Assume that you are using Microsoft SQL Server 2012 Analysis Service (SSAS 2012) or SQL Server 2014 Analysis Service (SSAS 2014). When you run a Multidimensional Expressions (MDX) query against a large database that has a sub-select of different granularities, the query may take a much longer time than the single granularity under the same logic.
The issue was first fixed in the following cumulative updates for SQL Server:
Cumulative Update 2 for SQL Server 2014 SP1
Cumulative Update 8 for SQL Server 2014
Cumulative Update 6 for SQL Server 2012 SP2
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. We recommend that you download and install the latest cumulative updates for SQL Server:
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.