Invalid SQL Generated for CTE with Count and Distinct

When running the following test (setup in CteTests) against sql server and SQLite Invalid SQL is generated

[Test]
public void Test5([CteContextSource] string context)
{
	using (var db = GetDataContext(context))
	{
		var cte1 = db.GetTable<Child>()
			.Where(c => c.ParentID > 1)
			.Select(child => new
			{
				child.ParentID,
				child.ChildID
			}).Distinct()
			.AsCte();
		var query = from p in db.Parent
			join c in cte1 on p.ParentID equals c.ParentID
			join c2 in cte1 on p.ParentID equals c2.ParentID
			select p;

		var cte1_ = db.GetTable<Child>().Where(c => c.ParentID > 1).Select(child => new
		{
			child.ParentID,
			child.ChildID
		}).Distinct();

		var expected =
			from p in db.Parent
			join c in cte1_ on p.ParentID equals c.ParentID
			join c2 in cte1_ on p.ParentID equals c2.ParentID
			select p;

		Assert.AreEqual(expected.Count(), query.Count());
	}
}

the SQL generated for the CTE query is as follows

-- SqlServer.2012
WITH [CTE_1] ([ParentID])
AS
(
	SELECT DISTINCT
		[t1].[ParentID],
		[t1].[ChildID]
	FROM
		[Child] [t1]
	WHERE
		[t1].[ParentID] > 1
)
SELECT
	Count(*) as [cnt]
FROM
	[Parent] [p]
		INNER JOIN [CTE_1] [c1] ON [p].[ParentID] = [c1].[ParentID]
		INNER JOIN [CTE_1] [c2] ON [p].[ParentID] = [c2].[ParentID]

As you can see, CTE_1 only declares ParentID as CTE columns, but ChildID is also selected because it has the DISTINCT clause, it looks like the CTE isn’t respecting the changes caused by the DISTINCT clause.

As a work around I can not use a CTE for now.

Exception message:
System.Data.SqlClient.SqlException : 'CTE_1' has more columns than were specified in the column list.

Steps to reproduce

Copy paste the snippet above into CteTests and run.

Environment details

linq2db version: 2.5.0 Database Server: SqlServer

[sdanyliv]

Will check. I’ll fix this today. @MaceWindu, I think we can prepare bug-fix release after merging this PR.

[hahn-kev]

Testing out release 2.6.0-rc2852 and my issue is resolved when using a CTE. Thanks!