ParallelPeriod + PeriodsToDate = Unexpected exception

Apparently, I have no luck with ParallelPeriod() function again, but now, on how it works together with PeriodsToDate() function. This example is run on SSAS 2005 SP2 and I didn’t have chance to run it on SSAS 2008 yet, so very possible, it’s not an issue anymore.

 

A very harmless, at first sight MDX combination, left me in limbo and I wish I knew more about internals of query parsing and resolving process. Let’s say, I am collecting my data at the Week level and I want to calculate rolling measure by using PeriodsToDate function. My first calculation member looks like this:

 

member firstQTD as

aggregate(PeriodsToDate([Date].[Marketing Calendar].[Market Quarter])

         , [Measures].[MyMeasure]) 

 

Now, I want to calculate firstQTD for the previous year. So, here is the second member:

 

member QTD_LY as

(firstQTD,  ParallelPeriod([Date].[Marketing Calendar].[Market Year]))

 

or even:

 

member QTD_LY as

(firstQTD, 

ParallelPeriod([Date].[Marketing Calendar].[Market Year], 1,

               [Date].[Marketing Calendar].CurrentMember))

 

Very basic. But when I run my query:

 

with

member firstQTD as

aggregate(PeriodsToDate([Date].[Marketing Calendar].[Market Quarter])

         , [Measures].[MyMeasure])

 

member QTD_LY as

(firstQTD,  ParallelPeriod([Date].[Marketing Calendar].[Market Year]))

 

select

{{

[Date].[Marketing Calendar].[Market Week].&[200821],

[Date].[Marketing Calendar].[Market Week].&[200921]} *

{

firstQTD, QTD_LY

}}

on 0,

non empty [MyDimension].Members on 1

from [Cube]

 

I get something totally unexpected to me and to SSAS internals. Literally:

 

Executing the query …

Internal error: An unexpected exception occured

Execution complete

 

 

By rewriting my query, I’ve got some explanation of the internal info about the error:

 

Executing the query …

Internal error: An unexpected error occurred (file ‘mdevaluator.cpp’, line 2721, function ‘MDDisjointUnionEvaluator::AddSplit’).

Execution complete

 

The new query is:

 

with

member firstQTD as

aggregate(PeriodsToDate([Date].[Marketing Calendar].[Market Quarter],

                        [Date].[Marketing Calendar].CurrentMember)

         , [Measures].[MyMeasure])

        

member QTD_LY as

(firstQTD,  ParallelPeriod([Date].[Marketing Calendar].[Market Year], 1,

                           [Date].[Marketing Calendar].CurrentMember))                

                  

select {QTD_LY} on 0,

{

[Date].[Marketing Calendar].[Market Quarter].&[2009]&[1].Children,

[Date].[Marketing Calendar].[Market Quarter].&[2009]&[2].Children

}

on 1

from [Cube]

 

By rewriting the firstQTD and making it inelegant and equal to:

 

member secondQTD as

aggregate({ancestor([Date].[Marketing Calendar].CurrentMember,

            [Date].[Marketing Calendar].[Market Quarter]).FirstChild :

                    [Date].[Marketing Calendar].CurrentMember}

                    , [Measures].[MyMeasure])

 

, I’ve got my both queries running, and myself puzzled:

 

 

This left me thinking about ability (tool) for a regular developer to look inside of the code parsing process and be able to at least follow the code flow or something….

 

Any ideas on what happened to my query?