QGIS API Documentation 3.40.0-Bratislava (b56115d8743)
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qgsalgorithmflattenrelationships.cpp
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1/***************************************************************************
2 qgsalgorithmflattenrelationships.h
3 ---------------------
4 begin : August 2020
5 copyright : (C) 2020 by Nyall Dawson
6 email : nyall dot dawson at gmail dot com
7 ***************************************************************************/
8
9/***************************************************************************
10 * *
11 * This program is free software; you can redistribute it and/or modify *
12 * it under the terms of the GNU General Public License as published by *
13 * the Free Software Foundation; either version 2 of the License, or *
14 * (at your option) any later version. *
15 * *
16 ***************************************************************************/
17
19#include "qgsrelationmanager.h"
20#include "qgsvectorlayer.h"
22
24
25QString QgsFlattenRelationshipsAlgorithm::name() const
26{
27 return QStringLiteral( "flattenrelationships" );
28}
29
30QString QgsFlattenRelationshipsAlgorithm::displayName() const
31{
32 return QObject::tr( "Flatten relationship" );
33}
34
35QStringList QgsFlattenRelationshipsAlgorithm::tags() const
36{
37 return QObject::tr( "join,export,single,table" ).split( ',' );
38}
39
40QString QgsFlattenRelationshipsAlgorithm::group() const
41{
42 return QObject::tr( "Vector general" );
43}
44
45QString QgsFlattenRelationshipsAlgorithm::groupId() const
46{
47 return QStringLiteral( "vectorgeneral" );
48}
49
50QString QgsFlattenRelationshipsAlgorithm::shortDescription() const
51{
52 return QObject::tr( "Flatten a relationship for a vector layer." );
53}
54
55QString QgsFlattenRelationshipsAlgorithm::shortHelpString() const
56{
57 return QObject::tr( "This algorithm flattens a relationship for a vector layer, exporting a single layer "
58 "containing one master feature per related feature. This master feature contains all "
59 "the attributes for the related features." );
60}
61
62Qgis::ProcessingAlgorithmDocumentationFlags QgsFlattenRelationshipsAlgorithm::documentationFlags() const
63{
65}
66
67Qgis::ProcessingAlgorithmFlags QgsFlattenRelationshipsAlgorithm::flags() const
68{
70}
71
72void QgsFlattenRelationshipsAlgorithm::initAlgorithm( const QVariantMap & )
73{
74 addParameter( new QgsProcessingParameterVectorLayer( QStringLiteral( "INPUT" ),
75 QObject::tr( "Input layer" ), QList< int>() << static_cast< int >( Qgis::ProcessingSourceType::Vector ) ) );
76
77 addParameter( new QgsProcessingParameterFeatureSink( QStringLiteral( "OUTPUT" ), QObject::tr( "Flattened layer" ), Qgis::ProcessingSourceType::VectorAnyGeometry ) );
78}
79
80QgsFlattenRelationshipsAlgorithm *QgsFlattenRelationshipsAlgorithm::createInstance() const
81{
82 return new QgsFlattenRelationshipsAlgorithm();
83}
84
85bool QgsFlattenRelationshipsAlgorithm::prepareAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback * )
86{
87 QgsProject *project = context.project();
88 if ( !project )
89 throw QgsProcessingException( QObject::tr( "No project available for relationships" ) );
90
91 QgsVectorLayer *layer = parameterAsVectorLayer( parameters, QStringLiteral( "INPUT" ), context );
92 if ( !layer )
93 throw QgsProcessingException( invalidSourceError( parameters, QStringLiteral( "INPUT" ) ) );
94
95 const QList<QgsRelation> relations = project->relationManager()->referencedRelations( layer );
96 if ( relations.size() > 1 )
97 throw QgsProcessingException( QObject::tr( "Found %n relation(s). This algorithm currently supports only a single relation.", nullptr, relations.size() ) );
98 else if ( relations.empty() )
99 throw QgsProcessingException( QObject::tr( "No relations found." ) );
100
101 mRelation = relations.at( 0 );
102
103 QgsVectorLayer *referencingLayer = mRelation.referencingLayer();
104 if ( !referencingLayer )
105 throw QgsProcessingException( QObject::tr( "Could not resolved referenced layer." ) );
106
107 mReferencingSource = std::make_unique< QgsVectorLayerFeatureSource >( referencingLayer );
108 mReferencingFields = referencingLayer->fields();
109
110 return true;
111}
112
113QVariantMap QgsFlattenRelationshipsAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
114{
115 std::unique_ptr< QgsProcessingFeatureSource > input( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
116 if ( !input )
117 throw QgsProcessingException( invalidSourceError( parameters, QStringLiteral( "INPUT" ) ) );
118
119 const QgsFields outFields = QgsProcessingUtils::combineFields( input->fields(), mReferencingFields );
120
121 QString dest;
122 std::unique_ptr< QgsFeatureSink > sink( parameterAsSink( parameters, QStringLiteral( "OUTPUT" ), context, dest, outFields,
123 input->wkbType(), input->sourceCrs(), QgsFeatureSink::RegeneratePrimaryKey ) );
124 if ( parameters.value( QStringLiteral( "OUTPUT" ) ).isValid() && !sink )
125 throw QgsProcessingException( invalidSinkError( parameters, QStringLiteral( "OUTPUT" ) ) );
126
127 // Create output vector layer with additional attributes
128 const double step = input->featureCount() > 0 ? 100.0 / input->featureCount() : 1;
130 long long i = 0;
131 QgsFeature feat;
132 while ( features.nextFeature( feat ) )
133 {
134 i++;
135 if ( feedback->isCanceled() )
136 {
137 break;
138 }
139
140 feedback->setProgress( i * step );
141
142 QgsFeatureRequest referencingRequest = mRelation.getRelatedFeaturesRequest( feat );
143 referencingRequest.setFlags( referencingRequest.flags() | Qgis::FeatureRequestFlag::NoGeometry );
144 QgsFeatureIterator childIt = mReferencingSource->getFeatures( referencingRequest );
145 QgsFeature relatedFeature;
146 while ( childIt.nextFeature( relatedFeature ) )
147 {
148 QgsAttributes attrs = feat.attributes();
149 attrs.append( relatedFeature.attributes() );
150 QgsFeature outFeat = feat;
151 outFeat.setAttributes( attrs );
152 if ( !sink->addFeature( outFeat, QgsFeatureSink::FastInsert ) )
153 throw QgsProcessingException( writeFeatureError( sink.get(), parameters, QStringLiteral( "OUTPUT" ) ) );
154 }
155 }
156
157 QVariantMap outputs;
158 if ( sink )
159 outputs.insert( QStringLiteral( "OUTPUT" ), dest );
160 return outputs;
161}
162
163
@ Vector
Tables (i.e. vector layers with or without geometry). When used for a sink this indicates the sink ha...
@ VectorAnyGeometry
Any vector layer with geometry.
@ NoGeometry
Geometry is not required. It may still be returned if e.g. required for a filter condition.
@ RegeneratesPrimaryKey
Algorithm always drops any existing primary keys or FID values and regenerates them in outputs.
QFlags< ProcessingAlgorithmFlag > ProcessingAlgorithmFlags
Flags indicating how and when an algorithm operates and should be exposed to users.
Definition qgis.h:3339
QFlags< ProcessingAlgorithmDocumentationFlag > ProcessingAlgorithmDocumentationFlags
Flags describing algorithm behavior for documentation purposes.
Definition qgis.h:3359
@ SkipGeometryValidityChecks
Invalid geometry checks should always be skipped. This flag can be useful for algorithms which always...
@ RequiresProject
The algorithm requires that a valid QgsProject is available from the processing context in order to e...
A vector of attributes.
Wrapper for iterator of features from vector data provider or vector layer.
bool nextFeature(QgsFeature &f)
Fetch next feature and stores in f, returns true on success.
This class wraps a request for features to a vector layer (or directly its vector data provider).
QgsFeatureRequest & setFlags(Qgis::FeatureRequestFlags flags)
Sets flags that affect how features will be fetched.
Qgis::FeatureRequestFlags flags() const
Returns the flags which affect how features are fetched.
@ FastInsert
Use faster inserts, at the cost of updating the passed features to reflect changes made at the provid...
@ RegeneratePrimaryKey
This flag indicates, that a primary key field cannot be guaranteed to be unique and the sink should i...
The feature class encapsulates a single feature including its unique ID, geometry and a list of field...
Definition qgsfeature.h:58
QgsAttributes attributes
Definition qgsfeature.h:67
void setAttributes(const QgsAttributes &attrs)
Sets the feature's attributes.
bool isCanceled() const
Tells whether the operation has been canceled already.
Definition qgsfeedback.h:53
void setProgress(double progress)
Sets the current progress for the feedback object.
Definition qgsfeedback.h:61
Container of fields for a vector layer.
Definition qgsfields.h:46
virtual Qgis::ProcessingAlgorithmFlags flags() const
Returns the flags indicating how and when the algorithm operates and should be exposed to users.
Contains information about the context in which a processing algorithm is executed.
QgsProject * project() const
Returns the project in which the algorithm is being executed.
Custom exception class for processing related exceptions.
Base class for providing feedback from a processing algorithm.
A feature sink output for processing algorithms.
A vector layer (with or without geometry) parameter for processing algorithms.
static QgsFields combineFields(const QgsFields &fieldsA, const QgsFields &fieldsB, const QString &fieldsBPrefix=QString())
Combines two field lists, avoiding duplicate field names (in a case-insensitive manner).
Encapsulates a QGIS project, including sets of map layers and their styles, layouts,...
Definition qgsproject.h:107
QgsRelationManager * relationManager
Definition qgsproject.h:117
QList< QgsRelation > referencedRelations(const QgsVectorLayer *layer=nullptr) const
Gets all relations where this layer is the referenced part (i.e.
Represents a vector layer which manages a vector based data sets.