This hotfix also applies to Microsoft SQL Server 2014 Analysis Services (SSAS 2014).
Symptoms
Assume that you use Microsoft SQL Server 2012 or SQL Server 2014. When you use the DistinctCount function in tabular mode, you encounter the following performance issue:
DistinctCount for a large set become slower when the number of distinct combination is greater than 1M.
Cause
The issue occurs because there is performance issue in the finding and the storing of a distinct combination when the set of distinct combination is greater than 1M.
Resolution
The issue was first fixed in the following cumulative update of SQL Server.
Cumulative Update 1 for SQL Server 2014 /en-us/help/2931693
Cumulative Update 9 for SQL Server 2012 SP1 /en-us/help/2931078
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:
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.