
	{
		return $this->__isset($offset);
	}
}