Cosmos: remove automatic composition of discriminator filter in raw SQL queries

To ensure the correct type is project for materialization, FromSqlRaw wraps the query passed, so that this:

var contacts = await context.Contacts.FromSqlRaw("select * from Contacts").ToListAsync();

Really gets resolved as this:

SELECT c FROM (SELECT * From Contacts) c WHERE c.Discriminator = "Contact"

While this works fine in most scenarios, it causes issues when users project explicit columns. Although this works fine as a raw query and returns multiple records:

SELECT Id, Name, Phone, Address FROM Contacts

This will never return any records and doesn’t throw an error or log a warning:

var contacts = await context.Contacts.FromSqlRaw("select Id, Name, Phone, Address from Contacts").ToListAsync();

Although this behavior is documented, it’s not obvious if the documentation hasn’t been read. It could lead to a lot of troubleshooting around a non-issue that just requires the user add one column to their select statement.

I suggest either logging a warning or throwing an exception when Discriminator isn’t included so it’s clear to the user it won’t behave as expected and what to do for mitigation.

EF Core version: EF Core 6.0 Database provider: All Target framework: .NET 6.0 Operating system: BeOS IDE: Visual Studio 2022

[ajcvickers]

@roji Nominating you to do this for 6.0. 😃

[AndriySvyryd]

Yes, otherwise it would be a “breaking” change