Class TDbCache
TDbCache class
TDbCache implements a cache application module by storing cached data in a database. TDbCache relies on PDO to retrieve data from databases. In order to use TDbCache, you need to enable the PDO extension as well as the corresponding PDO DB driver. For example, to use SQLite database to store cached data, you need both php_pdo and php_pdo_sqlite extensions. By default, TDbCache creates and uses an SQLite database under the application runtime directory. You may change this default setting by specifying the following properties: The cached data is stored in a table in the specified database. By default, the name of the table is called 'pradocache'. If the table does not exist in the database, it will be automatically created with the following structure: - CREATE TABLE pradocache (itemkey CHAR(128), value BLOB, expire INT)
- CREATE INDEX IX_itemkey ON pradocache (itemkey)
- CREATE INDEX IX_expire ON pradocache (expire)
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.) Important: Make sure that the indices are non-unique! If you want to change the cache table name, or if you want to create the table by yourself, you may set CacheTableName and AutoCreateCacheTableName properties. FlushInterval control how often expired items will be removed from cache. If you prefer to remove expired items manualy e.g. via cronjob you can disable automatic deletion by setting FlushInterval to '0'. The following basic cache operations are implemented: - get : retrieve the value with a key (if any) from cache
- set : store the value with a key into cache
- add : store the value only if cache does not have this key
- delete : delete the value with the specified key from cache
- flush : delete all values from cache
Each value is associated with an expiration time. The get operation ensures that any expired value will not be returned. The expiration time by the number of seconds. A expiration time 0 represents never expire. By definition, cache does not ensure the existence of a value even if it never expires. Cache is not meant to be an persistent storage. Do not use the same database file for multiple applications using TDbCache. Also note, cache is shared by all user sessions of an application. Some usage examples of TDbCache are as follows, - $cache=new TDbCache; // TDbCache may also be loaded as a Prado application module
- $cache->init(null);
- $cache->add('object',$object);
- $object2=$cache->get('object');
If loaded, TDbCache will register itself with TApplication as the cache module. It can be accessed via TApplication::getCache(). TDbCache may be configured in application configuration file as follows - <module id="cache" class="System.Caching.TDbCache" />
Method Summary |
protected
boolean
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addValue
( string $key, string $value, integer $expire)
Stores a value identified by a key into cache if the cache does not contain this key.
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protected
TDbConnection
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Creates the DB connection.
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protected
boolean
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Deletes a value with the specified key from cache This is the implementation of the method declared in the parent class.
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void
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Event listener for TApplication.OnSaveState
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void
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Event listener for TApplication.OnLoadStateComplete
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void
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Deletes all values from cache.
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void
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Flush expired values from cache depending on setFlushInterval
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boolean
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string
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string
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string
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TDbConnection
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integer
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string
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string
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protected
string
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Retrieves a value from cache with a specified key.
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void
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Initializes this module.
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protected
void
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Initialize TDbCache
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void
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void
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Sets the name of the DB table to store cache content.
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void
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Sets the ID of a TDataSourceConfig module.
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void
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void
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Sets interval expired items will be removed from cache
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void
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void
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protected
boolean
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setValue
( string $key, string $value, integer $expire)
Stores a value identified by a key in cache.
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Methods Inherited From TCache |
TCache::add(), TCache::delete(), TCache::flush(), TCache::generateUniqueKey(), TCache::get(), TCache::getKeyPrefix(), TCache::getPrimaryCache(), TCache::init(), TCache::offsetExists(), TCache::offsetGet(), TCache::offsetSet(), TCache::offsetUnset(), TCache::set(), TCache::setKeyPrefix(), TCache::setPrimaryCache(),
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Methods Inherited From TComponent |
TComponent::addParsedObject(), TComponent::attachEventHandler(), TComponent::canGetProperty(), TComponent::canSetProperty(), TComponent::createdOnTemplate(), TComponent::detachEventHandler(), TComponent::evaluateExpression(), TComponent::evaluateStatements(), TComponent::getEventHandlers(), TComponent::getSubProperty(), TComponent::hasEvent(), TComponent::hasEventHandler(), TComponent::hasProperty(), TComponent::raiseEvent(), TComponent::setSubProperty(), TComponent::__get(), TComponent::__set()
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Method Details |
addValue
protected boolean addValue |
(string $key , string $value , integer $expire ) |
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.
Input |
string | $key | the key identifying the value to be cached |
string | $value | the value to be cached |
integer | $expire | the number of seconds in which the cached value will expire. 0 means never expire. |
Output |
boolean
| true if the value is successfully stored into cache, false otherwise |
Exception |
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createDbConnection
Creates the DB connection.
Input |
string | 0 | the module ID for TDataSourceConfig |
Output |
TDbConnection
| the created DB connection |
Exception |
throws | TConfigurationException if module ID is invalid or empty |
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deleteValue
protected boolean deleteValue |
(string $key ) |
Deletes a value with the specified key from cache This is the implementation of the method declared in the parent class.
Input |
string | $key | the key of the value to be deleted |
Output |
boolean
| if no error happens during deletion |
Exception |
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doFlushCacheExpired
public void doFlushCacheExpired |
() |
Event listener for TApplication.OnSaveState
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doInitializeCache
public void doInitializeCache |
() |
Event listener for TApplication.OnLoadStateComplete
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flush
Deletes all values from cache.
Be careful of performing this operation if the cache is shared by multiple applications.
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flushCacheExpired
public void flushCacheExpired |
(boolean $force ) |
Flush expired values from cache depending on setFlushInterval
Input |
boolean | $force | override FlushInterval and force deletion of expired items |
Output |
Exception |
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getAutoCreateCacheTable
public boolean getAutoCreateCacheTable |
() |
Output |
boolean
| whether the cache DB table should be automatically created if not exists. Defaults to true. |
Exception |
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getCacheTableName
public string getCacheTableName |
() |
Output |
string
| the name of the DB table to store cache content. Defaults to 'pradocache'. |
Exception |
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getConnectionID
public string getConnectionID |
() |
Output |
string
| the ID of a TDataSourceConfig module. Defaults to empty string, meaning not set. |
Exception |
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getConnectionString
public string getConnectionString |
() |
Output |
string
| The Data Source Name, or DSN, contains the information required to connect to the database. |
Exception |
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getDbConnection
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getFlushInterval
public integer getFlushInterval |
() |
Output |
integer
| Interval in sec expired items will be removed from cache. Default to 60 |
Exception |
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getPassword
public string getPassword |
() |
Output |
string
| the password for establishing DB connection. Defaults to empty string. |
Exception |
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getUsername
public string getUsername |
() |
Output |
string
| the username for establishing DB connection. Defaults to empty string. |
Exception |
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getValue
protected string getValue |
(string $key ) |
Retrieves a value from cache with a specified key.
This is the implementation of the method declared in the parent class.
Input |
string | $key | a unique key identifying the cached value |
Output |
string
| the value stored in cache, false if the value is not in the cache or expired. |
Exception |
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init
Initializes this module.
This method is required by the IModule interface. attach doInitializeCache to TApplication.OnLoadStateComplete event attach doFlushCacheExpired to TApplication.OnSaveState event
Input |
TXmlElement | $config | configuration for this module, can be null |
Output |
Exception |
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initializeCache
protected void initializeCache |
(boolean $force ) |
Initialize TDbCache
If AutoCreateCacheTableName is 'true' check existence of cache table and create table if does not exist.
Input |
boolean | $force | Force override global state check |
Output |
Exception |
throws | TConfigurationException if any error happens during creating database or cache table. |
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setAutoCreateCacheTable
public void setAutoCreateCacheTable |
(boolean $value ) |
Input |
boolean | $value | whether the cache DB table should be automatically created if not exists. |
Output |
Exception |
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setCacheTableName
public void setCacheTableName |
(string $value ) |
Sets the name of the DB table to store cache content.
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: - CREATE TABLE pradocache (itemkey CHAR(128), value BLOB, expire INT)
- CREATE INDEX IX_itemkey ON pradocache (itemkey)
- CREATE INDEX IX_expire ON pradocache (expire)
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.) Important: Make sure that the indices are non-unique!
Input |
string | $value | the name of the DB table to store cache content |
Output |
Exception |
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setConnectionID
public void setConnectionID |
(string $value ) |
Sets the ID of a TDataSourceConfig module.
The datasource module will be used to establish the DB connection for this cache module. The database connection can also be specified via ConnectionString. When both ConnectionID and ConnectionString are specified, the former takes precedence.
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setConnectionString
public void setConnectionString |
(string $value ) |
Input |
string | $value | The Data Source Name, or DSN, contains the information required to connect to the database. |
Output |
Exception |
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setFlushInterval
public void setFlushInterval |
(integer $value ) |
Sets interval expired items will be removed from cache
To disable automatic deletion of expired items, e.g. for external flushing via cron you can set value to '0'
Input |
integer | $value | Interval in sec |
Output |
Exception |
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setPassword
public void setPassword |
(string $value ) |
Input |
string | $value | the password for establishing DB connection |
Output |
Exception |
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setUsername
public void setUsername |
(string $value ) |
Input |
string | $value | the username for establishing DB connection |
Output |
Exception |
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setValue
protected boolean setValue |
(string $key , string $value , integer $expire ) |
Stores a value identified by a key in cache.
This is the implementation of the method declared in the parent class.
Input |
string | $key | the key identifying the value to be cached |
string | $value | the value to be cached |
integer | $expire | the number of seconds in which the cached value will expire. 0 means never expire. |
Output |
boolean
| true if the value is successfully stored into cache, false otherwise |
Exception |
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