CDbCache
CDbCache implements a cache application component by storing cached data in a database.
CDbCache stores cache data in a DB table named
cacheTableName. If the table does not exist, it will be automatically created. By setting
autoCreateCacheTable to false, you can also manually create the DB table.
CDbCache relies on
PDO to access database. By default, it will use a SQLite3 database under the application runtime directory. You can also specify
connectionID so that it makes use of a DB application component to access database.
See
CCache manual for common cache operations that are supported by CDbCache.
Protected Methods
Method |
Description |
Defined By |
addValue() | Stores a value identified by a key into cache if the cache does not contain this key. | CDbCache |
createCacheTable() | Creates the cache DB table. | CDbCache |
deleteValue() | Deletes a value with the specified key from cache | CDbCache |
flushValues() | Deletes all values from cache. | CDbCache |
gc() | Removes the expired data values. | CDbCache |
generateUniqueKey() | | CCache |
getValue() | Retrieves a value from cache with a specified key. | CDbCache |
getValues() | Retrieves multiple values from cache with the specified keys. | CDbCache |
setValue() | Stores a value identified by a key in cache. | CDbCache |
Property Details
public boolean $autoCreateCacheTable;
whether the cache DB table should be created automatically if it does not exist. Defaults to true. If you already have the table created, it is recommended you set this property to be false to improve performance.
public string $cacheTableName;
name of the DB table to store cache content. Defaults to 'YiiCache'. Note, if autoCreateCacheTable is false and you want to create the DB table manually by yourself, you need to make sure the DB table is of the following structure:
(id CHAR(128) PRIMARY KEY, expire INTEGER, value BLOB)
Note, some DBMS might not support BLOB type. In this case, replace 'BLOB' with a suitable binary data type (e.g. LONGBLOB in MySQL, BYTEA in PostgreSQL.)
public string $connectionID;
the ID of the CDbConnection application component. If not set, a SQLite3 database will be automatically created and used. The SQLite database file is protected/runtime/cache-YiiVersion.db
.
public CDbConnection getDbConnection()
public void setDbConnection(CDbConnection $value)
the DB connection instance
public integer getGCProbability()
public void setGCProbability(integer $value)
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.
Method Details
protected boolean addValue(string $key, string $value, integer $expire) |
$key | string | the key identifying the value to be cached |
$value | string | the value to be cached |
$expire | integer | the number of seconds in which the cached value will expire. 0 means never expire. |
{return} | boolean | true if the value is successfully stored into cache, false otherwise |
Source Code: framework/caching/CDbCache.php#255 (
show)
protected function addValue($key,$value,$expire)
{
if(!$this->_gced && mt_rand(0,1000000)<$this->_gcProbability)
{
$this->gc();
$this->_gced=true;
}
if($expire>0)
$expire+=time();
else
$expire=0;
$sql="INSERT INTO {$this->cacheTableName} (id,expire,value) VALUES ('$key',$expire,:value)";
try
{
$command=$this->getDbConnection()->createCommand($sql);
$command->bindValue(':value',$value,PDO::PARAM_LOB);
$command->execute();
return true;
}
catch(Exception $e)
{
return false;
}
}
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.
protected void createCacheTable(CDbConnection $db, string $tableName) |
$db | CDbConnection | the database connection |
$tableName | string | the name of the table to be created |
Source Code: framework/caching/CDbCache.php#122 (
show)
protected function createCacheTable($db,$tableName)
{
$driver=$db->getDriverName();
if($driver==='mysql')
$blob='LONGBLOB';
elseif($driver==='pgsql')
$blob='BYTEA';
else
$blob='BLOB';
$sql=<<<EOD
CREATE TABLE $tableName
(
id CHAR(128) PRIMARY KEY,
expire INTEGER,
value $blob
)
EOD;
$db->createCommand($sql)->execute();
}
Creates the cache DB table.
protected boolean deleteValue(string $key) |
$key | string | the key of the value to be deleted |
{return} | boolean | if no error happens during deletion |
Source Code: framework/caching/CDbCache.php#287 (
show)
protected function deleteValue($key)
{
$sql="DELETE FROM {$this->cacheTableName} WHERE id='$key'";
$this->getDbConnection()->createCommand($sql)->execute();
return true;
}
Deletes a value with the specified key from cache This is the implementation of the method declared in the parent class.
protected boolean flushValues() |
{return} | boolean | whether the flush operation was successful. |
Source Code: framework/caching/CDbCache.php#308 (
show)
protected function flushValues()
{
$this->getDbConnection()->createCommand("DELETE FROM {$this->cacheTableName}")->execute();
return true;
}
Deletes all values from cache. This is the implementation of the method declared in the parent class.
Source Code: framework/caching/CDbCache.php#297 (
show)
protected function gc()
{
$this->getDbConnection()->createCommand("DELETE FROM {$this->cacheTableName} WHERE expire>0 AND expire<".time())->execute();
}
Removes the expired data values.
Source Code: framework/caching/CDbCache.php#146 (
show)
public function getDbConnection()
{
if($this->_db!==null)
return $this->_db;
elseif(($id=$this->connectionID)!==null)
{
if(($this->_db=Yii::app()->getComponent($id)) instanceof CDbConnection)
return $this->_db;
else
throw new CException(Yii::t('yii','CDbCache.connectionID "{id}" is invalid. Please make sure it refers to the ID of a CDbConnection application component.',
array('{id}'=>$id)));
}
else
{
$dbFile=Yii::app()->getRuntimePath().DIRECTORY_SEPARATOR.'cache-'.Yii::getVersion().'.db';
return $this->_db=new CDbConnection('sqlite:'.$dbFile);
}
}
public integer getGCProbability() |
{return} | 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. |
protected string|boolean getValue(string $key) |
$key | string | a unique key identifying the cached value |
{return} | string|boolean | the value stored in cache, false if the value is not in the cache or expired. |
Source Code: framework/caching/CDbCache.php#181 (
show)
protected function getValue($key)
{
$time=time();
$sql="SELECT value FROM {$this->cacheTableName} WHERE id='$key' AND (expire=0 OR expire>$time)";
$db=$this->getDbConnection();
if($db->queryCachingDuration>0)
{
$duration=$db->queryCachingDuration;
$db->queryCachingDuration=0;
$result=$db->createCommand($sql)->queryScalar();
$db->queryCachingDuration=$duration;
return $result;
}
else
return $db->createCommand($sql)->queryScalar();
}
Retrieves a value from cache with a specified key. This is the implementation of the method declared in the parent class.
protected array getValues(array $keys) |
$keys | array | a list of keys identifying the cached values |
{return} | array | a list of cached values indexed by the keys |
Source Code: framework/caching/CDbCache.php#203 (
show)
protected function getValues($keys)
{
if(empty($keys))
return array();
$ids=implode("','",$keys);
$time=time();
$sql="SELECT id, value FROM {$this->cacheTableName} WHERE id IN ('$ids') AND (expire=0 OR expire>$time)";
$db=$this->getDbConnection();
if($db->queryCachingDuration>0)
{
$duration=$db->queryCachingDuration;
$db->queryCachingDuration=0;
$rows=$db->createCommand($sql)->queryAll();
$db->queryCachingDuration=$duration;
}
else
$rows=$db->createCommand($sql)->queryAll();
$results=array();
foreach($keys as $key)
$results[$key]=false;
foreach($rows as $row)
$results[$row['id']]=$row['value'];
return $results;
}
Retrieves multiple values from cache with the specified keys.
Source Code: framework/caching/CDbCache.php#73 (
show)
public function init()
{
parent::init();
$db=$this->getDbConnection();
$db->setActive(true);
if($this->autoCreateCacheTable)
{
$sql="DELETE FROM {$this->cacheTableName} WHERE expire>0 AND expire<".time();
try
{
$db->createCommand($sql)->execute();
}
catch(Exception $e)
{
$this->createCacheTable($db,$this->cacheTableName);
}
}
}
Initializes this application component.
This method is required by the IApplicationComponent interface. It ensures the existence of the cache DB table. It also removes expired data items from the cache.
Sets the DB connection used by the cache component.
public void setGCProbability(integer $value) |
$value | integer | the probability (parts per million) that garbage collection (GC) should be performed when storing a piece of data in the cache. Defaults to 100, meaning 0.01% chance. This number should be between 0 and 1000000. A value 0 meaning no GC will be performed at all. |
Source Code: framework/caching/CDbCache.php#107 (
show)
public function setGCProbability($value)
{
$value=(int)$value;
if($value<0)
$value=0;
if($value>1000000)
$value=1000000;
$this->_gcProbability=$value;
}
protected boolean setValue(string $key, string $value, integer $expire) |
$key | string | the key identifying the value to be cached |
$value | string | the value to be cached |
$expire | integer | 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 |
Stores a value identified by a key in cache. This is the implementation of the method declared in the parent class.