DbDependency

API reference › yii › caching › DbDependency

class	`yii\caching\DbDependency`
Extends	`Dependency` » `yii\base\BaseObject`
Implements	`yii\base\Configurable`
Since	2.0
Source	`framework/caching/DbDependency.php`

DbDependency represents a dependency based on the query result of a SQL statement.

If the query result changes, the dependency is considered as changed. The query is specified via the $sql property.

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

Properties

Property	Type	Description	Defined by
`$data`	`mixed`	The dependency data that is saved in cache and later is compared with the latest dependency data. Default: `null`.	`Dependency`
`$db`	`yii\db\Connection\|string`	The DB connection object or the application component ID of the DB connection. Default: `'db'`.	`DbDependency`
`$params`	`array`	The parameters (name => value) to be bound to the SQL statement specified by `$sql`. Default: `[]`.	`DbDependency`
`$reusable`	`bool`	Whether this dependency is reusable or not. Default: `false`.	`Dependency`
`$sql`	`string\|null`	The SQL query whose result is used to determine if the dependency has been changed. Default: `null`.	`DbDependency`

Method	Description	Defined by
`__construct()`	Constructor.	`yii\base\BaseObject`
`__call()`	Calls the named method which is not a class method.	`yii\base\BaseObject`
`__get()`	Returns the value of an object property.	`yii\base\BaseObject`
`__isset()`	Checks if a property is set, i.e. defined and not null.	`yii\base\BaseObject`
`__set()`	Sets value of an object property.	`yii\base\BaseObject`
`__unset()`	Sets an object property to null.	`yii\base\BaseObject`
`canGetProperty()`	Returns a value indicating whether a property can be read.	`yii\base\BaseObject`
`canSetProperty()`	Returns a value indicating whether a property can be set.	`yii\base\BaseObject`
`className()` static	Returns the fully qualified name of this class.	`yii\base\BaseObject`
`evaluateDependency()`	Evaluates the dependency by generating and saving the data related with dependency.	`Dependency`
`hasMethod()`	Returns a value indicating whether a method is defined.	`yii\base\BaseObject`
`hasProperty()`	Returns a value indicating whether a property is defined.	`yii\base\BaseObject`
`init()`	Initializes the object.	`yii\base\BaseObject`
`isChanged()`	Checks whether the dependency is changed.	`Dependency`
`resetReusableData()` static	Resets all cached data for reusable dependencies.	`Dependency`
`generateDependencyData()` protected	Generates the data needed to determine if dependency has been changed.	`DbDependency`
`generateReusableHash()` protected	Generates a unique hash that can be used for retrieving reusable dependency data.	`Dependency`

public string|null $sql = null

The SQL query whose result is used to determine if the dependency has been changed.

Only the first row of the query result will be used.

protected function generateDependencyData(yii\caching\CacheInterface $cache): mixed

Generates the data needed to determine if dependency has been changed.

This method returns the value of the global state.

Parameters

Parameter	Type	Description
`$cache`	`CacheInterface`	The cache component that is currently evaluating this dependency

Returns

mixed: The data needed to determine if dependency has been changed.

Throws

yii\base\InvalidConfigException: if $db is not a valid application component ID