Monday, March 19, 2012

Degenerate Dimension with Partitions

Backgroud: My cube has 12 Partitions, and I set 12 fact tables to point to them. There is a Degenerate Dimension, which I point to fact table 11. By the Way, the Degenerate Dimension's Key is The fact Table 11's Table_ID, and the Table_ID is possible to be the same between diffrent fact tables 1 to 12.

Question 1: when I build the Degenerate Dimension, I can only choose one fact table to match, as you know. then if I ProcessFull the Degenerate Dimension, it will catch the data from other 11 fact tables? If the answer is YES, how about the same Table_ID?

Question 2: If I processFull the Question Degenerate Dimension, need I Process the Partitions 1 to 12, or only to Process the Partition 11, or not need to Process Partitions?

Question3: If I want to ProcessAdd the Degenerate Dimension,How could I do? I will decide by myself which fact table to chose new data?

Thanks, a lot.

Anyone know this?

I think this is a quite basic question if you want to use Degenerate Dimension, but nothing mentioned about this on MSDN.

Thanks.

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This previous thread in the Forum should address some of your questions:

http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=751457&SiteID=1

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Edward Melomed

Posts 771

Answer Re: Fact Dimension Relationships on Partitioned Cube
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If you decided to build your fact dimension based on the same table as your partitions are, you should create a view joining all paritition tables and base your fact dimension off that view.

Otherwise the fact dimension is only going to show the invoice numbers that appear only in the first partition table.

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If you're going to ProcessFull or ProcessUpdate your degenerate dimension, then the instructions above are what you need. If you want to ProcessAdd your degenerate dimension (recommended) the following might help:

Some full working examples of ProcessAdd:
http://www.artisconsulting.com/Blogs/tabid/94/EntryID/2/Default.aspx

And some performance tests showing the performance of ProcessAdd on large dimensions:
http://www.artisconsulting.com/Blogs/tabid/94/EntryID/3/Default.aspx

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