allow QgsFeatureListComboBox to handle multiple keys

python/core/auto_generated/qgsfeaturefiltermodel.sip.in

@@ -26,6 +26,7 @@ Features are fetched asynchronously.
     enum Role
     {
       IdentifierValueRole,
+      IdentifierValuesRole,
       ValueRole
     };
 
@@ -103,28 +104,69 @@ Can be used for spatial filtering etc.
 Indicator if the model is currently performing any feature iteration in the background.
 %End
 
-    QString identifierField() const;
+ QString identifierField() const;
 %Docstring
 The identifier field should be a unique field that can be used to identify individual features.
 It is normally set to the primary key of the layer.
+If there are several identifier fields defined, the behavior is not guaranteed
+
+.. deprecated:: since QGIS 3.10 use identifierFields instead
 %End
 
-    void setIdentifierField( const QString &identifierField );
+    QStringList identifierFields() const;
 %Docstring
 The identifier field should be a unique field that can be used to identify individual features.
 It is normally set to the primary key of the layer.
+
+.. versionadded:: 3.10
 %End
 
-    QVariant extraIdentifierValue() const;
+ void setIdentifierField( const QString &identifierField );
+%Docstring
+The identifier field should be a unique field that can be used to identify individual features.
+It is normally set to the primary key of the layer.
+
+.. deprecated:: since QGIS 3.10
+%End
+
+    void setIdentifierFields( const QStringList &identifierFields );
+%Docstring
+The identifier field should be a unique field that can be used to identify individual features.
+It is normally set to the primary key of the layer.
+
+.. versionadded:: 3.10
+%End
+
+ QVariant extraIdentifierValue() const;
 %Docstring
 Allows specifying one value that does not need to match the filter criteria but will
 still be available in the model.
+
+.. deprecated:: since QGIS 3.10
 %End
 
-    void setExtraIdentifierValue( const QVariant &extraIdentifierValue );
+    QVariantList extraIdentifierValues() const;
 %Docstring
 Allows specifying one value that does not need to match the filter criteria but will
 still be available in the model.
+
+.. versionadded:: 3.10
+%End
+
+ void setExtraIdentifierValue( const QVariant &extraIdentifierValue );
+%Docstring
+Allows specifying one value that does not need to match the filter criteria but will
+still be available in the model.
+
+.. deprecated:: since QGIS 3.10
+%End
+
+    void setExtraIdentifierValues( const QVariantList &extraIdentifierValues );
+%Docstring
+Allows specifying one value that does not need to match the filter criteria but will
+still be available in the model.
+
+.. versionadded:: 3.10
 %End
 
     int extraIdentifierValueIndex() const;

python/gui/auto_generated/qgsfeaturelistcombobox.sip.in

@@ -9,6 +9,7 @@
 
 
 
+
 class QgsFeatureListComboBox : QComboBox
 {
 %Docstring
@@ -38,6 +39,13 @@ The layer from which features should be listed.
     void setSourceLayer( QgsVectorLayer *sourceLayer );
 %Docstring
 The layer from which features should be listed.
+%End
+
+    void setCurrentFeature( const QgsFeature &feature );
+%Docstring
+Sets the current index by using the given feature
+
+.. versionadded:: 3.10
 %End
 
     QString displayExpression() const;
@@ -74,16 +82,37 @@ This can be used to integrate additional spatial or other constraints.
 TODO!
 %End
 
-    QVariant identifierValue() const;
+ QVariant identifierValue() const /Deprecated/;
 %Docstring
 The identifier value of the currently selected feature. A value from the
 identifierField.
+
+.. deprecated:: since QGIS 3.10
 %End
 
-    void setIdentifierValue( const QVariant &identifierValue );
+    QVariantList identifierValues() const;
+%Docstring
+The identifier values of the currently selected feature. A value from the
+identifierField.
+
+.. versionadded:: 3.10
+%End
+
+
+ void setIdentifierValue( const QVariant &identifierValue ) /Deprecated/;
 %Docstring
 The identifier value of the currently selected feature. A value from the
 identifierField.
+
+.. deprecated:: since QGIS 3.10 use setIdentifierValues
+%End
+
+    void setIdentifierValues( const QVariantList &identifierValues );
+%Docstring
+The identifier values of the currently selected feature. A value from the
+identifierFields.
+
+.. versionadded:: 3.10
 %End
 
     QgsFeatureRequest currentFeatureRequest() const;
@@ -102,16 +131,36 @@ Determines if a NULL value should be available in the list.
 Determines if a NULL value should be available in the list.
 %End
 
-    QString identifierField() const;
+ QString identifierField() const /Deprecated/;
 %Docstring
 Field name that will be used to uniquely identify the current feature.
 Normally the primary key of the layer.
+
+.. deprecated:: since QGIS 3.10
 %End
 
-    void setIdentifierField( const QString &identifierField );
+    QStringList identifierFields() const;
 %Docstring
 Field name that will be used to uniquely identify the current feature.
 Normally the primary key of the layer.
+
+.. versionadded:: 3.10
+%End
+
+ void setIdentifierField( const QString &identifierField ) /Deprecated/;
+%Docstring
+Field name that will be used to uniquely identify the current feature.
+Normally the primary key of the layer.
+
+.. deprecated:: since QGIS 3.10
+%End
+
+    void setIdentifierFields( const QStringList &identifierFields );
+%Docstring
+Field name that will be used to uniquely identify the current feature.
+Normally the primary key of the layer.
+
+.. versionadded:: 3.10
 %End
 
     QModelIndex currentModelIndex() const;
@@ -170,6 +219,8 @@ Determines if a NULL value should be available in the list.
 
 };
 
+
+
 /************************************************************************
  * This file has been generated automatically from                      *
  *                                                                      *

src/core/qgsfeaturefiltermodel.cpp

@@ -1,6 +1,5 @@
 /***************************************************************************
   qgsfeaturefiltermodel.cpp - QgsFeatureFilterModel
-
  ---------------------
  begin                : 10.3.2017
  copyright            : (C) 2017 by Matthias Kuhn
@@ -27,7 +26,7 @@ QgsFeatureFilterModel::QgsFeatureFilterModel( QObject *parent )
   mReloadTimer.setInterval( 100 );
   mReloadTimer.setSingleShot( true );
   connect( &mReloadTimer, &QTimer::timeout, this, &QgsFeatureFilterModel::scheduledReload );
-  setExtraIdentifierValueUnguarded( QVariant() );
+  setExtraIdentifierValuesUnguarded( QVariantList() );
 }
 
 QgsFeatureFilterModel::~QgsFeatureFilterModel()
@@ -102,6 +101,14 @@ bool QgsFeatureFilterModel::isLoading() const
   return mGatherer;
 }
 
+QString QgsFeatureFilterModel::identifierField() const
+{
+  if ( mIdentifierFields.isEmpty() )
+    return QString();
+  else
+    return mIdentifierFields.at( 0 );
+}
+
 QModelIndex QgsFeatureFilterModel::index( int row, int column, const QModelIndex &parent ) const
 {
   Q_UNUSED( parent )
@@ -140,30 +147,42 @@ QVariant QgsFeatureFilterModel::data( const QModelIndex &index, int role ) const
       return mEntries.value( index.row() ).value;
 
     case IdentifierValueRole:
-      return mEntries.value( index.row() ).identifierValue;
+    {
+      QVariantList values = mEntries.value( index.row() ).identifierValues;
+      return values.isEmpty() ? QVariant() : values.at( 0 );
+    }
+
+    case IdentifierValuesRole:
+      return mEntries.value( index.row() ).identifierValues;
 
     case Qt::BackgroundColorRole:
     case Qt::TextColorRole:
     case Qt::DecorationRole:
     case Qt::FontRole:
     {
-      if ( mEntries.value( index.row() ).identifierValue.isNull() )
+      bool isNull = true;
+      for ( const QVariant &value : mEntries.value( index.row() ).identifierValues )
+      {
+        if ( !value.isNull() )
+        {
+          isNull = false;
+          break;
+        }
+      }
+      if ( isNull )
       {
         // Representation for NULL value
         if ( role == Qt::TextColorRole )
         {
           return QBrush( QColor( Qt::gray ) );
         }
-        else if ( role == Qt::FontRole )
+        if ( role == Qt::FontRole )
         {
           QFont font = QFont();
           if ( index.row() == mExtraIdentifierValueIndex )
             font.setBold( true );
-
+          else
-          if ( mEntries.value( index.row() ).identifierValue.isNull() )
-          {
             font.setItalic( true );
-          }
           return font;
         }
       }
@@ -197,7 +216,7 @@ void QgsFeatureFilterModel::updateCompleter()
   QVector<Entry> entries = mGatherer->entries();
 
   if ( mExtraIdentifierValueIndex == -1 )
-    setExtraIdentifierValueUnguarded( QVariant() );
+    setExtraIdentifierValuesUnguarded( QVariantList() );
 
   // Only reloading the current entry?
   if ( mGatherer->data().toBool() )
@@ -225,7 +244,9 @@ void QgsFeatureFilterModel::updateCompleter()
     std::sort( entries.begin(), entries.end(), []( const Entry & a, const Entry & b ) { return a.value.localeAwareCompare( b.value ) < 0; } );
 
     if ( mAllowNull )
-      entries.prepend( Entry( QVariant( QVariant::Int ), QgsApplication::nullRepresentation(), QgsFeature() ) );
+    {
+      entries.prepend( nullEntry() );
+    }
 
     const int newEntriesSize = entries.size();
 
@@ -235,7 +256,7 @@ void QgsFeatureFilterModel::updateCompleter()
     {
       for ( int i = 0; i < newEntriesSize; ++i )
       {
-        if ( entries.at( i ).identifierValue == mExtraIdentifierValue )
+        if ( entries.at( i ).identifierValues == mExtraIdentifierValues )
         {
           currentEntryInNewList = i;
           mEntries.replace( mExtraIdentifierValueIndex, entries.at( i ) );
@@ -274,7 +295,7 @@ void QgsFeatureFilterModel::updateCompleter()
       beginInsertRows( QModelIndex(), 1, entries.size() + 1 );
       mEntries += entries;
       endInsertRows();
-      setExtraIdentifierValueIndex( 0 );
+      setExtraIdentifierValuesIndex( 0 );
     }
     else
     {
@@ -294,7 +315,7 @@ void QgsFeatureFilterModel::updateCompleter()
       beginInsertRows( QModelIndex(), currentEntryInNewList + 1, newEntriesSize - currentEntryInNewList - 1 );
       mEntries += entries.mid( currentEntryInNewList + 1 );
       endInsertRows();
-      setExtraIdentifierValueIndex( currentEntryInNewList );
+      setExtraIdentifierValuesIndex( currentEntryInNewList );
     }
 
     emit filterJobCompleted();
@@ -331,7 +352,19 @@ void QgsFeatureFilterModel::scheduledReload()
 
   if ( mShouldReloadCurrentFeature )
   {
-    request.setFilterExpression( QStringLiteral( "%1 = %2" ).arg( QgsExpression::quotedColumnRef( mIdentifierField ), QgsExpression::quotedValue( mExtraIdentifierValue ) ) );
+    QStringList conditions;
+    for ( int i = 0; i < mIdentifierFields.count(); i++ )
+    {
+      if ( i >= mExtraIdentifierValues.count() )
+      {
+        conditions << QgsExpression::createFieldEqualityExpression( mIdentifierFields.at( i ), QVariant() );
+      }
+      else
+      {
+        conditions << QgsExpression::createFieldEqualityExpression( mIdentifierFields.at( i ), mExtraIdentifierValues.at( i ) );
+      }
+    }
+    request.setFilterExpression( conditions.join( QStringLiteral( " AND " ) ) );
   }
   else
   {
@@ -350,13 +383,14 @@ void QgsFeatureFilterModel::scheduledReload()
   QSet<QString> attributes;
   if ( request.filterExpression() )
     attributes = request.filterExpression()->referencedColumns();
-  attributes << mIdentifierField;
+  for ( const QString &fieldName : qgis::as_const( mIdentifierFields ) )
+    attributes << fieldName;
   request.setSubsetOfAttributes( attributes, mSourceLayer->fields() );
   request.setFlags( QgsFeatureRequest::NoGeometry );
 
   request.setLimit( QgsSettings().value( QStringLiteral( "maxEntriesRelationWidget" ), 100, QgsSettings::Gui ).toInt() );
 
-  mGatherer = new QgsFieldExpressionValuesGatherer( mSourceLayer, mDisplayExpression, mIdentifierField, request );
+  mGatherer = new QgsFieldExpressionValuesGatherer( mSourceLayer, mDisplayExpression, mIdentifierFields, request );
   mGatherer->setData( mShouldReloadCurrentFeature );
 
   connect( mGatherer, &QgsFieldExpressionValuesGatherer::collectedValues, this, &QgsFeatureFilterModel::updateCompleter );
@@ -393,7 +427,7 @@ QSet<QString> QgsFeatureFilterModel::requestedAttributes() const
   return requestedAttrs;
 }
 
-void QgsFeatureFilterModel::setExtraIdentifierValueIndex( int index, bool force )
+void QgsFeatureFilterModel::setExtraIdentifierValuesIndex( int index, bool force )
 {
   if ( mExtraIdentifierValueIndex == index && !force )
     return;
@@ -408,18 +442,16 @@ void QgsFeatureFilterModel::reloadCurrentFeature()
   mReloadTimer.start();
 }
 
-void QgsFeatureFilterModel::setExtraIdentifierValueUnguarded( const QVariant &extraIdentifierValue )
+void QgsFeatureFilterModel::setExtraIdentifierValuesUnguarded( const QVariantList &extraIdentifierValues )
 {
   const QVector<Entry> entries = mEntries;
 
   int index = 0;
   for ( const Entry &entry : entries )
   {
-    if ( entry.identifierValue == extraIdentifierValue
+    if ( entry.identifierValues == extraIdentifierValues )
-         && entry.identifierValue.isNull() == extraIdentifierValue.isNull()
-         && entry.identifierValue.isValid() == extraIdentifierValue.isValid() )
     {
-      setExtraIdentifierValueIndex( index );
+      setExtraIdentifierValuesIndex( index );
       break;
     }
 
@@ -430,18 +462,37 @@ void QgsFeatureFilterModel::setExtraIdentifierValueUnguarded( const QVariant &ex
   if ( mExtraIdentifierValueIndex != index )
   {
     beginInsertRows( QModelIndex(), 0, 0 );
-    if ( extraIdentifierValue.isNull() )
+    if ( extraIdentifierValues.isEmpty() )
-      mEntries.prepend( Entry( QVariant( QVariant::Int ), QgsApplication::nullRepresentation( ), QgsFeature() ) );
+    {
+      mEntries.prepend( nullEntry() );
+    }
     else
-      mEntries.prepend( Entry( extraIdentifierValue, QStringLiteral( "(%1)" ).arg( extraIdentifierValue.toString() ), QgsFeature() ) );
+    {
+      QStringList values;
+      for ( const QVariant &v : qgis::as_const( extraIdentifierValues ) )
+        values << QStringLiteral( "(%1)" ).arg( v.toString() );
+
+      mEntries.prepend( Entry( extraIdentifierValues, values.join( QStringLiteral( " " ) ), QgsFeature() ) );
+    }
     endInsertRows();
 
-    setExtraIdentifierValueIndex( 0, true );
+    setExtraIdentifierValuesIndex( 0, true );
 
     reloadCurrentFeature();
   }
 }
 
+QgsFeatureFilterModel::Entry QgsFeatureFilterModel::nullEntry()
+{
+  QVariantList nullAttributes;
+  for ( const QString &fieldName : mIdentifierFields )
+  {
+    int idx = mSourceLayer->fields().indexOf( fieldName );
+    nullAttributes << QVariant( mSourceLayer->fields().at( idx ).type() );
+  }
+  return Entry( nullAttributes, QgsApplication::nullRepresentation(), QgsFeature() );
+}
+
 QgsConditionalStyle QgsFeatureFilterModel::featureStyle( const QgsFeature &feature ) const
 {
   if ( !mSourceLayer )
@@ -505,18 +556,24 @@ int QgsFeatureFilterModel::extraIdentifierValueIndex() const
   return mExtraIdentifierValueIndex;
 }
 
-QString QgsFeatureFilterModel::identifierField() const
+QStringList QgsFeatureFilterModel::identifierFields() const
 {
-  return mIdentifierField;
+  return mIdentifierFields;
 }
 
 void QgsFeatureFilterModel::setIdentifierField( const QString &identifierField )
 {
-  if ( mIdentifierField == identifierField )
+  setIdentifierFields( QStringList() << identifierField );
+}
+
+void QgsFeatureFilterModel::setIdentifierFields( const QStringList &identifierFields )
+{
+  if ( mIdentifierFields == identifierFields )
     return;
 
-  mIdentifierField = identifierField;
+  mIdentifierFields = identifierFields;
   emit identifierFieldChanged();
+  setExtraIdentifierValues( QVariantList() );
 }
 
 void QgsFeatureFilterModel::reload()
@@ -526,12 +583,25 @@ void QgsFeatureFilterModel::reload()
 
 QVariant QgsFeatureFilterModel::extraIdentifierValue() const
 {
-  return mExtraIdentifierValue;
+  if ( mExtraIdentifierValues.isEmpty() )
+    return QVariant();
+  else
+    return  mExtraIdentifierValues.at( 0 );
+}
+
+QVariantList QgsFeatureFilterModel::extraIdentifierValues() const
+{
+  return mExtraIdentifierValues;
 }
 
 void QgsFeatureFilterModel::setExtraIdentifierValue( const QVariant &extraIdentifierValue )
 {
-  if ( qgsVariantEqual( extraIdentifierValue, mExtraIdentifierValue ) && mExtraIdentifierValue.isValid() )
+  setExtraIdentifierValues( QVariantList() << extraIdentifierValue );
+}
+
+void QgsFeatureFilterModel::setExtraIdentifierValues( const QVariantList &extraIdentifierValues )
+{
+  if ( extraIdentifierValues == mExtraIdentifierValues && !mExtraIdentifierValues.isEmpty() )
     return;
 
   if ( mIsSettingExtraIdentifierValue )
@@ -539,9 +609,9 @@ void QgsFeatureFilterModel::setExtraIdentifierValue( const QVariant &extraIdenti
 
   mIsSettingExtraIdentifierValue = true;
 
-  mExtraIdentifierValue = extraIdentifierValue;
+  mExtraIdentifierValues = extraIdentifierValues;
 
-  setExtraIdentifierValueUnguarded( extraIdentifierValue );
+  setExtraIdentifierValuesUnguarded( extraIdentifierValues );
 
   mIsSettingExtraIdentifierValue = false;
 

src/core/qgsfeaturefiltermodel.h

@@ -1,6 +1,5 @@
 /***************************************************************************
   qgsfeaturefiltermodel.h - QgsFeatureFilterModel
-
  ---------------------
  begin                : 10.3.2017
  copyright            : (C) 2017 by Matthias Kuhn
@@ -61,7 +60,8 @@ class CORE_EXPORT QgsFeatureFilterModel : public QAbstractItemModel
      */
     enum Role
     {
-      IdentifierValueRole = Qt::UserRole, //!< Used to retrieve the identifierValue (primary key) of a feature.
+      IdentifierValueRole = Qt::UserRole, //!< \deprecated Use IdentifierValuesRole instead
+      IdentifierValuesRole, //!< Used to retrieve the identifierValues (primary keys) of a feature.
       ValueRole //!< Used to retrieve the displayExpression of a feature.
     };
 
@@ -137,26 +137,59 @@ class CORE_EXPORT QgsFeatureFilterModel : public QAbstractItemModel
     /**
      * The identifier field should be a unique field that can be used to identify individual features.
      * It is normally set to the primary key of the layer.
+     * If there are several identifier fields defined, the behavior is not guaranteed
+     * \deprecated since QGIS 3.10 use identifierFields instead
      */
-    QString identifierField() const;
+    Q_DECL_DEPRECATED QString identifierField() const;
 
     /**
      * The identifier field should be a unique field that can be used to identify individual features.
      * It is normally set to the primary key of the layer.
+     * \since QGIS 3.10
      */
-    void setIdentifierField( const QString &identifierField );
+    QStringList identifierFields() const;
+
+    /**
+     * The identifier field should be a unique field that can be used to identify individual features.
+     * It is normally set to the primary key of the layer.
+     * \deprecated since QGIS 3.10
+     */
+    Q_DECL_DEPRECATED void setIdentifierField( const QString &identifierField );
+
+    /**
+     * The identifier field should be a unique field that can be used to identify individual features.
+     * It is normally set to the primary key of the layer.
+     * \since QGIS 3.10
+     */
+    void setIdentifierFields( const QStringList &identifierFields );
 
     /**
      * Allows specifying one value that does not need to match the filter criteria but will
      * still be available in the model.
+     * \deprecated since QGIS 3.10
      */
-    QVariant extraIdentifierValue() const;
+    Q_DECL_DEPRECATED QVariant extraIdentifierValue() const;
 
     /**
      * Allows specifying one value that does not need to match the filter criteria but will
      * still be available in the model.
+     * \since QGIS 3.10
      */
-    void setExtraIdentifierValue( const QVariant &extraIdentifierValue );
+    QVariantList extraIdentifierValues() const;
+
+    /**
+     * Allows specifying one value that does not need to match the filter criteria but will
+     * still be available in the model.
+     * \deprecated since QGIS 3.10
+     */
+    Q_DECL_DEPRECATED void setExtraIdentifierValue( const QVariant &extraIdentifierValue );
+
+    /**
+     * Allows specifying one value that does not need to match the filter criteria but will
+     * still be available in the model.
+     * \since QGIS 3.10
+     */
+    void setExtraIdentifierValues( const QVariantList &extraIdentifierValues );
 
     /**
      * The index at which the extra identifier value is available within the model.
@@ -260,27 +293,28 @@ class CORE_EXPORT QgsFeatureFilterModel : public QAbstractItemModel
 
   private:
     QSet<QString> requestedAttributes() const;
-    void setExtraIdentifierValueIndex( int index, bool force = false );
+    void setExtraIdentifierValuesIndex( int index, bool force = false );
     void setExtraValueDoesNotExist( bool extraValueDoesNotExist );
     void reload();
     void reloadCurrentFeature();
-    void setExtraIdentifierValueUnguarded( const QVariant &extraIdentifierValue );
+    void setExtraIdentifierValuesUnguarded( const QVariantList &extraIdentifierValues );
     struct Entry
     {
       Entry() = default;
 
-      Entry( const QVariant &_identifierValue, const QString &_value, const QgsFeature &_feature )
+      Entry( const QVariantList &_identifierValues, const QString &_value, const QgsFeature &_feature )
-        : identifierValue( _identifierValue )
+        : identifierValues( _identifierValues )
         , value( _value )
         , feature( _feature )
       {}
 
-      QVariant identifierValue;
+      QVariantList identifierValues;
       QString value;
       QgsFeature feature;
 
       bool operator()( const Entry &lhs, const Entry &rhs ) const;
     };
+    Entry nullEntry();
 
     QgsConditionalStyle featureStyle( const QgsFeature &feature ) const;
 
@@ -299,9 +333,8 @@ class CORE_EXPORT QgsFeatureFilterModel : public QAbstractItemModel
     bool mAllowNull = false;
     bool mIsSettingExtraIdentifierValue = false;
 
-    QString mIdentifierField;
+    QStringList mIdentifierFields;
-
+    QVariantList mExtraIdentifierValues;
-    QVariant mExtraIdentifierValue;
 
     int mExtraIdentifierValueIndex = -1;
 

src/core/qgsfeaturefiltermodel_p.h

@@ -1,6 +1,5 @@
 /***************************************************************************
   qgsfeaturefiltermodel_p - QgsFieldExpressionValuesGatherer
-
  ---------------------
  begin                : 10.3.2017
  copyright            : (C) 2017 by Matthias Kuhn
@@ -37,11 +36,14 @@ class QgsFieldExpressionValuesGatherer: public QThread
     Q_OBJECT
 
   public:
-    QgsFieldExpressionValuesGatherer( QgsVectorLayer *layer, const QString &displayExpression, const QString &identifierField, const QgsFeatureRequest &request = QgsFeatureRequest() )
+    QgsFieldExpressionValuesGatherer( QgsVectorLayer *layer,
+                                      const QString &displayExpression,
+                                      const QStringList &identifierFields,
+                                      const QgsFeatureRequest &request = QgsFeatureRequest() )
       : mSource( new QgsVectorLayerFeatureSource( layer ) )
       , mDisplayExpression( displayExpression )
       , mRequest( request )
-      , mIdentifierField( identifierField )
+      , mIdentifierFields( identifierFields )
     {
     }
 
@@ -54,12 +56,17 @@ class QgsFieldExpressionValuesGatherer: public QThread
       mDisplayExpression.prepare( &mExpressionContext );
 
       QgsFeature feat;
-      const int attribute = mSource->fields().indexOf( mIdentifierField );
+      QList<int> attributeIndexes;
+      for ( const QString &fieldName : qgis::as_const( mIdentifierFields ) )
+        attributeIndexes << mSource->fields().indexOf( fieldName );
 
       while ( mIterator.nextFeature( feat ) )
       {
         mExpressionContext.setFeature( feat );
-        mEntries.append( QgsFeatureFilterModel::Entry( feat.attribute( attribute ), mDisplayExpression.evaluate( &mExpressionContext ).toString(), feat ) );
+        QVariantList attributes;
+        for ( const int idx : attributeIndexes )
+          attributes << feat.attribute( idx );
+        mEntries.append( QgsFeatureFilterModel::Entry( attributes, mDisplayExpression.evaluate( &mExpressionContext ).toString(), feat ) );
 
         if ( mWasCanceled )
           return;
@@ -120,7 +127,7 @@ class QgsFieldExpressionValuesGatherer: public QThread
     QgsFeatureIterator mIterator;
     bool mWasCanceled = false;
     QVector<QgsFeatureFilterModel::Entry> mEntries;
-    QString mIdentifierField;
+    QStringList mIdentifierFields;
     QVariant mData;
 };
 

src/gui/qgsfeaturelistcombobox.cpp

@@ -1,6 +1,5 @@
 /***************************************************************************
-  qgsfieldlistcombobox.cpp - QgsFieldListComboBox
+  qgsfeaturelistcombobox.cpp - QgsFeatureListComboBox
-
  ---------------------
  begin                : 10.3.2017
  copyright            : (C) 2017 by Matthias Kuhn
@@ -75,6 +74,17 @@ void QgsFeatureListComboBox::setSourceLayer( QgsVectorLayer *sourceLayer )
   mModel->setSourceLayer( sourceLayer );
 }
 
+void QgsFeatureListComboBox::setCurrentFeature( const QgsFeature &feature )
+{
+  QVariantList values;
+  const QStringList fields = mModel->identifierFields();
+  for ( const QString &field : fields )
+  {
+    values << feature.attribute( field );
+  }
+  setCurrentIndex( findData( values, QgsFeatureFilterModel::Role::IdentifierValueRole ) );
+}
+
 QString QgsFeatureListComboBox::displayExpression() const
 {
   return mModel->displayExpression();
@@ -115,7 +125,7 @@ void QgsFeatureListComboBox::onCurrentIndexChanged( int i )
   if ( !mHasStoredEditState )
     mIsCurrentlyEdited = false;
   QModelIndex modelIndex = mModel->index( i, 0, QModelIndex() );
-  mModel->setExtraIdentifierValue( mModel->data( modelIndex, QgsFeatureFilterModel::IdentifierValueRole ) );
+  mModel->setExtraIdentifierValues( mModel->data( modelIndex, QgsFeatureFilterModel::IdentifierValuesRole ).toList() );
   mLineEdit->setText( mModel->data( modelIndex, QgsFeatureFilterModel::ValueRole ).toString() );
   mLineEdit->setFont( mModel->data( modelIndex, Qt::FontRole ).value<QFont>() );
   QPalette palette = mLineEdit->palette();
@@ -125,7 +135,7 @@ void QgsFeatureListComboBox::onCurrentIndexChanged( int i )
 
 void QgsFeatureListComboBox::onActivated( QModelIndex modelIndex )
 {
-  setIdentifierValue( mModel->data( modelIndex, QgsFeatureFilterModel::IdentifierValueRole ) );
+  setIdentifierValues( mModel->data( modelIndex, QgsFeatureFilterModel::IdentifierValuesRole ).toList() );
   mLineEdit->setText( mModel->data( modelIndex, QgsFeatureFilterModel::ValueRole ).toString() );
 }
 
@@ -175,12 +185,26 @@ void QgsFeatureListComboBox::onDataChanged( const QModelIndex &topLeft, const QM
 
 QString QgsFeatureListComboBox::identifierField() const
 {
-  return mModel->identifierField();
+  QStringList list = mModel->identifierFields();
+  if ( list.isEmpty() )
+    return QString();
+  else
+    return list.at( 0 );
+}
+
+QStringList QgsFeatureListComboBox::identifierFields() const
+{
+  return mModel->identifierFields();
 }
 
 void QgsFeatureListComboBox::setIdentifierField( const QString &identifierField )
 {
-  mModel->setIdentifierField( identifierField );
+  mModel->setIdentifierFields( QStringList() << identifierField );
+}
+
+void QgsFeatureListComboBox::setIdentifierFields( const QStringList &identifierFields )
+{
+  mModel->setIdentifierFields( identifierFields );
 }
 
 QModelIndex QgsFeatureListComboBox::currentModelIndex() const
@@ -219,17 +243,46 @@ QVariant QgsFeatureListComboBox::identifierValue() const
   return mModel->extraIdentifierValue();
 }
 
+QVariantList QgsFeatureListComboBox::identifierValues() const
+{
+  return mModel->extraIdentifierValues();
+}
+
 void QgsFeatureListComboBox::setIdentifierValue( const QVariant &identifierValue )
 {
-  mModel->setExtraIdentifierValue( identifierValue );
+  setIdentifierValues( QVariantList() << identifierValue );
+}
+
+void QgsFeatureListComboBox::setIdentifierValues( const QVariantList &identifierValues )
+{
+  mModel->setExtraIdentifierValues( identifierValues );
 }
 
 QgsFeatureRequest QgsFeatureListComboBox::currentFeatureRequest() const
 {
-  if ( mModel->extraIdentifierValue().isNull() )
+  if ( mModel->extraIdentifierValues().isEmpty() )
+  {
     return QgsFeatureRequest().setFilterFids( QgsFeatureIds() ); // NULL: Return a request that's guaranteed to not return anything
+  }
   else
-    return QgsFeatureRequest().setFilterExpression( QStringLiteral( "%1 = %2" ).arg( QgsExpression::quotedColumnRef( mModel->identifierField() ), QgsExpression::quotedValue( mModel->extraIdentifierValue() ) ) );
+  {
+    QStringList filtersAttrs;
+    const QStringList identifierFields = mModel->identifierFields();
+    const QVariantList values = mModel->extraIdentifierValues();
+    for ( int i = 0; i < identifierFields.count(); i++ )
+    {
+      if ( i >= values.count() )
+      {
+        filtersAttrs << QgsExpression::createFieldEqualityExpression( identifierFields.at( i ), QVariant() );
+      }
+      else
+      {
+        filtersAttrs << QgsExpression::createFieldEqualityExpression( identifierFields.at( i ), values.at( i ) );
+      }
+    }
+    const QString expression = filtersAttrs.join( QStringLiteral( " AND " ) );
+    return QgsFeatureRequest().setFilterExpression( expression );
+  }
 }
 
 QString QgsFeatureListComboBox::filterExpression() const

src/gui/qgsfeaturelistcombobox.h

@@ -1,6 +1,5 @@
 /***************************************************************************
-  qgsfieldlistcombobox.h - QgsFieldListComboBox
+  qgsfeaturelistcombobox.h - QgsFeatureListComboBox
-
  ---------------------
  begin                : 10.3.2017
  copyright            : (C) 2017 by Matthias Kuhn
@@ -27,6 +26,7 @@ class QgsFeatureFilterModel;
 class QgsAnimatedIcon;
 class QgsFilterLineEdit;
 
+
 /**
  * \ingroup gui
  * This offers a combobox with autocompleter that allows selecting features from a layer.
@@ -44,6 +44,7 @@ class GUI_EXPORT QgsFeatureListComboBox : public QComboBox
     Q_PROPERTY( QString displayExpression READ displayExpression WRITE setDisplayExpression NOTIFY displayExpressionChanged )
     Q_PROPERTY( QString filterExpression READ filterExpression WRITE setFilterExpression NOTIFY filterExpressionChanged )
     Q_PROPERTY( QVariant identifierValue READ identifierValue WRITE setIdentifierValue NOTIFY identifierValueChanged )
+    Q_PROPERTY( QVariantList identifierValues READ identifierValues WRITE setIdentifierValues NOTIFY identifierValueChanged )
     Q_PROPERTY( QString identifierField READ identifierField WRITE setIdentifierField NOTIFY identifierFieldChanged )
     Q_PROPERTY( bool allowNull READ allowNull WRITE setAllowNull NOTIFY allowNullChanged )
 
@@ -64,6 +65,12 @@ class GUI_EXPORT QgsFeatureListComboBox : public QComboBox
      */
     void setSourceLayer( QgsVectorLayer *sourceLayer );
 
+    /**
+     * Sets the current index by using the given feature
+     * \since QGIS 3.10
+     */
+    void setCurrentFeature( const QgsFeature &feature );
+
     /**
      * The display expression will be used to display features as well as
      * the value to match the typed text against.
@@ -101,14 +108,31 @@ class GUI_EXPORT QgsFeatureListComboBox : public QComboBox
     /**
      * The identifier value of the currently selected feature. A value from the
      * identifierField.
+     * \deprecated since QGIS 3.10
      */
-    QVariant identifierValue() const;
+    Q_DECL_DEPRECATED QVariant identifierValue() const SIP_DEPRECATED;
+
+    /**
+     * The identifier values of the currently selected feature. A value from the
+     * identifierField.
+     * \since QGIS 3.10
+     */
+    QVariantList identifierValues() const;
+
 
     /**
      * The identifier value of the currently selected feature. A value from the
      * identifierField.
+     * \deprecated since QGIS 3.10 use setIdentifierValues
      */
-    void setIdentifierValue( const QVariant &identifierValue );
+    Q_DECL_DEPRECATED void setIdentifierValue( const QVariant &identifierValue ) SIP_DEPRECATED;
+
+    /**
+     * The identifier values of the currently selected feature. A value from the
+     * identifierFields.
+     * \since QGIS 3.10
+     */
+    void setIdentifierValues( const QVariantList &identifierValues );
 
     /**
      * Shorthand for getting a feature request to query the currently selected
@@ -129,14 +153,30 @@ class GUI_EXPORT QgsFeatureListComboBox : public QComboBox
     /**
      * Field name that will be used to uniquely identify the current feature.
      * Normally the primary key of the layer.
+     * \deprecated since QGIS 3.10
      */
-    QString identifierField() const;
+    Q_DECL_DEPRECATED QString identifierField() const SIP_DEPRECATED;
 
     /**
      * Field name that will be used to uniquely identify the current feature.
      * Normally the primary key of the layer.
+     * \since QGIS 3.10
      */
-    void setIdentifierField( const QString &identifierField );
+    QStringList identifierFields() const;
+
+    /**
+     * Field name that will be used to uniquely identify the current feature.
+     * Normally the primary key of the layer.
+     * \deprecated since QGIS 3.10
+     */
+    Q_DECL_DEPRECATED void setIdentifierField( const QString &identifierField ) SIP_DEPRECATED;
+
+    /**
+     * Field name that will be used to uniquely identify the current feature.
+     * Normally the primary key of the layer.
+     * \since QGIS 3.10
+     */
+    void setIdentifierFields( const QStringList &identifierFields );
 
     /**
      * The index of the currently selected item.
@@ -225,4 +265,6 @@ class GUI_EXPORT QgsFeatureListComboBox : public QComboBox
     friend class TestQgsFeatureListComboBox;
 };
 
+
+
 #endif // QGSFIELDLISTCOMBOBOX_H