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Microsoft commitment to DAXMD from Power BI RRS feed

  • Question

  • I'm familiar with OLAP MD and have been building cubes for many years.  Recently I was asked to help create some reports and dashboards in Power BI.  I see that the Power BI service is designed to send DAX queries to the OLAP MD cubes, instead of using MDX.  I've already encountered problems with the way that Power BI is generating  (and OLAP MD is processing) these so-called "DAXMD" queries.

    The queries in question are relatively simple.  I think there are some limitations in the DAX query processing engine.  For example, I see error messages that start with "Tabular metadata and DAX queries are not supported when  ...".  In other cases I have no problems.

    My question is a fairly general one.  Does Microsoft still intend to invest in this "DAXMD" technology that enables Power BI to query OLAP MD?  If there are problems and limitations then should I report bugs, or just "live with it".  I see that DAXMD is already quite mature and perhaps it has been left out of modernization efforts (like "super dax" or whatever).  I found a great PPT where Chris Webb introduces DAXMD and it is already quite dated: https://sqlbitscontent.blob.core.windows.net/sessioncontent/1750/88e523c6-60a8-453a-8fe4-5fcf6884deb7.pptx 

    I am a bit out of the loop on the DAX side of things and on Power BI as well.  If anyone has experience interacting with Microsoft tech-support on any matters related to DAXMD or Power BI for OLAP MD, then I would love to hear about those experiences, good or bad.


    David Beavon

    Tuesday, June 25, 2019 5:14 PM

Answers

  • DAXMD is not really a language, its functionality inside the MD engine that allows it to process DAX queries/expressions. It does not do a DAX to MDX translation, its a much deeper integration. As far as I am aware this is still being actively developed and worked on. It's still officially supported so if you do find bugs you should expect full support.

    http://darren.gosbell.com - please mark correct answers

    Thursday, June 27, 2019 6:26 AM

All replies

  • Hi David,

    Based on my research, I haven't heard your so-called "DAXMD" queries. If you would like to access multidimensional mode from power bi, servers must be running SQL Server 2012 SP1 CU4 or later versions of Analysis Services.

    Here are related articles for your reference.

    Connect to SSAS Multidimensional Models in Power BI Desktop

    Connect Live Power BI to SSAS Multidimensional

    Power BI and SSAS Multidimensional

    If you still have doubts about power bi, you could submit your questions to power bi forum for professional support.

    Best Regards,

    Will


    MSDN Community Support
    Please remember to click "Mark as Answer" the responses that resolved your issue, and to click "Unmark as Answer" if not. This can be beneficial to other community members reading this thread. If you have any compliments or complaints to MSDN Support, feel free to contact MSDNFSF@microsoft.com.

    Wednesday, June 26, 2019 5:56 AM
  • DAXMD is simply the query language that is need when Power BI reports are retrieving data from OLAP multidimensional.

    If you look at this link,

    https://docs.microsoft.com/en-us/sql/analysis-services/analysis-services-features-supported-by-the-editions-of-sql-server-2016?view=sql-server-2017

    ... you will see that DAX queries are supported both by tabular models and multidimensional as well. The DAX queries on the multidimensional side of things are called "DAXMD".

    Here is a slide deck with more information about DAX.  This is a bit old... I think the information is around five years old by now. 

    https://www.slideshare.net/plssug/sql-day2013-chriswebbdaxmd

    I was wondering if anyone here has ever interacted with Microsoft about these DAX queries for Multidimensional cubes, aka DAXMD.  Is this a technology that is actively being developed?  I'm hoping that if I find bugs, I will get full support.  I guess I will find out either way ... but I was hoping someone would help me set my expectations ahead of time.

    Thanks, David



    David Beavon

    Wednesday, June 26, 2019 3:40 PM
  • DAXMD is not really a language, its functionality inside the MD engine that allows it to process DAX queries/expressions. It does not do a DAX to MDX translation, its a much deeper integration. As far as I am aware this is still being actively developed and worked on. It's still officially supported so if you do find bugs you should expect full support.

    http://darren.gosbell.com - please mark correct answers

    Thursday, June 27, 2019 6:26 AM
  • Great to hear!  I just have a couple issues so far ... but I ran into these so fast that there are bound to be more.  The first is not so much with DAX but with the tabular metadata.  It appears that the  hierarchies which are hidden in a given cube (deliberately hidden by the cube metadata) still visible in the metadata that is exposed in power BI.  That is unfortunate.  In contrast, the *attribute* hierarchies are hidden properly if/when this is specified in the dimension itself.  But if/when the dimension defines a hierarchy which isn't hidden until it is presented in a cube, then the power BI seems to ignore the fact that I the hierarchy was supposed to be hidden to the users.

    The second issue I ran into right away is with "personalization extensions".  The extensions are used to define session members via CLR procedures (created from session events).  For whatever reason the DAX query engine will refuse to interact with any cube that has these session members.  I get the error that DAX queries are not supported under these conditions.  I would prefer if the DAX engine would just *disable* the "personalizations" in the session events .  That would be preferred over forcing me to create a secondary cube that is the same in every other way aside from the removal of the personalizations.

    Anyway, I will start interacting with Microsoft on this stuff, and hopefully they won't just tell me to go away.

    BTW, I watched the anniversary video for analysis services recently (20 years!) I recognized your name in there.  Thanks for all your contribution.  You certainly worked hard to earned those 50,000 points in this forum. 



    David Beavon

    Thursday, June 27, 2019 10:02 PM
  • The hidden hierarchies issue definitely sounds like a bug, so I would expect that they should fix that. Sometimes all it takes is for someone to officially raise an issue with them to get things like this fixed.

    The personalization extensions could be a different issue. I think you may get a "this is by design" answer for that one. It sounds like someone has gone to the effort of testing for this and providing a specific error message. I don't have any special inside knowledge about this, but I would guess that the usage of the personalization extensions was low enough and the complexity of supporting them was high enough that some executive made the decision not to support this (I have not checked, but I would expect .net stored procs in MD cubes to fall into the same bucket)

    Thanks for your kind words, I've been on these forums since they first started and actually had not noticed that I'd ticked over the 50k points!


    http://darren.gosbell.com - please mark correct answers

    Thursday, June 27, 2019 11:52 PM