[OGR provider] Fix opening of GeoPackage datasets with foreign key vi…

…olation

src/providers/ogr/qgsogrprovider.cpp

@@ -3694,11 +3694,21 @@ GDALDatasetH QgsOgrProviderUtils::GDALOpenWrapper( const char *pszPath, bool bUp
     bIsLocalGpkg = true;
   }
 
+  bool modify_OGR_GPKG_FOREIGN_KEY_CHECK = !CPLGetConfigOption( "OGR_GPKG_FOREIGN_KEY_CHECK", nullptr );
+  if ( modify_OGR_GPKG_FOREIGN_KEY_CHECK )
+  {
+    CPLSetThreadLocalConfigOption( "OGR_GPKG_FOREIGN_KEY_CHECK", "NO" );
+  }
+
   const int nOpenFlags = GDAL_OF_VECTOR | ( bUpdate ? GDAL_OF_UPDATE : 0 );
   GDALDatasetH hDS = GDALOpenEx( pszPath, nOpenFlags, nullptr, papszOpenOptions, nullptr );
   CSLDestroy( papszOpenOptions );
 
   CPLSetThreadLocalConfigOption( "OGR_SQLITE_JOURNAL", nullptr );
+  if ( modify_OGR_GPKG_FOREIGN_KEY_CHECK )
+  {
+    CPLSetThreadLocalConfigOption( "OGR_GPKG_FOREIGN_KEY_CHECK", nullptr );
+  }
 
   if ( !hDS )
   {

tests/src/python/test_provider_ogr_gpkg.py

@@ -1303,6 +1303,24 @@ def test_quote_identifier(self):
         for i in range(1, len(vl.fields())):
             self.assertEqual(vl.uniqueValues(i), {'a', 'b', 'c'})
 
+    def testForeignKeyViolation(self):
+        """Test that we can open a dataset with a foreign key violation"""
+
+        tmpfile = os.path.join(self.basetestpath, 'testForeignKeyViolation.gpkg')
+        ds = ogr.GetDriverByName('GPKG').CreateDataSource(tmpfile)
+        lyr = ds.CreateLayer('test', geom_type=ogr.wkbPoint)
+        f = ogr.Feature(lyr.GetLayerDefn())
+        f.SetGeometry(ogr.CreateGeometryFromWkt('POINT(0 1)'))
+        lyr.CreateFeature(f)
+        ds.ExecuteSQL("PRAGMA foreign_keys = OFF")
+        ds.ExecuteSQL("CREATE TABLE foo(id INTEGER)")
+        ds.ExecuteSQL("CREATE TABLE bar(fkey INTEGER, CONSTRAINT fkey_constraint FOREIGN KEY (fkey) REFERENCES foo(id))")
+        ds.ExecuteSQL("INSERT INTO bar VALUES (1)")
+        ds = None
+        vl = QgsVectorLayer('{}'.format(tmpfile) + "|layername=" + "test", 'test', 'ogr')
+        self.assertTrue(vl.isValid())
+        fids = set([f['fid'] for f in vl.getFeatures()])
+        self.assertEqual(len(fids), 1)
 
 if __name__ == '__main__':
     unittest.main()