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

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 271 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 275 of file qgsconnectionpool.h.

Constructor & Destructor Documentation

~QgsConnectionPool()

template<typename T , typename T_Group >

virtual QgsConnectionPool< T, T_Group >::~QgsConnectionPool ( )

inlinevirtual

Definition at line 277 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, bool  requestMayBeNested = false, QgsFeedback *  feedback = nullptr  )

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.

The optional feedback argument can be used to cancel the request before the connection is acquired.

Returns

initialized connection or nullptr if unsuccessful

Definition at line 298 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 349 of file qgsconnectionpool.h.

releaseConnection()

template<typename T , typename T_Group >

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

inline

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

Definition at line 331 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 359 of file qgsconnectionpool.h.

mMutex

template<typename T , typename T_Group >

QMutex QgsConnectionPool< T, T_Group >::mMutex

protected

Definition at line 360 of file qgsconnectionpool.h.

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

• /build/qgis-3.34.0+99sid/src/core/qgsconnectionpool.h