EntityFramework dbContext navigation properties causing duplicate joins

Question

I'm getting a lot of duplicate joins in the SQL generated from my DbContext object using the Entity Framework. Here's my basic structure

CatalogTable( CatalogID int Primary Key )

CategoryTable( CategoryID int PRIMARY KEY, CatalogID int NOT NULL )

DepartmentTable( DepartmentID int PRIMARY KEY, CatalogID int NOT NULL)

Product( CatalogID int NOT NULL, CategoryID int NOT NULL, DepartmentID int NOT NULL )

Quite simply, a product has to have a catalog, category and department. I've setup all of the navigation properties to reflect this. Yes, a 'product' could be associated to a catalog indirectly through either the category or the department. But because there are two possible paths, I chose to explicitly indicate that a product belonged to a catalog.

So the problem becomes the EF keeps joining in these required relationships basically spitting out double joins for category and department.

Model:

           //catalogs
            modelBuilder.Entity<Catalog>().ToTable("Catalog.Catalogs");
            modelBuilder.Entity<Catalog>().HasKey(k => k.CatalogID);

            //products
            modelBuilder.Entity<CatalogItem>().ToTable("Catalog.Products");
            modelBuilder.Entity<CatalogItem>().HasKey(k => k.ProductID);
            modelBuilder.Entity<CatalogItem>().HasRequired(req => req.CatalogCategory).WithMany().Map(m => m.MapKey("CatalogCategoryID"));
            modelBuilder.Entity<CatalogItem>().HasRequired(req => req.CatalogDepartment).WithMany().Map(m => m.MapKey("CatalogDepartmentID"));
            modelBuilder.Entity<CatalogItem>().HasRequired(req => req.Catalog).WithMany().Map(m => m.MapKey("CatalogID"));

            //departments
            modelBuilder.Entity<CatalogDepartment>().ToTable("Catalog.Departments");
            modelBuilder.Entity<CatalogDepartment>().HasKey(k => k.CatalogDepartmentID);
            modelBuilder.Entity<CatalogDepartment>().HasRequired(req => req.Catalog).WithMany().Map(m => m.MapKey("CatalogID"));

            //categories
            modelBuilder.Entity<CatalogCategory>().ToTable("Catalog.Categories");
            modelBuilder.Entity<CatalogCategory>().HasKey(k => k.CatalogCategoryID);
            modelBuilder.Entity<CatalogCategory>().HasRequired(req => req.Catalog).WithMany().Map(m => m.MapKey("CatalogID"));

Linq:

var query = Products
    .Include(inc=>inc.CatalogCategory)
    .Include(inc=>inc.CatalogDepartment)
    .Include(inc=>inc.Catalog);



query.ToList();

Generated Sql:

SELECT *
FROM     [Catalog].[Products] AS [Extent1]
INNER JOIN [Catalog].[Categories] AS [Extent2] ON [Extent1].[CatalogCategoryID] = [Extent2].[CatalogCategoryID]
LEFT OUTER JOIN [Catalog].[Categories] AS [Extent3] ON [Extent1].[CatalogCategoryID] = [Extent3].[CatalogCategoryID]
LEFT OUTER JOIN [Catalog].[Departments] AS [Extent4] ON [Extent1].[CatalogDepartmentID] = [Extent4].[CatalogDepartmentID]
LEFT OUTER JOIN [Catalog].[Catalogs] AS [Extent5] ON [Extent1].[CatalogID] = [Extent5].[CatalogID]

You can clearly see "Categories" being joined twice; once as an inner join and once as an outer join.

Any ideas here how to cleanly (and accurately) establish the relationships but prevent the duplicate binding? Thanks!