KB4538497 - FIX: Slow query performance when using query predicates with UPPER, LOWER or RTRIM with default CE in SQL Server 2017 and 2019

Applies to: SQL Server 2017 on WindowsSQL Server 2019 on Windows


Assume that you have Microsoft SQL Server 2017 or 2019 installed, and that it runs withdefault Cardinality Estimation (CE). You execute a query that has a filter predicate on column Col1. Querypredicates have intrinsic UPPER, LOWER, or RTRIM. Col1 has statistics to beused by the optimizer. In this scenario, you may observe inaccurate cardinalityestimates and that SQL Server uses an inefficient plan. The following are some queries that have predicates: 
SELECT person_id FROM Person WHERE (emailLIKE UPPER(N'@live.com%')) 
SELECT person_id FROM Person WHERE (email= UPPER(N'msft@live.com'))


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section. 


This issue is fixed in the following cumulative updates for SQL Server:
About cumulative updates for SQL Server:
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server:
Note This fix requires one of thefollowing to take effect:


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