Query: invalid SQL produced for queries with navigation inside predicate of SelectMany-Where-DefaultIfEmpty() pattern

So I have this query with two LEFT JOINS. Everything worked as expected when I had only one LEFT JOIN.

var dbQuery = from i in context.Ingredients
              from ii in i.CombinationIngredients.Where(ci => ci.IngredientId == forIngredientId).DefaultIfEmpty()
              select new
              {
                  i.Id,
                  i.Name,
                  Linked = ii != null
              };

However, when I add a second LEFT JOIN I see multiple queries in the database and I get an Exception.

var dbQuery = from i in context.Ingredients
              from ii in i.CombinationIngredients.Where(ci => ci.IngredientId == forIngredientId).DefaultIfEmpty()
              from t in i.Translations.Where(l => l.Language.Iso639_1 == language).DefaultIfEmpty()
              select new
              {
                  i.Id,
                  i.Name,
                  t.Translation,
                  Linked = ii != null
              };

I add a Skip(…).Take(100) elsewhere in my code, but one of the queries is a “SELECT [all columns] FROM Ingredient” making this a HUGE performance hit! But, what’s even worse is that it doesn’t work AT ALL.

Notice how I added t.Translation to the return value? I get the error “System.Data.SqlClient.SqlException: ‘Invalid column name ‘Translation’.’” EF somehow figures out that the column Translation is part of the Language table, while it’s part of the IngredientTranslation table (which is what i.Translations points to). One of the generated queries:

SELECT [i.Translations_groupItem.Language0].[Id], [i.Translations_groupItem.Language0].[Iso639_1], [i.Translations_groupItem.Language0].[Translation]
FROM [Language] AS [i.Translations_groupItem.Language0]

I do have a workaround, which is to just write the full join.

var dbQuery = from i in context.Ingredients
              from ii in i.CombinationIngredients.Where(ci => ci.IngredientId == forIngredientId).DefaultIfEmpty()
              join tran in context.IngredientTranslations.Where(l => l.Language.Iso639_1 == language) on i.Id equals tran.IngredientId into tranGroup
              from t in tranGroup.DefaultIfEmpty()
              select new
              {
                  i.Id,
                  i.Name,
                  t.Translation,
                  Linked = ii != null
              };

I’d prefer to use the much shorter “from x in …” syntax though. I know this works in the non-core EF version.

Further technical details

EF Core version: 2.1.0-preview1-final Database Provider: Microsoft.EntityFrameworkCore.SqlServer Operating system: Windows 10 IDE: Visual Studio 2017 15.6.7

[maumar]

EFCore was written from scratch so it usually doesn’t share issues with EF6. We will definitely fix this - navigation inside predicate of the LEFT JOIN pattern is a compelling scenario so it should work. However at this point we only accept critical issues and regressions for the 2.1 release, so the fix will most likely land after 2.1 has shipped.

[maumar]

Simplified repro:

    class Program
    {
        static void Main(string[] args)
        {
            using (var ctx = new MyContext())
            {
                ctx.Database.EnsureDeleted();
                ctx.Database.EnsureCreated();

                var apple = new Ingredient { Active = true, Name = "Apple" };
                var pear = new Ingredient { Active = true, Name = "Pear" };
                var dutch = new Language { Active = true, Iso639_1 = "nl", Name = "Dutch" };
                var english = new Language { Active = true, Iso639_1 = "en", Name = "English" };
                ctx.Add(apple);
                ctx.Add(pear);
                ctx.Add(dutch);
                ctx.Add(english);
                ctx.Add(new IngredientTranslation { Ingredient = apple, Language = dutch, Translation = "Appel" });
                ctx.Add(new IngredientTranslation { Ingredient = pear, Language = dutch, Translation = "Peer" });
                ctx.SaveChanges();
            }

            using (var ctx = new MyContext())
            {
                string language = "nl";

                var query = from i in ctx.Ingredients
                            from t in i.Translations.Where(l => l.Language.Iso639_1 == language).DefaultIfEmpty()
                            select new
                              {
                                  i.Id,
                                  i.Name,
                                  t.Translation,
                              };

                var result = query.ToList();
            }
        }
    }

    public class MyContext : DbContext
    {
        public virtual DbSet<Ingredient> Ingredients { get; set; }
        public virtual DbSet<IngredientTranslation> IngredientTranslations { get; set; }
        public virtual DbSet<Language> Languages { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlServer(@"Server=.;Database=Repro11847;Trusted_Connection=True;MultipleActiveResultSets=True");
        }
    }

    public class Ingredient
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public bool Active { get; set; }

        public virtual ICollection<IngredientTranslation> Translations { get; set; }
    }

    public class IngredientTranslation
    {
        public int Id { get; set; }
        public string Translation { get; set; }

        public int IngredientId { get; set; }
        public Ingredient Ingredient { get; set; }

        public int LanguageId { get; set; }
        public Language Language { get; set; }
    }

    public class Language
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public bool Active { get; set; }
        public string Iso639_1 { get; set; }
    }