QGIS API Documentation  3.20.0-Odense (decaadbb31)
qgsalgorithmattributeindex.cpp
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1 /***************************************************************************
2  qgsalgorithmattributeraster.cpp
3  ---------------------
4  begin : November 2019
5  copyright : (C) 2019 by Alexander Bruy
6  email : alexander dot bruy 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 "qgsvectorlayer.h"
20 #include "qgsvectordataprovider.h"
21 
23 
24 QString QgsAttributeIndexAlgorithm::name() const
25 {
26  return QStringLiteral( "createattributeindex" );
27 }
28 
29 QString QgsAttributeIndexAlgorithm::displayName() const
30 {
31  return QObject::tr( "Create attribute index" );
32 }
33 
34 QStringList QgsAttributeIndexAlgorithm::tags() const
35 {
36  return QObject::tr( "table,attribute,index,create,vector" ).split( ',' );
37 }
38 
39 QString QgsAttributeIndexAlgorithm::group() const
40 {
41  return QObject::tr( "Vector general" );
42 }
43 
44 QString QgsAttributeIndexAlgorithm::groupId() const
45 {
46  return QStringLiteral( "vectorgeneral" );
47 }
48 
49 QgsProcessingAlgorithm::Flags QgsAttributeIndexAlgorithm::flags() const
50 {
52 }
53 
54 
55 QString QgsAttributeIndexAlgorithm::shortHelpString() const
56 {
57  return QObject::tr( "Creates an index to speed up queries made against "
58  "a field in a table. Support for index creation is "
59  "dependent on the layer's data provider and the field type." );
60 }
61 
62 QgsAttributeIndexAlgorithm *QgsAttributeIndexAlgorithm::createInstance() const
63 {
64  return new QgsAttributeIndexAlgorithm();
65 }
66 
67 void QgsAttributeIndexAlgorithm::initAlgorithm( const QVariantMap & )
68 {
69  addParameter( new QgsProcessingParameterVectorLayer( QStringLiteral( "INPUT" ), QObject::tr( "Input layer" ) ) );
70  addParameter( new QgsProcessingParameterField( QStringLiteral( "FIELD" ), QObject::tr( "Attribute to index" ), QVariant(), QStringLiteral( "INPUT" ) ) );
71 
72  addOutput( new QgsProcessingOutputVectorLayer( QStringLiteral( "OUTPUT" ), QObject::tr( "Indexed layer" ) ) );
73 }
74 
75 QVariantMap QgsAttributeIndexAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
76 {
77  QgsVectorLayer *layer = parameterAsVectorLayer( parameters, QStringLiteral( "INPUT" ), context );
78 
79  if ( !layer )
80  throw QgsProcessingException( QObject::tr( "Could not load source layer for %1." ).arg( QLatin1String( "INPUT" ) ) );
81 
82  QString field = parameterAsString( parameters, QStringLiteral( "FIELD" ), context );
83 
84  QgsVectorDataProvider *provider = layer->dataProvider();
85 
86  int fieldIndex = layer->fields().lookupField( field );
87  if ( fieldIndex < 0 || layer->fields().fieldOrigin( fieldIndex ) != QgsFields::OriginProvider )
88  {
89  feedback->pushInfo( QObject::tr( "Can not create attribute index on %1" ).arg( field ) );
90  }
91  else
92  {
93  int providerIndex = layer->fields().fieldOriginIndex( fieldIndex );
95  {
96  if ( !provider->createAttributeIndex( providerIndex ) )
97  {
98  feedback->pushInfo( QObject::tr( "Could not create attribute index" ) );
99  }
100  }
101  else
102  {
103  feedback->pushInfo( QObject::tr( "Layer's data provider does not support creating attribute indexes" ) );
104  }
105  }
106 
107  QVariantMap outputs;
108  outputs.insert( QStringLiteral( "OUTPUT" ), layer->id() );
109  return outputs;
110 }
111 
@ OriginProvider
Field comes from the underlying data provider of the vector layer (originIndex = index in provider's ...
Definition: qgsfields.h:51
int fieldOriginIndex(int fieldIdx) const
Returns the field's origin index (its meaning is specific to each type of origin).
Definition: qgsfields.cpp:197
int lookupField(const QString &fieldName) const
Looks up field's index from the field name.
Definition: qgsfields.cpp:344
QString id() const
Returns the layer's unique ID, which is used to access this layer from QgsProject.
virtual Flags flags() const
Returns the flags indicating how and when the algorithm operates and should be exposed to users.
@ FlagNoThreading
Algorithm is not thread safe and cannot be run in a background thread, e.g. for algorithms which mani...
Contains information about the context in which a processing algorithm is executed.
Custom exception class for processing related exceptions.
Definition: qgsexception.h:83
Base class for providing feedback from a processing algorithm.
virtual void pushInfo(const QString &info)
Pushes a general informational message from the algorithm.
A vector layer output for processing algorithms.
A vector layer or feature source field parameter for processing algorithms.
A vector layer (with or without geometry) parameter for processing algorithms.
This is the base class for vector data providers.
@ CreateAttributeIndex
Can create indexes on provider's fields.
virtual bool createAttributeIndex(int field)
Create an attribute index on the datasource.
virtual Q_INVOKABLE QgsVectorDataProvider::Capabilities capabilities() const
Returns flags containing the supported capabilities.
Represents a vector layer which manages a vector based data sets.
QgsFields fields() const FINAL
Returns the list of fields of this layer.
QgsVectorDataProvider * dataProvider() FINAL
Returns the layer's data provider, it may be nullptr.
const QgsField & field
Definition: qgsfield.h:463