This is the base class for vector data providers. More...

#include <qgsvectordataprovider.h>

Inheritance diagram for QgsVectorDataProvider:

Classes
struct	NativeType

Public Types
enum	Capability { NoCapabilities = 0, AddFeatures = 1, DeleteFeatures = 1 << 1, ChangeAttributeValues = 1 << 2, AddAttributes = 1 << 3, DeleteAttributes = 1 << 4, CreateSpatialIndex = 1 << 6, SelectAtId = 1 << 7, ChangeGeometries = 1 << 8, SelectEncoding = 1 << 13, CreateAttributeIndex = 1 << 12, SimplifyGeometries = 1 << 14, SimplifyGeometriesWithTopologicalValidation = 1 << 15, TransactionSupport = 1 << 16, CircularGeometries = 1 << 17, ChangeFeatures = 1 << 18, RenameAttributes = 1 << 19, FastTruncate = 1 << 20, ReadLayerMetadata = 1 << 21, WriteLayerMetadata = 1 << 22, CancelSupport = 1 << 23, CreateRenderer = 1 << 24 }
	enumeration with capabilities that providers might implement More...

enum	FeatureCountState { Uncounted = -2, UnknownCount = -1 }
	Enumeration of feature count states. More...

Public Types inherited from QgsDataProvider
enum	DataCapability { NoDataCapabilities = 0, File = 1, Dir = 1 << 1, Database = 1 << 2, Net = 1 << 3 }

enum	ProviderProperty { EvaluateDefaultValues, CustomData = 3000 }
	Properties are used to pass custom configuration options into data providers. More...

Public Types inherited from QgsFeatureSink
enum	Flag { FastInsert = 1 << 1 }
	Flags controlling how features are added to a sink. More...

Signals
void	raiseError (const QString &msg) const
	Signals an error in this provider. More...

Signals inherited from QgsDataProvider
void	dataChanged ()
	This is emitted whenever an asynchronous operation has finished and the data should be redrawn. More...

void	fullExtentCalculated ()
	This is emitted whenever the worker thread has fully calculated the PostGIS extents for this layer, and its event has been received by this provider. More...

void	notify (const QString &msg)
	Emitted when datasource issues a notification. More...

Public Member Functions
	QgsVectorDataProvider (const QString &uri=QString(), const QgsDataProvider::ProviderOptions &options=QgsDataProvider::ProviderOptions())
	Constructor for a vector data provider. More...

virtual bool	addAttributes (const QList< QgsField > &attributes)
	Adds new attributes to the provider. More...

bool	addFeatures (QgsFeatureList &flist, QgsFeatureSink::Flags flags=nullptr) override
	Adds a list of features to the sink. More...

virtual QVariant	aggregate (QgsAggregateCalculator::Aggregate aggregate, int index, const QgsAggregateCalculator::AggregateParameters &parameters, QgsExpressionContext *context, bool &ok) const
	Calculates an aggregated value from the layer's features. More...

virtual QgsAttributeList	attributeIndexes () const
	Returns list of indexes to fetch all attributes in nextFeature() More...

virtual bool	cancelReload ()
	Cancels the current reloading of data. More...

virtual QgsVectorDataProvider::Capabilities	capabilities () const
	Returns flags containing the supported capabilities. More...

QString	capabilitiesString () const
	Returns the above in friendly format. More...

virtual bool	changeAttributeValues (const QgsChangedAttributesMap &attr_map)
	Changes attribute values of existing features. More...

virtual bool	changeFeatures (const QgsChangedAttributesMap &attr_map, const QgsGeometryMap &geometry_map)
	Changes attribute values and geometries of existing features. More...

virtual bool	changeGeometryValues (const QgsGeometryMap &geometry_map)
	Changes geometries of existing features. More...

void	clearErrors ()
	Clear recorded errors. More...

virtual bool	createAttributeIndex (int field)
	Create an attribute index on the datasource. More...

virtual QgsFeatureRenderer *	createRenderer (const QVariantMap &configuration=QVariantMap()) const
	Creates a new vector layer feature renderer, using provider backend specific information. More...

virtual bool	createSpatialIndex ()
	Creates a spatial index on the datasource (if supported by the provider type). More...

virtual QString	dataComment () const
	Returns a short comment for the data that this provider is providing access to (e.g. More...

virtual QVariant	defaultValue (int fieldIndex) const
	Returns any literal default values which are present at the provider for a specified field index. More...

virtual QString	defaultValueClause (int fieldIndex) const
	Returns any default value clauses which are present at the provider for a specified field index. More...

virtual bool	deleteAttributes (const QgsAttributeIds &attributes)
	Deletes existing attributes from the provider. More...

virtual bool	deleteFeatures (const QgsFeatureIds &id)
	Deletes one or more features from the provider. More...

virtual QSet< QgsMapLayerDependency >	dependencies () const
	Gets the list of layer ids on which this layer depends. More...

virtual QList< QgsRelation >	discoverRelations (const QgsVectorLayer self, const QList< QgsVectorLayer > &layers) const
	Discover the available relations with the given layers. More...

virtual bool	doesStrictFeatureTypeCheck () const
	Returns true if the provider is strict about the type of inserted features (e.g. More...

QString	encoding () const
	Gets encoding which is used for accessing data. More...

virtual void	enumValues (int index, QStringList &enumList) const
	Returns the possible enum values of an attribute. More...

QStringList	errors () const
	Gets recorded errors. More...

long	featureCount () const override=0
	Number of features in the layer. More...

virtual QgsAbstractFeatureSource *	featureSource () const =0
	Returns feature source object that can be used for querying provider's data. More...

QgsFieldConstraints::Constraints	fieldConstraints (int fieldIndex) const
	Returns any constraints which are present at the provider for a specified field index. More...

int	fieldNameIndex (const QString &fieldName) const
	Returns the index of a field name or -1 if the field does not exist. More...

QMap< QString, int >	fieldNameMap () const
	Returns a map where the key is the name of the field and the value is its index. More...

QgsFields	fields () const override=0
	Returns the fields associated with this data provider. More...

virtual void	forceReload ()
	Forces a reload of the underlying datasource if the provider implements this method. More...

QgsFeatureIterator	getFeatures (const QgsFeatureRequest &request=QgsFeatureRequest()) const override=0
	Query the provider for features specified in request. More...

bool	hasErrors () const
	Provider has errors to report. More...

virtual bool	hasMetadata () const
	Returns true if the data source has metadata, false otherwise. More...

virtual bool	isDeleteStyleFromDatabaseSupported () const
	It returns false by default. More...

virtual bool	isSaveAndLoadStyleToDatabaseSupported () const
	It returns false by default. More...

QVariant	maximumValue (int index) const override
	Returns the maximum value of an attribute. More...

virtual QVariantMap	metadata () const
	Gets metadata, dependent on the provider type, that will be display in the metadata tab of the layer properties. More...

QVariant	minimumValue (int index) const override
	Returns the minimum value of an attribute. More...

QList< QgsVectorDataProvider::NativeType >	nativeTypes () const
	Returns the names of the supported types. More...

virtual QgsAttrPalIndexNameHash	palAttributeIndexNames () const
	Returns list of indexes to names for QgsPalLabeling fix. More...

virtual QgsAttributeList	pkAttributeIndexes () const
	Returns list of indexes of fields that make up the primary key. More...

virtual bool	renameAttributes (const QgsFieldNameMap &renamedAttributes)
	Renames existing attributes. More...

virtual void	setEncoding (const QString &e)
	Set encoding used for accessing data from layer. More...

virtual bool	skipConstraintCheck (int fieldIndex, QgsFieldConstraints::Constraint constraint, const QVariant &value=QVariant()) const
	Returns true if a constraint check should be skipped for a specified field (e.g., if the value returned by defaultValue() is trusted implicitly. More...

QgsCoordinateReferenceSystem	sourceCrs () const override
	Returns the coordinate reference system for features in the source. More...

QgsRectangle	sourceExtent () const override
	Returns the extent of all geometries from the source. More...

QString	sourceName () const override
	Returns a friendly display name for the source. More...

virtual QString	storageType () const
	Returns the permanent storage type for this layer as a friendly name. More...

bool	supportedType (const QgsField &field) const
	check if provider supports type of field More...

virtual QgsTransaction *	transaction () const
	Returns the transaction this data provider is included in, if any. More...

virtual QString	translateMetadataKey (const QString &mdKey) const
	Gets the translated metadata key. More...

virtual QString	translateMetadataValue (const QString &mdKey, const QVariant &value) const
	Gets the translated metadata value. More...

virtual bool	truncate ()
	Removes all features from the layer. More...

virtual QStringList	uniqueStringsMatching (int index, const QString &substring, int limit=-1, QgsFeedback *feedback=nullptr) const
	Returns unique string values of an attribute which contain a specified subset string. More...

QgsWkbTypes::Type	wkbType () const override=0
	Returns the geometry type which is returned by this layer. More...

Public Member Functions inherited from QgsDataProvider
	QgsDataProvider (const QString &uri=QString(), const QgsDataProvider::ProviderOptions &options=QgsDataProvider::ProviderOptions())
	Create a new dataprovider with the specified in the uri. More...

virtual QgsCoordinateReferenceSystem	crs () const =0
	Returns the coordinate system for the data source. More...

virtual QString	dataSourceUri (bool expandAuthConfig=false) const
	Gets the data source specification. More...

virtual QDateTime	dataTimestamp () const
	Current time stamp of data source. More...

virtual QString	description () const =0
	Returns description. More...

virtual bool	enterUpdateMode ()
	Enter update mode. More...

virtual QgsError	error () const
	Gets current status error. More...

virtual QgsRectangle	extent () const =0
	Returns the extent of the layer. More...

virtual QString	fileRasterFilters () const
	Returns raster file filter string. More...

virtual QString	fileVectorFilters () const
	Returns vector file filter string. More...

virtual void	invalidateConnections (const QString &connection)
	Invalidate connections corresponding to specified name. More...

virtual bool	isValid () const =0
	Returns true if this is a valid layer. More...

virtual QgsLayerMetadata	layerMetadata () const
	Returns layer metadata collected from the provider's source. More...

virtual bool	leaveUpdateMode ()
	Leave update mode. More...

virtual QString	name () const =0
	Returns a provider name. More...

QVariant	providerProperty (ProviderProperty property, const QVariant &defaultValue=QVariant()) const
	Gets the current value of a certain provider property. More...

QVariant	providerProperty (int property, const QVariant &defaultValue) const
	Gets the current value of a certain provider property. More...

virtual void	reloadData ()
	Reloads the data from the source. More...

virtual bool	renderInPreview (const QgsDataProvider::PreviewContext &context)
	Returns whether the layer must be rendered in preview jobs. More...

virtual void	setDataSourceUri (const QString &uri)
	Set the data source specification. More...

virtual void	setLayerOrder (const QStringList &layers)
	Reorder the list of layer names to be rendered by this provider (in order from bottom to top) More...

virtual void	setListening (bool isListening)
	Set whether the provider will listen to datasource notifications If set, the provider will issue notify signals. More...

void	setProviderProperty (ProviderProperty property, const QVariant &value)
	Allows setting arbitrary properties on the provider. More...

void	setProviderProperty (int property, const QVariant &value)
	Allows setting arbitrary properties on the provider. More...

virtual void	setSubLayerVisibility (const QString &name, bool vis)
	Set the visibility of the given sublayer name. More...

virtual bool	setSubsetString (const QString &subset, bool updateFeatureCount=true)
	Set the subset string used to create a subset of features in the layer. More...

void	setUri (const QgsDataSourceUri &uri)
	Set the data source specification. More...

virtual uint	subLayerCount () const
	Returns the number of layers for the current data source. More...

virtual QStringList	subLayers () const
	Sub-layers handled by this provider, in order from bottom to top. More...

virtual QStringList	subLayerStyles () const
	Sub-layer styles for each sub-layer handled by this provider, in order from bottom to top. More...

virtual QString	subsetString () const
	Returns the subset definition string (typically sql) currently in use by the layer and used by the provider to limit the feature set. More...

virtual bool	supportsSubsetString () const
	Returns true if the provider supports setting of subset strings. More...

virtual QDateTime	timestamp () const
	Time stamp of data source in the moment when data/metadata were loaded by provider. More...

virtual void	updateExtents ()
	Update the extents of the layer. More...

QgsDataSourceUri	uri () const
	Gets the data source specification. More...

virtual bool	writeLayerMetadata (const QgsLayerMetadata &metadata)
	Writes layer metadata to the underlying provider source. More...

Public Member Functions inherited from QgsFeatureSink
virtual	~QgsFeatureSink ()=default

virtual bool	addFeature (QgsFeature &feature, QgsFeatureSink::Flags flags=nullptr)
	Adds a single feature to the sink. More...

virtual bool	addFeatures (QgsFeatureIterator &iterator, QgsFeatureSink::Flags flags=nullptr)
	Adds all features from the specified iterator to the sink. More...

virtual bool	flushBuffer ()
	Flushes any internal buffer which may exist in the sink, causing any buffered features to be added to the sink's destination. More...

Public Member Functions inherited from QgsFeatureSource
virtual	~QgsFeatureSource ()=default

virtual QgsFeatureIds	allFeatureIds () const
	Returns a list of all feature IDs for features present in the source. More...

QgsVectorLayer *	materialize (const QgsFeatureRequest &request, QgsFeedback *feedback=nullptr)
	Materializes a request (query) made against this feature source, by running it over the source and returning a new memory based vector layer containing the result. More...

virtual QSet< QVariant >	uniqueValues (int fieldIndex, int limit=-1) const
	Returns the set of unique values contained within the specified fieldIndex from this source. More...

Static Public Member Functions
static QStringList	availableEncodings ()
	Returns a list of available encodings. More...

static QVariant	convertValue (QVariant::Type type, const QString &value)

Static Public Attributes
static const int	EditingCapabilities
	Bitmask of all provider's editing capabilities. More...

Static Public Attributes inherited from QgsDataProvider
static QString	SUBLAYER_SEPARATOR = QString( "!!::!!" )
	String sequence used for separating components of sublayers strings. More...

Protected Member Functions
void	clearMinMaxCache ()
	Invalidates the min/max cache. More...

QgsGeometry	convertToProviderType (const QgsGeometry &geom) const
	Converts the geometry to the provider type if possible / necessary. More...

void	fillMinMaxCache () const
	Populates the cache of minimum and maximum attribute values. More...

void	pushError (const QString &msg) const
	Push a notification about errors that happened in this providers scope. More...

void	setNativeTypes (const QList< QgsVectorDataProvider::NativeType > &nativeTypes)
	Set the list of native types supported by this provider. More...

QTextCodec *	textEncoding () const
	Gets this providers encoding. More...

Protected Member Functions inherited from QgsDataProvider
void	appendError (const QgsErrorMessage &message)
	Add error message. More...

void	setError (const QgsError &error)
	Sets error message. More...

Friends
class	QgsTransaction

class	QgsVectorLayerEditBuffer

Additional Inherited Members
Protected Attributes inherited from QgsDataProvider
QgsError	mError
	Error. More...

QDateTime	mTimestamp
	Timestamp of data in the moment when the data were loaded by provider. More...

Detailed Description

This is the base class for vector data providers.

Data providers abstract the retrieval and writing (where supported) of feature and attribute information from a spatial datasource.

Definition at line 56 of file qgsvectordataprovider.h.

Member Enumeration Documentation

◆ Capability

enum QgsVectorDataProvider::Capability

enumeration with capabilities that providers might implement

Enumerator
NoCapabilities	Provider has no capabilities.
AddFeatures	Allows adding features.
DeleteFeatures	Allows deletion of features.
ChangeAttributeValues	Allows modification of attribute values.
AddAttributes	Allows addition of new attributes (fields)
DeleteAttributes	Allows deletion of attributes (fields)
CreateSpatialIndex	Allows creation of spatial index.
SelectAtId	Fast access to features using their ID.
ChangeGeometries	Allows modifications of geometries.
SelectEncoding	Allows user to select encoding.
CreateAttributeIndex	Can create indexes on provider's fields.
SimplifyGeometries	Supports simplification of geometries on provider side according to a distance tolerance.
SimplifyGeometriesWithTopologicalValidation	Supports topological simplification of geometries on provider side according to a distance tolerance.
TransactionSupport	Supports transactions.
CircularGeometries	Supports circular geometry types (circularstring, compoundcurve, curvepolygon)
ChangeFeatures
RenameAttributes	Supports joint updates for attributes and geometry Providers supporting this should still define ChangeGeometries \| ChangeAttributeValues. Supports renaming attributes (fields). Since QGIS 2.16
FastTruncate	Supports fast truncation of the layer (removing all features). Since QGIS 3.0.
ReadLayerMetadata	Provider can read layer metadata from data store. Since QGIS 3.0. See QgsDataProvider::layerMetadata()
WriteLayerMetadata	Provider can write layer metadata to the data store. Since QGIS 3.0. See QgsDataProvider::writeLayerMetadata()
CancelSupport	Supports interruption of pending queries from a separated thread. Since QGIS 3.2.
CreateRenderer	Provider can create feature renderers using backend-specific formatting information. Since QGIS 3.2. See QgsVectorDataProvider::createRenderer().

Definition at line 70 of file qgsvectordataprovider.h.

◆ FeatureCountState

enum QgsVectorDataProvider::FeatureCountState

Enumeration of feature count states.

Enumerator
Uncounted	Feature count not yet computed.
UnknownCount	Provider returned an unknown feature count.

Definition at line 108 of file qgsvectordataprovider.h.

Constructor & Destructor Documentation

◆ QgsVectorDataProvider()

QgsVectorDataProvider::QgsVectorDataProvider	(	const QString &	uri = `QString()`,
		const QgsDataProvider::ProviderOptions &	options = `QgsDataProvider::ProviderOptions()`
	)

Constructor for a vector data provider.

The uri argument specifies the uniform resource locator (URI) for the associated dataset.

Additional creation options are specified within the options value.

Definition at line 37 of file qgsvectordataprovider.cpp.

Member Function Documentation

◆ addAttributes()

bool QgsVectorDataProvider::addAttributes ( const QList< QgsField > & attributes )

virtual

Adds new attributes to the provider.

Returns true in case of success and false in case of failure. If attributes are added using this method then QgsVectorLayer::updateFields() must be called manually to ensure that the layer's field are correctly reported.

Definition at line 91 of file qgsvectordataprovider.cpp.

◆ addFeatures()

bool QgsVectorDataProvider::addFeatures	(	QgsFeatureList &	features,
		QgsFeatureSink::Flags	flags = `nullptr`
	)

overridevirtual

Adds a list of features to the sink.

Feature addition behavior is controlled by the specified flags.

See also: addFeature()

Returns: true in case of success and false in case of failure

Implements QgsFeatureSink.

Definition at line 64 of file qgsvectordataprovider.cpp.

◆ aggregate()

QVariant QgsVectorDataProvider::aggregate	(	QgsAggregateCalculator::Aggregate	aggregate,
		int	index,
		const QgsAggregateCalculator::AggregateParameters &	parameters,
		QgsExpressionContext *	context,
		bool &	ok
	)		const

virtual

Calculates an aggregated value from the layer's features.

The base implementation does nothing, but subclasses can override this method to handoff calculation of aggregates to the provider.

Parameters

aggregate	aggregate to calculate
index	the index of the attribute to calculate aggregate over
parameters	parameters controlling aggregate calculation
context	expression context for filter
ok	will be set to true if calculation was successfully performed by the data provider

Returns: calculated aggregate value

Since: QGIS 2.16

Definition at line 445 of file qgsvectordataprovider.cpp.

◆ attributeIndexes()

QgsAttributeList QgsVectorDataProvider::attributeIndexes ( ) const

virtual

Returns list of indexes to fetch all attributes in nextFeature()

Definition at line 306 of file qgsvectordataprovider.cpp.

◆ availableEncodings()

QStringList QgsVectorDataProvider::availableEncodings ( )

static

Returns a list of available encodings.

Definition at line 585 of file qgsvectordataprovider.cpp.

◆ cancelReload()

bool QgsVectorDataProvider::cancelReload ( )

virtual

Cancels the current reloading of data.

Returns: true if the reloading has been correctly interrupted, false otherwise

See also: reloadData()

Since: QGIS 3.2

Definition at line 801 of file qgsvectordataprovider.cpp.

◆ capabilities()

QgsVectorDataProvider::Capabilities QgsVectorDataProvider::capabilities ( ) const

virtual

Returns flags containing the supported capabilities.

Note: , some capabilities may change depending on whether a spatial filter is active on this provider, so it may be prudent to check this value per intended operation.

Definition at line 170 of file qgsvectordataprovider.cpp.

◆ capabilitiesString()

QString QgsVectorDataProvider::capabilitiesString ( ) const

Returns the above in friendly format.

Definition at line 202 of file qgsvectordataprovider.cpp.

◆ changeAttributeValues()

bool QgsVectorDataProvider::changeAttributeValues ( const QgsChangedAttributesMap & attr_map )

virtual

Changes attribute values of existing features.

This should succeed if the provider reports the ChangeAttributeValues capability.

Parameters

attr_map a map containing changed attributes

Returns: true in case of success and false in case of failure

Definition at line 109 of file qgsvectordataprovider.cpp.

◆ changeFeatures()

bool QgsVectorDataProvider::changeFeatures	(	const QgsChangedAttributesMap &	attr_map,
		const QgsGeometryMap &	geometry_map
	)

virtual

Changes attribute values and geometries of existing features.

This should succeed if the provider reports both the ChangeAttributeValues and ChangeGeometries capabilities. Providers which report the ChangeFeatures capability implement an optimised version of this method.

Parameters

attr_map	a map containing changed attributes
geometry_map	A QgsGeometryMap whose index contains the feature IDs that will have their geometries changed. The second map parameter being the new geometries themselves

Returns: true in case of success and false in case of failure

Definition at line 147 of file qgsvectordataprovider.cpp.

◆ changeGeometryValues()

bool QgsVectorDataProvider::changeGeometryValues ( const QgsGeometryMap & geometry_map )

virtual

Changes geometries of existing features.

Parameters

geometry_map A QgsGeometryMap whose index contains the feature IDs that will have their geometries changed. The second map parameter being the new geometries themselves

Returns: True in case of success and false in case of failure

Definition at line 141 of file qgsvectordataprovider.cpp.

◆ clearErrors()

void QgsVectorDataProvider::clearErrors ( )

Clear recorded errors.

Definition at line 648 of file qgsvectordataprovider.cpp.

◆ clearMinMaxCache()

void QgsVectorDataProvider::clearMinMaxCache ( )

protected

Invalidates the min/max cache.

This will force the provider to recalculate the cache the next time it is requested.

Definition at line 458 of file qgsvectordataprovider.cpp.

◆ convertToProviderType()

QgsGeometry QgsVectorDataProvider::convertToProviderType ( const QgsGeometry & geom ) const

protected

Converts the geometry to the provider type if possible / necessary.

Returns: the converted geometry or nullptr if no conversion was necessary or possible

Definition at line 690 of file qgsvectordataprovider.cpp.

◆ convertValue()

QVariant QgsVectorDataProvider::convertValue	(	QVariant::Type	type,
		const QString &	value
	)

static

Definition at line 560 of file qgsvectordataprovider.cpp.

◆ createAttributeIndex()

bool QgsVectorDataProvider::createAttributeIndex ( int field )

virtual

Create an attribute index on the datasource.

Definition at line 164 of file qgsvectordataprovider.cpp.

◆ createRenderer()

QgsFeatureRenderer * QgsVectorDataProvider::createRenderer ( const QVariantMap & configuration = QVariantMap() ) const

virtual

Creates a new vector layer feature renderer, using provider backend specific information.

The configuration map can be used to pass provider-specific configuration maps to the provider to allow customization of the returned renderer. Support and format of configuration varies by provider.

When called with an empty configuration map the provider's default renderer will be returned.

This method returns a new renderer and the caller takes ownership of the returned object.

Only providers which report the CreateRenderer capability will return a feature renderer. Other providers will return nullptr.

Since: QGIS 3.2

Definition at line 673 of file qgsvectordataprovider.cpp.

◆ createSpatialIndex()

bool QgsVectorDataProvider::createSpatialIndex ( )

virtual

Creates a spatial index on the datasource (if supported by the provider type).

Returns: true in case of success

Definition at line 159 of file qgsvectordataprovider.cpp.

◆ dataComment()

QString QgsVectorDataProvider::dataComment ( ) const

virtual

Returns a short comment for the data that this provider is providing access to (e.g.

the comment for postgres table).

Definition at line 59 of file qgsvectordataprovider.cpp.

◆ defaultValue()

QVariant QgsVectorDataProvider::defaultValue ( int fieldIndex ) const

virtual

Returns any literal default values which are present at the provider for a specified field index.

Important - this should ONLY be called when creating an attribute to insert directly into the database. Do not call this method for non-feature creation or modification, e.g., when validating an attribute or to compare it against an existing value, as calling it can cause changes to the underlying data source (e.g., Postgres provider where the default value is calculated as a result of a sequence). It is recommended that you instead use the methods in QgsVectorLayerUtils such as QgsVectorLayerUtils::createFeature() so that default value handling and validation is automatically carried out.

See also: defaultValueClause()

Definition at line 115 of file qgsvectordataprovider.cpp.

◆ defaultValueClause()

QString QgsVectorDataProvider::defaultValueClause ( int fieldIndex ) const

virtual

Returns any default value clauses which are present at the provider for a specified field index.

These clauses are usually SQL fragments which must be evaluated by the provider, e.g., sequence values.

See also: defaultValue()

Since: QGIS 3.0

Definition at line 121 of file qgsvectordataprovider.cpp.

◆ deleteAttributes()

bool QgsVectorDataProvider::deleteAttributes ( const QgsAttributeIds & attributes )

virtual

Deletes existing attributes from the provider.

If attributes are deleted using this method then QgsVectorLayer::updateFields() must be called manually to ensure that the layer's field are correctly reported.

Parameters

attributes a set containing indices of attributes

Returns: true in case of success and false in case of failure

Definition at line 97 of file qgsvectordataprovider.cpp.

◆ deleteFeatures()

bool QgsVectorDataProvider::deleteFeatures ( const QgsFeatureIds & id )

virtual

Deletes one or more features from the provider.

This requires the DeleteFeatures capability.

Parameters

id	list containing feature ids to delete

Returns: true in case of success and false in case of failure

See also: truncate()

Definition at line 71 of file qgsvectordataprovider.cpp.

◆ dependencies()

QSet< QgsMapLayerDependency > QgsVectorDataProvider::dependencies ( ) const

virtual

Gets the list of layer ids on which this layer depends.

This in particular determines the order of layer loading.

Definition at line 685 of file qgsvectordataprovider.cpp.

◆ discoverRelations()

QList< QgsRelation > QgsVectorDataProvider::discoverRelations	(	const QgsVectorLayer *	self,
		const QList< QgsVectorLayer *> &	layers
	)		const

virtual

Discover the available relations with the given layers.

Parameters

self	the layer using this data provider.
layers	the other layers.

Returns: the list of N-1 relations from this provider.

Since: QGIS 3.0

Definition at line 808 of file qgsvectordataprovider.cpp.

◆ doesStrictFeatureTypeCheck()

virtual bool QgsVectorDataProvider::doesStrictFeatureTypeCheck ( ) const

inlinevirtual

Returns true if the provider is strict about the type of inserted features (e.g.

no multipolygon in a polygon layer)

Definition at line 455 of file qgsvectordataprovider.h.

◆ encoding()

QString QgsVectorDataProvider::encoding ( ) const

Gets encoding which is used for accessing data.

Definition at line 192 of file qgsvectordataprovider.cpp.

◆ enumValues()

virtual void QgsVectorDataProvider::enumValues	(	int	index,
		QStringList &	enumList
	)		const

inlinevirtual

Returns the possible enum values of an attribute.

Returns an empty stringlist if a provider does not support enum types or if the given attribute is not an enum type.

Parameters

index	the index of the attribute
enumList	reference to the list to fill

Definition at line 236 of file qgsvectordataprovider.h.

◆ errors()

QStringList QgsVectorDataProvider::errors ( ) const

Gets recorded errors.

Definition at line 658 of file qgsvectordataprovider.cpp.

◆ featureCount()

long QgsVectorDataProvider::featureCount ( ) const

overridepure virtual

Number of features in the layer.

Returns: long containing number of features

Implements QgsFeatureSource.

◆ featureSource()

virtual QgsAbstractFeatureSource* QgsVectorDataProvider::featureSource ( ) const

pure virtual

Returns feature source object that can be used for querying provider's data.

The returned feature source is independent from provider - any changes to provider's state (e.g. change of subset string) will not be reflected in the feature source, therefore it can be safely used for processing in background without having to care about possible changes within provider that may happen concurrently. Also, even in the case of provider being deleted, any feature source obtained from the provider will be kept alive and working (they are independent and owned by the caller).

Sometimes there are cases when some data needs to be shared between vector data provider and its feature source. In such cases, the implementation must ensure that the data is not susceptible to run condition. For example, if it is possible that both feature source and provider may need reading/writing to some shared data at the same time, some synchronization mechanisms must be used (e.g. mutexes) to prevent data corruption.

Returns: new instance of QgsAbstractFeatureSource (caller is responsible for deleting it)

Since: QGIS 2.4

◆ fieldConstraints()

QgsFieldConstraints::Constraints QgsVectorDataProvider::fieldConstraints ( int fieldIndex ) const

Returns any constraints which are present at the provider for a specified field index.

See also: skipConstraintCheck()

Since: QGIS 3.0

Definition at line 127 of file qgsvectordataprovider.cpp.

◆ fieldNameIndex()

int QgsVectorDataProvider::fieldNameIndex ( const QString & fieldName ) const

Returns the index of a field name or -1 if the field does not exist.

Definition at line 288 of file qgsvectordataprovider.cpp.

◆ fieldNameMap()

QMap< QString, int > QgsVectorDataProvider::fieldNameMap ( ) const

Returns a map where the key is the name of the field and the value is its index.

Definition at line 293 of file qgsvectordataprovider.cpp.

◆ fields()

QgsFields QgsVectorDataProvider::fields ( ) const

overridepure virtual

Returns the fields associated with this data provider.

Implements QgsFeatureSource.

◆ fillMinMaxCache()

void QgsVectorDataProvider::fillMinMaxCache ( ) const

protected

Populates the cache of minimum and maximum attribute values.

Definition at line 465 of file qgsvectordataprovider.cpp.

◆ forceReload()

void QgsVectorDataProvider::forceReload ( )

virtual

Forces a reload of the underlying datasource if the provider implements this method.

In particular on the OGR provider, a pooled connection will be invalidated. This forces QGIS to reopen a file or connection. This can be required if the underlying file is replaced.

Definition at line 575 of file qgsvectordataprovider.cpp.

◆ getFeatures()

QgsFeatureIterator QgsVectorDataProvider::getFeatures ( const QgsFeatureRequest & request = QgsFeatureRequest() ) const

overridepure virtual

Query the provider for features specified in request.

Parameters

request feature request describing parameters of features to return

Returns: iterator for matching features from provider

Implements QgsFeatureSource.

◆ hasErrors()

bool QgsVectorDataProvider::hasErrors ( ) const

Provider has errors to report.

Definition at line 653 of file qgsvectordataprovider.cpp.

◆ hasMetadata()

virtual bool QgsVectorDataProvider::hasMetadata ( ) const

inlinevirtual

Returns true if the data source has metadata, false otherwise.

Returns: true if data source has metadata, false otherwise.

Since: QGIS 3.0

Definition at line 562 of file qgsvectordataprovider.h.

◆ isDeleteStyleFromDatabaseSupported()

bool QgsVectorDataProvider::isDeleteStyleFromDatabaseSupported ( ) const

virtual

It returns false by default.

Must be implemented by providers that support delete styles from db returning true

Definition at line 668 of file qgsvectordataprovider.cpp.

◆ isSaveAndLoadStyleToDatabaseSupported()

bool QgsVectorDataProvider::isSaveAndLoadStyleToDatabaseSupported ( ) const

virtual

It returns false by default.

Must be implemented by providers that support saving and loading styles to db returning true

Definition at line 663 of file qgsvectordataprovider.cpp.

◆ maximumValue()

QVariant QgsVectorDataProvider::maximumValue ( int index ) const

overridevirtual

Returns the maximum value of an attribute.

Parameters

index the index of the attribute

Default implementation walks all numeric attributes and caches minimal and maximal values. If provider has facilities to retrieve maximal value directly, override this function.

Reimplemented from QgsFeatureSource.

Definition at line 392 of file qgsvectordataprovider.cpp.

◆ metadata()

virtual QVariantMap QgsVectorDataProvider::metadata ( ) const

inlinevirtual

Gets metadata, dependent on the provider type, that will be display in the metadata tab of the layer properties.

Returns: The provider metadata

Definition at line 538 of file qgsvectordataprovider.h.

◆ minimumValue()

QVariant QgsVectorDataProvider::minimumValue ( int index ) const

overridevirtual

Returns the minimum value of an attribute.

Parameters

index the index of the attribute

Default implementation walks all numeric attributes and caches minimal and maximal values. If provider has facilities to retrieve minimal value directly, override this function.

Reimplemented from QgsFeatureSource.

Definition at line 376 of file qgsvectordataprovider.cpp.

◆ nativeTypes()

QList< QgsVectorDataProvider::NativeType > QgsVectorDataProvider::nativeTypes ( ) const

Returns the names of the supported types.

Definition at line 316 of file qgsvectordataprovider.cpp.

◆ palAttributeIndexNames()

QgsAttrPalIndexNameHash QgsVectorDataProvider::palAttributeIndexNames ( ) const

virtual

Returns list of indexes to names for QgsPalLabeling fix.

Definition at line 321 of file qgsvectordataprovider.cpp.

◆ pkAttributeIndexes()

QgsAttributeList QgsVectorDataProvider::pkAttributeIndexes ( ) const

virtual

Returns list of indexes of fields that make up the primary key.

Definition at line 311 of file qgsvectordataprovider.cpp.

◆ pushError()

void QgsVectorDataProvider::pushError ( const QString & msg ) const

protected

Push a notification about errors that happened in this providers scope.

Errors should be translated strings that require the users immediate attention.

For general debug information use QgsMessageLog::logMessage() instead.

Since: QGIS 3.0

Definition at line 678 of file qgsvectordataprovider.cpp.

◆ raiseError

void QgsVectorDataProvider::raiseError ( const QString & msg ) const

signal

Signals an error in this provider.

Since: QGIS 3.0

◆ renameAttributes()

bool QgsVectorDataProvider::renameAttributes ( const QgsFieldNameMap & renamedAttributes )

virtual

Renames existing attributes.

If attributes are renamed using this method then QgsVectorLayer::updateFields() must be called manually to ensure that the layer's field are correctly reported.

Parameters

renamedAttributes map of attribute index to new attribute name

Returns: true in case of success and false in case of failure

Since: QGIS 2.16

Definition at line 103 of file qgsvectordataprovider.cpp.

◆ setEncoding()

void QgsVectorDataProvider::setEncoding ( const QString & e )

virtual

Set encoding used for accessing data from layer.

Definition at line 176 of file qgsvectordataprovider.cpp.

◆ setNativeTypes()

void QgsVectorDataProvider::setNativeTypes ( const QList< QgsVectorDataProvider::NativeType > & nativeTypes )

protected

Set the list of native types supported by this provider.

Usually done in the constructor.

Since: QGIS 3.0

Definition at line 791 of file qgsvectordataprovider.cpp.

◆ skipConstraintCheck()

bool QgsVectorDataProvider::skipConstraintCheck	(	int	fieldIndex,
		QgsFieldConstraints::Constraint	constraint,
		const QVariant &	value = `QVariant()`
	)		const

virtual

Returns true if a constraint check should be skipped for a specified field (e.g., if the value returned by defaultValue() is trusted implicitly.

An optional attribute value can be passed which can help refine the skip constraint check.

See also: fieldConstraints()

Since: QGIS 3.0

Definition at line 136 of file qgsvectordataprovider.cpp.

◆ sourceCrs()

QgsCoordinateReferenceSystem QgsVectorDataProvider::sourceCrs ( ) const

overridevirtual

Returns the coordinate reference system for features in the source.

Implements QgsFeatureSource.

Definition at line 49 of file qgsvectordataprovider.cpp.

◆ sourceExtent()

QgsRectangle QgsVectorDataProvider::sourceExtent ( ) const

overridevirtual

Returns the extent of all geometries from the source.

The base class implementation uses a non-optimised approach of looping through all features in the source.

Reimplemented from QgsFeatureSource.

Definition at line 54 of file qgsvectordataprovider.cpp.

◆ sourceName()

QString QgsVectorDataProvider::sourceName ( ) const

inlineoverridevirtual

Returns a friendly display name for the source.

The returned value can be an empty string.

Implements QgsFeatureSource.

Definition at line 173 of file qgsvectordataprovider.h.

◆ storageType()

QString QgsVectorDataProvider::storageType ( ) const

virtual

Returns the permanent storage type for this layer as a friendly name.

Definition at line 44 of file qgsvectordataprovider.cpp.

◆ supportedType()

bool QgsVectorDataProvider::supportedType ( const QgsField & field ) const

check if provider supports type of field

Definition at line 326 of file qgsvectordataprovider.cpp.

◆ textEncoding()

QTextCodec * QgsVectorDataProvider::textEncoding ( ) const

protected

Gets this providers encoding.

Since: QGIS 3.0

Definition at line 796 of file qgsvectordataprovider.cpp.

◆ transaction()

QgsTransaction * QgsVectorDataProvider::transaction ( ) const

virtual

Returns the transaction this data provider is included in, if any.

Definition at line 570 of file qgsvectordataprovider.cpp.

◆ translateMetadataKey()

virtual QString QgsVectorDataProvider::translateMetadataKey ( const QString & mdKey ) const

inlinevirtual

Gets the translated metadata key.

Parameters

mdKey The metadata key

Returns: The translated metadata value

Definition at line 545 of file qgsvectordataprovider.h.

◆ translateMetadataValue()

virtual QString QgsVectorDataProvider::translateMetadataValue	(	const QString &	mdKey,
		const QVariant &	value
	)		const

inlinevirtual

Gets the translated metadata value.

Parameters

mdKey	The metadata key
value	The metadata value

Returns: The translated metadata value

Definition at line 553 of file qgsvectordataprovider.h.

◆ truncate()

bool QgsVectorDataProvider::truncate ( )

virtual

Removes all features from the layer.

This requires either the FastTruncate or DeleteFeatures capability. Providers with the FastTruncate capability will use an optimised method to truncate the layer.

Returns: true in case of success and false in case of failure.

See also: deleteFeatures()

Since: QGIS 3.0

Definition at line 77 of file qgsvectordataprovider.cpp.

◆ uniqueStringsMatching()

QStringList QgsVectorDataProvider::uniqueStringsMatching	(	int	index,
		const QString &	substring,
		int	limit = `-1`,
		QgsFeedback *	feedback = `nullptr`
	)		const

virtual

Returns unique string values of an attribute which contain a specified subset string.

Subset matching is done in a case-insensitive manner.

Parameters

index	the index of the attribute
substring	substring to match (case insensitive)
limit	maxmum number of the values to return, or -1 to return all unique values
feedback	optional feedback object for canceling request

Returns: list of unique strings containing substring

Definition at line 409 of file qgsvectordataprovider.cpp.

◆ wkbType()

QgsWkbTypes::Type QgsVectorDataProvider::wkbType ( ) const

overridepure virtual

Returns the geometry type which is returned by this layer.

Implements QgsFeatureSource.

Friends And Related Function Documentation

◆ QgsTransaction

friend class QgsTransaction

friend

Definition at line 60 of file qgsvectordataprovider.h.

◆ QgsVectorLayerEditBuffer

friend class QgsVectorLayerEditBuffer

friend

Definition at line 61 of file qgsvectordataprovider.h.

Member Data Documentation

◆ EditingCapabilities

const int QgsVectorDataProvider::EditingCapabilities

static

Initial value:

= AddFeatures | DeleteFeatures |
                                           ChangeAttributeValues | ChangeGeometries | AddAttributes | DeleteAttributes |
                                           RenameAttributes

Bitmask of all provider's editing capabilities.

Definition at line 101 of file qgsvectordataprovider.h.

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

/tmp/buildd/qgis-3.2.0+99unstable/src/core/qgsvectordataprovider.h
/tmp/buildd/qgis-3.2.0+99unstable/src/core/qgsvectordataprovider.cpp

Classes

Public Types

Signals

Public Member Functions

Static Public Member Functions

Static Public Attributes

Protected Member Functions

Friends

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

◆ Capability

◆ FeatureCountState

Constructor & Destructor Documentation

◆ QgsVectorDataProvider()

Member Function Documentation

◆ addAttributes()

◆ addFeatures()

◆ aggregate()

◆ attributeIndexes()

◆ availableEncodings()

◆ cancelReload()

◆ capabilities()

◆ capabilitiesString()

◆ changeAttributeValues()

◆ changeFeatures()

◆ changeGeometryValues()

◆ clearErrors()

◆ clearMinMaxCache()

◆ convertToProviderType()

◆ convertValue()

◆ createAttributeIndex()

◆ createRenderer()

◆ createSpatialIndex()

◆ dataComment()

◆ defaultValue()

◆ defaultValueClause()

◆ deleteAttributes()

◆ deleteFeatures()

◆ dependencies()

◆ discoverRelations()

◆ doesStrictFeatureTypeCheck()

◆ encoding()

◆ enumValues()

◆ errors()

◆ featureCount()

◆ featureSource()

◆ fieldConstraints()

◆ fieldNameIndex()

◆ fieldNameMap()

◆ fields()

◆ fillMinMaxCache()

◆ forceReload()

◆ getFeatures()

◆ hasErrors()

◆ hasMetadata()

◆ isDeleteStyleFromDatabaseSupported()

◆ isSaveAndLoadStyleToDatabaseSupported()

◆ maximumValue()

◆ metadata()

◆ minimumValue()

◆ nativeTypes()

◆ palAttributeIndexNames()

◆ pkAttributeIndexes()

◆ pushError()

◆ raiseError

◆ renameAttributes()

◆ setEncoding()

◆ setNativeTypes()

◆ skipConstraintCheck()

◆ sourceCrs()

◆ sourceExtent()

◆ sourceName()

◆ storageType()

◆ supportedType()

◆ textEncoding()

◆ transaction()

◆ translateMetadataKey()

◆ translateMetadataValue()

◆ truncate()