Dynamic Range, Time Property Filter = Empty Matrix – A bug?

I think I’ve found a bug in the way the Excel Add-In generates MDX under certain ‘rolling’ conditions.  The requirement I have is to be able to forecast at the day level for a rolling 6 months; starting from the current period (which is to be updated each week) running for a period of 180 days (~ 6 months)

To prevent requiring 180 columns, a dimension property based filter must be available to select the month in which to forecast.  This will provide a more concise data entry form detailing up to 31 days of the selected month in which to add forecast values.

My form is dimensioned up as follows:

I set up the columns as a dynamic range to ensure that the forecast ‘rolls’ with changes in current period.  The range was set from current member id + 0 : current member id + 180.  [Current Period is set to 16th September 2008 – today).

The simplified MDX that this produces is below:

select 
    {
        
        Ancestor([Time].[Base View].[MemberId].&[20080916], [Time].[Base View].[MemberId]).Lag(0)
        :
        Ancestor([Time].[Base View].[MemberId].&[20080916], [Time].[Base View].[MemberId]).Lag(-180)
    }
    *
    {
        [Measures].[Value]
    } on columns, 
    
    {
        descendants([Location].[Standard].[All].[All Locations],,after)
    } on rows 
from 
(
    select 
        {[Time].[Month].[All].[September 2008]} on columns from [LocationPlan]) 
where 

    {[Employee].[Employee].[All].[John Doe]}
    *
    {[Scenario].[All Members].[All].[Forecast]}

The first element to notice is that the columns have been set to a range using ancestor at the member id level and lag to cover the 180 days:

Ancestor([Time].[Base View].[MemberId].&[20080916], [Time].[Base View].[MemberId]).Lag(0)
:
Ancestor([Time].[Base View].[MemberId].&[20080916], [Time].[Base View].[MemberId]).Lag(-180)

The next point to highlight is the sub=query that represents the selected time dimension property value (September 2008):

{[Time].[Month].[All].[September 2008]} on columns from [LocationPlan])

When you run this in SSMS, the following data set is returned:

The Locations appear on the rows, the days appear on the columns – exactly as required.

By changing the sub-query filter to October 2008 – the next month in the range, and definitely covered by the -180 day lag (Not sure why the Lead function isn’t used here?) – results in a problem, the results returned now are missing the day level columns:

The root of this problem is the column expression – if you replace the column expression with a direct lag on the current period member the expected results are returned:

select 
    {
        
        [Time].[Base View].[MemberId].&[20080916].Lag(0)
        :
        [Time].[Base View].[MemberId].&[20080916].Lag(-180)
    }
    *
    {
        [Measures].[Value]
    } on columns, 
    
    {
        descendants([Location].[Standard].[All].[All Locations],,after)
    } on rows 
from 
(
    select 
        {[Time].[Month].[All].[September 2008]} on columns from [LocationPlan]) 
where 

    {[Employee].[Employee].[All].[John Doe]}
    *
    {[Scenario].[All Members].[All].[Forecast]}

Now, the only workaround I can come up with is to build the form using a custom MDX formula so I reckon this warrants raising a bug on connect – which I’ve logged here:

https://connect.microsoft.com/feedback/ViewFeedback.aspx?FeedbackID=368206&SiteID=181