Subgroup: Vector
Class: QgsVectorDataProvider¶
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class
qgis.core.
QgsVectorDataProvider
(uri: str = '')¶ Bases:
qgis._core.QgsDataProvider
,qgis._core.QgsFeatureSink
,qgis._core.QgsFeatureSource
Constructor of the vector provider
Parameters: uri – uniform resource locator (URI) for a dataset 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.
Methods
addAttributes
Adds new attributes
to the provider.addFeatures
aggregate
Calculates an aggregated value from the layer’s features. appendError
attributeIndexes
Return list of indexes to fetch all attributes in nextFeature() availableEncodings
Returns a list of available encodings capabilities
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. capabilitiesString
Returns the above in friendly format. changeAttributeValues
Changes attribute values of existing features. changeFeatures
Changes attribute values and geometries of existing features. changeGeometryValues
Changes geometries of existing features childEvent
clearErrors
Clear recorded errors clearMinMaxCache
Invalidates the min/max cache. connectNotify
convertToProviderType
Converts the geometry to the provider type if possible / necessary convertValue
createAttributeIndex
Create an attribute index on the datasource createSpatialIndex
Creates a spatial index on the datasource (if supported by the provider type). customEvent
dataComment
Return a short comment for the data that this provider is providing access to (e. defaultValue
Returns any literal default values which are present at the provider for a specified field index. defaultValueClause
Returns any default value clauses which are present at the provider for a specified field index. deleteAttributes
Deletes existing attributes
from the provider.deleteFeatures
Deletes one or more features from the provider. dependencies
Get the list of layer ids on which this layer depends. disconnectNotify
discoverRelations
Discover the available relations with the given layers. doesStrictFeatureTypeCheck
Returns true if the provider is strict about the type of inserted features (e. encoding
Get encoding which is used for accessing data enumValues
Returns the possible enum values of an attribute. errors
Get recorded errors featureCount
Number of features in the layer featureSource
Return feature source object that can be used for querying provider’s data. fieldConstraints
Returns any constraints which are present at the provider for a specified field index. fieldNameIndex
Returns the index of a field name or -1 if the field does not exist fieldNameMap
Return a map where the key is the name of the field and the value is its index fields
Returns the fields associated with this data provider. fillMinMaxCache
Populates the cache of minimum and maximum attribute values. forceReload
Forces a reload of the underlying datasource if the provider implements this method. getFeatures
Query the provider for features specified in request. hasErrors
Provider has errors to report hasMetadata
Returns true if the data source has metadata, false otherwise. isDeleteStyleFromDatabaseSupported
It returns false by default. isSaveAndLoadStyleToDatabaseSupported
It returns false by default. isSignalConnected
maximumValue
Returns the maximum value of an attribute metadata
Get metadata, dependent on the provider type, that will be display in the metadata tab of the layer properties. minimumValue
Returns the minimum value of an attribute nativeTypes
Returns the names of the supported types palAttributeIndexNames
Return list of indexes to names for QgsPalLabeling fix pkAttributeIndexes
Return list of indexes of fields that make up the primary key pushError
Push a notification about errors that happened in this providers scope. receivers
renameAttributes
Renames existing attributes. sender
senderSignalIndex
setEncoding
Set encoding used for accessing data from layer setError
setNativeTypes
Set the list of native types supported by this provider. skipConstraintCheck
Returns true if a constraint check should be skipped for a specified field (e. sourceCrs
sourceExtent
sourceName
storageType
Returns the permanent storage type for this layer as a friendly name. supportedType
check if provider supports type of field textEncoding
Get this providers encoding timerEvent
transaction
Returns the transaction this data provider is included in, if any. translateMetadataKey
Get the translated metadata key. translateMetadataValue
Get the translated metadata value. truncate
Removes all features from the layer. uniqueStringsMatching
Returns unique string values of an attribute which contain a specified subset string. wkbType
Returns the geometry type which is returned by this layer Signals
raiseError
Signals an error in this provider Attributes
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AddAttributes
= 8¶
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AddFeatures
= 1¶
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class
Capabilities
¶ Bases:
sip.wrapper
QgsVectorDataProvider.Capabilities(Union[QgsVectorDataProvider.Capabilities, QgsVectorDataProvider.Capability]) QgsVectorDataProvider.Capabilities(QgsVectorDataProvider.Capabilities)
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class
Capability
¶ Bases:
int
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ChangeAttributeValues
= 4¶
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ChangeFeatures
= 262144¶
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ChangeGeometries
= 256¶
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CircularGeometries
= 131072¶
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CreateAttributeIndex
= 4096¶
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CreateSpatialIndex
= 64¶
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DeleteAttributes
= 16¶
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DeleteFeatures
= 2¶
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EditingCapabilities
= 524575¶
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FastTruncate
= 1048576¶
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class
FeatureCountState
¶ Bases:
int
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class
NativeType
(typeDesc: str, typeName: str, type: QVariant.Type, minLen: int = 0, maxLen: int = 0, minPrec: int = 0, maxPrec: int = 0, subType: QVariant.Type = QVariant.Invalid)¶ Bases:
sip.wrapper
QgsVectorDataProvider.NativeType(QgsVectorDataProvider.NativeType)
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mMaxLen
¶
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mMaxPrec
¶
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mMinLen
¶
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mMinPrec
¶
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mSubType
¶
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mType
¶
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mTypeDesc
¶
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mTypeName
¶
-
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NoCapabilities
= 0¶
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ReadLayerMetadata
= 2097152¶
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RenameAttributes
= 524288¶
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SelectAtId
= 128¶
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SelectEncoding
= 8192¶
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SimplifyGeometries
= 16384¶
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SimplifyGeometriesWithTopologicalValidation
= 32768¶
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TransactionSupport
= 65536¶
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Uncounted
= -2¶
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UnknownCount
= -1¶
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WriteLayerMetadata
= 4194304¶
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addAttributes
(self, attributes: object) → bool¶ 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.
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addFeatures
(self, flist: object, flags: Union[QgsFeatureSink.Flags, QgsFeatureSink.Flag] = 0) → Tuple[bool, object]¶
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aggregate
(self, aggregate: QgsAggregateCalculator.Aggregate, index: int, parameters: QgsAggregateCalculator.AggregateParameters, context: QgsExpressionContext) → Tuple[Any, bool]¶ 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
New in version 2.16.
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appendError
()¶
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attributeIndexes
(self) → List[int]¶ Return list of indexes to fetch all attributes in nextFeature()
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availableEncodings
() → List[str]¶ Returns a list of available encodings
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capabilities
(self) → QgsVectorDataProvider.Capabilities¶ 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.
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capabilitiesString
(self) → str¶ Returns the above in friendly format.
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changeAttributeValues
(self, attr_map: object) → bool¶ 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
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changeFeatures
(self, attr_map: object, geometry_map: object) → bool¶ 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
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changeGeometryValues
(self, geometry_map: object) → bool¶ 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
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childEvent
()¶
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clearErrors
(self)¶ Clear recorded errors
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clearMinMaxCache
(self)¶ Invalidates the min/max cache. This will force the provider to recalculate the cache the next time it is requested.
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connectNotify
()¶
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convertToProviderType
(self, geom: QgsGeometry) → QgsGeometry¶ Converts the geometry to the provider type if possible / necessary
Returns: the converted geometry or None if no conversion was necessary or possible
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convertValue
(type: QVariant.Type, value: str) → Any¶
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createAttributeIndex
(self, field: int) → bool¶ Create an attribute index on the datasource
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createSpatialIndex
(self) → bool¶ Creates a spatial index on the datasource (if supported by the provider type).
Returns: true in case of success
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customEvent
()¶
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dataComment
(self) → str¶ Return a short comment for the data that this provider is providing access to (e.g. the comment for postgres table).
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defaultValue
(self, fieldIndex: int) → Any¶ 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
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defaultValueClause
(self, fieldIndex: int) → str¶ 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
New in version 3.0.
-
deleteAttributes
(self, attributes: object) → bool¶ 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
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deleteFeatures
(self, id: object) → bool¶ 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
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dependencies
(self) → object¶ Get the list of layer ids on which this layer depends. This in particular determines the order of layer loading.
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disconnectNotify
()¶
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discoverRelations
(self, self: QgsVectorLayer, layers: Iterable[QgsVectorLayer]) → object¶ 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.
New in version 3.0.
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doesStrictFeatureTypeCheck
(self) → bool¶ Returns true if the provider is strict about the type of inserted features (e.g. no multipolygon in a polygon layer)
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encoding
(self) → str¶ Get encoding which is used for accessing data
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enumValues
(self, index: int) → List[str]¶ 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
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errors
(self) → List[str]¶ Get recorded errors
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featureCount
(self) → int¶ Number of features in the layer
Returns: long containing number of features
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featureSource
(self) → QgsAbstractFeatureSource¶ Return 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)New in version 2.4.
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fieldConstraints
(self, fieldIndex: int) → QgsFieldConstraints.Constraints¶ Returns any constraints which are present at the provider for a specified field index.
New in version 3.0.
See also
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fieldNameIndex
(self, fieldName: str) → int¶ Returns the index of a field name or -1 if the field does not exist
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fieldNameMap
(self) → object¶ Return a map where the key is the name of the field and the value is its index
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fields
(self) → QgsFields¶ Returns the fields associated with this data provider.
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fillMinMaxCache
(self)¶ Populates the cache of minimum and maximum attribute values.
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forceReload
(self)¶ 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.
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getFeatures
(self, request: QgsFeatureRequest = QgsFeatureRequest()) → QgsFeatureIterator¶ 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
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hasErrors
(self) → bool¶ Provider has errors to report
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hasMetadata
(self) → bool¶ Returns true if the data source has metadata, false otherwise.
Returns: true if data source has metadata, false otherwise. New in version 3.0.
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isDeleteStyleFromDatabaseSupported
(self) → bool¶ It returns false by default. Must be implemented by providers that support delete styles from db returning true
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isSaveAndLoadStyleToDatabaseSupported
(self) → bool¶ It returns false by default. Must be implemented by providers that support saving and loading styles to db returning true
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isSignalConnected
()¶
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maximumValue
(self, index: int) → Any¶ 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.
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metadata
(self) → Dict[str, Any]¶ Get metadata, dependent on the provider type, that will be display in the metadata tab of the layer properties.
Returns: The provider metadata
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minimumValue
(self, index: int) → Any¶ 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.
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nativeTypes
(self) → object¶ Returns the names of the supported types
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palAttributeIndexNames
(self) → object¶ Return list of indexes to names for QgsPalLabeling fix
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pkAttributeIndexes
(self) → List[int]¶ Return list of indexes of fields that make up the primary key
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pushError
(self, msg: str)¶ 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.
New in version 3.0.
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raiseError
¶ Signals an error in this provider
New in version 3.0: [signal]
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receivers
()¶
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renameAttributes
(self, renamedAttributes: object) → bool¶ 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 New in version 2.16.
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sender
()¶
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senderSignalIndex
()¶
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setEncoding
(self, e: str)¶ Set encoding used for accessing data from layer
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setError
()¶
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setNativeTypes
(self, nativeTypes: Iterable[QgsVectorDataProvider.NativeType])¶ Set the list of native types supported by this provider. Usually done in the constructor.
New in version 3.0.
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skipConstraintCheck
(self, fieldIndex: int, constraint: QgsFieldConstraints.Constraint, value: Any = None) → bool¶ 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.
New in version 3.0.
See also
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sourceCrs
(self) → QgsCoordinateReferenceSystem¶
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sourceExtent
(self) → QgsRectangle¶
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sourceName
(self) → str¶
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storageType
(self) → str¶ Returns the permanent storage type for this layer as a friendly name.
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supportedType
(self, field: QgsField) → bool¶ check if provider supports type of field
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textEncoding
(self) → QTextCodec¶ Get this providers encoding
New in version 3.0.
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timerEvent
()¶
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transaction
(self) → QgsTransaction¶ Returns the transaction this data provider is included in, if any.
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translateMetadataKey
(self, mdKey: str) → str¶ Get the translated metadata key.
Parameters: mdKey – The metadata key Returns: The translated metadata value
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translateMetadataValue
(self, mdKey: str, value: Any) → str¶ Get the translated metadata value.
Parameters: - mdKey – The metadata key
- value – The metadata value
Returns: The translated metadata value
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truncate
(self) → bool¶ 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. New in version 3.0.
See also
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uniqueStringsMatching
(self, index: int, substring: str, limit: int = -1, feedback: QgsFeedback = None) → List[str]¶ 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
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wkbType
(self) → QgsWkbTypes.Type¶ Returns the geometry type which is returned by this layer
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