mirror of
https://github.com/qgis/QGIS.git
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d47d31d13c
Motivations: - consistency - we generally use expanded names, and this also matches Qt API which uses Database instead of Db - avoids unpredictable capitalization throughout API (mix of "Db" and "DB")
524 lines
19 KiB
Plaintext
524 lines
19 KiB
Plaintext
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class QgsVectorDataProvider : QgsDataProvider
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{
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%TypeHeaderCode
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#include <qgsvectordataprovider.h>
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%End
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public:
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// If you add to this, please also add to capabilitiesString()
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/**
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* enumeration with capabilities that providers might implement
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*/
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enum Capability
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{
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/** Provider has no capabilities */
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NoCapabilities,
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/** Allows adding features */
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AddFeatures,
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/** Allows deletion of features */
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DeleteFeatures,
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/** Allows modification of attribute values */
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ChangeAttributeValues,
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/** Allows addition of new attributes (fields) */
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AddAttributes,
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/** Allows deletion of attributes (fields) */
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DeleteAttributes,
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/** Allows creation of spatial index */
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CreateSpatialIndex,
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/** Fast access to features using their ID */
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SelectAtId,
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/** Allows modifications of geometries */
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ChangeGeometries,
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/** Can create indexes on provider's fields */
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CreateAttributeIndex,
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/** Allows user to select encoding */
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SelectEncoding,
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/** Supports simplification of geometries on provider side according to a distance tolerance */
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SimplifyGeometries,
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/** Supports topological simplification of geometries on provider side according to a distance tolerance */
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SimplifyGeometriesWithTopologicalValidation,
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/** Supports transactions*/
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TransactionSupport,
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/** Supports circular geometry types (circularstring, compoundcurve, curvepolygon)*/
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CircularGeometries,
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/** Supports joint updates for attributes and geometry
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* Providers supporting this should still define ChangeGeometries | ChangeAttributeValues
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*/
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ChangeFeatures,
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/** Supports renaming attributes (fields). Added in QGIS 2.16 */
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RenameAttributes,
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//! Supports fast truncation of the layer (removing all features). Added in QGIS 3.0
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FastTruncate,
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};
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typedef QFlags<QgsVectorDataProvider::Capability> Capabilities;
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/** Bitmask of all provider's editing capabilities */
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static const int EditingCapabilities;
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/**
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* Constructor of the vector provider
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* @param uri uniform resource locator (URI) for a dataset
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*/
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QgsVectorDataProvider( const QString& uri = QString() );
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/**
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* Destructor
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*/
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virtual ~QgsVectorDataProvider();
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/**
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* Return feature source object that can be used for querying provider's data. The returned feature source
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* is independent from provider - any changes to provider's state (e.g. change of subset string) will not be
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* reflected in the feature source, therefore it can be safely used for processing in background without
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* having to care about possible changes within provider that may happen concurrently. Also, even in the case
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* of provider being deleted, any feature source obtained from the provider will be kept alive and working
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* (they are independent and owned by the caller).
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*
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* Sometimes there are cases when some data needs to be shared between vector data provider and its feature source.
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* In such cases, the implementation must ensure that the data is not susceptible to run condition. For example,
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* if it is possible that both feature source and provider may need reading/writing to some shared data at the
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* same time, some synchronization mechanisms must be used (e.g. mutexes) to prevent data corruption.
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*
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* @note added in 2.4
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* @return new instance of QgsAbstractFeatureSource (caller is responsible for deleting it)
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*/
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virtual QgsAbstractFeatureSource *featureSource() const = 0 /Factory/;
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/**
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* Returns the permanent storage type for this layer as a friendly name.
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*/
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virtual QString storageType() const;
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/**
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* Query the provider for features specified in request.
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* @param request feature request describing parameters of features to return
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* @returns iterator for matching features from provider
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*/
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virtual QgsFeatureIterator getFeatures( const QgsFeatureRequest& request = QgsFeatureRequest() ) const = 0;
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/**
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* Returns the geometry type which is returned by this layer
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*/
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virtual QgsWkbTypes::Type wkbType() const = 0;
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/**
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* Number of features in the layer
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* @return long containing number of features
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*/
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virtual long featureCount() const = 0;
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/**
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* Returns the fields associated with this data provider.
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*/
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virtual QgsFields fields() const = 0;
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/**
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* Return a short comment for the data that this provider is
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* providing access to (e.g. the comment for postgres table).
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*/
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virtual QString dataComment() const;
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/**
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* Returns the minimum value of an attribute
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* @param index the index of the attribute
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*
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* Default implementation walks all numeric attributes and caches minimal
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* and maximal values. If provider has facilities to retrieve minimal
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* value directly, override this function.
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*/
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virtual QVariant minimumValue( int index ) const;
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/**
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* Returns the maximum value of an attribute
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* @param index the index of the attribute
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*
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* Default implementation walks all numeric attributes and caches minimal
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* and maximal values. If provider has facilities to retrieve maximal
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* value directly, override this function.
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*/
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virtual QVariant maximumValue( int index ) const;
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/**
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* Return unique values of an attribute
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* @param index the index of the attribute
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* @param uniqueValues values reference to the list to fill
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* @param limit maxmum number of the values to return
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*
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* Default implementation simply iterates the features
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*/
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virtual void uniqueValues( int index, QList<QVariant> &uniqueValues /Out/, int limit = -1 ) const;
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/**
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* Returns unique string values of an attribute which contain a specified subset string. Subset
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* matching is done in a case-insensitive manner.
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* @param index the index of the attribute
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* @param substring substring to match (case insensitive)
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* @param limit maxmum number of the values to return, or -1 to return all unique values
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* @param feedback optional feedback object for canceling request
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* @returns list of unique strings containing substring
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*/
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virtual QStringList uniqueStringsMatching( int index, const QString& substring, int limit = -1,
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QgsFeedback* feedback = nullptr ) const;
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/** Calculates an aggregated value from the layer's features. The base implementation does nothing,
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* but subclasses can override this method to handoff calculation of aggregates to the provider.
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* @param aggregate aggregate to calculate
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* @param index the index of the attribute to calculate aggregate over
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* @param parameters parameters controlling aggregate calculation
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* @param context expression context for filter
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* @param ok will be set to true if calculation was successfully performed by the data provider
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* @return calculated aggregate value
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* @note added in QGIS 2.16
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*/
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virtual QVariant aggregate( QgsAggregateCalculator::Aggregate aggregate,
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int index,
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const QgsAggregateCalculator::AggregateParameters& parameters,
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QgsExpressionContext* context,
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bool& ok ) const;
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/**
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* Returns the possible enum values of an attribute. Returns an empty stringlist if a provider does not support enum types
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* or if the given attribute is not an enum type.
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* @param index the index of the attribute
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* @param enumList reference to the list to fill
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*/
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virtual void enumValues( int index, QStringList& enumList /Out/ ) const;
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/**
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* Adds a list of features
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* @return true in case of success and false in case of failure
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*/
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virtual bool addFeatures( QList<QgsFeature> &flist /In,Out/ );
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/**
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* Deletes one or more features from the provider. This requires the DeleteFeatures capability.
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* @param id list containing feature ids to delete
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* @return true in case of success and false in case of failure
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* @see truncate()
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*/
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virtual bool deleteFeatures( const QgsFeatureIds &id );
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/**
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* Removes all features from the layer. This requires either the FastTruncate or DeleteFeatures capability.
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* Providers with the FastTruncate capability will use an optimised method to truncate the layer.
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* @returns true in case of success and false in case of failure.
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* @note added in QGIS 3.0
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* @see deleteFeatures()
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*/
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virtual bool truncate();
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/**
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* Adds new attributes
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* @param attributes list of new attributes
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* @return true in case of success and false in case of failure
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*/
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virtual bool addAttributes( const QList<QgsField> &attributes );
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/**
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* Deletes existing attributes
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* @param attributes a set containing indices of attributes
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* @return true in case of success and false in case of failure
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*/
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virtual bool deleteAttributes( const QSet<int> &attributes );
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/**
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* Renames existing attributes.
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* @param renamedAttributes map of attribute index to new attribute name
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* @return true in case of success and false in case of failure
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* @note added in QGIS 2.16
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*/
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virtual bool renameAttributes( const QgsFieldNameMap& renamedAttributes );
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/**
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* Changes attribute values of existing features.
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* @param attr_map a map containing changed attributes
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* @return true in case of success and false in case of failure
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*/
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virtual bool changeAttributeValues( const QMap<qint64, QMap<int, QVariant> > &attr_map );
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/**
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* Changes attribute values and geometries of existing features.
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* @param attr_map a map containing changed attributes
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* @param geometry_map A QgsGeometryMap whose index contains the feature IDs
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* that will have their geometries changed.
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* The second map parameter being the new geometries themselves
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* @return true in case of success and false in case of failure
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*/
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virtual bool changeFeatures( const QMap<qint64, QMap<int, QVariant> > &attr_map,
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const QMap<qint64, QgsGeometry> &geometry_map );
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/**
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* Returns any literal default values which are present at the provider for a specified
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* field index. Important - this should ONLY be called when creating an attribute to insert
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* directly into the database. Do not call this method for non-feature creation or modification,
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* e.g., when validating an attribute or to compare it against an existing value, as calling it
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* can cause changes to the underlying data source (e.g., Postgres provider where the default value
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* is calculated as a result of a sequence). It is recommended that you instead use the methods
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* in QgsVectorLayerUtils such as QgsVectorLayerUtils::createFeature()
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* so that default value handling and validation is automatically carried out.
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* @see defaultValueClause()
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*/
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virtual QVariant defaultValue( int fieldIndex ) const;
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/**
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* Returns any default value clauses which are present at the provider for a specified
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* field index. These clauses are usually SQL fragments which must be evaluated by the
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* provider, e.g., sequence values.
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* @see defaultValue()
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* @note added in QGIS 3.0
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*/
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virtual QString defaultValueClause( int fieldIndex ) const;
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/**
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* Returns any constraints which are present at the provider for a specified
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* field index.
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* @note added in QGIS 3.0
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* @see skipConstraintCheck()
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*/
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QgsFieldConstraints::Constraints fieldConstraints( int fieldIndex ) const;
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/**
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* Returns true if a constraint check should be skipped for a specified field (e.g., if
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* the value returned by defaultValue() is trusted implicitly. An optional attribute value can be
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* passed which can help refine the skip constraint check.
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* @note added in QGIS 3.0
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* @see fieldConstraints()
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*/
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virtual bool skipConstraintCheck( int fieldIndex, QgsFieldConstraints::Constraint constraint, const QVariant& value = QVariant() ) const;
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/**
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* Changes geometries of existing features
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* @param geometry_map A QgsGeometryMap whose index contains the feature IDs
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* that will have their geometries changed.
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* The second map parameter being the new geometries themselves
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* @return True in case of success and false in case of failure
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*/
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virtual bool changeGeometryValues( const QMap<qint64, QgsGeometry> &geometry_map );
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/**
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* Creates a spatial index on the datasource (if supported by the provider type).
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* @return true in case of success
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*/
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virtual bool createSpatialIndex();
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/** Create an attribute index on the datasource*/
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virtual bool createAttributeIndex( int field );
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/** Returns a bitmask containing the supported capabilities
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@note, some capabilities may change depending on whether
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a spatial filter is active on this provider, so it may
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be prudent to check this value per intended operation.
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*/
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virtual Capabilities capabilities() const;
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/**
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* Returns the above in friendly format.
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*/
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QString capabilitiesString() const;
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/**
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* Set encoding used for accessing data from layer
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*/
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virtual void setEncoding( const QString& e );
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/**
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* Get encoding which is used for accessing data
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*/
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QString encoding() const;
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/**
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* Returns the index of a field name or -1 if the field does not exist
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*/
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int fieldNameIndex( const QString& fieldName ) const;
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/**
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* Return a map where the key is the name of the field and the value is its index
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*/
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QMap<QString, int> fieldNameMap() const;
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/**
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* Return list of indexes to fetch all attributes in nextFeature()
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*/
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virtual QList<int> attributeIndexes() const;
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/**
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* Return list of indexes of fields that make up the primary key
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*/
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virtual QList<int> pkAttributeIndexes() const;
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/**
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* Return list of indexes to names for QgsPalLabeling fix
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*/
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virtual QHash<int, QString> palAttributeIndexNames() const;
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/**
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* check if provider supports type of field
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*/
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bool supportedType( const QgsField &field ) const;
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struct NativeType
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{
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NativeType( const QString& typeDesc, const QString& typeName, QVariant::Type type, int minLen = 0, int maxLen = 0, int minPrec = 0, int maxPrec = 0, QVariant::Type subType = QVariant::Invalid );
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QString mTypeDesc;
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QString mTypeName;
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QVariant::Type mType;
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int mMinLen;
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int mMaxLen;
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int mMinPrec;
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int mMaxPrec;
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QVariant::Type mSubType;
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};
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/**
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* Returns the names of the supported types
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*/
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QList< QgsVectorDataProvider::NativeType > nativeTypes() const;
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/**
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* Returns true if the provider is strict about the type of inserted features
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* (e.g. no multipolygon in a polygon layer)
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*/
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virtual bool doesStrictFeatureTypeCheck() const;
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/** Returns a list of available encodings */
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static QStringList availableEncodings();
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/**
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* Provider has errors to report
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*/
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bool hasErrors() const;
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/**
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* Clear recorded errors
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*/
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void clearErrors();
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/**
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* Get recorded errors
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*/
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QStringList errors() const;
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/**
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* It returns false by default.
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* Must be implemented by providers that support saving and loading styles to db returning true
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*/
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virtual bool isSaveAndLoadStyleToDatabaseSupported() const;
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/**
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* Checks if the provider supports style removal
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* Must be implemented by providers that support delete styles from db returning true
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* @note added in QGIS 3.0
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* @return true if delete operation is supported by the provider
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*/
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virtual bool isDeleteStyleFromDatabaseSupported() const;
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static QVariant convertValue( QVariant::Type type, const QString& value );
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/**
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* Returns the transaction this data provider is included in, if any.
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*/
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virtual QgsTransaction* transaction() const;
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/**
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* Forces a reload of the underlying datasource if the provider implements this
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* method.
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* In particular on the OGR provider, a pooled connection will be invalidated.
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* This forces QGIS to reopen a file or connection.
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* This can be required if the underlying file is replaced.
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*/
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virtual void forceReload();
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/**
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* Get the list of layer ids on which this layer depends. This in particular determines the order of layer loading.
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*/
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virtual QSet<QgsMapLayerDependency> dependencies() const;
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/**
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* Discover the available relations with the given layers.
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* @param self the layer using this data provider.
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* @param layers the other layers.
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* @return the list of N-1 relations from this provider.
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* @note added in QGIS 3.0
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*/
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virtual QList<QgsRelation> discoverRelations( const QgsVectorLayer* self, const QList<QgsVectorLayer*>& layers ) const;
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/**
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* Get some metadata that will be display in the metadata tab of the layer properties.
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* @return The provider metadata
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*/
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virtual QVariantMap metadata() const;
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/**
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* Get the translated metadata key.
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* @param mdKey The metadata key
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* @return The translated metadata value
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*/
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virtual QString translateMetadataKey( const QString& mdKey ) const;
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/**
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* Get the translated metadata value.
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* @param mdKey The metadata key
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* @param value The metadata value
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* @return The translated metadata value
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*/
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virtual QString translateMetadataValue( const QString& mdKey, const QVariant& value ) const;
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signals:
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/**
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* Signals an error in this provider
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*
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* @note Added const in QGIS 3.0
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*/
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void raiseError( const QString& msg ) const;
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protected:
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/**
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* Invalidates the min/max cache. This will force the provider to recalculate the
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* cache the next time it is requested.
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*/
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void clearMinMaxCache();
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/**
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* Populates the cache of minimum and maximum attribute values.
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*/
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void fillMinMaxCache() const;
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/**
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* Push a notification about errors that happened in this providers scope.
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* Errors should be translated strings that require the users immediate
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* attention.
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*
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* For general debug information use QgsMessageLog::logMessage() instead.
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*
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* @note Added in QGIS 3.0
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*/
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void pushError( const QString& msg ) const;
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/**
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* Converts the geometry to the provider type if possible / necessary
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* @return the converted geometry or nullptr if no conversion was necessary or possible
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*/
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QgsGeometry* convertToProviderType( const QgsGeometry& geom ) const /Factory/;
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/**
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* Set the list of native types supported by this provider.
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* Usually done in the constructor.
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*
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* @note Added in QGIS 3.0
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*/
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void setNativeTypes(const QList<QgsVectorDataProvider::NativeType>& nativeTypes);
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/**
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* Get this providers encoding
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*
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* @note Added in QGIS 3.0
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*/
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QTextCodec* textEncoding() const;
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};
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QFlags<QgsVectorDataProvider::Capability> operator|(QgsVectorDataProvider::Capability f1, QFlags<QgsVectorDataProvider::Capability> f2);
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