This class caches features of a given QgsVectorLayer. More...

#include <qgsvectorlayercache.h>

Inheritance diagram for QgsVectorLayerCache:

Signals
void	attributeValueChanged (QgsFeatureId fid, int field, const QVariant &value)
	Is emitted when an attribute is changed. More...

void	cachedLayerDeleted ()
	Is emitted when the cached layer is deleted. More...

void	featureAdded (QgsFeatureId fid)
	Is emitted, when a new feature has been added to the layer and this cache. More...

void	finished ()
	When filling the cache, this signal gets emitted once the cache is fully initialized. More...

void	invalidated ()
	The cache has been invalidated and cleared. More...

void	progress (int i, bool &cancel)
	When filling the cache, this signal gets emitted periodically to notify about the progress and to be able to cancel an operation. More...

Public Member Functions
	QgsVectorLayerCache (QgsVectorLayer layer, int cacheSize, QObject parent=nullptr)

	~QgsVectorLayerCache ()

void	addCacheIndex (QgsAbstractCacheIndex *cacheIndex)
	Adds a QgsAbstractCacheIndex to this cache. More...

QgsFeatureIds	cachedFeatureIds () const
	Returns the set of feature IDs for features which are cached. More...

bool	cacheGeometry () const
	Returns true if the cache will fetch and cache feature geometries. More...

int	cacheSize ()
	Returns the maximum number of features this cache will hold. More...

bool	featureAtId (QgsFeatureId featureId, QgsFeature &feature, bool skipCache=false)
	Gets the feature at the given feature id. More...

QgsFeatureIterator	getFeatures (const QgsFeatureRequest &featureRequest=QgsFeatureRequest())
	Query this VectorLayerCache for features. More...

bool	hasFullCache () const
	Returns true if the cache is complete, ie it contains all features. More...

bool	isFidCached (const QgsFeatureId fid) const
	Check if a certain feature id is cached. More...

QgsVectorLayer *	layer ()
	Returns the layer to which this cache belongs. More...

bool	removeCachedFeature (QgsFeatureId fid)
	Removes the feature identified by fid from the cache if present. More...

void	setCacheAddedAttributes (bool cacheAddedAttributes)
	If this is enabled, the subset of cached attributes will automatically be extended to also include newly added attributes. More...

void	setCacheGeometry (bool cacheGeometry)
	Enable or disable the caching of geometries. More...

void	setCacheSize (int cacheSize)
	Sets the maximum number of features to keep in the cache. More...

void	setCacheSubsetOfAttributes (const QgsAttributeList &attributes)
	Set the subset of attributes to be cached. More...

void	setFullCache (bool fullCache)
	This enables or disables full caching. More...

Public Member Functions inherited from QObject
	QObject (QObject *parent)

	QObject (QObject parent, const char name)

virtual	~QObject ()

bool	blockSignals (bool block)

QObject *	child (const char objName, const char inheritsClass, bool recursiveSearch) const

const QObjectList &	children () const

const char *	className () const

bool	connect (const QObject sender, const char signal, const char *method, Qt::ConnectionType type) const

void	deleteLater ()

void	destroyed (QObject *obj)

bool	disconnect (const QObject receiver, const char method)

bool	disconnect (const char signal, const QObject receiver, const char *method)

void	dumpObjectInfo ()

void	dumpObjectTree ()

QList< QByteArray >	dynamicPropertyNames () const

virtual bool	event (QEvent *e)

virtual bool	eventFilter (QObject watched, QEvent event)

T	findChild (const QString &name) const

QList< T >	findChildren (const QRegExp &regExp) const

QList< T >	findChildren (const QString &name) const

bool	inherits (const char *className) const

void	insertChild (QObject *object)

void	installEventFilter (QObject *filterObj)

bool	isA (const char *className) const

bool	isWidgetType () const

void	killTimer (int id)

virtual const QMetaObject *	metaObject () const

void	moveToThread (QThread *targetThread)

const char *	name () const

const char *	name (const char *defaultName) const

QString	objectName () const

QObject *	parent () const

QVariant	property (const char *name) const

void	removeChild (QObject *object)

void	removeEventFilter (QObject *obj)

void	setName (const char *name)

void	setObjectName (const QString &name)

void	setParent (QObject *parent)

bool	setProperty (const char *name, const QVariant &value)

bool	signalsBlocked () const

int	startTimer (int interval)

QThread *	thread () const

Protected Member Functions
bool	checkInformationCovered (const QgsFeatureRequest &featureRequest)
	Checks if the information required to complete the request is cached. More...

void	featureRemoved (QgsFeatureId fid)
	Gets called, whenever a feature has been removed. More...

void	requestCompleted (const QgsFeatureRequest &featureRequest, const QgsFeatureIds &fids)
	Gets called, whenever the full list of feature ids for a certain request is known. More...

Protected Member Functions inherited from QObject
bool	checkConnectArgs (const char signal, const QObject object, const char *method)

virtual void	childEvent (QChildEvent *event)

virtual void	connectNotify (const char *signal)

virtual void	customEvent (QEvent *event)

virtual void	disconnectNotify (const char *signal)

int	receivers (const char *signal) const

QObject *	sender () const

int	senderSignalIndex () const

virtual void	timerEvent (QTimerEvent *event)

Friends
class	QgsCachedFeature

class	QgsCachedFeatureIterator

class	QgsCachedFeatureWriterIterator

class	TestVectorLayerCache

Additional Inherited Members
Static Public Member Functions inherited from QObject
bool	connect (const QObject sender, const char signal, const QObject receiver, const char method, Qt::ConnectionType type)

bool	connect (const QObject sender, const QMetaMethod &signal, const QObject receiver, const QMetaMethod &method, Qt::ConnectionType type)

bool	disconnect (const QObject sender, const char signal, const QObject receiver, const char method)

bool	disconnect (const QObject sender, const QMetaMethod &signal, const QObject receiver, const QMetaMethod &method)

QString	tr (const char sourceText, const char disambiguation, int n)

QString	trUtf8 (const char sourceText, const char disambiguation, int n)

Static Protected Member Functions inherited from QObject
QByteArray	normalizeSignalSlot (const char *signalSlot)

Properties inherited from QObject
	objectName

Detailed Description

This class caches features of a given QgsVectorLayer.

The cached features can be indexed by QgsAbstractCacheIndex.

Proper indexing for a given use-case may speed up performance substantially.

Definition at line 38 of file qgsvectorlayercache.h.

Constructor & Destructor Documentation

◆ QgsVectorLayerCache()

QgsVectorLayerCache::QgsVectorLayerCache	(	QgsVectorLayer *	layer,
		int	cacheSize,
		QObject *	parent = `nullptr`
	)

Definition at line 22 of file qgsvectorlayercache.cpp.

◆ ~QgsVectorLayerCache()

QgsVectorLayerCache::~QgsVectorLayerCache ( )

Definition at line 44 of file qgsvectorlayercache.cpp.

Member Function Documentation

◆ addCacheIndex()

void QgsVectorLayerCache::addCacheIndex ( QgsAbstractCacheIndex * cacheIndex )

Adds a QgsAbstractCacheIndex to this cache.

Cache indices know about features present in this cache and decide, if enough information is present in the cache to respond to a QgsFeatureRequest. The layer cache will take ownership of the index.

Parameters

cacheIndex The cache index to add.

Definition at line 125 of file qgsvectorlayercache.cpp.

◆ attributeValueChanged

void QgsVectorLayerCache::attributeValueChanged	(	QgsFeatureId	fid,
		int	field,
		const QVariant &	value
	)

signal

Is emitted when an attribute is changed.

Is re-emitted after the layer itself emits this signal. You should connect to this signal, to be sure, to not get a cached value if querying the cache.

◆ cachedFeatureIds()

QgsFeatureIds QgsVectorLayerCache::cachedFeatureIds ( ) const

inline

Returns the set of feature IDs for features which are cached.

Note: added in QGIS 2.18

See also: isFidCached()

Definition at line 188 of file qgsvectorlayercache.h.

◆ cachedLayerDeleted

void QgsVectorLayerCache::cachedLayerDeleted ( )

signal

Is emitted when the cached layer is deleted.

Is emitted when the cached layers layerDelete() signal is being emitted, but before the local reference to it has been set to NULL. So call to layer() will still return a valid pointer for cleanup purpose.

◆ cacheGeometry()

bool QgsVectorLayerCache::cacheGeometry ( ) const

inline

Returns true if the cache will fetch and cache feature geometries.

Note: added in QGIS 3.0

See also: setCacheGeometry()

Definition at line 115 of file qgsvectorlayercache.h.

◆ cacheSize()

int QgsVectorLayerCache::cacheSize ( )

Returns the maximum number of features this cache will hold.

In case full caching is enabled, this number can change, as new features get added.

Returns: int

Definition at line 55 of file qgsvectorlayercache.cpp.

◆ checkInformationCovered()

bool QgsVectorLayerCache::checkInformationCovered ( const QgsFeatureRequest & featureRequest )

protected

Checks if the information required to complete the request is cached.

i.e. If all attributes required and the geometry is held in the cache. Please note, that this does not check, if the requested features are cached.

Parameters

featureRequest The QgsFeatureRequest to be answered

Returns: True if the information is being cached, false if not

Definition at line 380 of file qgsvectorlayercache.cpp.

◆ featureAdded

void QgsVectorLayerCache::featureAdded ( QgsFeatureId fid )

signal

Is emitted, when a new feature has been added to the layer and this cache.

You should connect to this signal instead of the layers', if you want to be sure that this cache has updated information for the new feature

Parameters

fid	The featureid of the changed feature

◆ featureAtId()

bool QgsVectorLayerCache::featureAtId	(	QgsFeatureId	featureId,
		QgsFeature &	feature,
		bool	skipCache = `false`
	)

Gets the feature at the given feature id.

Considers the changed, added, deleted and permanent features

Parameters

featureId	The id of the feature to query
feature	The result of the operation will be written to this feature
skipCache	Will query the layer regardless if the feature is in the cache already

Returns: true in case of success

Definition at line 142 of file qgsvectorlayercache.cpp.

◆ featureRemoved()

void QgsVectorLayerCache::featureRemoved ( QgsFeatureId fid )

protected

Gets called, whenever a feature has been removed.

Broadcasts this information to indices, so they can invalidate their cache if required.

Parameters

fid	The feature id of the removed feature.

Definition at line 197 of file qgsvectorlayercache.cpp.

◆ finished

void QgsVectorLayerCache::finished ( )

signal

When filling the cache, this signal gets emitted once the cache is fully initialized.

◆ getFeatures()

QgsFeatureIterator QgsVectorLayerCache::getFeatures ( const QgsFeatureRequest & featureRequest = QgsFeatureRequest() )

Query this VectorLayerCache for features.

If the VectorLayerCache (and moreover any of its indices) is able to satisfy the request, the returned QgsFeatureIterator will iterate over cached features. If it's not possible to fully satisfy the request from the cache, part or all of the features will be requested from the data provider.

Parameters

featureRequest The request specifying filter and required data.

Returns: An iterator over the requested data.

Definition at line 329 of file qgsvectorlayercache.cpp.

◆ hasFullCache()

bool QgsVectorLayerCache::hasFullCache ( ) const

inline

Returns true if the cache is complete, ie it contains all features.

This may happen as a result of a call to setFullCache() or by through a feature request which resulted in all available features being cached.

See also: setFullCache()

Note: added in QGIS 2.18

Definition at line 153 of file qgsvectorlayercache.h.

◆ invalidated

void QgsVectorLayerCache::invalidated ( )

signal

The cache has been invalidated and cleared.

Note that when a cache is invalidated the fullCache() setting will be cleared, and a full cache rebuild via setFullCache( true ) will need to be performed.

◆ isFidCached()

bool QgsVectorLayerCache::isFidCached ( const QgsFeatureId fid ) const

Check if a certain feature id is cached.

Parameters

fid	The feature id to look for

Returns: True if this id is in the cache

See also: cachedFeatureIds()

Definition at line 375 of file qgsvectorlayercache.cpp.

◆ layer()

QgsVectorLayer * QgsVectorLayerCache::layer ( )

Returns the layer to which this cache belongs.

Definition at line 176 of file qgsvectorlayercache.cpp.

◆ progress

void QgsVectorLayerCache::progress	(	int	i,
		bool &	cancel
	)

signal

When filling the cache, this signal gets emitted periodically to notify about the progress and to be able to cancel an operation.

Parameters

i	The number of already fetched features
cancel	A reference to a boolean variable. Set to true and the operation will be canceled.

Note: not available in python bindings

◆ removeCachedFeature()

bool QgsVectorLayerCache::removeCachedFeature ( QgsFeatureId fid )

Removes the feature identified by fid from the cache if present.

Parameters

fid	The id of the feature to delete

Returns: true if the feature was removed, false if the feature id was not found in the cache

Definition at line 171 of file qgsvectorlayercache.cpp.

◆ requestCompleted()

void QgsVectorLayerCache::requestCompleted	(	const QgsFeatureRequest &	featureRequest,
		const QgsFeatureIds &	fids
	)

protected

Gets called, whenever the full list of feature ids for a certain request is known.

Broadcasts this information to indices, so they can update their tables.

Parameters

featureRequest	The feature request that was answered
fids	The feature ids that have been returned

Definition at line 181 of file qgsvectorlayercache.cpp.

◆ setCacheAddedAttributes()

void QgsVectorLayerCache::setCacheAddedAttributes ( bool cacheAddedAttributes )

If this is enabled, the subset of cached attributes will automatically be extended to also include newly added attributes.

Parameters

cacheAddedAttributes Automatically cache new attributes

Definition at line 130 of file qgsvectorlayercache.cpp.

◆ setCacheGeometry()

void QgsVectorLayerCache::setCacheGeometry ( bool cacheGeometry )

Enable or disable the caching of geometries.

Parameters

cacheGeometry Enable or disable the caching of geometries

See also: cacheGeometry()

Definition at line 60 of file qgsvectorlayercache.cpp.

◆ setCacheSize()

void QgsVectorLayerCache::setCacheSize ( int cacheSize )

Sets the maximum number of features to keep in the cache.

Some features will be removed from the cache if the number is smaller than the previous size of the cache.

Parameters

cacheSize indicates the maximum number of features to keep in the cache

Definition at line 50 of file qgsvectorlayercache.cpp.

◆ setCacheSubsetOfAttributes()

void QgsVectorLayerCache::setCacheSubsetOfAttributes ( const QgsAttributeList & attributes )

Set the subset of attributes to be cached.

Parameters

attributes The attributes to be cached

Definition at line 79 of file qgsvectorlayercache.cpp.

◆ setFullCache()

void QgsVectorLayerCache::setFullCache ( bool fullCache )

This enables or disables full caching.

If enabled, all features will be held in the cache. The cache size will incrementally be increased to offer space for all features. When enabled, all features will be read into cache. As this feature will most likely be used for slow data sources, be aware, that the call to this method might take a long time.

Parameters

fullCache True: enable full caching, False: disable full caching

Note: when a cache is invalidated() (e.g. by adding an attribute to a layer) this setting is reset. A full cache rebuild must be performed by calling setFullCache( true ) again.

See also: hasFullCache()

Definition at line 84 of file qgsvectorlayercache.cpp.

Friends And Related Function Documentation

◆ QgsCachedFeature

friend class QgsCachedFeature

friend

Definition at line 320 of file qgsvectorlayercache.h.

◆ QgsCachedFeatureIterator

friend class QgsCachedFeatureIterator

friend

Definition at line 318 of file qgsvectorlayercache.h.

◆ QgsCachedFeatureWriterIterator

friend class QgsCachedFeatureWriterIterator

friend

Definition at line 319 of file qgsvectorlayercache.h.

◆ TestVectorLayerCache

friend class TestVectorLayerCache

friend

Definition at line 331 of file qgsvectorlayercache.h.

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

/tmp/buildd/qgis-2.18.21+99unstable/src/core/qgsvectorlayercache.h
/tmp/buildd/qgis-2.18.21+99unstable/src/core/qgsvectorlayercache.cpp

Signals

Public Member Functions

Protected Member Functions

Friends

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ QgsVectorLayerCache()

◆ ~QgsVectorLayerCache()

Member Function Documentation

◆ addCacheIndex()

◆ attributeValueChanged

◆ cachedFeatureIds()

◆ cachedLayerDeleted

◆ cacheGeometry()

◆ cacheSize()

◆ checkInformationCovered()

◆ featureAdded

◆ featureAtId()

◆ featureRemoved()

◆ finished

◆ getFeatures()

◆ hasFullCache()

◆ invalidated

◆ isFidCached()

◆ layer()

◆ progress

◆ removeCachedFeature()

◆ requestCompleted()

◆ setCacheAddedAttributes()

◆ setCacheGeometry()

◆ setCacheSize()

◆ setCacheSubsetOfAttributes()

◆ setFullCache()

Friends And Related Function Documentation

◆ QgsCachedFeature

◆ QgsCachedFeatureIterator

◆ QgsCachedFeatureWriterIterator

◆ TestVectorLayerCache