FIX: Parallel query execution plan with "merge join" slow to execute in Cumulative Update 3, 4, or 5 for SQL Server 2016 Service Pack 1 Content provided by Microsoft Applies to: SQL Server 2016 Enterprise CoreSQL Server 2016 EnterpriseSQL Server 2016 DeveloperSQL Server 2016 Standard More Select Product Version All Products Symptoms When you use Cumulative Update 3, Cumulative Update 4, or Cumulative Update 5 for SQL Server 2016 Service Pack 1, a query that uses a parallel query execution plan that contains a merge join operator may take longer to execute with extremely skewed data. Resolution This fix is included in the following cumulative updates for SQL Server: Cumulative Update 2 for SQL Server 2017Cumulative Update 6 for SQL Server 2016 SP1 About SQL Server builds 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. Last Updated: Nov 28, 2017 Did this solve your problem? Yes No Tell us what we can do to improve the article Submit Thanks! Your feedback will help us improve the support experience.