Don't join fkey table when linq comparison with composite id

.gitattributes

@@ -11,6 +11,7 @@
 *.cmd     text
 *.msbuild text
 *.md      text
+*.sql     text
 
 *.sln text eol=crlf
 *.csproj text eol=crlf

src/NHibernate.DomainModel/NHibernate.DomainModel.csproj

@@ -15,4 +15,7 @@
   <ItemGroup>
     <ProjectReference Include="..\NHibernate\NHibernate.csproj" />
   </ItemGroup>
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Bcl.HashCode" Version="1.1.1" />
+  </ItemGroup>
 </Project>

src/NHibernate.DomainModel/Northwind/Entities/AnotherEntity.cs

@@ -4,6 +4,7 @@ public class AnotherEntity
     {
         public virtual int Id { get; set; }
         public virtual string Output { get; set; }
-		public virtual string Input { get; set; }
+        public virtual string Input { get; set; } 
+        public virtual CompositeIdEntity CompositeIdEntity { get; set; }
     }
-}
+}

src/NHibernate.DomainModel/Northwind/Entities/CompositeIdEntity.cs

@@ -0,0 +1,58 @@
+using System;
+
+namespace NHibernate.DomainModel.Northwind.Entities
+{
+	public class CompositeId : IComparable<CompositeId>
+	{
+		public int ObjectId { get; set; } 
+		public int TenantId { get; set; }
+
+		public CompositeId() { }
+		public CompositeId(int objectId, int tenantId)
+		{
+			ObjectId = objectId;
+			TenantId = tenantId;
+		}
+
+		public override string ToString() => ObjectId + "|" + TenantId;
+		protected bool Equals(CompositeId other) => ObjectId == other.ObjectId && TenantId == other.TenantId;
+		public static bool operator ==(CompositeId left, CompositeId right) => Equals(left, right);
+		public static bool operator !=(CompositeId left, CompositeId right) => !Equals(left, right);
+
+		public override bool Equals(object obj)
+		{
+			if (ReferenceEquals(null, obj) || obj.GetType() != this.GetType())
+			{
+				return false;
+			}
+			return ReferenceEquals(this, obj) || Equals((CompositeId)obj);
+		}
+
+		public override int GetHashCode() => HashCode.Combine(ObjectId, TenantId);
+
+		public int CompareTo(CompositeId other)
+		{
+			if (ReferenceEquals(this, other))
+			{
+				return 0;
+			}
+			else if (ReferenceEquals(other, null))
+			{
+				return 1;
+			}
+
+			var idComparison = ObjectId.CompareTo(other.ObjectId);
+			if (idComparison != 0)
+			{
+				return idComparison;
+			}
+
+			return TenantId.CompareTo(other);
+		}
+	}
+    public class CompositeIdEntity
+    {
+        public virtual CompositeId Id { get; set; }
+        public virtual string Name { get; set; }
+    }
+}

src/NHibernate.DomainModel/Northwind/Entities/Northwind.cs

@@ -59,10 +59,10 @@ public IQueryable<Timesheet> Timesheets
             get { return _session.Query<Timesheet>(); }
         }
 
-    	public IQueryable<Animal> Animals
-    	{
-			get { return _session.Query<Animal>(); }
-    	}
+        public IQueryable<Animal> Animals
+        {
+            get { return _session.Query<Animal>(); }
+        }
 
         public IQueryable<Mammal> Mammals
         {
@@ -113,5 +113,10 @@ public IQueryable<IUser> IUsers
         {
             get { return _session.Query<IUser>(); }
         }
+
+        public IQueryable<AnotherEntity> AnotherEntity
+        {
+            get { return _session.Query<AnotherEntity>(); }
+        }
     }
 }

src/NHibernate.DomainModel/Northwind/Mappings/AnotherEntity.hbm.xml

@@ -6,5 +6,9 @@
     </id>
     <property name="Output" />
     <property name="Input" />
+    <many-to-one name="CompositeIdEntity" fetch="select">
+      <column name="CompositeObjectId" />
+      <column name="CompositeTenantId" />
+    </many-to-one>
   </class>
 </hibernate-mapping>

src/NHibernate.DomainModel/Northwind/Mappings/CompositeIdEntity.hbm.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" namespace="NHibernate.DomainModel.Northwind.Entities" assembly="NHibernate.DomainModel">
+  <class name="CompositeIdEntity" table="CompositeIdEntity">
+    <composite-id name="Id">
+      <key-property name="ObjectId" column="ObjectId" />
+      <key-property name="TenantId" column="TenantId" />
+    </composite-id>
+    <property name="Name" length="128" />
+  </class>
+</hibernate-mapping>

src/NHibernate.Test/Async/CompositeId/CompositeIdFixture.cs

@@ -18,6 +18,7 @@
 namespace NHibernate.Test.CompositeId
 {
 	using System.Threading.Tasks;
+	using System.Threading;
 	[TestFixture]
 	public class CompositeIdFixtureAsync : TestCase
 	{
@@ -33,7 +34,7 @@ protected override string[] Mappings
 				return new string[]
 				       	{
 				       		"CompositeId.Customer.hbm.xml", "CompositeId.Order.hbm.xml", "CompositeId.LineItem.hbm.xml",
-				       		"CompositeId.Product.hbm.xml"
+				       		"CompositeId.Product.hbm.xml", "CompositeId.Shipper.hbm.xml"
 				       	};
 			}
 		}
@@ -76,9 +77,13 @@ public async Task CompositeIdsAsync()
 
 				Order o = new Order(c);
 				o.OrderDate = DateTime.Today;
+				o.Shipper = new Shipper() { Id = new NullableId(null, 13) };
+				await (s.PersistAsync(o));
+
 				LineItem li = new LineItem(o, p);
 				li.Quantity = 2;
-
+				await (s.PersistAsync(li));
+
 				await (t.CommitAsync());
 			}
 
@@ -135,6 +140,19 @@ public async Task CompositeIdsAsync()
 				await (t.CommitAsync());
 			}
 
+			using (s = OpenSession())
+			{
+				t = s.BeginTransaction();
+				var noShippersForWarehouse = await (s.Query<Order>()
+					// NOTE: .Where(x => x.Shipper.Id == new NullableId(null, 13)) improperly renders
+					// "where (ShipperId = @p1 and WarehouseId = @p2)" with @p1 = NULL (needs to be is null)
+					// But the effort to fix is pretty high due to how component tuples are managed in linq / hql.
+					.Where(x => x.Shipper.Id.WarehouseId == 13 && x.Shipper.Id.Id == null)
+					.ToListAsync());
+				Assert.AreEqual(1, noShippersForWarehouse.Count);
+				await (t.CommitAsync());
+			}
+
 			using (s = OpenSession())
 			{
 				t = s.BeginTransaction();
@@ -303,5 +321,14 @@ public async Task AnyOnCompositeIdAsync()
 				await (s.Query<Order>().Select(o => o.LineItems.Any()).ToListAsync());
 			}
 		}
+
+		public async Task NullCompositeIdAsync(CancellationToken cancellationToken = default(CancellationToken))
+		{
+			using (var s = OpenSession())
+			{
+				await (s.Query<Order>().Where(o => o.LineItems.Any()).ToListAsync(cancellationToken));
+				await (s.Query<Order>().Select(o => o.LineItems.Any()).ToListAsync(cancellationToken));
+			}
+		}
 	}
 }

src/NHibernate.Test/Async/Linq/JoinTests.cs

@@ -297,6 +297,17 @@ public async Task OrderLinesWithSelectingCustomerNameInCaseShouldProduceTwoJoins
 				Assert.That(countJoins, Is.EqualTo(2));
 			}
 		}
+
+		[Test]
+		public async Task ShouldConstipateJoinsWhenOnlyComparingCompositeIdPropertiesAsync()
+		{
+			using (var spy = new SqlLogSpy())
+			{
+				await (db.AnotherEntity.Where(x => x.CompositeIdEntity.Id.TenantId == 3).ToListAsync());
+				var countJoins = CountJoins(spy);
+				Assert.That(countJoins, Is.EqualTo(0));
+			}
+		}
 
 		private static int CountJoins(LogSpy sqlLog)
 		{

src/NHibernate.Test/Async/QueryTranslator/CustomQueryLoaderFixture.cs

@@ -42,7 +42,8 @@ internal sealed class CustomQueryLoaderFixtureAsync : TestCase
 				"Northwind.Mappings.TimeSheet.hbm.xml",
 				"Northwind.Mappings.Animal.hbm.xml",
 				"Northwind.Mappings.Patient.hbm.xml",
-				"Northwind.Mappings.NumericEntity.hbm.xml"
+				"Northwind.Mappings.NumericEntity.hbm.xml",
+				"Northwind.Mappings.CompositeIdEntity.hbm.xml"
 			};
 
 		protected override string MappingsAssembly => "NHibernate.DomainModel";

src/NHibernate.Test/CompositeId/CompositeIdFixture.cs

@@ -21,7 +21,7 @@ protected override string[] Mappings
 				return new string[]
 				       	{
 				       		"CompositeId.Customer.hbm.xml", "CompositeId.Order.hbm.xml", "CompositeId.LineItem.hbm.xml",
-				       		"CompositeId.Product.hbm.xml"
+				       		"CompositeId.Product.hbm.xml", "CompositeId.Shipper.hbm.xml"
 				       	};
 			}
 		}
@@ -64,9 +64,13 @@ public void CompositeIds()
 
 				Order o = new Order(c);
 				o.OrderDate = DateTime.Today;
+				o.Shipper = new Shipper() { Id = new NullableId(null, 13) };
+				s.Persist(o);
+
 				LineItem li = new LineItem(o, p);
 				li.Quantity = 2;
-
+				s.Persist(li);
+
 				t.Commit();
 			}
 
@@ -123,6 +127,19 @@ public void CompositeIds()
 				t.Commit();
 			}
 
+			using (s = OpenSession())
+			{
+				t = s.BeginTransaction();
+				var noShippersForWarehouse = s.Query<Order>()
+					// NOTE: .Where(x => x.Shipper.Id == new NullableId(null, 13)) improperly renders
+					// "where (ShipperId = @p1 and WarehouseId = @p2)" with @p1 = NULL (needs to be is null)
+					// But the effort to fix is pretty high due to how component tuples are managed in linq / hql.
+					.Where(x => x.Shipper.Id.WarehouseId == 13 && x.Shipper.Id.Id == null)
+					.ToList();
+				Assert.AreEqual(1, noShippersForWarehouse.Count);
+				t.Commit();
+			}
+
 			using (s = OpenSession())
 			{
 				t = s.BeginTransaction();
@@ -291,5 +308,14 @@ public void AnyOnCompositeId()
 				s.Query<Order>().Select(o => o.LineItems.Any()).ToList();
 			}
 		}
+
+		public void NullCompositeId()
+		{
+			using (var s = OpenSession())
+			{
+				s.Query<Order>().Where(o => o.LineItems.Any()).ToList();
+				s.Query<Order>().Select(o => o.LineItems.Any()).ToList();
+			}
+		}
 	}
 }

src/NHibernate.Test/CompositeId/NullableId.cs

@@ -0,0 +1,58 @@
+using System;
+
+namespace NHibernate.Test.CompositeId
+{
+	public class NullableId : IComparable<NullableId>
+	{
+		public int? Id { get; set; } 
+		public int WarehouseId { get; set; }
+
+		public NullableId() { }
+		public NullableId(int? id, int warehouseId)
+		{
+			Id = id;
+			WarehouseId = warehouseId;
+		}
+
+		public override string ToString() => Id + "|" + WarehouseId;
+		protected bool Equals(NullableId other) => Id == other.Id && WarehouseId == other.WarehouseId;
+		public static bool operator ==(NullableId left, NullableId right) => Equals(left, right);
+		public static bool operator !=(NullableId left, NullableId right) => !Equals(left, right);
+
+		public override bool Equals(object obj)
+		{
+			if (ReferenceEquals(null, obj) || obj.GetType() != this.GetType())
+			{
+				return false;
+			}
+
+			return ReferenceEquals(this, obj) || Equals((NullableId)obj);
+		}
+
+		public override int GetHashCode() => HashCode.Combine(Id, WarehouseId);
+
+		public int CompareTo(NullableId other)
+		{
+			if (ReferenceEquals(this, other))
+			{
+				return 0;
+			}
+			else if (ReferenceEquals(other, null) || !other.Id.HasValue)
+			{
+				return 1;
+			}
+			else if (!Id.HasValue)
+			{
+				return -1;
+			}
+
+			var idComparison = Id.Value.CompareTo(other.Id);
+			if (idComparison != 0)
+			{
+				return idComparison;
+			}
+
+			return WarehouseId.CompareTo(other.WarehouseId);
+		}
+	}
+}

src/NHibernate.Test/CompositeId/Order.cs

@@ -48,6 +48,7 @@ public override int GetHashCode()
 		private Customer customer;
 		private IList<LineItem> lineItems = new List<LineItem>();
 		private decimal total;
+		private Shipper shipper;
 
 		public Order() {}
 		public Order(Customer customer)
@@ -87,6 +88,12 @@ public virtual decimal Total
 			get { return total; }
 			set { total = value; }
 		}
+
+		public virtual Shipper Shipper
+		{
+			get { return shipper; }
+			set { shipper = value; }
+		}
 
 		public virtual LineItem GenerateLineItem(Product product, int quantity)
 		{
@@ -96,4 +103,4 @@ public virtual LineItem GenerateLineItem(Product product, int quantity)
 			return li;
 		}
 	}
-}
+}

src/NHibernate.Test/CompositeId/Order.hbm.xml

@@ -43,6 +43,11 @@
     		insert="false"
 			update="false" 
 			not-null="true"/>
+
+      <many-to-one name="Shipper" fetch="select">
+        <column name="ShipperId" not-null="false"/>
+        <column name="WarehouseId" />
+      </many-to-one>
 
     	<bag name="LineItems"
     		fetch="join" 

src/NHibernate.Test/CompositeId/Shipper.cs

@@ -0,0 +1,8 @@
+namespace NHibernate.Test.CompositeId
+{
+	public class Shipper
+	{
+		public virtual NullableId Id { get; set; }
+		public virtual string Name { get; set; }
+	}
+}

src/NHibernate.Test/CompositeId/Shipper.hbm.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0"?>
+<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
+         namespace="NHibernate.Test.CompositeId"
+         assembly="NHibernate.Test">
+
+<class name="Shipper">
+  <composite-id name="Id">
+    <key-property name="Id" column="Id" />
+    <key-property name="WarehouseId" column="WarehouseId" />
+  </composite-id>
+
+  <property name="Name" length="128"/>
+</class>
+
+</hibernate-mapping>

src/NHibernate.Test/Criteria/ReadonlyTests/CriteriaNorthwindReadonlyTestCase.cs

@@ -32,7 +32,8 @@ protected override string[] Mappings
 					"Northwind.Mappings.User.hbm.xml",
 					"Northwind.Mappings.TimeSheet.hbm.xml",
 					"Northwind.Mappings.Animal.hbm.xml",
-					"Northwind.Mappings.Patient.hbm.xml"
+					"Northwind.Mappings.Patient.hbm.xml",
+					"Northwind.Mappings.CompositeIdEntity.hbm.xml"
 				};
 			}
 		}

src/NHibernate.Test/DbScripts/MsSql2012DialectLinqReadonlyCreateScript.sql

@@ -149,6 +149,8 @@ CREATE TABLE [dbo].[AnotherEntity](
 	[Id] [int] IDENTITY(1,1) NOT NULL,
 	[Output] [nvarchar](255) NULL,
 	[Input] [nvarchar](255) NULL,
+	[CompositeObjectId] INT NULL,
+	[CompositeTenantId] INT NULL,
 PRIMARY KEY CLUSTERED 
 (
 	[Id] ASC
@@ -159,9 +161,27 @@ SET IDENTITY_INSERT [dbo].[AnotherEntity] ON
 INSERT [dbo].[AnotherEntity] ([Id], [Output]) VALUES (1, N'output')
 INSERT [dbo].[AnotherEntity] ([Id], [Input]) VALUES (2, N'input')
 INSERT [dbo].[AnotherEntity] ([Id], [Input], [Output]) VALUES (3, N'i/o', N'i/o')
-INSERT [dbo].[AnotherEntity] ([Id], [Input], [Output]) VALUES (4, N'input', N'output')
+INSERT [dbo].[AnotherEntity] ([Id], [Input], [Output], [CompositeObjectId], [CompositeTenantId]) VALUES (4, N'input', N'output', 1, 10)
 INSERT [dbo].[AnotherEntity] ([Id], [Input], [Output]) VALUES (5, NULL, NULL)
 SET IDENTITY_INSERT [dbo].[AnotherEntity] OFF
+/****** Object:  Table [dbo].[CompositeIdEntity] ******/
+SET ANSI_NULLS ON
+GO
+SET QUOTED_IDENTIFIER ON
+GO
+CREATE TABLE [dbo].[CompositeIdEntity](
+	[ObjectId] [int] NOT NULL,
+	[TenantId] [int] NOT NULL,
+	[Name] [nvarchar](128) NULL
+PRIMARY KEY CLUSTERED 
+(
+	[ObjectId] ASC,
+	[TenantId] ASC
+)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
+) ON [PRIMARY]
+GO
+INSERT [dbo].[CompositeIdEntity] ([ObjectId], [TenantId], [Name]) VALUES (1, 10, N'Jack Stephan')
+
 /****** Object:  Table [dbo].[Animal]    Script Date: 06/17/2010 13:08:54 ******/
 SET ANSI_NULLS ON
 GO
@@ -3953,6 +3973,12 @@ REFERENCES [dbo].[AnotherEntity] ([Id])
 GO
 ALTER TABLE [dbo].[Roles] CHECK CONSTRAINT [FK1A2E670F36A436]
 GO
+/****** Object:  ForeignKey [FK_AnotherEntity_CompositeIdEntity] ******/
+ALTER TABLE [dbo].[AnotherEntity]  WITH CHECK ADD  CONSTRAINT [FK_AnotherEntity_CompositeIdEntity] FOREIGN KEY([CompositeObjectId], [CompositeTenantId])
+REFERENCES [dbo].[CompositeIdEntity] ([ObjectId], [TenantId])
+GO
+ALTER TABLE [dbo].[AnotherEntity] CHECK CONSTRAINT [FK_AnotherEntity_CompositeIdEntity]
+GO
 /****** Object:  ForeignKey [FK1A2E670F9E248253]    Script Date: 06/17/2010 13:08:54 ******/
 ALTER TABLE [dbo].[Roles]  WITH CHECK ADD  CONSTRAINT [FK1A2E670F9E248253] FOREIGN KEY([ParentId])
 REFERENCES [dbo].[Roles] ([Id])

src/NHibernate.Test/DbScripts/MsSql2012DialectLinqReadonlyDropScript.sql

@@ -26,6 +26,7 @@ ALTER TABLE [dbo].[TimesheetEntries] DROP CONSTRAINT [FK7E222050C7D0B317]
 ALTER TABLE [dbo].[TimeSheetUsers] DROP CONSTRAINT [FKA6EEF73795E61DFF]
 ALTER TABLE [dbo].[TimeSheetUsers] DROP CONSTRAINT [FKA6EEF737C7D0B317]
 ALTER TABLE [dbo].[Users] DROP CONSTRAINT [FK2C1C7FE5D8C957C7]
+ALTER TABLE [dbo].[AnotherEntity] DROP CONSTRAINT [FK_AnotherEntity_CompositeIdEntity]
 DROP TABLE [dbo].[TimeSheetUsers]
 DROP TABLE [dbo].[Users]
 DROP TABLE [dbo].[OrderLines]
@@ -48,6 +49,7 @@ DROP TABLE [dbo].[Categories]
 DROP TABLE [dbo].[Customers]
 DROP TABLE [dbo].[Animal]
 DROP TABLE [dbo].[AnotherEntity]
+DROP TABLE [dbo].[CompositeIdEntity]
 DROP TABLE [dbo].[Shippers]
 DROP TABLE [dbo].[States]
 DROP TABLE [dbo].[Suppliers]

src/NHibernate.Test/Linq/JoinTests.cs

@@ -315,6 +315,17 @@ public void OrderLinesWithSelectingCustomerNameInCaseShouldProduceTwoJoinsAltern
 				Assert.That(countJoins, Is.EqualTo(2));
 			}
 		}
+
+		[Test]
+		public void ShouldConstipateJoinsWhenOnlyComparingCompositeIdProperties()
+		{
+			using (var spy = new SqlLogSpy())
+			{
+				db.AnotherEntity.Where(x => x.CompositeIdEntity.Id.TenantId == 3).ToList();
+				var countJoins = CountJoins(spy);
+				Assert.That(countJoins, Is.EqualTo(0));
+			}
+		}
 
 		private static int CountJoins(LogSpy sqlLog)
 		{

src/NHibernate.Test/Linq/LinqReadonlyTestsContext.cs

@@ -44,7 +44,8 @@ private IEnumerable<string> Mappings
 					"Northwind.Mappings.TimeSheet.hbm.xml",
 					"Northwind.Mappings.Animal.hbm.xml",
 					"Northwind.Mappings.Patient.hbm.xml",
-					"Northwind.Mappings.NumericEntity.hbm.xml"
+					"Northwind.Mappings.NumericEntity.hbm.xml",
+					"Northwind.Mappings.CompositeIdEntity.hbm.xml"
 				};
 			}
 		}

src/NHibernate.Test/Linq/LinqTestCase.cs

@@ -37,7 +37,8 @@ protected override string[] Mappings
 					"Northwind.Mappings.Patient.hbm.xml",
 					"Northwind.Mappings.DynamicUser.hbm.xml",
 					"Northwind.Mappings.NumericEntity.hbm.xml",
-					"Northwind.Mappings.CompositeOrder.hbm.xml"
+					"Northwind.Mappings.CompositeOrder.hbm.xml",
+					"Northwind.Mappings.CompositeIdEntity.hbm.xml"
 				};
 			}
 		}

src/NHibernate.Test/QueryTranslator/CustomQueryLoaderFixture.cs

@@ -30,7 +30,8 @@ internal sealed class CustomQueryLoaderFixture : TestCase
 				"Northwind.Mappings.TimeSheet.hbm.xml",
 				"Northwind.Mappings.Animal.hbm.xml",
 				"Northwind.Mappings.Patient.hbm.xml",
-				"Northwind.Mappings.NumericEntity.hbm.xml"
+				"Northwind.Mappings.NumericEntity.hbm.xml",
+				"Northwind.Mappings.CompositeIdEntity.hbm.xml"
 			};
 
 		protected override string MappingsAssembly => "NHibernate.DomainModel";

src/NHibernate.sln.DotSettings

@@ -21,6 +21,9 @@
 	<s:String x:Key="/Default/CodeStyle/Naming/CSharpNaming/PredefinedNamingRules/=PrivateConstants/@EntryIndexedValue">&lt;Policy Inspect="True" Prefix="" Suffix="" Style="aaBb" /&gt;</s:String>
 	<s:String x:Key="/Default/CodeStyle/Naming/CSharpNaming/PredefinedNamingRules/=PrivateInstanceFields/@EntryIndexedValue">&lt;Policy Inspect="True" Prefix="_" Suffix="" Style="aaBb" /&gt;</s:String>
 	<s:String x:Key="/Default/CodeStyle/Naming/CSharpNaming/PredefinedNamingRules/=PrivateStaticReadonly/@EntryIndexedValue">&lt;Policy Inspect="True" Prefix="" Suffix="" Style="AaBb" /&gt;</s:String>
+	<s:String x:Key="/Default/CodeStyle/Naming/CSharpNaming/UserRules/=15b5b1f1_002D457c_002D4ca6_002Db278_002D5615aedc07d3/@EntryIndexedValue">&lt;Policy&gt;&lt;Descriptor Staticness="Static" AccessRightKinds="Private" Description="Static readonly fields (private)"&gt;&lt;ElementKinds&gt;&lt;Kind Name="READONLY_FIELD" /&gt;&lt;/ElementKinds&gt;&lt;/Descriptor&gt;&lt;Policy Inspect="True" Prefix="" Suffix="" Style="AaBb" /&gt;&lt;/Policy&gt;</s:String>
+	<s:String x:Key="/Default/CodeStyle/Naming/CSharpNaming/UserRules/=236f7aa5_002D7b06_002D43ca_002Dbf2a_002D9b31bfcff09a/@EntryIndexedValue">&lt;Policy&gt;&lt;Descriptor Staticness="Any" AccessRightKinds="Private" Description="Constant fields (private)"&gt;&lt;ElementKinds&gt;&lt;Kind Name="CONSTANT_FIELD" /&gt;&lt;/ElementKinds&gt;&lt;/Descriptor&gt;&lt;Policy Inspect="True" Prefix="" Suffix="" Style="aaBb" /&gt;&lt;/Policy&gt;</s:String>
+	<s:String x:Key="/Default/CodeStyle/Naming/CSharpNaming/UserRules/=4a98fdf6_002D7d98_002D4f5a_002Dafeb_002Dea44ad98c70c/@EntryIndexedValue">&lt;Policy&gt;&lt;Descriptor Staticness="Instance" AccessRightKinds="Private" Description="Instance fields (private)"&gt;&lt;ElementKinds&gt;&lt;Kind Name="FIELD" /&gt;&lt;Kind Name="READONLY_FIELD" /&gt;&lt;/ElementKinds&gt;&lt;/Descriptor&gt;&lt;Policy Inspect="True" Prefix="_" Suffix="" Style="aaBb" /&gt;&lt;/Policy&gt;</s:String>
 	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ECSharpAttributeForSingleLineMethodUpgrade/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ECSharpKeepExistingMigration/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ECSharpPlaceEmbeddedOnSameLineMigration/@EntryIndexedValue">True</s:Boolean>
@@ -29,6 +32,7 @@
 	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ESettingsUpgrade_002ECSharpPlaceAttributeOnSameLineMigration/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ESettingsUpgrade_002EMigrateBlankLinesAroundFieldToBlankLinesAroundProperty/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ESettingsUpgrade_002EMigrateThisQualifierSettings/@EntryIndexedValue">True</s:Boolean>
+	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ESettingsUpgrade_002EPredefinedNamingRulesToUserRulesUpgrade/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002EFormat_002ESettingsUpgrade_002EAlignmentTabFillStyleMigration/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/Environment/UnitTesting/SeparateAppDomainPerAssembly/@EntryValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/PatternsAndTemplates/StructuralSearch/Pattern/=0BE95D01E0F2244E97F5FEFAD1EB1A63/@KeyIndexDefined">True</s:Boolean>

src/NHibernate/Linq/ReWriters/AddJoinsReWriter.cs

@@ -4,6 +4,8 @@
 using NHibernate.Engine;
 using NHibernate.Linq.Clauses;
 using NHibernate.Linq.Visitors;
+using NHibernate.Persister.Entity;
+using NHibernate.Type;
 using NHibernate.Util;
 using Remotion.Linq;
 using Remotion.Linq.Clauses;
@@ -92,11 +94,35 @@ public bool IsIdentifier(System.Type type, string propertyName)
 
 		bool IIsEntityDecider.IsEntity(MemberExpression expression, out bool isIdentifier)
 		{
-			isIdentifier =
-				ExpressionsHelper.TryGetMappedType(_sessionFactory, expression, out var mappedType, out var entityPersister, out _, out var memberPath)
-				&& entityPersister?.IdentifierPropertyName == memberPath;
+			if (ExpressionsHelper.TryGetMappedType(_sessionFactory, expression, out var mappedType, out var entityPersister, out var componentType, out var memberPath))
+			{
+				isIdentifier = IsIdentifierPath(entityPersister, componentType, memberPath);
+				return mappedType?.IsEntityType == true;
+			}
+			isIdentifier = false;
+			return false;
+		}
 
-			return mappedType?.IsEntityType == true;
+		bool IsIdentifierPath(IEntityPersister entityPersister, IAbstractComponentType componentType, string memberPath)
+		{
+			if (entityPersister == null)
+			{
+				return false;
+			}
+			if (entityPersister.IdentifierPropertyName == memberPath)
+			{
+				return true;
+			}
+			// Don't bother to add the join if we're just comparing properties of the composite id
+			if (componentType != null)
+			{
+				var pathParts = memberPath.Split('.');
+				return pathParts.Length == 2
+					&& pathParts[0] == entityPersister.IdentifierPropertyName
+					&& componentType.PropertyNames.Any(name => name == pathParts[1]);
+			}
+
+			return false;
 		}
 	}
 }