Versions
Look up a class, method, property or event

CDbCache

Package system.caching
Inheritance class CDbCache » CCache » CApplicationComponent » CComponent
Implements ArrayAccess, ICache, IApplicationComponent
Since 1.0
Source Code framework/caching/CDbCache.php
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.

Public Properties

Hide inherited properties

PropertyTypeDescriptionDefined By
autoCreateCacheTable boolean whether the cache DB table should be created automatically if it does not exist. CDbCache
behaviors array the behaviors that should be attached to this component. CApplicationComponent
cacheTableName string name of the DB table to store cache content. CDbCache
connectionID string the ID of the CDbConnection application component. CDbCache
dbConnection CDbConnection the DB connection instance CDbCache
gCProbability integer the probability (parts per million) that garbage collection (GC) should be performed when storing a piece of data in the cache. CDbCache
hashKey boolean whether to md5-hash the cache key for normalization purposes. CCache
isInitialized boolean Checks if this application component has been initialized. CApplicationComponent
keyPrefix string a string prefixed to every cache key so that it is unique. CCache
serializer array|boolean the functions used to serialize and unserialize cached data. CCache

Public Methods

Hide inherited methods

MethodDescriptionDefined By
__call() Calls the named method which is not a class method. CComponent
__get() Returns a property value, an event handler list or a behavior based on its name. CComponent
__isset() Checks if a property value is null. CComponent
__set() Sets value of a component property. CComponent
__unset() Sets a component property to be null. CComponent
add() Stores a value identified by a key into cache if the cache does not contain this key. CCache
asa() Returns the named behavior object. CComponent
attachBehavior() Attaches a behavior to this component. CComponent
attachBehaviors() Attaches a list of behaviors to the component. CComponent
attachEventHandler() Attaches an event handler to an event. CComponent
canGetProperty() Determines whether a property can be read. CComponent
canSetProperty() Determines whether a property can be set. CComponent
delete() Deletes a value with the specified key from cache CCache
detachBehavior() Detaches a behavior from the component. CComponent
detachBehaviors() Detaches all behaviors from the component. CComponent
detachEventHandler() Detaches an existing event handler. CComponent
disableBehavior() Disables an attached behavior. CComponent
disableBehaviors() Disables all behaviors attached to this component. CComponent
enableBehavior() Enables an attached behavior. CComponent
enableBehaviors() Enables all behaviors attached to this component. CComponent
evaluateExpression() Evaluates a PHP expression or callback under the context of this component. CComponent
flush() Deletes all values from cache. CCache
get() Retrieves a value from cache with a specified key. CCache
getDbConnection() Returns the DB connection instance CDbCache
getEventHandlers() Returns the list of attached event handlers for an event. CComponent
getGCProbability() Returns 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. CDbCache
getIsInitialized() Checks if this application component has been initialized. CApplicationComponent
hasEvent() Determines whether an event is defined. CComponent
hasEventHandler() Checks whether the named event has attached handlers. CComponent
hasProperty() Determines whether a property is defined. CComponent
init() Initializes this application component. CDbCache
mget() Retrieves multiple values from cache with the specified keys. CCache
offsetExists() Returns whether there is a cache entry with a specified key. CCache
offsetGet() Retrieves the value from cache with a specified key. CCache
offsetSet() Stores the value identified by a key into cache. CCache
offsetUnset() Deletes the value with the specified key from cache CCache
raiseEvent() Raises an event. CComponent
set() Stores a value identified by a key into cache. CCache
setDbConnection() Sets the DB connection used by the cache component. CDbCache
setGCProbability() Sets 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. CDbCache

Protected Methods

Hide inherited methods

MethodDescriptionDefined 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

autoCreateCacheTable property
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.

See Also

cacheTableName property
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.)

connectionID property
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.

dbConnection property

the DB connection instance

gCProbability property
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

addValue() method
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.

createCacheTable() method
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.

deleteValue() method
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.

flushValues() method (available since v1.1.5)
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.

gc() method
protected void gc()
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.

getDbConnection() method
public CDbConnection getDbConnection()
{return} CDbConnection the DB connection instance
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);
    }
}

getGCProbability() method
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.
Source Code: framework/caching/CDbCache.php#97 (show)
public function getGCProbability()
{
    return 
$this->_gcProbability;
}

getValue() method
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.

getValues() method
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.

init() method
public void init()
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.

setDbConnection() method (available since v1.1.5)
public void setDbConnection(CDbConnection $value)
$value CDbConnection the DB connection instance
Source Code: framework/caching/CDbCache.php#170 (show)
public function setDbConnection($value)
{
    
$this->_db=$value;
}

Sets the DB connection used by the cache component.

setGCProbability() method
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;
}

setValue() method
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
$expire integer the number of seconds in which the cached value will expire. 0 means never expire.
{return} boolean true if the value is successfully stored into cache, false otherwise
Source Code: framework/caching/CDbCache.php#240 (show)
protected function setValue($key,$value,$expire)
{
    
$this->deleteValue($key);
    return 
$this->addValue($key,$value,$expire);
}

Stores a value identified by a key in cache. This is the implementation of the method declared in the parent class.

Be the first person to leave a comment

Please to leave your comment.