diff --git a/src/database/Track.cpp b/src/database/Track.cpp
index a46a570b..a423abbf 100644
--- a/src/database/Track.cpp
+++ b/src/database/Track.cpp
@@ -17,6 +17,8 @@
  * along with LMS.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <boost/property_tree/json_parser.hpp>
+
 #include <Wt/Dbo/QueryModel>
 
 #include "logger/Logger.hpp"
@@ -47,6 +49,7 @@ Track::getAll(Wt::Dbo::Session& session)
 std::vector<Track::id_type>
 Track::getAllIds(Wt::Dbo::Session& session)
 {
+	Wt::Dbo::Transaction transaction(session);
 	Wt::Dbo::collection<Track::id_type> res = session.query<Track::id_type>("SELECT id from track");
 	return std::vector<Track::id_type>(res.begin(), res.end());
 }
@@ -105,14 +108,6 @@ Track::getClusters(void) const
 	return clusters;
 }
 
-std::vector< Wt::Dbo::ptr<Feature> >
-Track::getFeatures(void) const
-{
-	std::vector< Wt::Dbo::ptr<Feature> > features;
-	std::copy(_features.begin(), _features.end(), std::back_inserter(features));
-	return features;
-}
-
 Wt::Dbo::Query< Track::pointer >
 Track::getQuery(Wt::Dbo::Session& session, SearchFilter filter)
 {
@@ -248,12 +243,12 @@ Cluster::create(Wt::Dbo::Session& session, std::string type, std::string name)
 }
 
 void
-Cluster::removeByType(Wt::Dbo::Session& session, std::string type)
+Cluster::remove(Wt::Dbo::Session& session, std::string type)
 {
-	session.execute( "DELETE FROM cluster WHERE type = ?").bind(type);
+	Wt::Dbo::Transaction transaction(session);
+	session.execute("DELETE FROM cluster WHERE type = ?").bind(type);
 }
 
-
 Wt::Dbo::Query<Cluster::pointer>
 Cluster::getQuery(Wt::Dbo::Session& session, SearchFilter filter)
 {
@@ -274,7 +269,7 @@ Cluster::getUIQuery(Wt::Dbo::Session& session, SearchFilter filter)
 	SqlQuery sqlQuery = generatePartialQuery(filter);
 
 	Wt::Dbo::Query<UIQueryResult> query
-		= session.query<UIQueryResult>( "SELECT c.id, c.type, c.name, COUNT(DISTINCT t.id) FROM cluster c INNER JOIN track_cluster t_c ON t_c.cluster_id = c.id INNER JOIN artist a ON t.artist_id = a.id INNER JOIN release r ON r.id = t.release_id INNER JOIN track t ON t.id = t_c.track_id " + sqlQuery.where().get()).groupBy("c.name").orderBy("c.name");
+		= session.query<UIQueryResult>( "SELECT c.id, c.name, COUNT(DISTINCT t.id) FROM cluster c INNER JOIN track_cluster t_c ON t_c.cluster_id = c.id INNER JOIN artist a ON t.artist_id = a.id INNER JOIN release r ON r.id = t.release_id INNER JOIN track t ON t.id = t_c.track_id " + sqlQuery.where().get()).groupBy("c.name").orderBy("c.name");
 
 	for (const std::string& bindArg : sqlQuery.where().getBindArgs())
 		query.bind(bindArg);
@@ -289,11 +284,10 @@ Cluster::updateUIQueryModel(Wt::Dbo::Session& session,  Wt::Dbo::QueryModel<UIQu
 	model.setQuery(query, columnNames.empty() ? true : false);
 
 	// TODO do something better
-	if (columnNames.size() == 3)
+	if (columnNames.size() == 2)
 	{
-		model.addColumn( "c.type", columnNames[0] );
-		model.addColumn( "c.name", columnNames[1] );
-		model.addColumn( "COUNT(DISTINCT t.id)", columnNames[2] );
+		model.addColumn( "c.name", columnNames[0] );
+		model.addColumn( "COUNT(DISTINCT t.id)", columnNames[1] );
 	}
 }
 
@@ -305,25 +299,6 @@ Cluster::getByFilter(Wt::Dbo::Session& session, SearchFilter filter, int offset,
 	return std::vector<pointer>(res.begin(), res.end());
 }
 
-Feature::Feature(Wt::Dbo::ptr<Track> track, const std::string& type, const std::string& value)
-: _type(type),
-_value(value),
-_track(track)
-{
-}
-
-Feature::pointer
-Feature::create(Wt::Dbo::Session& session, Wt::Dbo::ptr<Track> track, const std::string& type, const std::string& value)
-{
-	return session.add(new Feature(track, type, value));
-}
-
-std::vector<Feature::pointer>
-Feature::getByTrack(Wt::Dbo::Session& session, Track::id_type trackId, const std::string& type)
-{
-	Wt::Dbo::collection<pointer> res = session.find<Feature>().where("track_id = ? AND type = ?").bind( trackId).bind(type);
-	return std::vector<pointer>(res.begin(), res.end());
-}
 
 } // namespace Database
 
diff --git a/src/database/Track.hpp b/src/database/Track.hpp
index 004eec11..3d523814 100644
--- a/src/database/Track.hpp
+++ b/src/database/Track.hpp
@@ -23,6 +23,7 @@
 #include <vector>
 
 #include <boost/filesystem.hpp>
+#include <boost/property_tree/ptree.hpp>
 
 #include <Wt/Dbo/Dbo>
 #include <Wt/Dbo/WtSqlTraits>
@@ -38,7 +39,6 @@ class Artist;
 class Release;
 class Track;
 class PlaylistEntry;
-class Feature;
 
 class Cluster
 {
@@ -59,7 +59,7 @@ class Cluster
 
 		// MVC models for the user interface
 		// ClusterID, type, name, track count
-		typedef boost::tuple<id_type, std::string, std::string, int> UIQueryResult;
+		typedef boost::tuple<id_type, std::string, int> UIQueryResult;
 		static Wt::Dbo::Query<UIQueryResult> getUIQuery(Wt::Dbo::Session& session, SearchFilter filter);
 		static void updateUIQueryModel(Wt::Dbo::Session& session, Wt::Dbo::QueryModel<UIQueryResult>& model, SearchFilter filter, const std::vector<Wt::WString>& columnNames = std::vector<Wt::WString>());
 
@@ -67,7 +67,7 @@ class Cluster
 		static pointer create(Wt::Dbo::Session& session, std::string type, std::string name);
 
 		// Remove utility
-		static void removeByType(Wt::Dbo::Session& session, std::string type);
+		static void remove(Wt::Dbo::Session& session, std::string type); // nested transaction
 
 		// Accessors
 		const std::string& getName(void) const { return _name; }
@@ -75,7 +75,7 @@ class Cluster
 		bool isNone(void) const;
 		const Wt::Dbo::collection< Wt::Dbo::ptr<Track> >&	getTracks() const { return _tracks;}
 
-		void addTrack(Wt::Dbo::dbo_traits<Track>::IdType trackId);
+		void addTrack(Wt::Dbo::Session& session, Wt::Dbo::dbo_traits<Track>::IdType trackId);
 		void addTrack(Wt::Dbo::ptr<Track> track) { _tracks.insert(track); }
 
 		template<class Action>
@@ -121,15 +121,15 @@ class Track
 		static std::vector<pointer> 	getByFilter(Wt::Dbo::Session& session, SearchFilter filter, int offset = -1, int size = -1);
 		static std::vector<pointer> 	getByFilter(Wt::Dbo::Session& session, SearchFilter filter, int offset, int size, bool &moreResults);
 		static Wt::Dbo::collection< pointer > getAll(Wt::Dbo::Session& session);
-		static std::vector<id_type> getAllIds(Wt::Dbo::Session& session);
-		static std::vector<boost::filesystem::path> getAllPaths(Wt::Dbo::Session& session);
+		static std::vector<id_type> getAllIds(Wt::Dbo::Session& session); // nested transaction
+		static std::vector<boost::filesystem::path> getAllPaths(Wt::Dbo::Session& session); // nested transaction
 		static std::vector<pointer> getMBIDDuplicates(Wt::Dbo::Session& session);
 		static std::vector<pointer> getChecksumDuplicates(Wt::Dbo::Session& session);
 
 		// Utility fonctions
 		// MVC models for the user interface
 		// ID, Artist name, Release Name, DiscNumber, TrackNumber, Name, duration, date, original date, genre list
-		typedef boost::tuple<id_type,			//ID
+		typedef boost::tuple<id_type,			// ID
 			std::string,				// Artist name
 			std::string,				// Release Name
 			int,					// Disc Number
@@ -153,6 +153,9 @@ class Track
 		// Create utility
 		static pointer	create(Wt::Dbo::Session& session, const boost::filesystem::path& p);
 
+		// Remove utility
+		static void removeClusters(std::string type);
+
 		// Accessors
 		void setTrackNumber(int num)					{ _trackNumber = num; }
 		void setTotalTrackNumber(int num)				{ _totalTrackNumber = num; }
@@ -170,7 +173,6 @@ class Track
 		void setMBID(const std::string& MBID)				{ _MBID = MBID; }
 		void setArtist(Wt::Dbo::ptr<Artist> artist)			{ _artist = artist; }
 		void setRelease(Wt::Dbo::ptr<Release> release)			{ _release = release; }
-		void addFeature(Wt::Dbo::ptr<Feature> feature);
 
 		int				getTrackNumber(void) const		{ return _trackNumber; }
 		int				getTotalTrackNumber(void) const		{ return _totalTrackNumber; }
@@ -189,7 +191,6 @@ class Track
 		Wt::Dbo::ptr<Artist>		getArtist(void) const			{ return _artist; }
 		Wt::Dbo::ptr<Release>		getRelease(void) const			{ return _release; }
 		std::vector< Cluster::pointer >	getClusters(void) const;
-		std::vector< Wt::Dbo::ptr<Feature> >	getFeatures(void) const;
 
 		template<class Action>
 			void persist(Action& a)
@@ -213,7 +214,6 @@ class Track
 				Wt::Dbo::belongsTo(a, _artist, "artist", Wt::Dbo::OnDeleteCascade);
 				Wt::Dbo::hasMany(a, _clusters, Wt::Dbo::ManyToMany, "track_cluster", "", Wt::Dbo::OnDeleteCascade);
 				Wt::Dbo::hasMany(a, _playlistEntries, Wt::Dbo::ManyToOne, "track");
-				Wt::Dbo::hasMany(a, _features, Wt::Dbo::ManyToOne, "track");
 			}
 
 	private:
@@ -242,43 +242,11 @@ class Track
 
 		Wt::Dbo::ptr<Artist>			_artist;
 		Wt::Dbo::ptr<Release>			_release;
-		Wt::Dbo::collection< Wt::Dbo::ptr<Feature> > 	_features;
 		Wt::Dbo::collection< Wt::Dbo::ptr<Cluster> >	_clusters;
 		Wt::Dbo::collection< Wt::Dbo::ptr<PlaylistEntry> >	_playlistEntries;
 
 };
 
-/* A track feature */
-class Feature
-{
-	public:
-		typedef Wt::Dbo::ptr<Feature> pointer;
-
-		Feature() {}
-		Feature(Wt::Dbo::ptr<Track> track, const std::string& type, const std::string& value);
-
-		static pointer create(Wt::Dbo::Session& session, Wt::Dbo::ptr<Track> track, const std::string& type, const std::string& value);
-
-		static std::vector<pointer> getByTrack(Wt::Dbo::Session& session, Track::id_type trackId, const std::string& type);
-
-		std::string getType(void) const { return _type; }
-		std::string getValue(void) const { return _value; }
-
-		template<class Action>
-			void persist(Action& a)
-			{
-				Wt::Dbo::field(a, _type,	"type");
-				Wt::Dbo::field(a, _value,	"value");
-				Wt::Dbo::belongsTo(a,	_track, "track", Wt::Dbo::OnDeleteCascade);
-			}
-
-	private:
-		std::string	_type;
-		std::string	_value;
-
-		Wt::Dbo::ptr<Track>	_track;
-};
-
 } // namespace database