Using Power Pivot I discovered–Huston we’ve got a problem…

New Toy! A new toy is always the best.  Old toys are OK, and certainly fun but there is nothing like a new toy.  So, I started playing with Power Pivot and found that the tool is really great at visibly showing issues.  Being able to visualize the data makes it easier to determine if there is a problem.  Traditionally, you could be down days, weeks even, before an issue like this could come to light and really slow down your whole process…

This is the story…

Ok, it was time to see what this puppy could do with my 39 million row record set.  Now, frankly I expect it to totally choke.  And I thought it had… but instead, it told me that the whole report would not fit on the sheet and then went ahead and produced one…


It didn’t freeze and it returned a pretty large set of data.  My set up was really basic:


The data was really raw.  So the next step is to do a little processing on the data and then return to PowerPivot. 

So, to start with I have total records of:


While I’ve proved that PowerPivot can work with this size of a data set, the limitations are the physical limitations of my system.  I’m running on a fairly beefy workstation as it is and it looks like I’ll need to reboot to recover some of the memory.   Things to keep in mind when working with large datasets.  What do I mean?  Oh, things like images stopped showing and the system just didn’t feel stable.

Next step, it’s time to think about some of the dimensions.  Sadly, the source database I’m working with is a pretty flat structure in many ways.  It’s what happens when you create a database that is to be all things to all people when it really should have been split apart.

Going on…

This is the staging table…


Description is the first Slicer.  It contains:


The numbers are pretty much what was expected except for City and County.   I’ll have to go back to the source draw to see why that is.

  • So first I looked at County: 528 rows
  • Ran the same check with City: 528 rows
    I sorted by the the “value” column to see if the counts varied by the value.  From a high level, that will be a sufficient test to proceed.  Actually, as I build out the dimensions I’ll be able to validate if the right data is coming across.

Hmmm… this is not looking good.  I retract that this is good enough for now.  It looks like the process needs to be re-evaluated.

After evaluating the data, I discovered the County and City Columns were reversed with each other.  So, I made the change on the back end.  Checked the results…

Now the data lines up but is it correct?  Cities and Counties still match.  Back to the source…

  • The first Slicer value returns 1993
  • The next ‘County’ returns 1523
  • Then ‘City’ also returns 1523
  • The last ‘Zip’ returns 2112
  • This all agrees with the Total Records picture.  Area and Zip have more records with a a slight edge to Zip.  That certainly plays true with the aggregated totals.  City and County do as well.  Now for the $64 question.  Is this correct?  My brain continues to argue that it is not…

    And then the light came on…
    Because of the way the query is structured, the following rule was applied:

Even if the filter (slicer) should return fewer rows, the minimum number of records returned will be the minimum that is determined by the uniqueness of the row returned.

To roll it all up:

Was there a problem?  Yes, two columns were reversed.  Did using power pivot help?  Yes, by showing a segment of data that intuitively looked incorrect  I discovered the error.  Part of this was user error also.  By relying on simple row counts, the picture presented was true but it did not have enough data.  Here’s the true picture…



While investigating PowerPivot, the right questions came up.  Would these questions have been asked later before the system went live?  Yes, as part of the Q&A process vetting the data is normal.  Using PowerPivot allowed me to save a lot of time by exposing issues and allowing the data to be visible without a lot of processing normally associated with large data sets.

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Originally, this was a pretty darn boring post. Kinda like... Well I won't go there. Perhaps its still on the robotic side but... I could say I like music. Safe, generic and non-comittal. Or, I could say that I've been having a blast tuning up my old guitars, getting blisters on my fingers and turning the amp up past 2. Amazaing what a little overdrive and a half pressed wahwah pedal can do for a sound. Get that cool "Money for Nothin" vibe happening. I get a real kick out of reading old Sci Fi. Reading Asimov's vision about the future is really entertaining now. When he wrote much of the material, the items that were futuristic were day to day tools I used in the early part of my career. Microfiche and the like. I also remember that upstart Microsoft and MS DOS...and can you say Lotus 123? So maybe this is a little better than "I like to read and play music". My career is focused on Team Leadership and Technology. Both share the attributes of continual growth and education. Currently, I manage a team of 4 programmers as direct reports. I've been in this role since 08/2007. Prior to that, I was the team lead (on site) for integration with the customer. Customers ranged from local government to manufacturing and medical. Teams ranged in size from one to six additional team members. On the other side is technology. I've been keeping current with .net technologies focusing on C# and Sharepoint (2007/2010). Specialties Team Building and Management Technical Staff Recruiting Microsoft Visual Studio 7 through 2010 (VB.NET and C#.NET) Microsoft SQL Server 6.5-2008R2 (DTS, TSQL, SSIS, SSAS, and SSRS ) SharePoint 2010 (Office Integration, InfoPath, Site Management and planning) Windows Server 2008 R2 AD DS PowerShell Techology analysis Puchasng and working with vendors Microsoft licensing management and compliance Business Systems Analysis Traning plans Mentoring Training coordination.

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