I Am Done Using Visual Studio …for BI data model development

For several years, Visual Studio has been my go-to tool for designing semantic data models used for Business Intelligent reporting. Back in 2005, I used the Business Intelligence Development Studio (BIDS) Visual Studio add-in for SSIS, SSRS and SSAS projects to develop BI solutions with multidimensional cubes. In 2012 when Microsoft began the transition from on-disk cubes to in-memory SSAS Tabular models, I used SQL Server Data Tools (SSDT) to create tabular models. It was a rocky road at first. The Tabular designer was fragile to put it mildly.

Enter Power BI… Initially intended for self-service data model and report design, Power BI Desktop has quickly grown into a robust and full-featured BI design tool. Not only does Power BI Desktop include a lot of great features, it is stable and streamlined. It’s a joy to use compared with my early experiences using SSDT for tabular model design. I prefer to use Desktop to perform model design. It’s faster, more convenient and just easier than SSDT. However, at some point I the life of a project it just makes more sense to transition the data model to an enterprise-scale effort.

Now, before anyone has a chance to comment and say “Paul, what the #$@! are thinking? Visual Studio is an essential tool and there are certain things that you can’t do with out it!”, I agree and will continue to use SSDT for a few key features. So, yes, I am not absolutely done using Visual Studio for managing projects other than SSAS, and perhaps for code check-in …I’ll finish this part of the story in a bit.

I want to be clear – I love Visual Studio.  It’s a great product for developing software and a variety of business and data solutions. However, history has demonstrated that the notion of stitching together several different products and expecting them all to just work together seamlessly is just untenable. Without getting into all the reasons that it has been difficult for Microsoft to develop and maintain a rock-solid tabular model design add-in for Visual Studio, contrast that effort with the evolution of the Power BI product.  The Power BI product team is entirely focused on developing one product by a development team under unified leadership, with a focused set of objectives. Negotiating co-development of any product by several different teams is difficult within any organization, particularly one as large as Microsoft. The reason that new features can be added weekly to the Power BI service and monthly to Power BI Desktop is that one product team manages all those features.

Some of you will remember the time when the Business Intelligence message from Microsoft was that we supposed to create solutions relying on coordinated components of many products like SQL Server (relational, SSIS, SSAS and SSRS), Windows Server, SharePoint and Office – all orchestrated to work together seamlessly. It was a good idea – and still is in moderation – but this approach produced a delicate and complicated beast that was difficult to manage and had many potential points of failure.

One of the reasons Power BI Desktop is such a wonderfully streamlined product is that the feature set is optimized for data analysts and not for IT developers. To maintain a streamlined product, we are not at all likely to see enterprise capabilities (like version control, multi-developer code merging and scriptable objects) added to this product. These capabilities do exist, however, for Analysis Services projects and community supported tools like Tabular Editor and DAX Studio. But now (drum-roll, please) Power BI dataset can be developed and deployed to a workspace using enterprise tools through the magic of the XMLA endpoint.

The Visual Studio/SSDT Quandary

<RANT>

Call it a learning disability, but I have tried time and time again to use the Visual Studio tabular designer to manage SSAS projects with the same outcome.  Smallish demo and POC projects go well but not-so-much when tackling the complexities of product-scale design. I guess it is just my natural optimism to hope things work out better than they did last time, but the laws of the universe dictate that if you do the same thing, history will be repeated.

Here’s how it goes… I start developing a data model in SSDT by importing some tables and queries, and adding relationships and measures.  All good, right?  At this point in the timeline, I often convince myself that development environment is stable and that everything will work-out so I forge ahead, believing that all will be good. I then add some more tables and a whole bunch of new DAX calculations – and soon everything goes to hell.  The model designer stops responding or behaves sporadically, Visual Studio crashes, the model definition file gets corrupted and I then I remember that I’ve been down this dark road before.

Recounting the painful past, it is frustrating to open a support ticket and explain to the engineer that “sometimes when I do that, this happens but not always” and “in all the confusion, I really can’t remember exactly how I got to this state.”

Pondering these memories, then I draft a blog post titled “I Am Done Using Visual Studio”

</RANT>

I sincerely appreciate the efforts of Kasper DeJonge from the SSAS product team back in 2012 as we spent hours in remote meetings trying to reproduce various odd behaviors in the tabular designer with a large data model. The fundamental problem was that the Model.bim file, which defines all the objects in the data model, was an enormous XML document (ours was approaching 100,000 lines.) Every change in the designer required the entire file to be re-written to disk and the loaded back into memory. Things improved significantly in 2016 and 2017 when the model definition was streamlined using JSON rather than XML, and the file structure was simplified to reduce the file size. Similar meetings with several other product leaders have proven that the product team are seriously dedicated to optimizing the enterprise tabular model experience.

I’m all about solutions and not just ranting about problems.  So what’s the answer? How should we manage enterprise BI data model and Power BI solutions from now one? Using Tabular Editor alongside Visual Studio is really a best-of-both-worlds experience. You can open the Model.bim file stored in the Visual Studio SSAS project folder.

Tabular Editor

Tabular Editor is a superb tool for developing and managing tabular data models for SQL Server Analysis Services (SSAS), Azure Analysis Services (AAS) and Power BI. It is a community supported tool created by Daniel Otykier, a Microsoft MVP and Senior Business Intelligence Architect with Kapacity.dk in Denmark. The most comprehensive resource to find this and other community supported BI tools for the Microsoft platform is on the Italians’ site at SqlBi.com/Tools

If the project is under source code control, changes made with Tabular Editor will be detected and can be synchronized with the remote source repository from Team Explorer in Visual Studio.

Here are some quick facts and recommendations:

Power BI and Version Control
Power BI Desktop files (.PBIX) do not support version control and code merging.
Recommendation:
Don’t try to do this – It will turn out badly. Starting model design in Power BI Desktop will save you time but once you transition to the Model.bim file format, use Tabular Editor.

Separating Reports and Dataset
A monolythic PBIX file created with Power BI Desktop containing reports, data model and queries is simple and easy to manage until you need to move beyond several limitations that this imposes.
Recommendation:
Power BI reports and datasets (data models) should be managed separately in all serious projects. Period. …whether you need to transition the data model to Model.bim or not.
Separating Power BI reports from the data model/dataset has many advantages which include allowing report and data model development to be performed in parallel and by different team members. This is an absolute must to create a certified dataset for users to connect and do their own reporting and analysis.

Visual Studio and Version Control
Visual Studio SSAS projects allow you to manage version control.
Recommendation:
This is a good thing. Keep doing this but use Tabular Editor as your primary model design tool.

A data model stored as a Model.bim file can have changes compared, split and merged between data model version files, deployed AS databases or Power BI datasets. Manage integrated source control with Azure DevOps or GitHub. Check-in changes, branch, merge, push and pull changes made by other developers but don’t use the Visual Studio Compare tool. Dependencies within the model definition can easily get you into trouble

Tabular Editor
Tabular Editor is a far superior design experience than Visual Studio. It is streamlined, easy to use and it won’t blow up when writing measure calculations. You can switch back and forth between tools since each tool has features that the other lacks. Just be sure to save and close the model file with one tool before opening it in the other …AND MAKE BACKUPS! The more that I do this, the more I prefer using Tabular Editor.

Tabular Editor doesn’t have a graphical model designer so I prefer to use Visual Studio to model tables and relationships. Set table and column properties, create calculated columns and measures, manage partitions and other tabular model features in Tabular Editor.

Start in Power BI Desktop and Migrate to an Enterprise Model
From Power BI Desktop, save the file as a .PBIT (template) which and then be opened in Tabular Editor. Once you save the file to the .BIM format, this is a one-way trip since a an Enterprise model cannot be saved back to a PBIT or PBIX file. Of course, if you start designing the data model in Visual Studio, there is no need to resave the model. You can just and use Tabular Editor to make new model enhancements.

Power BI Premium, AAS & SSAS
Power BI Premium capacity is required to deploy a Model.bim file as a dataset in a Power BI workspace.

Power BI Premium capacity is the E-ticket and is the best way to access all Power BI enterprise capabilities. With the XMLA endpoint, it will make more sense for most customers to deploy enterprise data models as datasets to a workspace rather than Azure Analysis Services (AAS) models.

Future-Proofing Data Models

If your organization chooses not to use Premium, which might be a more economical choice until you have enough licensed users to justify the cost, you can use AAS data models or on-prem SSAS data models to exceed the capacity limits of Power BI datasets under only Pro licensing.

If industry certification or compliance restrictions prevent your organization from using Power BI in the cloud, using enterprise models is the norm. Use a local instance of SQL Server Analysis Services Tabular. If you move to the cloud in the future, the transition should be relatively simple.

Keep in mind that Premium Capacity, or perhaps a more attractive licensing alternative, may be in your future so architect solutions in such as way that you can easily make that transition.