Time Calculation Shell dimension is slow compared to hardcoded measure?

Question

Hi,
I have a measuregroup with 200m+ rows with about 20 measures (sums). I've created a shell dimension to hold my time calculation members such as mtd, qtd, ytd, etc. My problem is that it performs REALLY poorly when using the time calculation dimension.
 My script looks like this:
SCOPE
Measuregroupmeasures("MyMeasureGroup");
SCOPE
[Time Calculation].[Calculation].&[None];
THIS =
[Measures].CurrentMember;
END SCOPE;
SCOPE
[Time Calculation].[Calculation].&[MTD];
THIS =
Aggregate
[Time Calculation].[Calculation].&[None]
MTD([Date].[Calendar (YQMD)].CurrentMember)
END SCOPE;
SCOPE
[Time Calculation].[Calculation].&[QTD];
THIS =
Aggregate
[Time Calculation].[Calculation].&[None]
QTD([Date].[Calendar (YQMD)].CurrentMember)
END SCOPE;
SCOPE
[Time Calculation].[Calculation].&[YTD];
THIS =
Aggregate
[Time Calculation].[Calculation].&[None]
YTD([Date].[Calendar (YQMD)].CurrentMember)
END SCOPE;
END SCOPE;
When I use my Calendar hierarchy and time calculation dimension as a background selection it takes forever. It never returns anything. A profiler trace shows that it's just pushing 1 and 21 events (cache data).
If I create the following measure:
CREATE
MEMBER CURRENTCUBE.[Measures].[TestMTD] AS
SUM(MTD([Date].[Calendar (YQMD)].CurrentMember), [Measures].[MyMeasure]),
VISIBLE = 1 ;
it works just fine but the whole point here is I want to avoid creating new measure for every time calculation.
The measuregroup has been partitioned by month and I've set each partition slice to the corresponding month in the calendar hierarchy.
Why doesn't my script perform - please advice :)
Thanks.

Answer 1

Hi Mortenbpost,
According to your description, the issue was solved by change Aggregate() function to Sum() function, now you want to know why it behaves like that, right?
In Aggregate function, if a numeric expression is not provided, this function aggregates each measure within the current query context by using the default aggregation operator that is specified for each measure. Here is a thread which discuss difference
between AGGREGATE() and SUM()https://social.msdn.microsoft.com/Forums/sqlserver/en-US/ef4b2555-45f2-4871-9137-a12a637ce2f5/whats-the-difference-between-aggregate-and-sum?forum=sqlanalysisservices
Besides, you can use SQL profiler to monitor what's the difference between using AGGREGATE() and using SUM().
Regards,
Charlie Liao
TechNet Community Support