Writeback bug or feature in SSAS 2008 R2

I wrote on my last project a .net desktop application used for forecast and

monitoring in contact centers as reflected in the blog entry 'Cube writeback with multiple values in one shot'.

I won't reveal all the details of this application but it is based on OWC on a windows form, cube actions intercepted in events fired when user invokes a context menu and finally writing the changes to the cube.

You may recall that cube changes are not written directly to cube cells but to a relational table

called writeback table.

    

The writeback table in my case has columns for all measures in the measure group

- [OfferedCalls_0], [ForecastedOfferedCalls_1], [AdvisorsAbsent_2] ,

 [Distribution_4], [EmployeesPlanned_5], [CallsPerAdvisorDistribution_6] -,

the interecting dimensions :

[SKTime_7] foreign key which points to a Time dimension covering all the 96 quarters of the hours during a day ,

[SKCallFlowDepartment_8] foreign key which points to an organisational dimension  

[SKDate_9] foreign key pointing to the Date Dimension

and two additional columns for auditing purposes - MS_AUDIT_TIME_10] ,  [MS_AUDIT_USER_11] .

The table looks like :

CREATE TABLE [dbo].[WriteTable_Forecast Measures](

 [OfferedCalls_0] [int] NULL,

 [ForecastedOfferedCalls_1] [int] NULL,

 [AdvisorsAbsent_2] [int] NULL,

 [Support_3] [int] NULL,

 [Distribution_4] [float] NULL,

 [EmployeesPlanned_5] [int] NULL,

 [CallsPerAdvisorDistribution_6] [float] NULL,

 [SKTime_7] [bigint] NULL,

 [SKCallFlowDepartment_8] [bigint] NULL,

 [SKDate_9] [bigint] NULL,

 [MS_AUDIT_TIME_10] [datetime] NULL,

 [MS_AUDIT_USER_11] [nvarchar](255) NULL

) ON [fgCurrent]

What it really happens is that the delta changes written to the writeback table inserts a row with a null value for the [SKTime_7] column and this is certainly neither expected or desired.

Cube processing with the default settings fails due to the null key. If you ignore the errors and succeed in processing the cube, the numbers the users entered once are different then the ones displayed by the client, so you have a very serious problem.

You have no influence of this process: playing with the mdx update cube ... statement, changing among the four allocation options ( USE_EQUAL_ALLOCATION is the default option) or

trying to enforce the foreing key constrains will not help you.

So I had to find a work-around based on the following steps : 

• Retrieve the row with the null key in a temporary table with a select into statement.
• Update the writeback table by adding the values retrieved from the temporary table to the values of the corresponding measure for a particular row generated by the client.
• Delete the 'orphan' row.

 as implemented in the bellow script .

select ForecastedOfferedCalls_1 , SKCallFlowDepartment_8 , SKDate_9 , SKTime_7, MS_AUDIT_TIME_10 , MS_AUDIT_USER_11
into #Write_Temp   from dbo.[WriteTable_Forecast Measures]
where SKTime_7 is null

update  dbo.[WriteTable_Forecast Measures]
set ForecastedOfferedCalls_1 = a.ForecastedOfferedCalls_1 + b.ForecastedOfferedCalls_1
from dbo.[WriteTable_Forecast Measures] a, #Write_temp b
where a.SKDate_9 = b.SKDate_9
and a.SKCallFlowDepartment_8 = b.SKCallFlowDepartment_8
and a.MS_AUDIT_TIME_10 = b.MS_AUDIT_TIME_10
and a.MS_AUDIT_USER_11 = b.MS_AUDIT_USER_11
and a.SKTime_7 in ( select SKTime from dim.LocalTimeOfDay
where MNQuarterInterval = '00:00-00:15' )

delete dbo.[WriteTable_Forecast Measures]
where SKTime_7 is null

This seems to solve the problem. But I did not encounter this issue when running the application in the previous SSAS release and this makes me think of the never ending dilemma : bug or feature of the latest SSAS release. This is the question...