Class yii\caching\DbCache

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Inheritance	yii\caching\DbCache » yii\caching\Cache » yii\base\Component » yii\base\BaseObject
Implements	yii\base\Configurable, yii\caching\CacheInterface
Available since version	2.0
Source Code	https://github.com/yiisoft/yii2/blob/master/framework/caching/DbCache.php

DbCache implements a cache application component by storing cached data in a database.

By default, DbCache stores session data in a DB table named 'cache'. This table must be pre-created. The table name can be changed by setting $cacheTable.

Please refer to yii\caching\Cache for common cache operations that are supported by DbCache.

The following example shows how you can configure the application to use DbCache:

'cache' => [
    'class' => 'yii\caching\DbCache',
    // 'db' => 'mydb',
    // 'cacheTable' => 'my_cache',
]

For more details and usage information on Cache, see the guide article on caching.

Public Properties

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Property	Type	Description	Defined By
$behaviors	yii\base\Behavior[]	List of behaviors attached to this component.	yii\base\Component
$cacheTable	string	Name of the DB table to store cache content.	yii\caching\DbCache
$db	yii\db\Connection\|array\|string	The DB connection object or the application component ID of the DB connection.	yii\caching\DbCache
$defaultDuration	integer	Default duration in seconds before a cache entry will expire.	yii\caching\Cache
$gcProbability	integer	The probability (parts per million) that garbage collection (GC) should be performed when storing a piece of data in the cache.	yii\caching\DbCache
$keyPrefix	string	A string prefixed to every cache key so that it is unique globally in the whole cache storage.	yii\caching\Cache
$serializer	array\|null\|false	The functions used to serialize and unserialize cached data.	yii\caching\Cache

Protected Properties

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Property	Type	Description	Defined By
$isVarbinaryDataField			yii\caching\DbCache

Public Methods

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Method	Description	Defined By
__call()	Calls the named method which is not a class method.	yii\base\Component
__clone()	This method is called after the object is created by cloning an existing one.	yii\base\Component
__construct()	Constructor.	yii\base\BaseObject
__get()	Returns the value of a component property.	yii\base\Component
__isset()	Checks if a property is set, i.e. defined and not null.	yii\base\Component
__set()	Sets the value of a component property.	yii\base\Component
__unset()	Sets a component property to be null.	yii\base\Component
add()	Stores a value identified by a key into cache if the cache does not contain this key.	yii\caching\Cache
attachBehavior()	Attaches a behavior to this component.	yii\base\Component
attachBehaviors()	Attaches a list of behaviors to the component.	yii\base\Component
behaviors()	Returns a list of behaviors that this component should behave as.	yii\base\Component
buildKey()	Builds a normalized cache key from a given key.	yii\caching\Cache
canGetProperty()	Returns a value indicating whether a property can be read.	yii\base\Component
canSetProperty()	Returns a value indicating whether a property can be set.	yii\base\Component
className()	Returns the fully qualified name of this class.	yii\base\BaseObject
delete()	Deletes a value with the specified key from cache.	yii\caching\Cache
detachBehavior()	Detaches a behavior from the component.	yii\base\Component
detachBehaviors()	Detaches all behaviors from the component.	yii\base\Component
ensureBehaviors()	Makes sure that the behaviors declared in behaviors() are attached to this component.	yii\base\Component
exists()	Checks whether a specified key exists in the cache.	yii\caching\DbCache
flush()	Deletes all values from cache.	yii\caching\Cache
gc()	Removes the expired data values.	yii\caching\DbCache
get()	Retrieves a value from cache with a specified key.	yii\caching\Cache
getBehavior()	Returns the named behavior object.	yii\base\Component
getBehaviors()	Returns all behaviors attached to this component.	yii\base\Component
getOrSet()	Method combines both set() and get() methods to retrieve value identified by a $key, or to store the result of $callable execution if there is no cache available for the $key.	yii\caching\Cache
hasEventHandlers()	Returns a value indicating whether there is any handler attached to the named event.	yii\base\Component
hasMethod()	Returns a value indicating whether a method is defined.	yii\base\Component
hasProperty()	Returns a value indicating whether a property is defined for this component.	yii\base\Component
init()	Initializes the DbCache component.	yii\caching\DbCache
madd()	Stores multiple items in cache. Each item contains a value identified by a key.	yii\caching\Cache
mget()	Retrieves multiple values from cache with the specified keys.	yii\caching\Cache
mset()	Stores multiple items in cache. Each item contains a value identified by a key.	yii\caching\Cache
multiAdd()	Stores multiple items in cache. Each item contains a value identified by a key.	yii\caching\Cache
multiGet()	Retrieves multiple values from cache with the specified keys.	yii\caching\Cache
multiSet()	Stores multiple items in cache. Each item contains a value identified by a key.	yii\caching\Cache
off()	Detaches an existing event handler from this component.	yii\base\Component
offsetExists()		yii\caching\Cache
offsetGet()		yii\caching\Cache
offsetSet()		yii\caching\Cache
offsetUnset()		yii\caching\Cache
on()	Attaches an event handler to an event.	yii\base\Component
set()	Stores a value identified by a key into cache.	yii\caching\Cache
trigger()	Triggers an event.	yii\base\Component

Protected Methods

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Method	Description	Defined By
addValue()	Stores a value identified by a key into cache if the cache does not contain this key.	yii\caching\DbCache
addValues()	Adds multiple key-value pairs to cache.	yii\caching\Cache
deleteValue()	Deletes a value with the specified key from cache This is the implementation of the method declared in the parent class.	yii\caching\DbCache
flushValues()	Deletes all values from cache.	yii\caching\DbCache
getDataFieldName()		yii\caching\DbCache
getDataFieldValue()		yii\caching\DbCache
getValue()	Retrieves a value from cache with a specified key.	yii\caching\DbCache
getValues()	Retrieves multiple values from cache with the specified keys.	yii\caching\DbCache
isVarbinaryDataField()		yii\caching\DbCache
setValue()	Stores a value identified by a key in cache.	yii\caching\DbCache
setValues()	Stores multiple key-value pairs in cache.	yii\caching\Cache

Property Details

$cacheTable public property

Name of the DB table to store cache content. The table should be pre-created as follows:

CREATE TABLE cache (
    id char(128) NOT NULL PRIMARY KEY,
    expire int(11),
    data BLOB
);

For MSSQL: `php CREATE TABLE cache (

id VARCHAR(128) NOT NULL PRIMARY KEY,
expire INT(11),
data VARBINARY(MAX)

); `

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

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 string $cacheTable = '{{%cache}}'

$db public property

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. Starting from version 2.0.2, this can also be a configuration array for creating the object.

public yii\db\Connection|array|string $db = 'db'

$gcProbability public property

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 integer $gcProbability = 100

$isVarbinaryDataField protected property

protected $isVarbinaryDataField = null

Method Details

addValue() protected method

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 boolean addValue ( $key, $value, $duration )
$key	string	The key identifying the value to be cached
$value	string	The value to be cached. Other types (if you have disabled $serializer) cannot be saved.
$duration	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

deleteValue() protected method

Deletes a value with the specified key from cache This is the implementation of the method declared in the parent class.

protected boolean deleteValue ( $key )
$key	string	The key of the value to be deleted
return	boolean	If no error happens during deletion

exists() public method

Checks whether a specified key exists in the cache.

This can be faster than getting the value from the cache if the data is big. Note that this method does not check whether the dependency associated with the cached data, if there is any, has changed. So a call to get() may return false while exists returns true.

public boolean exists ( $key )
$key	mixed	A key identifying the cached value. This can be a simple string or a complex data structure consisting of factors representing the key.
return	boolean	True if a value exists in cache, false if the value is not in the cache or expired.

flushValues() protected method

Deletes all values 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.

gc() public method

Removes the expired data values.

public void gc ( $force = false )
$force	boolean	Whether to enforce the garbage collection regardless of $gcProbability. Defaults to false, meaning the actual deletion happens with the probability as specified by $gcProbability.

getDataFieldName() protected method (available since version 2.0.42)

protected string getDataFieldName ( )
return	string	`data` field name converted for usage in MSSQL (if needed)

getDataFieldValue() protected method (available since version 2.0.42)

protected yii\db\PdoValue getDataFieldValue ( $value )
$value
return	yii\db\PdoValue	PdoValue or direct $value for usage in MSSQL

getValue() protected method

Retrieves a value from cache with a specified key.

This is the implementation of the method declared in the parent class.

protected string\|false getValue ( $key )
$key	string	A unique key identifying the cached value
return	string\|false	The value stored in cache, false if the value is not in the cache or expired.

getValues() protected method

Retrieves multiple values from cache with the specified keys.

protected array getValues ( $keys )
$keys	array	A list of keys identifying the cached values
return	array	A list of cached values indexed by the keys

init() public method

Initializes the DbCache component.

This method will initialize the $db property to make sure it refers to a valid DB connection.

public void init ( )
throws	yii\base\InvalidConfigException	if $db is invalid.

isVarbinaryDataField() protected method (available since version 2.0.42)

protected boolean isVarbinaryDataField ( )
return	boolean	Whether field is MSSQL varbinary

setValue() protected method

Stores a value identified by a key in cache.

This is the implementation of the method declared in the parent class.

protected boolean setValue ( $key, $value, $duration )
$key	string	The key identifying the value to be cached
$value	string	The value to be cached. Other types (if you have disabled $serializer) cannot be saved.
$duration	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