NH-3797 - Moved the GroupByKeys expression list into the VisitorParameters class to make it more reusable and refactored the Group By key extraction into an extension method for possible reuse

Author: PleasantD

src/NHibernate/Linq/GroupBy/AggregatingGroupByRewriter.cs

@@ -5,6 +5,7 @@
 using NHibernate.Linq.Clauses;
 using NHibernate.Linq.ReWriters;
 using NHibernate.Linq.Visitors;
+using NHibernate.Util;
 using Remotion.Linq;
 using Remotion.Linq.Clauses.Expressions;
 using Remotion.Linq.Clauses.ResultOperators;
@@ -43,9 +44,8 @@ public static class AggregatingGroupByRewriter
 				typeof (CacheableResultOperator)
 			};
 
-        public static IEnumerable<Expression> ReWrite(QueryModel queryModel)
+        public static void ReWrite(QueryModel queryModel, IList<Expression> groupByKeys)
 		{
-            IEnumerable<Expression> groupByKeys = Enumerable.Empty<Expression>();
             var subQueryExpression = queryModel.MainFromClause.FromExpression as SubQueryExpression;
 
 			if (subQueryExpression != null)
@@ -59,17 +59,11 @@ public static IEnumerable<Expression> ReWrite(QueryModel queryModel)
 					var groupBy = operators[0] as GroupResultOperator;
 					if (groupBy != null)
 					{
-                        if (groupBy.KeySelector is NewExpression)
-                            groupByKeys = (groupBy.KeySelector as NewExpression).Arguments;
-                        else if (groupBy.KeySelector is NewArrayExpression)
-                            groupByKeys = (groupBy.KeySelector as NewArrayExpression).Expressions;
-                        else
-                            groupByKeys = new[] { groupBy.KeySelector };
+                        groupBy.ExtractKeyExpressions(groupByKeys);
                         FlattenSubQuery(queryModel, subQueryExpression.QueryModel, groupBy);
 					}
 				}
 			}
-		    return groupByKeys;
 		}
 
 		private static void FlattenSubQuery(QueryModel queryModel, QueryModel subQueryModel, GroupResultOperator groupBy)

src/NHibernate/Linq/GroupResultOperatorExtensions.cs

@@ -0,0 +1,23 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Linq.Expressions;
+using System.Text;
+using NHibernate.Util;
+using Remotion.Linq.Clauses.ResultOperators;
+
+namespace NHibernate.Linq
+{
+    internal static class GroupResultOperatorExtensions
+    {
+        public static void ExtractKeyExpressions(this GroupResultOperator groupResult, IList<Expression> groupByKeys)
+        {
+            if (groupResult.KeySelector is NewExpression)
+                (groupResult.KeySelector as NewExpression).Arguments.ForEach(groupByKeys.Add);
+            else if (groupResult.KeySelector is NewArrayExpression)
+                (groupResult.KeySelector as NewArrayExpression).Expressions.ForEach(groupByKeys.Add);
+            else
+                groupByKeys.Add(groupResult.KeySelector);
+        }
+    }
+}

src/NHibernate/Linq/Visitors/QueryModelVisitor.cs

@@ -34,7 +34,7 @@ public static ExpressionToHqlTranslationResults GenerateHqlQuery(QueryModel quer
 			NonAggregatingGroupByRewriter.ReWrite(queryModel);
 
 			// Rewrite aggregate group-by statements
-			var groupByKeys = AggregatingGroupByRewriter.ReWrite(queryModel);
+            AggregatingGroupByRewriter.ReWrite(queryModel, parameters.GroupByKeys);
 
 			// Rewrite aggregating group-joins
 			AggregatingGroupJoinRewriter.ReWrite(queryModel);
@@ -79,7 +79,6 @@ public static ExpressionToHqlTranslationResults GenerateHqlQuery(QueryModel quer
 			var visitor = new QueryModelVisitor(parameters, root, queryModel)
 			{
 			    RewrittenOperatorResult = result,
-                GroupByKeys = groupByKeys,
 			};
 			visitor.Visit();
 
@@ -100,9 +99,7 @@ public static ExpressionToHqlTranslationResults GenerateHqlQuery(QueryModel quer
 
 		public ResultOperatorRewriterResult RewrittenOperatorResult { get; private set; }
 
-        public IEnumerable<Expression> GroupByKeys { get; private set; }
-
-		static QueryModelVisitor()
+        static QueryModelVisitor()
 		{
 			// TODO - reflection to build map
 			ResultOperatorMap = new ResultOperatorMap();
@@ -238,7 +235,7 @@ public override void VisitSelectClause(SelectClause selectClause, QueryModel que
 		{
 			CurrentEvaluationType = selectClause.GetOutputDataInfo();
 
-			var visitor = new SelectClauseVisitor(typeof(object[]), VisitorParameters, GroupByKeys);
+			var visitor = new SelectClauseVisitor(typeof(object[]), VisitorParameters, VisitorParameters.GroupByKeys);
 
 			visitor.Visit(selectClause.Selector);
 

src/NHibernate/Linq/Visitors/VisitorParameters.cs

@@ -16,6 +16,8 @@ public class VisitorParameters
 
 		public QuerySourceNamer QuerySourceNamer { get; set; }
 
+        public IList<Expression> GroupByKeys { get; private set; } 
+
 		public VisitorParameters(
 			ISessionFactoryImplementor sessionFactory, 
 			IDictionary<ConstantExpression, NamedParameter> constantToParameterMap, 
@@ -26,6 +28,7 @@ public VisitorParameters(
 			ConstantToParameterMap = constantToParameterMap;
 			RequiredHqlParameters = requiredHqlParameters;
 			QuerySourceNamer = querySourceNamer;
+            GroupByKeys = new List<Expression>();
 		}
 	}
 }

src/NHibernate/NHibernate.csproj

@@ -299,6 +299,7 @@
     <Compile Include="Linq\Functions\EqualsGenerator.cs" />
     <Compile Include="Linq\GroupBy\KeySelectorVisitor.cs" />
     <Compile Include="Linq\GroupBy\PagingRewriter.cs" />
+    <Compile Include="Linq\GroupResultOperatorExtensions.cs" />
     <Compile Include="Linq\NestedSelects\NestedSelectDetector.cs" />
     <Compile Include="Linq\NestedSelects\Tuple.cs" />
     <Compile Include="Linq\NestedSelects\SelectClauseRewriter.cs" />