NH-3486 - Cache ProjectedColumnAliases in CriteriaLoader (#468)

Previosly, CriteriaLoader was calculating the column aliases for every row, this led to the performance bottlenecks.

Author: lnu

src/NHibernate/Loader/Criteria/CriteriaLoader.cs

@@ -30,6 +30,8 @@ public class CriteriaLoader : OuterJoinLoader
 		private readonly string[] userAliases;
 		private readonly bool[] includeInResultRow;
 		private readonly int resultRowLength;
+		// caching NH-3486
+		private readonly string[] cachedProjectedColumnAliases;
 
 		public CriteriaLoader(IOuterJoinLoadable persister, ISessionFactoryImplementor factory, CriteriaImpl rootCriteria,
 							  string rootEntityName, IDictionary<string, IFilter> enabledFilters)
@@ -48,6 +50,11 @@ public CriteriaLoader(IOuterJoinLoadable persister, ISessionFactoryImplementor f
 			resultTypes = walker.ResultTypes;
 			includeInResultRow = walker.IncludeInResultRow;
 			resultRowLength = ArrayHelper.CountTrue(IncludeInResultRow);
+			// fill caching objects only if there is a projection
+			if (translator.HasProjection)
+			{
+				cachedProjectedColumnAliases = translator.ProjectedColumnAliases;
+			}
 
 			PostInstantiate();
 		}
@@ -74,7 +81,7 @@ public IType[] ResultTypes
 			get { return resultTypes; }
 		}
 
-		protected override  string[] ResultRowAliases
+		protected override string[] ResultRowAliases
 		{
 			get { return userAliases; }
 		}
@@ -113,22 +120,20 @@ protected override object[] GetResultRow(object[] row, IDataReader rs, ISessionI
 
 			if (translator.HasProjection)
 			{
-				IType[] types = translator.ProjectedTypes;
-				result = new object[types.Length];
-				string[] columnAliases = translator.ProjectedColumnAliases;
-				
+				result = new object[ResultTypes.Length];
+
 				for (int i = 0, position = 0; i < result.Length; i++)
 				{
-					int numColumns = types[i].GetColumnSpan(session.Factory);
-					
-					if ( numColumns > 1 ) 
+					int numColumns = ResultTypes[i].GetColumnSpan(session.Factory);
+
+					if (numColumns > 1)
 					{
-						string[] typeColumnAliases = ArrayHelper.Slice(columnAliases, position, numColumns);
-						result[i] = types[i].NullSafeGet(rs, typeColumnAliases, session, null);
+						string[] typeColumnAliases = ArrayHelper.Slice(cachedProjectedColumnAliases, position, numColumns);
+						result[i] = ResultTypes[i].NullSafeGet(rs, typeColumnAliases, session, null);
 					}
 					else
 					{
-						result[i] = types[i].NullSafeGet(rs, columnAliases[position], session, null);
+						result[i] = ResultTypes[i].NullSafeGet(rs, cachedProjectedColumnAliases[position], session, null);
 					}
 					position += numColumns;
 				}
@@ -222,4 +227,4 @@ protected override IEnumerable<IParameterSpecification> GetParameterSpecificatio
 			return translator.CollectedParameterSpecifications;
 		}
 	}
-}
+}