Symptoms
Assume that you have Microsoft SQL Server 2017 or 2019 installed, and that it runs with default Cardinality Estimation (CE). You execute a query that has a filter predicate on column Col1. Query predicates have intrinsic UPPER, LOWER, or RTRIM. Col1 has statistics to be used by the optimizer. In this scenario, you may observe inaccurate cardinality estimates and that SQL Server uses an inefficient plan. The following are some queries that have predicates:
SELECT person_id FROM Person WHERE (email LIKE UPPER(N'@live.com%'))
SELECT person_id FROM Person WHERE (email = UPPER(N'msft@live.com'))
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Resolution
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 the following to take effect:
-
QUERY_OPTIMIZER_HOTFIXES database-scoped configuration set to ON
-
Use the ENABLE_QUERY_OPTIMIZER_HOTFIXES USE HINT
-
Enable Trace Flag 4199
References
Learn about the terminology that Microsoft uses to describe software updates.
