QGIS API Documentation  2.99.0-Master (f1c3692)
Public Types | Public Member Functions | Protected Attributes | List of all members
QgsConnectionPool< T, T_Group > Class Template Reference

Template class responsible for keeping a pool of open connections. More...

#include <qgsconnectionpool.h>

Public Types

typedef QMap< QString, T_Group * > T_Groups
 

Public Member Functions

virtual ~QgsConnectionPool ()
 
acquireConnection (const QString &connInfo, int timeout=-1)
 Try to acquire a connection for a maximum of timeout milliseconds. More...
 
void invalidateConnections (const QString &connInfo)
 Invalidates all connections to the specified resource. More...
 
void releaseConnection (T conn)
 Release an existing connection so it will get back into the pool and can be reused. More...
 

Protected Attributes

T_Groups mGroups
 
QMutex mMutex
 

Detailed Description

template<typename T, typename T_Group>
class QgsConnectionPool< T, T_Group >

Template class responsible for keeping a pool of open connections.

This is desired to avoid the overhead of creation of new connection every time.

The methods are thread safe.

The connection pool has a limit on maximum number of concurrent connections (per server), once the limit is reached, the acquireConnection() function will block. All connections that have been acquired must be then released with releaseConnection() function.

When the connections are not used for some time, they will get closed automatically to save resources.

Note
not available in Python bindings

Definition at line 263 of file qgsconnectionpool.h.

Member Typedef Documentation

◆ T_Groups

template<typename T , typename T_Group >
typedef QMap<QString, T_Group *> QgsConnectionPool< T, T_Group >::T_Groups

Definition at line 267 of file qgsconnectionpool.h.

Constructor & Destructor Documentation

◆ ~QgsConnectionPool()

template<typename T , typename T_Group >
virtual QgsConnectionPool< T, T_Group >::~QgsConnectionPool ( )
inlinevirtual

Definition at line 269 of file qgsconnectionpool.h.

Member Function Documentation

◆ acquireConnection()

template<typename T , typename T_Group >
T QgsConnectionPool< T, T_Group >::acquireConnection ( const QString &  connInfo,
int  timeout = -1 
)
inline

Try to acquire a connection for a maximum of timeout milliseconds.

If timeout is a negative value the calling thread will be blocked until a connection becomes available. This is the default behavior.

Returns
initialized connection or nullptr if unsuccessful

Definition at line 287 of file qgsconnectionpool.h.

◆ invalidateConnections()

template<typename T , typename T_Group >
void QgsConnectionPool< T, T_Group >::invalidateConnections ( const QString &  connInfo)
inline

Invalidates all connections to the specified resource.

The internal state of certain handles (for instance OGR) are altered when a dataset is modified. Consquently, all open handles need to be invalidated when such datasets are changed to ensure the handles are refreshed. See the OGR provider for an example where this is needed.

Definition at line 320 of file qgsconnectionpool.h.

◆ releaseConnection()

template<typename T , typename T_Group >
void QgsConnectionPool< T, T_Group >::releaseConnection ( conn)
inline

Release an existing connection so it will get back into the pool and can be reused.

Definition at line 302 of file qgsconnectionpool.h.

Member Data Documentation

◆ mGroups

template<typename T , typename T_Group >
T_Groups QgsConnectionPool< T, T_Group >::mGroups
protected

Definition at line 330 of file qgsconnectionpool.h.

◆ mMutex

template<typename T , typename T_Group >
QMutex QgsConnectionPool< T, T_Group >::mMutex
protected

Definition at line 331 of file qgsconnectionpool.h.


The documentation for this class was generated from the following file: