diff --git a/doc/api_break.dox b/doc/api_break.dox
index a7d453bb9a3..93cbe3ea41d 100644
--- a/doc/api_break.dox
+++ b/doc/api_break.dox
@@ -33,6 +33,14 @@ attributeIndexes(), pkAttributeIndexes(), isSaveAndLoadStyleToDBSupported()</li>
 </li>
 </ul>
 
+\subsection qgis_api_break_3_0_DataProviders Data Providers
+
+<ul>
+<li>QgsVectorDataProvider::fields() now returns a copy, rather than a const reference. Since QgsFields
+objects are implicitly shared, returning a copy helps simplify and make code more robust. This change
+only affects third party c++ providers, and does not affect PyQGIS scripts.</li>
+</ul>
+
 \subsection qgis_api_break_3_0_QgsVectorFileWriter QgsVectorFileWriter
 
 <ul>
diff --git a/python/core/qgsvectordataprovider.sip b/python/core/qgsvectordataprovider.sip
index 525c9e4a51e..8d74077e697 100644
--- a/python/core/qgsvectordataprovider.sip
+++ b/python/core/qgsvectordataprovider.sip
@@ -116,11 +116,9 @@ class QgsVectorDataProvider : QgsDataProvider
     virtual long featureCount() const = 0;
 
     /**
-     * Return a map of indexes with field names for this layer
-     * @return map of fields
-     * @see QgsFields
+     * Returns the fields associated with this data provider.
      */
-    virtual const QgsFields &fields() const = 0;
+    virtual QgsFields fields() const = 0;
 
     /**
      * Return a short comment for the data that this provider is
diff --git a/src/analysis/vector/qgszonalstatistics.cpp b/src/analysis/vector/qgszonalstatistics.cpp
index 289a156e21b..f9357ebf2b8 100644
--- a/src/analysis/vector/qgszonalstatistics.cpp
+++ b/src/analysis/vector/qgszonalstatistics.cpp
@@ -533,13 +533,13 @@ QString QgsZonalStatistics::getUniqueFieldName( const QString& fieldName )
     return fieldName;
   }
 
-  const QgsFields& providerFields = dp->fields();
+  QgsFields providerFields = dp->fields();
   QString shortName = fieldName.mid( 0, 10 );
 
   bool found = false;
   for ( int idx = 0; idx < providerFields.count(); ++idx )
   {
-    if ( shortName == providerFields[idx].name() )
+    if ( shortName == providerFields.at( idx ).name() )
     {
       found = true;
       break;
@@ -559,7 +559,7 @@ QString QgsZonalStatistics::getUniqueFieldName( const QString& fieldName )
     found = false;
     for ( int idx = 0; idx < providerFields.count(); ++idx )
     {
-      if ( shortName == providerFields[idx].name() )
+      if ( shortName == providerFields.at( idx ).name() )
       {
         n += 1;
         if ( n < 9 )
diff --git a/src/core/qgsvectordataprovider.cpp b/src/core/qgsvectordataprovider.cpp
index 92e3c606d9c..c9186b24de6 100644
--- a/src/core/qgsvectordataprovider.cpp
+++ b/src/core/qgsvectordataprovider.cpp
@@ -266,10 +266,10 @@ QMap<QString, int> QgsVectorDataProvider::fieldNameMap() const
 {
   QMap<QString, int> resultMap;
 
-  const QgsFields& theFields = fields();
+  QgsFields theFields = fields();
   for ( int i = 0; i < theFields.count(); ++i )
   {
-    resultMap.insert( theFields[i].name(), i );
+    resultMap.insert( theFields.at( i ).name(), i );
   }
 
   return resultMap;
@@ -431,20 +431,20 @@ void QgsVectorDataProvider::fillMinMaxCache() const
   if ( !mCacheMinMaxDirty )
     return;
 
-  const QgsFields& flds = fields();
+  QgsFields flds = fields();
   for ( int i = 0; i < flds.count(); ++i )
   {
-    if ( flds[i].type() == QVariant::Int )
+    if ( flds.at( i ).type() == QVariant::Int )
     {
       mCacheMinValues[i] = QVariant( INT_MAX );
       mCacheMaxValues[i] = QVariant( INT_MIN );
     }
-    else if ( flds[i].type() == QVariant::LongLong )
+    else if ( flds.at( i ).type() == QVariant::LongLong )
     {
       mCacheMinValues[i] = QVariant( std::numeric_limits<qlonglong>::max() );
       mCacheMaxValues[i] = QVariant( std::numeric_limits<qlonglong>::min() );
     }
-    else if ( flds[i].type() == QVariant::Double )
+    else if ( flds.at( i ).type() == QVariant::Double )
     {
       mCacheMinValues[i] = QVariant( DBL_MAX );
       mCacheMaxValues[i] = QVariant( -DBL_MAX );
@@ -470,7 +470,7 @@ void QgsVectorDataProvider::fillMinMaxCache() const
       if ( varValue.isNull() )
         continue;
 
-      if ( flds[*it].type() == QVariant::Int )
+      if ( flds.at( *it ).type() == QVariant::Int )
       {
         int value = varValue.toInt();
         if ( value < mCacheMinValues[*it].toInt() )
@@ -478,7 +478,7 @@ void QgsVectorDataProvider::fillMinMaxCache() const
         if ( value > mCacheMaxValues[*it].toInt() )
           mCacheMaxValues[*it] = value;
       }
-      else if ( flds[*it].type() == QVariant::LongLong )
+      else if ( flds.at( *it ).type() == QVariant::LongLong )
       {
         qlonglong value = varValue.toLongLong();
         if ( value < mCacheMinValues[*it].toLongLong() )
@@ -486,7 +486,7 @@ void QgsVectorDataProvider::fillMinMaxCache() const
         if ( value > mCacheMaxValues[*it].toLongLong() )
           mCacheMaxValues[*it] = value;
       }
-      else if ( flds[*it].type() == QVariant::Double )
+      else if ( flds.at( *it ).type() == QVariant::Double )
       {
         double value = varValue.toDouble();
         if ( value < mCacheMinValues[*it].toDouble() )
diff --git a/src/core/qgsvectordataprovider.h b/src/core/qgsvectordataprovider.h
index 3af8588fc19..6f7f14155f9 100644
--- a/src/core/qgsvectordataprovider.h
+++ b/src/core/qgsvectordataprovider.h
@@ -166,12 +166,9 @@ class CORE_EXPORT QgsVectorDataProvider : public QgsDataProvider
     virtual long featureCount() const = 0;
 
     /**
-     * Return a map of indexes with field names for this layer
-     * @return map of fields
-     * @see QgsFields
+     * Returns the fields associated with this data provider.
      */
-    // TODO QGIS 3: return by value
-    virtual const QgsFields &fields() const = 0;
+    virtual QgsFields fields() const = 0;
 
     /**
      * Return a short comment for the data that this provider is
diff --git a/src/core/qgsvirtuallayerdefinitionutils.cpp b/src/core/qgsvirtuallayerdefinitionutils.cpp
index d1706ffae6d..a24444a2397 100644
--- a/src/core/qgsvirtuallayerdefinitionutils.cpp
+++ b/src/core/qgsvirtuallayerdefinitionutils.cpp
@@ -27,7 +27,7 @@ QgsVirtualLayerDefinition QgsVirtualLayerDefinitionUtils::fromJoinedLayer( QgsVe
   QStringList columns;
 
   // look for the uid
-  const QgsFields& fields = layer->dataProvider()->fields();
+  QgsFields fields = layer->dataProvider()->fields();
   {
     QgsAttributeList pk = layer->dataProvider()->pkAttributeIndexes();
     if ( pk.size() == 1 )
diff --git a/src/plugins/evis/eventbrowser/evisgenericeventbrowsergui.cpp b/src/plugins/evis/eventbrowser/evisgenericeventbrowsergui.cpp
index 80d3ab3f35c..3cb4c44020d 100644
--- a/src/plugins/evis/eventbrowser/evisgenericeventbrowsergui.cpp
+++ b/src/plugins/evis/eventbrowser/evisgenericeventbrowsergui.cpp
@@ -282,11 +282,11 @@ bool eVisGenericEventBrowserGui::initBrowser()
     return false;
   }
 
-  const QgsFields& myFields = mDataProvider->fields();
+  QgsFields myFields = mDataProvider->fields();
   mIgnoreEvent = true; //Ignore indexChanged event when adding items to combo boxes
   for ( int x = 0; x < myFields.count(); x++ )
   {
-    QString name = myFields[x].name();
+    QString name = myFields.at( x ).name();
     cboxEventImagePathField->addItem( name );
     cboxCompassBearingField->addItem( name );
     cboxCompassOffsetField->addItem( name );
@@ -594,13 +594,13 @@ void eVisGenericEventBrowserGui::loadRecord()
   QString myCompassBearingField = cboxCompassBearingField->currentText();
   QString myCompassOffsetField = cboxCompassOffsetField->currentText();
   QString myEventImagePathField = cboxEventImagePathField->currentText();
-  const QgsFields& myFields = mDataProvider->fields();
+  QgsFields myFields = mDataProvider->fields();
   QgsAttributes myAttrs = myFeature->attributes();
   //loop through the attributes and display their contents
   for ( int i = 0; i < myAttrs.count(); ++i )
   {
     QStringList myValues;
-    QString fieldName = myFields[i].name();
+    QString fieldName = myFields.at( i ).name();
     myValues << fieldName << myAttrs.at( i ).toString();
     QTreeWidgetItem* myItem = new QTreeWidgetItem( myValues );
     if ( fieldName == myEventImagePathField )
@@ -836,7 +836,7 @@ void eVisGenericEventBrowserGui::on_cboxEventImagePathField_currentIndexChanged(
   {
     mConfiguration.setEventImagePathField( cboxEventImagePathField->currentText() );
 
-    const QgsFields& myFields = mDataProvider->fields();
+    QgsFields myFields = mDataProvider->fields();
     QgsFeature* myFeature = featureAtId( mFeatureIds.at( mCurrentFeatureIndex ) );
 
     if ( !myFeature )
@@ -864,7 +864,7 @@ void eVisGenericEventBrowserGui::on_cboxCompassBearingField_currentIndexChanged(
   {
     mConfiguration.setCompassBearingField( cboxCompassBearingField->currentText() );
 
-    const QgsFields& myFields = mDataProvider->fields();
+    QgsFields myFields = mDataProvider->fields();
     QgsFeature* myFeature = featureAtId( mFeatureIds.at( mCurrentFeatureIndex ) );
 
     if ( !myFeature )
@@ -873,7 +873,7 @@ void eVisGenericEventBrowserGui::on_cboxCompassBearingField_currentIndexChanged(
     QgsAttributes myAttrs = myFeature->attributes();
     for ( int i = 0; i < myAttrs.count(); ++i )
     {
-      if ( myFields[i].name() == cboxCompassBearingField->currentText() )
+      if ( myFields.at( i ).name() == cboxCompassBearingField->currentText() )
       {
         mCompassBearing = myAttrs.at( i ).toDouble();
       }
@@ -892,7 +892,7 @@ void eVisGenericEventBrowserGui::on_cboxCompassOffsetField_currentIndexChanged(
   {
     mConfiguration.setCompassOffsetField( cboxCompassOffsetField->currentText() );
 
-    const QgsFields& myFields = mDataProvider->fields();
+    QgsFields myFields = mDataProvider->fields();
     QgsFeature* myFeature = featureAtId( mFeatureIds.at( mCurrentFeatureIndex ) );
 
     if ( !myFeature )
@@ -901,7 +901,7 @@ void eVisGenericEventBrowserGui::on_cboxCompassOffsetField_currentIndexChanged(
     QgsAttributes myAttrs = myFeature->attributes();
     for ( int i = 0; i < myAttrs.count(); ++i )
     {
-      if ( myFields[i].name() == cboxCompassOffsetField->currentText() )
+      if ( myFields.at( i ).name() == cboxCompassOffsetField->currentText() )
       {
         mCompassOffset = myAttrs.at( i ).toDouble();
       }
diff --git a/src/providers/arcgisrest/qgsafsprovider.h b/src/providers/arcgisrest/qgsafsprovider.h
index c239a07f6e8..a9bba23c2bb 100644
--- a/src/providers/arcgisrest/qgsafsprovider.h
+++ b/src/providers/arcgisrest/qgsafsprovider.h
@@ -43,7 +43,7 @@ class QgsAfsProvider : public QgsVectorDataProvider
     QgsFeatureIterator getFeatures( const QgsFeatureRequest& request = QgsFeatureRequest() ) const override;
     QGis::WkbType geometryType() const override { return static_cast<QGis::WkbType>( mGeometryType ); }
     long featureCount() const override { return mObjectIds.size(); }
-    const QgsFields &fields() const override { return mFields; }
+    QgsFields fields() const override { return mFields; }
     /* Read only for the moment
     bool addFeatures( QgsFeatureList &flist ) override{ return false; }
     bool deleteFeatures( const QgsFeatureIds &id ) override{ return false; }
diff --git a/src/providers/db2/qgsdb2provider.cpp b/src/providers/db2/qgsdb2provider.cpp
index 5cb00401a94..1182babfec3 100644
--- a/src/providers/db2/qgsdb2provider.cpp
+++ b/src/providers/db2/qgsdb2provider.cpp
@@ -494,7 +494,7 @@ long QgsDb2Provider::featureCount() const
   }
 }
 
-const QgsFields &QgsDb2Provider::fields() const
+QgsFields QgsDb2Provider::fields() const
 {
   return mAttributeFields;
 }
diff --git a/src/providers/db2/qgsdb2provider.h b/src/providers/db2/qgsdb2provider.h
index dc1f59e98d4..a125fb1d4c1 100644
--- a/src/providers/db2/qgsdb2provider.h
+++ b/src/providers/db2/qgsdb2provider.h
@@ -70,11 +70,8 @@ class QgsDb2Provider : public QgsVectorDataProvider
      */
     void updateStatistics() const;
 
-    /**
-     * Return a map of indexes with field names for this layer.
-     * @return map of fields
-     */
-    virtual const QgsFields &fields() const override;
+
+    virtual QgsFields fields() const override;
 
     virtual QgsCoordinateReferenceSystem crs() const override;
     virtual QgsRectangle extent() const override;
diff --git a/src/providers/delimitedtext/qgsdelimitedtextprovider.cpp b/src/providers/delimitedtext/qgsdelimitedtextprovider.cpp
index 9edf2ed95c0..6c150116b9e 100644
--- a/src/providers/delimitedtext/qgsdelimitedtextprovider.cpp
+++ b/src/providers/delimitedtext/qgsdelimitedtextprovider.cpp
@@ -1135,7 +1135,7 @@ long QgsDelimitedTextProvider::featureCount() const
 }
 
 
-const QgsFields & QgsDelimitedTextProvider::fields() const
+QgsFields QgsDelimitedTextProvider::fields() const
 {
   return attributeFields;
 }
diff --git a/src/providers/delimitedtext/qgsdelimitedtextprovider.h b/src/providers/delimitedtext/qgsdelimitedtextprovider.h
index c2f78daf197..b5b5d7b299a 100644
--- a/src/providers/delimitedtext/qgsdelimitedtextprovider.h
+++ b/src/providers/delimitedtext/qgsdelimitedtextprovider.h
@@ -101,11 +101,7 @@ class QgsDelimitedTextProvider : public QgsVectorDataProvider
      */
     virtual long featureCount() const override;
 
-    /**
-     * Return a map of indexes with field names for this layer
-     * @return map of fields
-     */
-    virtual const QgsFields & fields() const override;
+    virtual QgsFields fields() const override;
 
     /** Returns a bitmask containing the supported capabilities
      * Note, some capabilities may change depending on whether
diff --git a/src/providers/gpx/qgsgpxprovider.cpp b/src/providers/gpx/qgsgpxprovider.cpp
index 9ec41cb8066..08a907a1256 100644
--- a/src/providers/gpx/qgsgpxprovider.cpp
+++ b/src/providers/gpx/qgsgpxprovider.cpp
@@ -171,7 +171,7 @@ long QgsGPXProvider::featureCount() const
 }
 
 
-const QgsFields& QgsGPXProvider::fields() const
+QgsFields QgsGPXProvider::fields() const
 {
   return attributeFields;
 }
diff --git a/src/providers/gpx/qgsgpxprovider.h b/src/providers/gpx/qgsgpxprovider.h
index de97c0d9094..cf31210c771 100644
--- a/src/providers/gpx/qgsgpxprovider.h
+++ b/src/providers/gpx/qgsgpxprovider.h
@@ -69,10 +69,7 @@ class QgsGPXProvider : public QgsVectorDataProvider
      */
     virtual long featureCount() const override;
 
-    /**
-     * Get the field information for the layer
-     */
-    virtual const QgsFields& fields() const override;
+    virtual QgsFields fields() const override;
 
     /**
      * Adds a list of features
diff --git a/src/providers/grass/qgsgrassprovider.cpp b/src/providers/grass/qgsgrassprovider.cpp
index 7c81e0eb1f3..cf122acd3f7 100644
--- a/src/providers/grass/qgsgrassprovider.cpp
+++ b/src/providers/grass/qgsgrassprovider.cpp
@@ -453,7 +453,7 @@ long QgsGrassProvider::featureCount() const
   return mNumberFeatures;
 }
 
-const QgsFields & QgsGrassProvider::fields() const
+QgsFields QgsGrassProvider::fields() const
 {
   if ( isTopoType() )
   {
diff --git a/src/providers/grass/qgsgrassprovider.h b/src/providers/grass/qgsgrassprovider.h
index 92d9ba67220..43f822f486d 100644
--- a/src/providers/grass/qgsgrassprovider.h
+++ b/src/providers/grass/qgsgrassprovider.h
@@ -88,10 +88,7 @@ class GRASS_LIB_EXPORT QgsGrassProvider : public QgsVectorDataProvider
 
     virtual QgsRectangle extent() const override;
 
-    /**
-     * Get the field information for the layer
-     */
-    const QgsFields & fields() const override;
+    QgsFields fields() const override;
 
     // ! Key (category) field index
     int keyField();
diff --git a/src/providers/memory/qgsmemoryprovider.cpp b/src/providers/memory/qgsmemoryprovider.cpp
index 3aefe0d0d58..9fe44ca0697 100644
--- a/src/providers/memory/qgsmemoryprovider.cpp
+++ b/src/providers/memory/qgsmemoryprovider.cpp
@@ -309,7 +309,7 @@ long QgsMemoryProvider::featureCount() const
   return count;
 }
 
-const QgsFields & QgsMemoryProvider::fields() const
+QgsFields QgsMemoryProvider::fields() const
 {
   return mFields;
 }
diff --git a/src/providers/memory/qgsmemoryprovider.h b/src/providers/memory/qgsmemoryprovider.h
index d1512d34440..3cf87f1da94 100644
--- a/src/providers/memory/qgsmemoryprovider.h
+++ b/src/providers/memory/qgsmemoryprovider.h
@@ -61,12 +61,7 @@ class QgsMemoryProvider : public QgsVectorDataProvider
      */
     virtual long featureCount() const override;
 
-    /**
-     * Return a map of indexes with field names for this layer
-     * @return map of fields
-     */
-    virtual const QgsFields & fields() const override;
-
+    virtual QgsFields fields() const override;
 
     /**
       * Adds a list of features
diff --git a/src/providers/mssql/qgsmssqlprovider.cpp b/src/providers/mssql/qgsmssqlprovider.cpp
index 19c9f5a17f4..c4adb30e271 100644
--- a/src/providers/mssql/qgsmssqlprovider.cpp
+++ b/src/providers/mssql/qgsmssqlprovider.cpp
@@ -778,7 +778,7 @@ long QgsMssqlProvider::featureCount() const
   }
 }
 
-const QgsFields & QgsMssqlProvider::fields() const
+QgsFields QgsMssqlProvider::fields() const
 {
   return mAttributeFields;
 }
diff --git a/src/providers/mssql/qgsmssqlprovider.h b/src/providers/mssql/qgsmssqlprovider.h
index ddd53b49828..533d3115d45 100644
--- a/src/providers/mssql/qgsmssqlprovider.h
+++ b/src/providers/mssql/qgsmssqlprovider.h
@@ -93,11 +93,7 @@ class QgsMssqlProvider : public QgsVectorDataProvider
     /** Update the extent, feature count, wkb type and srid for this layer */
     void UpdateStatistics( bool estimate ) const;
 
-    /**
-     * Return a map of indexes with field names for this layer
-     * @return map of fields
-     */
-    virtual const QgsFields & fields() const override;
+    virtual QgsFields fields() const override;
 
     QString subsetString() const override;
 
diff --git a/src/providers/ogr/qgsogrprovider.cpp b/src/providers/ogr/qgsogrprovider.cpp
index 8f074e80425..903cf7a6439 100644
--- a/src/providers/ogr/qgsogrprovider.cpp
+++ b/src/providers/ogr/qgsogrprovider.cpp
@@ -1035,7 +1035,7 @@ long QgsOgrProvider::featureCount() const
 }
 
 
-const QgsFields & QgsOgrProvider::fields() const
+QgsFields QgsOgrProvider::fields() const
 {
   return mAttributeFields;
 }
@@ -1666,7 +1666,7 @@ bool QgsOgrProvider::createAttributeIndex( int field )
   QByteArray quotedLayerName = quotedIdentifier( OGR_FD_GetName( OGR_L_GetLayerDefn( ogrOrigLayer ) ) );
   QByteArray dropSql = "DROP INDEX ON " + quotedLayerName;
   OGR_DS_ExecuteSQL( ogrDataSource, dropSql.constData(), OGR_L_GetSpatialFilter( ogrOrigLayer ), nullptr );
-  QByteArray createSql = "CREATE INDEX ON " + quotedLayerName + " USING " + mEncoding->fromUnicode( fields()[field].name() );
+  QByteArray createSql = "CREATE INDEX ON " + quotedLayerName + " USING " + mEncoding->fromUnicode( fields().at( field ).name() );
   OGR_DS_ExecuteSQL( ogrDataSource, createSql.constData(), OGR_L_GetSpatialFilter( ogrOrigLayer ), nullptr );
 
   QFileInfo fi( mFilePath );     // to get the base name
diff --git a/src/providers/ogr/qgsogrprovider.h b/src/providers/ogr/qgsogrprovider.h
index 54bdacaa90f..44b4ad1689c 100644
--- a/src/providers/ogr/qgsogrprovider.h
+++ b/src/providers/ogr/qgsogrprovider.h
@@ -117,10 +117,7 @@ class QgsOgrProvider : public QgsVectorDataProvider
      */
     virtual long featureCount() const override;
 
-    /**
-     * Get the field information for the layer
-     */
-    virtual const QgsFields & fields() const override;
+    virtual QgsFields fields() const override;
 
     virtual QgsRectangle extent() const override;
 
diff --git a/src/providers/postgres/qgspostgresprovider.cpp b/src/providers/postgres/qgspostgresprovider.cpp
index 272984ba094..0f7be8c9668 100644
--- a/src/providers/postgres/qgspostgresprovider.cpp
+++ b/src/providers/postgres/qgspostgresprovider.cpp
@@ -703,7 +703,7 @@ const QgsField &QgsPostgresProvider::field( int index ) const
   return mAttributeFields[index];
 }
 
-const QgsFields & QgsPostgresProvider::fields() const
+QgsFields QgsPostgresProvider::fields() const
 {
   return mAttributeFields;
 }
diff --git a/src/providers/postgres/qgspostgresprovider.h b/src/providers/postgres/qgspostgresprovider.h
index 83c954269fa..3b640198769 100644
--- a/src/providers/postgres/qgspostgresprovider.h
+++ b/src/providers/postgres/qgspostgresprovider.h
@@ -133,11 +133,7 @@ class QgsPostgresProvider : public QgsVectorDataProvider
      */
     void determinePrimaryKeyFromUriKeyColumn();
 
-    /**
-     * Get the field information for the layer
-     * @return vector of QgsField objects
-     */
-    const QgsFields &fields() const override;
+    QgsFields fields() const override;
 
     /**
      * Return a short comment for the data that this provider is
diff --git a/src/providers/spatialite/qgsspatialiteprovider.cpp b/src/providers/spatialite/qgsspatialiteprovider.cpp
index 71b21b67291..b4fc2980adc 100644
--- a/src/providers/spatialite/qgsspatialiteprovider.cpp
+++ b/src/providers/spatialite/qgsspatialiteprovider.cpp
@@ -3365,7 +3365,7 @@ QString QgsSpatiaLiteProvider::description() const
   return SPATIALITE_DESCRIPTION;
 }                               //  QgsSpatiaLiteProvider::description()
 
-const QgsFields& QgsSpatiaLiteProvider::fields() const
+QgsFields QgsSpatiaLiteProvider::fields() const
 {
   return mAttributeFields;
 }
diff --git a/src/providers/spatialite/qgsspatialiteprovider.h b/src/providers/spatialite/qgsspatialiteprovider.h
index d8a471445fa..09c5ce4190d 100644
--- a/src/providers/spatialite/qgsspatialiteprovider.h
+++ b/src/providers/spatialite/qgsspatialiteprovider.h
@@ -124,11 +124,7 @@ class QgsSpatiaLiteProvider: public QgsVectorDataProvider
      */
     virtual void updateExtents() override;
 
-    /**
-      * Get the field information for the layer
-      * @return vector of QgsField objects
-      */
-    const QgsFields & fields() const override;
+    QgsFields fields() const override;
 
     QVariant minimumValue( int index ) const override;
     QVariant maximumValue( int index ) const override;
diff --git a/src/providers/virtual/qgsvirtuallayerprovider.cpp b/src/providers/virtual/qgsvirtuallayerprovider.cpp
index ab096d80adb..f683cbb10b9 100644
--- a/src/providers/virtual/qgsvirtuallayerprovider.cpp
+++ b/src/providers/virtual/qgsvirtuallayerprovider.cpp
@@ -553,7 +553,7 @@ void QgsVirtualLayerProvider::invalidateStatistics()
   mCachedStatistics = false;
 }
 
-const QgsFields & QgsVirtualLayerProvider::fields() const
+QgsFields QgsVirtualLayerProvider::fields() const
 {
   return mDefinition.fields();
 }
diff --git a/src/providers/virtual/qgsvirtuallayerprovider.h b/src/providers/virtual/qgsvirtuallayerprovider.h
index 449ef470209..00cd5f5b894 100644
--- a/src/providers/virtual/qgsvirtuallayerprovider.h
+++ b/src/providers/virtual/qgsvirtuallayerprovider.h
@@ -63,11 +63,7 @@ class QgsVirtualLayerProvider: public QgsVectorDataProvider
 
     virtual bool supportsSubsetString() const override { return true; }
 
-    /**
-     * Get the field information for the layer
-     * @return vector of QgsField objects
-     */
-    const QgsFields & fields() const override;
+    QgsFields fields() const override;
 
     bool isValid() const override;
 
diff --git a/src/providers/wfs/qgswfsfeatureiterator.cpp b/src/providers/wfs/qgswfsfeatureiterator.cpp
index f208c92ac91..f14b1b58a2b 100644
--- a/src/providers/wfs/qgswfsfeatureiterator.cpp
+++ b/src/providers/wfs/qgswfsfeatureiterator.cpp
@@ -792,7 +792,7 @@ QgsWFSFeatureIterator::QgsWFSFeatureIterator( QgsWFSFeatureSource* source,
 
   if ( mRequest.flags() & QgsFeatureRequest::SubsetOfAttributes )
   {
-    const QgsFields & dataProviderFields = mShared->mCacheDataProvider->fields();
+    QgsFields dataProviderFields = mShared->mCacheDataProvider->fields();
     QgsAttributeList cacheSubSet;
     Q_FOREACH ( int i, mRequest.subsetOfAttributes() )
     {
diff --git a/src/providers/wfs/qgswfsprovider.cpp b/src/providers/wfs/qgswfsprovider.cpp
index 8069fd09eb0..95b0e42473a 100644
--- a/src/providers/wfs/qgswfsprovider.cpp
+++ b/src/providers/wfs/qgswfsprovider.cpp
@@ -724,7 +724,7 @@ long QgsWFSProvider::featureCount() const
   return mShared->getFeatureCount();
 }
 
-const QgsFields& QgsWFSProvider::fields() const
+QgsFields QgsWFSProvider::fields() const
 {
   return mShared->mFields;
 }
diff --git a/src/providers/wfs/qgswfsprovider.h b/src/providers/wfs/qgswfsprovider.h
index 0c9127198e7..f7bc246ccf6 100644
--- a/src/providers/wfs/qgswfsprovider.h
+++ b/src/providers/wfs/qgswfsprovider.h
@@ -74,7 +74,7 @@ class QgsWFSProvider : public QgsVectorDataProvider
     QGis::WkbType geometryType() const override;
     long featureCount() const override;
 
-    const QgsFields& fields() const override;
+    QgsFields fields() const override;
 
     virtual QgsCoordinateReferenceSystem crs() const override;
 
diff --git a/src/providers/wfs/qgswfsshareddata.cpp b/src/providers/wfs/qgswfsshareddata.cpp
index cf398e774e0..6a427bf02d9 100644
--- a/src/providers/wfs/qgswfsshareddata.cpp
+++ b/src/providers/wfs/qgswfsshareddata.cpp
@@ -581,7 +581,7 @@ QSet<QString> QgsWFSSharedData::getExistingCachedGmlIds( const QVector<QgsWFSFea
   bool first = true;
   QSet<QString> setExistingGmlIds;
 
-  const QgsFields & dataProviderFields = mCacheDataProvider->fields();
+  QgsFields dataProviderFields = mCacheDataProvider->fields();
   const int gmlidIdx = dataProviderFields.indexFromName( QgsWFSConstants::FIELD_GMLID );
 
   // To avoid excessive memory consumption in expression building, do not
@@ -632,7 +632,7 @@ QSet<QString> QgsWFSSharedData::getExistingCachedMD5( const QVector<QgsWFSFeatur
   bool first = true;
   QSet<QString> setExistingMD5;
 
-  const QgsFields & dataProviderFields = mCacheDataProvider->fields();
+  QgsFields dataProviderFields = mCacheDataProvider->fields();
   const int md5Idx = dataProviderFields.indexFromName( QgsWFSConstants::FIELD_MD5 );
 
   // To avoid excessive memory consumption in expression building, do not
@@ -685,7 +685,7 @@ QString QgsWFSSharedData::findGmlId( QgsFeatureId fid )
   QgsFeatureRequest request;
   request.setFilterFid( fid );
 
-  const QgsFields & dataProviderFields = mCacheDataProvider->fields();
+  QgsFields dataProviderFields = mCacheDataProvider->fields();
   int gmlidIdx = dataProviderFields.indexFromName( QgsWFSConstants::FIELD_GMLID );
 
   QgsAttributeList attList;
@@ -765,7 +765,7 @@ bool QgsWFSSharedData::changeAttributeValues( const QgsChangedAttributesMap &att
   if ( !mCacheDataProvider )
     return false;
 
-  const QgsFields & dataProviderFields = mCacheDataProvider->fields();
+  QgsFields dataProviderFields = mCacheDataProvider->fields();
   QgsChangedAttributesMap newMap;
   for ( QgsChangedAttributesMap::const_iterator iter = attr_map.begin(); iter != attr_map.end(); ++iter )
   {
@@ -812,7 +812,7 @@ void QgsWFSSharedData::serializeFeatures( QVector<QgsWFSFeatureGmlIdPair>& featu
   }
 
   QgsFeatureList featureListToCache;
-  const QgsFields & dataProviderFields = mCacheDataProvider->fields();
+  QgsFields dataProviderFields = mCacheDataProvider->fields();
   int gmlidIdx = dataProviderFields.indexFromName( QgsWFSConstants::FIELD_GMLID );
   Q_ASSERT( gmlidIdx >= 0 );
   int genCounterIdx = dataProviderFields.indexFromName( QgsWFSConstants::FIELD_GEN_COUNTER );
diff --git a/src/server/qgswfsserver.cpp b/src/server/qgswfsserver.cpp
index 660b161ad33..03839ae6c1f 100644
--- a/src/server/qgswfsserver.cpp
+++ b/src/server/qgswfsserver.cpp
@@ -1575,7 +1575,7 @@ QDomDocument QgsWFSServer::transaction( const QString& requestBody )
           }
 
           // Update the features
-          const QgsFields& fields = provider->fields();
+          QgsFields fields = provider->fields();
           QMap<QString, int> fieldMap = provider->fieldNameMap();
           QMap<QString, int>::const_iterator fieldMapIt;
           QString fieldName;
@@ -1605,7 +1605,7 @@ QDomDocument QgsWFSServer::transaction( const QString& requestBody )
               {
                 continue;
               }
-              const QgsField& field = fields[fieldMapIt.value()];
+              const QgsField& field = fields.at( fieldMapIt.value() );
               if ( field.type() == 2 )
                 layer->changeAttributeValue( *fidIt, fieldMapIt.value(), it.value().toInt( &conversionSuccess ) );
               else if ( field.type() == 6 )
@@ -1694,7 +1694,7 @@ QDomDocument QgsWFSServer::transaction( const QString& requestBody )
       if ( cap & QgsVectorDataProvider::AddFeatures )
       {
         // Get Layer Field Information
-        const QgsFields& fields = provider->fields();
+        QgsFields fields = provider->fields();
         QMap<QString, int> fieldMap = provider->fieldNameMap();
         QMap<QString, int>::const_iterator fieldMapIt;
 
@@ -1739,7 +1739,7 @@ QDomDocument QgsWFSServer::transaction( const QString& requestBody )
                   {
                     continue;
                   }
-                  const QgsField& field = fields[fieldMapIt.value()];
+                  const QgsField& field = fields.at( fieldMapIt.value() );
                   QString attrValue = currentAttributeElement.text();
                   int attrType = field.type();
                   QgsMessageLog::logMessage( QString( "attr: name=%1 idx=%2 value=%3" ).arg( attrName ).arg( fieldMapIt.value() ).arg( attrValue ) );
@@ -1845,7 +1845,7 @@ QgsFeatureIds QgsWFSServer::getFeatureIdsFromFilter( const QDomElement& filterEl
         throw QgsMapServiceException( "RequestNotWellFormed", filter->parserErrorString() );
       }
       QgsFeature feature;
-      const QgsFields& fields = provider->fields();
+      QgsFields fields = provider->fields();
       QgsFeatureIterator fit = layer->getFeatures();
       QgsExpressionContext context = QgsExpressionContextUtils::createFeatureBasedContext( feature, fields );