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)
	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 266 of file qgsconnectionpool.h.

Member Typedef Documentation

template<typename T , typename T_Group >

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

Definition at line 270 of file qgsconnectionpool.h.

Constructor & Destructor Documentation

template<typename T , typename T_Group >

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

inlinevirtual

Definition at line 272 of file qgsconnectionpool.h.

Member Function Documentation

template<typename T , typename T_Group >

T QgsConnectionPool< T, T_Group >::acquireConnection ( const QString &  connInfo, int  timeout = -1, bool  requestMayBeNested = false  )

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 292 of file qgsconnectionpool.h.

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 325 of file qgsconnectionpool.h.

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 307 of file qgsconnectionpool.h.

Member Data Documentation

template<typename T , typename T_Group >

T_Groups QgsConnectionPool< T, T_Group >::mGroups

protected

Definition at line 335 of file qgsconnectionpool.h.

template<typename T , typename T_Group >

QMutex QgsConnectionPool< T, T_Group >::mMutex

protected

Definition at line 336 of file qgsconnectionpool.h.

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

• /build/qgis-3.4.15+24xenial/src/core/qgsconnectionpool.h