Class yii\caching\DbCache
| 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
| 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 | null|array|false | The functions used to serialize and unserialize cached data. | yii\caching\Cache |
Public Methods
| 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() | Returns whether there is a cache entry with a specified key. | yii\caching\Cache |
| offsetGet() | Retrieves the value from cache with a specified key. | yii\caching\Cache |
| offsetSet() | Stores the value identified by a key into cache. | yii\caching\Cache |
| offsetUnset() | Deletes the value with the specified key from cache This method is required by the interface ArrayAccess. | 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
| 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 |
| 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 |
| 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
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
);
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.
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.
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.
Method Details
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 |
|---|---|---|
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 |
|---|---|---|
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. |
|---|---|---|
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. |
|---|---|---|
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. |
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. |
|---|---|---|
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 |
|---|---|---|
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. |
|---|---|---|
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 |
|---|---|---|
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