Different results (and SQL queries) by SingleAsyncEF and SingleAsyncLinqToDB with self-referenced entity

[parus95]

A very simple query with an entity referencing itself gives an incorrect result (the relation unfolds in the opposite direction).

My database: PostgreSQL

Software versions

    <TargetFramework>netcoreapp3.1</TargetFramework>
    <PackageReference Include="linq2db.EntityFrameworkCore" Version="3.7.0" />
    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="3.1.9" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="3.1.9"/>
    <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="3.1.4" />

My entity:

        public sealed class TestEntity
        {
            public int Id { get; set; }

            public int? ParentId { get; set; }

            public TestEntity Parent { get; set; }
            public List<TestEntity> Childs { get; set; }

            public string Name { get; set; }
        }

Configuration

modelBuilder.Entity<TestEntity>(b =>
{
    b.HasKey(x => new { x.Id });

    b.HasOne(x => x.Parent)
        .WithMany(x => x.Childs)
        .HasForeignKey(x => new { x.ParentId })
        .HasPrincipalKey(x => new { x.Id });

    b.HasData(new[]
    {
        new TestEntity
        {
            Id=2,
            Name = "Name1_2",
        },
        new TestEntity
        {
            Id=3,
            Name = "Name1_3",
            ParentId=2
        },
    });
});

query:

var q = dbContext.TestEntities
    .Where(x => x.Name == "Name1_3")
    .Select(x => x.Parent.Name + ">" + x.Name);

EF result (correct):

var efResult = await q.SingleAsyncEF();
/*
* SQL generated by EF Core
SELECT (t0."Name" || '>') || t."Name"
FROM "TestEntities" AS t
LEFT JOIN "TestEntities" AS t0 ON t."ParentId" = t0."Id"
WHERE t."Name" = 'Name1_3'
LIMIT 2
*/

// Prints: Name1_2>Name1_3
Console.WriteLine("EF result: " + efResult);

linq2db.EntityFrameworkCore result (incorrect):

var l2dbResult = await q.SingleAsyncLinqToDB();

var lq = q.ToLinqToDB();
/* SQL generated by linq2db
SELECT
        "a_Parent"."Name",
        x."Name"
FROM
        "TestEntities" x
        -- !!! Error on next line !!!!
                LEFT JOIN "TestEntities" "a_Parent" ON x."Id" = "a_Parent"."ParentId"
WHERE
        x."Name" = 'Name1_3'
LIMIT $1
*/
// Prints: ">Name1_3"
Console.WriteLine("L2DB result: " + l2dbResult);

Test project attached to current issue:

TestAppToSend.zip

[sdanyliv]

Thanks for reporting. Will check that.