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<?php
/**
* @link http://www.yiiframework.com/
* @copyright Copyright (c) 2008 Yii Software LLC
* @license http://www.yiiframework.com/license/
*/
namespace yii\caching;
use Yii;
use yii\base\InvalidConfigException;
use yii\db\Connection;
use yii\db\Query;
/**
* DbCache implements a cache application component by storing cached data in a database.
*
* By default, DbCache stores session data in a DB table named 'tbl_cache'. This table
* must be pre-created. The table name can be changed by setting [[cacheTable]].
*
* Please refer to [[Cache]] for common cache operations that are supported by DbCache.
*
* The following example shows how you can configure the application to use DbCache:
*
* ~~~
* 'cache' => array(
* 'class' => 'yii\caching\DbCache',
* // 'db' => 'mydb',
* // 'cacheTable' => 'my_cache',
* )
* ~~~
*
* @author Qiang Xue <qiang.xue@gmail.com>
* @since 2.0
*/
class DbCache extends Cache
{
/**
* @var Connection|string the DB connection object or the application component ID of the DB connection.
* After the DbCache object is created, if you want to change this property, you should only assign it
* with a DB connection object.
*/
public $db = 'db';
/**
* @var string name of the DB table to store cache content.
* The table should be pre-created as follows:
*
* ~~~
* CREATE TABLE tbl_cache (
* id char(128) NOT NULL PRIMARY KEY,
* expire int(11),
* data BLOB
* );
* ~~~
*
* where 'BLOB' refers to the BLOB-type of your preferred DBMS. Below are the BLOB type
* that can be used for some popular DBMS:
*
* - MySQL: LONGBLOB
* - PostgreSQL: BYTEA
* - MSSQL: BLOB
*
* When using DbCache in a production server, we recommend you create a DB index for the 'expire'
* column in the cache table to improve the performance.
*/
public $cacheTable = 'tbl_cache';
/**
* @var integer the probability (parts per million) that garbage collection (GC) should be performed
* when storing a piece of data in the cache. Defaults to 100, meaning 0.01% chance.
* This number should be between 0 and 1000000. A value 0 meaning no GC will be performed at all.
**/
public $gcProbability = 100;
/**
* Initializes the DbCache component.
* This method will initialize the [[db]] property to make sure it refers to a valid DB connection.
* @throws InvalidConfigException if [[db]] is invalid.
*/
public function init()
{
parent::init();
if (is_string($this->db)) {
$this->db = Yii::$app->getComponent($this->db);
}
if (!$this->db instanceof Connection) {
throw new InvalidConfigException("DbCache::db must be either a DB connection instance or the application component ID of a DB connection.");
}
}
/**
* Retrieves a value from cache with a specified key.
* This is the implementation of the method declared in the parent class.
* @param string $key a unique key identifying the cached value
* @return string the value stored in cache, false if the value is not in the cache or expired.
*/
protected function getValue($key)
{
$query = new Query;
$query->select(array('data'))
->from($this->cacheTable)
->where('id = :id AND (expire = 0 OR expire >' . time() . ')', array(':id' => $key));
if ($this->db->enableQueryCache) {
// temporarily disable and re-enable query caching
$this->db->enableQueryCache = false;
$result = $query->createCommand($this->db)->queryScalar();
$this->db->enableQueryCache = true;
return $result;
} else {
return $query->createCommand($this->db)->queryScalar();
}
}
/**
* Retrieves multiple values from cache with the specified keys.
* @param array $keys a list of keys identifying the cached values
* @return array a list of cached values indexed by the keys
*/
protected function getValues($keys)
{
if (empty($keys)) {
return array();
}
$query = new Query;
$query->select(array('id', 'data'))
->from($this->cacheTable)
->where(array('id' => $keys))
->andWhere('(expire = 0 OR expire > ' . time() . ')');
if ($this->db->enableQueryCache) {
$this->db->enableQueryCache = false;
$rows = $query->createCommand($this->db)->queryAll();
$this->db->enableQueryCache = true;
} else {
$rows = $query->createCommand($this->db)->queryAll();
}
$results = array();
foreach ($keys as $key) {
$results[$key] = false;
}
foreach ($rows as $row) {
$results[$row['id']] = $row['data'];
}
return $results;
}
/**
* Stores a value identified by a key in cache.
* This is the implementation of the method declared in the parent class.
*
* @param string $key the key identifying the value to be cached
* @param string $value the value to be cached
* @param integer $expire the number of seconds in which the cached value will expire. 0 means never expire.
* @return boolean true if the value is successfully stored into cache, false otherwise
*/
protected function setValue($key, $value, $expire)
{
$command = $this->db->createCommand()
->update($this->cacheTable, array(
'expire' => $expire > 0 ? $expire + time() : 0,
'data' => array($value, \PDO::PARAM_LOB),
), array(
'id' => $key,
));
if ($command->execute()) {
$this->gc();
return true;
} else {
return $this->addValue($key, $value, $expire);
}
}
/**
* Stores a value identified by a key into cache if the cache does not contain this key.
* This is the implementation of the method declared in the parent class.
*
* @param string $key the key identifying the value to be cached
* @param string $value the value to be cached
* @param integer $expire the number of seconds in which the cached value will expire. 0 means never expire.
* @return boolean true if the value is successfully stored into cache, false otherwise
*/
protected function addValue($key, $value, $expire)
{
$this->gc();
if ($expire > 0) {
$expire += time();
} else {
$expire = 0;
}
try {
$this->db->createCommand()
->insert($this->cacheTable, array(
'id' => $key,
'expire' => $expire,
'data' => array($value, \PDO::PARAM_LOB),
))->execute();
return true;
} catch (\Exception $e) {
return false;
}
}
/**
* Deletes a value with the specified key from cache
* This is the implementation of the method declared in the parent class.
* @param string $key the key of the value to be deleted
* @return boolean if no error happens during deletion
*/
protected function deleteValue($key)
{
$this->db->createCommand()
->delete($this->cacheTable, array('id' => $key))
->execute();
return true;
}
/**
* Removes the expired data values.
* @param boolean $force whether to enforce the garbage collection regardless of [[gcProbability]].
* Defaults to false, meaning the actual deletion happens with the probability as specified by [[gcProbability]].
*/
public function gc($force = false)
{
if ($force || mt_rand(0, 1000000) < $this->gcProbability) {
$this->db->createCommand()
->delete($this->cacheTable, 'expire > 0 AND expire < ' . time())
->execute();
}
}
/**
* Deletes all values from cache.
* This is the implementation of the method declared in the parent class.
* @return boolean whether the flush operation was successful.
*/
protected function flushValues()
{
$this->db->createCommand()
->delete($this->cacheTable)
->execute();
return true;
}
}