demo_marten_bug.cs

using Marten;
using Marten.Linq;
using System;
using System.Linq;

namespace DemoBugMarten
{
	class User
	{
		public Guid Id { get; set; }

		public string RealName { get; set; }

		public string DisplayName { get; set; }
	}

	class MegaUser : User
	{
	}

	public class UserMartenRegistry : MartenRegistry
	{
		public UserMartenRegistry()
		{
			this.For<User>().AddSubClass<MegaUser>();
		}
	}

	class Program
    {
        static void Main(string[] args)
        {
			var megaUser1 = new MegaUser() { DisplayName = "Yann", RealName = "Yann Yann" };
			var megaUser2 = new MegaUser() { DisplayName = "Robin", RealName = "Robin Robin" };
			var megaUser3 = new MegaUser() { DisplayName = "Marten", RealName = "Marten Marten" };

			var cs = "Host=localhost;Port=5432;Database=demo;User ID=postgres;Password=password";
			var store = DocumentStore.For(_ =>
			{
				_.AutoCreateSchemaObjects = AutoCreate.CreateOrUpdate;
				_.Connection(cs);
				_.CreateDatabasesForTenants(c =>
					c.ForTenant()
					.CheckAgainstPgDatabase()
					.WithOwner("postgres")
					.WithEncoding("UTF-8")
					.ConnectionLimit(-1));
				_.Schema.Include<UserMartenRegistry>();
			});

			var session = store.OpenSession();

			session.DeleteWhere<MegaUser>(_ => true);
			session.Insert(megaUser1);
			session.Insert(megaUser2);
			session.Insert(megaUser3);

			session.SaveChanges();

				var query = session.Query<MegaUser>()
					.Where(_ => _.DisplayName == "Yann" || _.DisplayName == "Robin");

			var cmd = query.ToCommand(FetchType.FetchMany);
			Console.WriteLine(cmd.CommandText);

			var queryList = query.ToList();
			foreach (var item in queryList)
			{
				Console.WriteLine(item.DisplayName);
			}
			Console.ReadLine();
		}
    }
}