Improve generated SQL for nested Any.

Author: ngbrown

src/NHibernate.Test/Linq/ByMethod/AnyTests.cs

@@ -75,5 +75,27 @@ public void AnyWithFetchInSubQuery()
 				}
 			);
 		}
+
+		[Test(Description = "GH2479")]
+		public void NestedAnyWithPaging()
+		{
+			using (var sqlSpy = new SqlLogSpy())
+			{
+				var ordersQuery = db.Orders
+				                    .Where(x => x.Employee.EmployeeId > 5)
+				                    .OrderBy(x => x.OrderId)
+				                    .Take(2);
+
+				var orderLines = db.OrderLines
+				                   .Where(x => ordersQuery.Any(o => o == x.Order))
+				                   .OrderBy(x => x.Id)
+				                   .ToList();
+
+				var sql = sqlSpy.GetWholeLog();
+
+				Assert.That(orderLines.Count, Is.EqualTo(6), nameof(orderLines));
+				Assert.That(GetTotalOccurrences(sql, "select"), Is.EqualTo(2));
+			}
+		}
 	}
 }

src/NHibernate/Linq/GroupBy/PagingRewriter.cs

@@ -1,4 +1,5 @@
 using System.Linq;
+using System.Linq.Expressions;
 using NHibernate.Linq.Visitors;
 using Remotion.Linq;
 using Remotion.Linq.Clauses;
@@ -42,6 +43,31 @@ private static void FlattenSubQuery(SubQueryExpression subQueryExpression, Query
 				var visitor1 = new PagingRewriterSelectClauseVisitor(queryModel.MainFromClause);
 				queryModel.SelectClause.TransformExpressions(visitor1.Swap);
 			}
+			else if (queryModel.ResultOperators.Count == 1 && queryModel.ResultOperators[0] is AnyResultOperator &&
+			         queryModel.BodyClauses.Count == 1 && queryModel.BodyClauses[0] is WhereClause whereClause &&
+			         whereClause.Predicate is BinaryExpression whereClausePredicate &&
+			         new[] {whereClausePredicate.Left, whereClausePredicate.Right}.Count(x => x.NodeType == ExpressionType.MemberAccess) == 1)
+			{
+				var joinOnBodyClause = whereClausePredicate.Right.NodeType == ExpressionType.MemberAccess
+					? whereClausePredicate.Right
+					: whereClausePredicate.Left;
+				var cro = new ContainsResultOperator(joinOnBodyClause);
+
+				queryModel.BodyClauses.Clear();
+				foreach (var orderByClause in subQueryModel.BodyClauses)
+				{
+					queryModel.BodyClauses.Add(orderByClause);
+				}
+
+				queryModel.ResultOperators.Clear();
+				foreach (var resultOperator in subQueryModel.ResultOperators)
+				{
+					queryModel.ResultOperators.Add(resultOperator);
+				}
+
+				queryModel.ResultOperators.Add(cro);
+				queryModel.ResultTypeOverride = typeof(bool);
+			}
 			else
 			{
 				var cro = new ContainsResultOperator(new QuerySourceReferenceExpression(subQueryMainFromClause));