Nice blogpost about this is here : https://sqlperformance.com/2013/04/t-sql-queries/optimizer-limitations-with-filtered-indexes

...Filtered unique indexes do not provide uniqueness information to the optimizer...

I have no idea if this kind of limitation will change in future....

• This reply was modified 5 years, 6 months ago by vojtech.moravec.

EDIT : MSSQL2019 Developer acts the same 🙁