Skip null checks on required navigations and AsNoTracking before Select

src/GraphQL.EntityFramework/Filters/FilterEntry.cs

@@ -109,7 +109,7 @@ public FieldProjectionInfo AddRequirements(
                 var navMetadata = FindNavigation(navigationProperties, navName)!;
                 mergedNavigations[navName] = mergedNavigations.TryGetValue(navName, out var existingNav)
                     ? existingNav with { IsWhole = true }
-                    : new(navMetadata.Type, navMetadata.IsCollection, new([], null, null, null), true);
+                    : new(navMetadata.Type, navMetadata.IsCollection, new([], null, null, null), true, IsRequired: navMetadata.IsRequired);
             }
         }
 
@@ -135,7 +135,7 @@ public FieldProjectionInfo AddRequirements(
                 }
                 else
                 {
-                    mergedNavigations[navName] = new(navMetadata.Type, navMetadata.IsCollection, new(requiredProps, null, null, null));
+                    mergedNavigations[navName] = new(navMetadata.Type, navMetadata.IsCollection, new(requiredProps, null, null, null), IsRequired: navMetadata.IsRequired);
                 }
             }
         }

src/GraphQL.EntityFramework/GraphApi/EfGraphQLService_First.cs

@@ -159,14 +159,9 @@ FieldType BuildFirstField<TSource, TReturn>(
                     return ReturnNullable();
                 }
 
-                if (disableTracking)
-                {
-                    query = query.AsNoTracking();
-                }
-
                 query = query.ApplyGraphQlArguments(context, names, false, omitQueryArguments);
 
-                query = includeAppender.ApplyProjection(context, fieldContext.Filters, query);
+                query = includeAppender.ApplyProjection(context, fieldContext.Filters, query, disableTracking);
 
                 QueryLogger.Write(query);
 

src/GraphQL.EntityFramework/GraphApi/EfGraphQLService_Queryable.cs

@@ -105,17 +105,12 @@ FieldType BuildQueryField<TSource, TReturn>(
                         return Array.Empty<TReturn>();
                     }
 
-                    if (disableTracking)
-                    {
-                        query = query.AsNoTracking();
-                    }
-
                     if (!omitQueryArguments)
                     {
                         query = query.ApplyGraphQlArguments(context, names, true, omitQueryArguments);
                     }
 
-                    query = includeAppender.ApplyProjection(context, fieldContext.Filters, query);
+                    query = includeAppender.ApplyProjection(context, fieldContext.Filters, query, disableTracking);
 
                     QueryLogger.Write(query);
 

src/GraphQL.EntityFramework/GraphApi/EfGraphQLService_QueryableConnection.cs

@@ -78,14 +78,9 @@ ConnectionBuilder<TSource> BuildQueryConnection<TSource, TReturn>(
                     return Empty(context);
                 }
 
-                if (disableTracking)
-                {
-                    query = query.AsNoTracking();
-                }
-
                 query = query.ApplyGraphQlArguments(context, names, true, omitQueryArguments);
 
-                query = includeAppender.ApplyProjection(context, fieldContext.Filters, query);
+                query = includeAppender.ApplyProjection(context, fieldContext.Filters, query, disableTracking);
 
                 try
                 {

src/GraphQL.EntityFramework/GraphApi/EfGraphQLService_Single.cs

@@ -159,14 +159,9 @@ FieldType BuildSingleField<TSource, TReturn>(
                         return ReturnNullable();
                     }
 
-                    if (disableTracking)
-                    {
-                        query = query.AsNoTracking();
-                    }
-
                     query = query.ApplyGraphQlArguments(context, names, false, omitQueryArguments);
 
-                    query = includeAppender.ApplyProjection(context, fieldContext.Filters, query);
+                    query = includeAppender.ApplyProjection(context, fieldContext.Filters, query, disableTracking);
 
                     QueryLogger.Write(query);
 

src/GraphQL.EntityFramework/IncludeAppender.cs

@@ -9,17 +9,20 @@
     /// where the entity can be projected, otherwise includes. A projected navigation whose type
     /// cannot be projected is bound whole, and the navigations under it are then loaded through
     /// includes alongside the select, since EF applies includes to the entities in a projection.
+    /// <paramref name="disableTracking"/> applies AsNoTracking only when no select is added, since
+    /// a select creates new instances that EF does not track, so AsNoTracking would do nothing.
     /// </summary>
     public IQueryable<TItem> ApplyProjection<TDbContext, TItem>(
         IResolveFieldContext context,
         Filters<TDbContext>? filters,
-        IQueryable<TItem> query)
+        IQueryable<TItem> query,
+        bool disableTracking = false)
         where TDbContext : DbContext
         where TItem : class
     {
         if (context.SubFields is null)
         {
-            return query;
+            return ApplyTracking(query, disableTracking);
         }
 
         var type = typeof(TItem);
@@ -43,7 +46,7 @@ public IQueryable<TItem> ApplyProjection<TDbContext, TItem>(
 
         if (!SelectExpressionBuilder.TryBuild<TItem>(projection, keyNames, derivedTypes, out var expression, out var includePaths, out var argumentFields))
         {
-            return AddIncludesFromProjection(query, projection);
+            return ApplyTracking(AddIncludesFromProjection(query, projection), disableTracking);
         }
 
         foreach (var includePath in includePaths)
@@ -56,6 +59,10 @@ public IQueryable<TItem> ApplyProjection<TDbContext, TItem>(
         return query.Select(expression);
     }
 
+    static IQueryable<TItem> ApplyTracking<TItem>(IQueryable<TItem> query, bool disableTracking)
+        where TItem : class =>
+        disableTracking ? query.AsNoTracking() : query;
+
     /// <summary>
     /// Whether the projection loads a collection at any depth, the only case where query splitting
     /// changes anything.
@@ -432,7 +439,8 @@ void ProcessSelectionSet(
                 new(
                     navType,
                     navigation.IsCollection,
-                    GetNestedProjection(field.SelectionSet, navGraphType, navType, nestedNavProps, nestedKeys, nestedFks, context)));
+                    GetNestedProjection(field.SelectionSet, navGraphType, navType, nestedNavProps, nestedKeys, nestedFks, context),
+                    IsRequired: navigation.IsRequired));
         }
 
         return result;
@@ -686,7 +694,7 @@ void ProcessProjectionExpression(
                 nestedProjection = new(nestedScalarFields, nestedKeys ?? [], nestedFks ?? new HashSet<string>(), []);
             }
 
-            AddNavigation(navProjections, navigation.Name, new(navType, navigation.IsCollection, nestedProjection, isWhole, arguments));
+            AddNavigation(navProjections, navigation.Name, new(navType, navigation.IsCollection, nestedProjection, isWhole, arguments, navigation.IsRequired));
         }
     }
 
@@ -891,7 +899,8 @@ void ProcessNavigationOrScalar(
             new(
                 navType,
                 navigation.IsCollection,
-                GetNestedProjection(field.SelectionSet, GetComplexGraphType(fieldType), navType, nestedNavProps, nestedKeys, nestedFks, context)));
+                GetNestedProjection(field.SelectionSet, GetComplexGraphType(fieldType), navType, nestedNavProps, nestedKeys, nestedFks, context),
+                IsRequired: navigation.IsRequired));
     }
 
     /// <summary>

src/GraphQL.EntityFramework/Navigation.cs

@@ -7,5 +7,6 @@ public record Navigation
     Type Type,
     bool IsNullable,
     bool IsCollection,
-    string? InverseName = null
+    string? InverseName = null,
+    bool IsRequired = false
 );

src/GraphQL.EntityFramework/NavigationReader.cs

@@ -20,11 +20,19 @@ static IReadOnlyDictionary<string, Navigation> GetNavigations(IEntityType entity
                 _ =>
                 {
                     var (itemType, isCollection) = GetNavigationType(_);
-                    return new Navigation(_.Name, itemType, _.PropertyInfo!.IsNullable(), isCollection, _.Inverse?.Name);
+                    return new Navigation(_.Name, itemType, _.PropertyInfo!.IsNullable(), isCollection, _.Inverse?.Name, IsRequired(_));
                 })
             .ToDictionary(_ => _.Name.ToLowerInvariant(), StringComparer.OrdinalIgnoreCase);
     }
 
+    // EF never materializes a required reference navigation as null, so the select projection
+    // can skip the null check on it
+    static bool IsRequired(INavigationBase navigation) =>
+        navigation is INavigation { IsCollection: false } reference &&
+        (reference.IsOnDependent
+            ? reference.ForeignKey.IsRequired
+            : reference.ForeignKey.IsRequiredDependent);
+
     static (Type itemType, bool isCollection) GetNavigationType(INavigationBase navigation)
     {
         var navigationType = navigation.ClrType;

src/GraphQL.EntityFramework/SelectProjection/NavigationProjectionInfo.cs

@@ -3,6 +3,10 @@
 /// itself rather than properties of it. The select projection then binds the navigation whole
 /// instead of building a member init from <paramref name="Projection"/>.
 /// </param>
+/// <param name="IsRequired">
+/// The navigation is required in the EF model, so is never null. The select projection then
+/// skips the null check, which EF would otherwise translate to an always false comparison.
+/// </param>
 /// <param name="Arguments">
 /// The field's ids, where and orderBy, to apply inside the collection subquery. Null when the
 /// navigation was selected more than once, since one loaded collection cannot satisfy two sets
@@ -13,7 +17,8 @@ record NavigationProjectionInfo(
     bool IsCollection,
     FieldProjectionInfo Projection,
     bool IsWhole = false,
-    NavigationArguments? Arguments = null)
+    NavigationArguments? Arguments = null,
+    bool IsRequired = false)
 {
     public NavigationProjectionInfo Merge(NavigationProjectionInfo other) =>
         this with

src/GraphQL.EntityFramework/SelectProjection/SelectExpressionBuilder.cs

@@ -381,6 +381,14 @@ static bool TryBuildNavigationBinding(
             return false;
         }
 
+        // A required navigation is never null, and EF translates a null check on one to an always
+        // false comparison, so it is only checked when optional
+        if (navProjection.IsRequired)
+        {
+            binding = Expression.Bind(navAccess.Member, init);
+            return true;
+        }
+
         // source.Parent == null ? null : new Parent { ... }
         var conditional = Expression.Condition(
             Expression.Equal(navAccess, navMetadata.NullConstant),

src/Tests/IntegrationTests/IntegrationTests.AddSingleField_with_filter_accessing_navigation_denies_when_no_match.verified.txt

@@ -6,8 +6,7 @@
   },
   sql: {
     Text:
-select top (2) cast (0 as bit),
-               case when f0.Discriminator = N'FilterDerivedEntity' then cast (1 as bit) else cast (0 as bit) end,
+select top (2) case when f0.Discriminator = N'FilterDerivedEntity' then cast (1 as bit) else cast (0 as bit) end,
                f0.CommonProperty,
                f.BaseEntityId,
                f.Id,

src/Tests/IntegrationTests/IntegrationTests.AddSingleField_with_filter_accessing_navigation_uses_include.verified.txt

@@ -9,8 +9,7 @@
   },
   sql: {
     Text:
-select top (2) cast (0 as bit),
-               case when f0.Discriminator = N'FilterDerivedEntity' then cast (1 as bit) else cast (0 as bit) end,
+select top (2) case when f0.Discriminator = N'FilterDerivedEntity' then cast (1 as bit) else cast (0 as bit) end,
                f0.CommonProperty,
                f.BaseEntityId,
                f.Id,

src/Tests/IntegrationTests/IntegrationTests.Aliased_navigation_selections_merge.verified.txt

@@ -16,8 +16,7 @@
   },
   sql: {
     Text:
-select   cast (0 as bit),
-         d.Id,
+select   d.Id,
          d.IsActive,
          d.Name,
          e.DepartmentId,

src/Tests/IntegrationTests/IntegrationTests.Filter_projection_with_TPH_inheritance_should_not_select_all_fields.verified.txt

@@ -8,8 +8,7 @@
   },
   sql: {
     Text:
-select top (2) cast (0 as bit),
-               case when f0.Discriminator = N'FilterDerivedEntity' then cast (1 as bit) else cast (0 as bit) end,
+select top (2) case when f0.Discriminator = N'FilterDerivedEntity' then cast (1 as bit) else cast (0 as bit) end,
                f0.CommonProperty,
                f0.Id,
                f.BaseEntityId,

src/Tests/IntegrationTests/IntegrationTests.Many_children.verified.txt

@@ -12,8 +12,7 @@
   },
   sql: {
     Text:
-select case when c.Id is null then cast (1 as bit) else cast (0 as bit) end,
-       c.Id,
+select c.Id,
        c.ParentId,
        c0.Id,
        c0.ParentId,

src/Tests/IntegrationTests/IntegrationTests.Owned.verified.txt

@@ -11,8 +11,7 @@
   },
   sql: {
     Text:
-select top (2) cast (0 as bit),
-               o.Child1_Property,
+select top (2) o.Child1_Property as Property,
                o.Id,
                o.Property
 from   OwnedParents as o

src/Tests/IntegrationTests/IntegrationTests.Query_with_select_projection_and_filter_accessing_navigation.verified.txt

@@ -11,7 +11,6 @@
   sql: {
     Text:
 select i0.Id,
-       case when i1.Id is null then cast (1 as bit) else cast (0 as bit) end,
        i1.Id
 from   IncludeNonQueryableBs as i
        inner join

src/Tests/IntegrationTests/IntegrationTests.Selection_applies_to_navigation_of_field_type.verified.txt

@@ -15,8 +15,7 @@
   },
   sql: {
     Text:
-select case when c.Id is null then cast (1 as bit) else cast (0 as bit) end,
-       c.Id,
+select c.Id,
        case when w0.Id is null then cast (1 as bit) else cast (0 as bit) end,
        w0.Id,
        c.ParentId,

src/Tests/IntegrationTests/IntegrationTests.Where_owned.verified.txt

@@ -11,8 +11,7 @@
   },
   sql: {
     Text:
-select top (2) cast (0 as bit),
-               o.Child1_Property,
+select top (2) o.Child1_Property as Property,
                o.Id,
                o.Property
 from   OwnedParents as o