奇妙なパフォーマンスの問題:インライン ユーザー定義関数の共通テーブル式

ハハ、これを試してみてください:

IF OBJECT_ID('_HappyFunction' ) IS NOT NULL DROP FUNCTION _HappyFunction
IF OBJECT_ID('_SadFunction'   ) IS NOT NULL DROP FUNCTION _SadFunction
IF TYPE_ID  ('_UniqueIntTable') IS NOT NULL DROP TYPE _UniqueIntTable
GO

CREATE TYPE _UniqueIntTable AS TABLE (Value int NOT NULL PRIMARY KEY)
GO

CREATE FUNCTION _HappyFunction (@IDs _UniqueIntTable READONLY)
RETURNS TABLE AS RETURN
  SELECT Value FROM @IDs
GO

CREATE FUNCTION _SadFunction (@IDs _UniqueIntTable READONLY)
RETURNS TABLE AS RETURN 
  WITH CTE AS (SELECT Value FROM @IDs)
  SELECT Value FROM CTE
GO

-- this will return an empty record set
DECLARE @IDs _UniqueIntTable 
SELECT * FROM _HappyFunction(@IDs)
GO

-- this will hang
DECLARE @IDs _UniqueIntTable 
SELECT * FROM _SadFunction(@IDs)
GO
  

 誰が予想したでしょうか?