[IGNITE-4460] .NET: Unhelpful error message for same-table SelectMany in LINQ

• Type: Bug
• Status: Resolved
• Priority: Trivial
• Resolution: Fixed
• Fix Version/s: 2.0
• Component/s: platforms
• Labels: .NET LINQ
• Assignee: Pavel Tupitsyn
• Reporter: Pavel Tupitsyn
• Created: 19/Dec/16 14:50
• Updated: 17/Apr/17 10:51
• Resolved: 17/Apr/17 10:51

Description

The following LINQ is not supported (RegionToRole is a collection, which is not understood by SQL):

users.Where(w => w.Value.ID == userId && !w.Value.IsDeleted)
                .SelectMany(sm => sm.Value.RegionToRole)

However, LINQ engine proceeds to generate an invalid query, which fails later in SQL engine:

Failed to parse query: select _T0._key, _T0._val from "User".User as _T0 , "User".User as _T0 where  ...

We should detect invalid LINQ early and throw an error with explanation.