Symptoms
When you operate Data Analysis Expressions (DAX) functions on the string or Boolean column on a multidimensional Analysis Services instance in Microsoft SQL Server 2012, performance regression occurs.
Resolution
The issue was first fixed in the following cumulative update of SQL Server.
Cumulative Update 1 for SQL Server 2012 SP2 /en-us/help/2976982
Cumulative Update 10 for SQL Server 2012 SP1 /en-us/help/2954099
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.