Explanation of Oslo error "M2037: SQL Generation Internal Error: Missing generator for variable"?

Question

In Microsoft Oslo SDK CTP 2008 (using Intellipad) the following code compiles fine:

module T {

    type A {
        Id : Integer32 = AutoNumber();
    } where identity Id;

    As : A*;

    type B {
        Id : Integer32 = AutoNumber();
//        A : A;
//    } where A in As && identity Id;
    } where identity Id;

    Bs : B*;

    type C {
        Id : Integer32 = AutoNumber();
        B : B;
    } where B in Bs && identity Id;

    Cs : C*;

}

and results in the following Reach SQL output:

set xact_abort on;
go

begin transaction;
go

set ansi_nulls on;
go

create schema [T];
go

create table [T].[As]
(
    [Id] int not null identity,
    constraint [PK_As] primary key clustered ([Id])
);
go

create table [T].[Bs]
(
    [Id] int not null identity,
    constraint [PK_Bs] primary key clustered ([Id])
);
go

create table [T].[Cs]
(
    [Id] int not null identity,
    [B] int not null,
    constraint [PK_Cs] primary key clustered ([Id]),
    constraint [FK_Cs_B_T_Bs] foreign key ([B]) references [T].[Bs] ([Id])
);
go

commit transaction;
go

But after changing the commented line in module T as follows

        A : A;
    } where A in As && identity Id;
//    } where identity Id;

the error message "M2037: SQL Generation Internal Error: Missing generator for variable 'A'" is displayed (in Intellipad's Reach SQL Window).

Any Ideas?

Regards, tamberg

Answer 1

I think what you want is:

type A {
    Id : Integer32 = AutoNumber();
} where identity Id;

As : A*;

type B {
    Id : Integer32 = AutoNumber();
    A : A;
} where identity Id;

Bs : (B where value.A in As)*;

type C {
    Id : Integer32 = AutoNumber();
    B : B;
} where identity Id && B in Bs;

Cs : (C where value.B in Bs)*;

Note that the constraints are on the externs, not the types here. I was able to get similar code when the constraints where on the types but not able to go more than one relationship deep. Moving them to the externs seems correct and generates the expected Reach SQL.

Answer 2

http://social.msdn.microsoft.com/Forums/en-US/oslo/thread/05103bf8-4e0f-4976-bcdd-2c724cb08738/