Query: Make keyless entity type materialization checks part of DiscriminatorCondition

If DiscriminatorCondition returns null for IEntityType then return null instance.

Part of #18923

Author: smitpatel

src/EFCore/Query/EntityShaperExpression.cs

@@ -45,9 +45,7 @@ protected EntityShaperExpression(
 
             if (discriminatorCondition == null)
             {
-                // Generate condition to discriminator if TPH
-                discriminatorCondition = GenerateDiscriminatorCondition(entityType);
-
+                discriminatorCondition = GenerateDiscriminatorCondition(entityType, nullable);
             }
             else if (discriminatorCondition.Parameters.Count != 1
                     || discriminatorCondition.Parameters[0].Type != typeof(ValueBuffer)
@@ -63,11 +61,11 @@ protected EntityShaperExpression(
             DiscriminatorCondition = discriminatorCondition;
         }
 
-        private LambdaExpression GenerateDiscriminatorCondition(IEntityType entityType)
+        private LambdaExpression GenerateDiscriminatorCondition(IEntityType entityType, bool nullable)
         {
             var valueBufferParameter = Parameter(typeof(ValueBuffer));
             Expression body;
-            var concreteEntityTypes = entityType.GetConcreteDerivedTypesInclusive().ToList();
+            var concreteEntityTypes = entityType.GetConcreteDerivedTypesInclusive().ToArray();
             var discriminatorProperty = entityType.GetDiscriminatorProperty();
             if (discriminatorProperty != null)
             {
@@ -80,8 +78,8 @@ private LambdaExpression GenerateDiscriminatorCondition(IEntityType entityType)
                             discriminatorProperty.ClrType, discriminatorProperty.GetIndex(), discriminatorProperty))
                 };
 
-                var switchCases = new SwitchCase[concreteEntityTypes.Count];
-                for (var i = 0; i < concreteEntityTypes.Count; i++)
+                var switchCases = new SwitchCase[concreteEntityTypes.Length];
+                for (var i = 0; i < concreteEntityTypes.Length; i++)
                 {
                     var discriminatorValue = Constant(concreteEntityTypes[i].GetDiscriminatorValue(), discriminatorProperty.ClrType);
                     switchCases[i] = SwitchCase(Constant(concreteEntityTypes[i], typeof(IEntityType)), discriminatorValue);
@@ -97,7 +95,20 @@ private LambdaExpression GenerateDiscriminatorCondition(IEntityType entityType)
             }
             else
             {
-                body = Constant(concreteEntityTypes.Count == 1 ? concreteEntityTypes[0] : entityType, typeof(IEntityType));
+                body = Constant(concreteEntityTypes.Length == 1 ? concreteEntityTypes[0] : entityType, typeof(IEntityType));
+            }
+
+            if (entityType.FindPrimaryKey() == null
+                && nullable)
+            {
+                body = Condition(
+                    entityType.GetProperties()
+                        .Select(p => NotEqual(
+                            valueBufferParameter.CreateValueBufferReadValueExpression(typeof(object), p.GetIndex(), p),
+                            Constant(null)))
+                        .Aggregate((a, b) => OrElse(a, b)),
+                    body,
+                    Default(typeof(IEntityType)));
             }
 
             return Lambda(body, valueBufferParameter);
@@ -128,7 +139,8 @@ public virtual EntityShaperExpression WithEntityType([NotNull] IEntityType entit
 
         public virtual EntityShaperExpression MarkAsNullable()
             => !IsNullable
-                ? new EntityShaperExpression(EntityType, ValueBufferExpression, true, DiscriminatorCondition)
+                // Marking nullable requires recomputation of Discriminator condition
+                ? new EntityShaperExpression(EntityType, ValueBufferExpression, true)
                 : this;
 
         public virtual EntityShaperExpression Update([NotNull] Expression valueBufferExpression)

src/EFCore/Query/ShapedQueryCompilingExpressionVisitor.cs

@@ -414,29 +414,9 @@ private Expression ProcessEntityShaper(EntityShaperExpression entityShaperExpres
                     }
                     else
                     {
-                        if (entityShaperExpression.IsNullable)
-                        {
-                            expressions.Add(
-                                Expression.IfThen(
-                                    entityType.GetProperties()
-                                        .Select(
-                                            p =>
-                                                Expression.NotEqual(
-                                                    valueBufferExpression.CreateValueBufferReadValueExpression(
-                                                        typeof(object),
-                                                        p.GetIndex(),
-                                                        p),
-                                                    Expression.Constant(null)))
-                                        .Aggregate((a, b) => Expression.OrElse(a, b)),
-                                MaterializeEntity(
-                                    entityShaperExpression, materializationContextVariable, concreteEntityTypeVariable, instanceVariable, null)));
-                        }
-                        else
-                        {
-                            expressions.Add(
-                                MaterializeEntity(
-                                    entityShaperExpression, materializationContextVariable, concreteEntityTypeVariable, instanceVariable, null));
-                        }
+                        expressions.Add(
+                            MaterializeEntity(
+                                entityShaperExpression, materializationContextVariable, concreteEntityTypeVariable, instanceVariable, null));
                     }
                 }
 
@@ -476,30 +456,27 @@ private Expression MaterializeEntity(
                             valueBufferExpression,
                             entityShaperExpression.DiscriminatorCondition.Body)));
 
-                var concreteEntityTypes = entityType.GetConcreteDerivedTypesInclusive().ToList();
+                var concreteEntityTypes = entityType.GetConcreteDerivedTypesInclusive().ToArray();
                 var discriminatorProperty = entityType.GetDiscriminatorProperty();
-                if (discriminatorProperty != null)
+                if (discriminatorProperty == null
+                    && concreteEntityTypes.Length > 1)
                 {
-                    var switchCases = new SwitchCase[concreteEntityTypes.Count];
-                    for (var i = 0; i < concreteEntityTypes.Count; i++)
-                    {
-                        switchCases[i] = Expression.SwitchCase(
-                            CreateFullMaterializeExpression(concreteEntityTypes[i], expressionContext),
-                            Expression.Constant(concreteEntityTypes[i], typeof(IEntityType)));
-                    }
-
-                    materializationExpression = Expression.Switch(
-                        concreteEntityTypeVariable,
-                        Expression.Constant(null, returnType),
-                        switchCases);
+                    concreteEntityTypes = new [] { entityType };
                 }
-                else
+
+                var switchCases = new SwitchCase[concreteEntityTypes.Length];
+                for (var i = 0; i < concreteEntityTypes.Length; i++)
                 {
-                    materializationExpression = CreateFullMaterializeExpression(
-                        concreteEntityTypes.Count == 1 ? concreteEntityTypes[0] : entityType,
-                        expressionContext);
+                    switchCases[i] = Expression.SwitchCase(
+                        CreateFullMaterializeExpression(concreteEntityTypes[i], expressionContext),
+                        Expression.Constant(concreteEntityTypes[i], typeof(IEntityType)));
                 }
 
+                materializationExpression = Expression.Switch(
+                    concreteEntityTypeVariable,
+                    Expression.Constant(null, returnType),
+                    switchCases);
+
                 expressions.Add(Expression.Assign(instanceVariable, materializationExpression));
 
                 if (_trackQueryResults