DistinctRootEntityResultTransformer.cs

using System;
using System.Collections;

using Iesi.Collections;

using log4net;

namespace NHibernate.Transform
{
	public class DistinctRootEntityResultTransformer : IResultTransformer
	{
		private static readonly ILog log = LogManager.GetLogger( typeof( DistinctRootEntityResultTransformer ) );
		private static readonly IHashCodeProvider IdentityHashCodeProvider = new HashCodeProvider.IdentityHashCodeProvider();

		internal sealed class Identity
		{
			internal readonly object entity;

			internal Identity( object entity )
			{
				this.entity = entity;
			}

			public override bool Equals(object other)
			{
				Identity that = (Identity) other;
				return entity == that.entity;
			}

			public override int GetHashCode()
			{
				return IdentityHashCodeProvider.GetHashCode( entity );
			}
		}

		public object TransformTuple(object[] tuple, string[] aliases)
		{
			return tuple[ tuple.Length - 1 ];
		}

		public IList TransformList(IList list)
		{
			IList result = new ArrayList();
			ISet distinct = new HashedSet();

			for( int i = 0; i < list.Count; i++ )
			{
				object entity = list[ i ];
				if( distinct.Add( new Identity( entity ) ) )
				{
					result.Add( entity );
				}
			}

			if( log.IsDebugEnabled )
			{
				log.Debug( string.Format( "transformed: {0} rows to: {1} distinct results",
					list.Count, result.Count ) );
			}
			return result;
		}
	}
}