KB3192154 - A non-optimal query plan choice causes poor performance when values outside the range represented in statistics are searched in SQL Server 2016 and 2017

Symptoms

Consider the following scenario:

  • You use a cardinality estimation (CE) configuration that corresponds to database compatibility level 120 or a later level for your Microsoft SQL Server 2016 and 2017 system.

  • You run a query that contains a search predicate.

  • The query searches for values that are less than or equal to any number that's less than the minimum value of RANGE_HI_KEY that's stored in the statistics object. Or, the query searches for values that are greater than the maximum value of RANGE_HI_KEY for the same statistics.

In this scenario, the query optimizer overestimates the number of rows. This could cause a less-than-optimal query plan choice and poor performance.

Resolution

The fix for this issue is included in the following cumulative updates for SQL Server:

Cumulative update 6 for SQL Server 2017

Cumulative update 8 for SQL Server 2016 SP1

Cumulative Update 2 for SQL Server 2016
Note After you install this update, you must enable trace flag 4199 in order to enable this fix. To enable trace flag 4199, see the Trace Flags (Transact-SQL) topic on the Microsoft Developer Network (MSDN) website.

 

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:

Latest cumulative update for SQL Server 2017

Latest cumulative update for SQL Server 2016

Status

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

References

Learn about the terminology Microsoft uses to describe software updates.

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