Updated: Nov 16, 2020
If you are serious about optimizing your tabular model (be it in Power BI, Azure Analysis Services, or SSAS), then you are likely familiar with Vertipaq Analyzer. It is a great tool which allows you to investigate detailed information as to the structure and compression of objects in your model. Earlier this year, Vertipaq Analyzer was integrated into DAX Studio which makes this information even more accessible. In this post I'll show you how we can take things a step further.
Best Practice Analyzer
If you are interested in ensuring your tabular models follow best practices for naming, formatting, and performance, Tabular Editor has a great feature called Best Practice Analyzer. If you are not using it yet, I highly recommend that you try it out. It is an efficient way to automatically scan your entire model and ensure that your team's best practices are kept.
Now, when it comes to optimizing performance we often use Vertipaq Analyzer. And I just mentioned that we can codify best practice rules in Tabular Editor's Best Practice Analyzer. The natural next thought is - "what if we could write Best Practice Analyzer rules taking the Vertipaq Analyzer statistics into account?". One may think this is not possible as Tabular Editor only contains the metadata for the model (based on the .bim file) so Vertipaq stats are not available. However, this is no longer the case!
As shown in my previous post, Tabular Editor is now able (when connected to a server or a Power BI Desktop model) to run live DAX queries. It turns out that you can also run Dynamic Management Views (DMVs). Since all the Vertipaq Analyzer data comes from DMVs, we can extract this information and make it available in Tabular Editor. In fact, here is how to run a DMV query in Tabular Editor.
var DMV_Tables = ExecuteDax("SELECT * FROM $SYSTEM.TMSCHEMA_TABLES").Tables; DMV_Tables.Output();
The Script & What It Does
Here is a link to the script. In short, this script extracts a model's Vertipaq Analyzer statistics and saves them as annotations to the model's file. All values are shown in bytes (unless they are indicated as a percentage). These annotations can easily be browsed and the best part is that they can easily be referenced using Advanced Scripting or the Best Practice Analyzer.
Running the Script
Here are the steps:
Download the script.
Open your model in Tabular Editor*
Copy the script and paste it into the Advanced Scripting window.
Click the Play button (or press F5).
* The model must be connected to a server or via Power BI Desktop.
After completing these steps, the Vertipaq Analyzer statistics have been saved as annotations in your model.
Show Me the Annotations
Annotations are simply notes that can be made on any object in the model. They can easily be viewed in Tabular Editor by selecting an object and expanding the Annotations dropdown in the Properties window.
Which Vertipaq Statistics are saved?
Here is the full list of Vertipaq stats that are saved as annotations on the model. Each stat is saved within the respective object. For example, Relationship Size is stored as an annotation on each relationship in the model. Navigate to a relationship to see this statistic.
Model: Model Size
Tables: Row Count; Table Size; Table Size as a Percentage of the Model Size
Partitions: Record Count; Segment Count; Records Per Segment
Columns: Cardinality; Column Hierarchy Size; Column Size; Data Size; Dictionary Size; Column Size as a Percentage of the Table Size; Column Size as a Percentage of the Model Size
Hierarchies: User Hierarchy Size
Relationships: Relationship Size; Max From Cardinality; Max To Cardinality
This is also documented on the README section on my GitHub page.
Setting up a Rule based on Vertipaq
Now that we have the annotations stored, let's see how easy it is to create a Best Practice Analyzer rule. We know that bi-directional relationships are costly - but they are especially costly if they cross between large tables. Let's create a rule that detects this.
Here are the steps:
Within Tabular Editor, go to Tools -> Manage BPA Rules
Click Add if you have not created any rules yet.
Click New Rule
Name the rule (i.e. Bi-Directional High Cardinality)
In the Applies to section, select the following: Calculated Columns, Calculated Table Columns, Data Columns
Enter the following in the Rule Expression Editor
UsedInRelationships.Any(CrossFilteringBehavior == CrossFilteringBehavior.BothDirections) and Convert.ToInt32(GetAnnotation("Vertipaq_Cardinality")) > 1000000
This rule scans all the columns (of any type) in your model, checks whether they are used in a bi-directional relationship and if the cardinality of the column is more than 1 million unique records. Checking this manually would be quite a bit of work. Now, it's checked automatically and can be easily done for all your models.
The BPA rule shown above is just an example to show a glimpse of what is now possible when combining Vertipaq Analyzer and Tabular Editor's Best Practice Analyzer. Ensuring your model follows an optimized structure and compression has never been easier. For more information on analyzing Vertipaq Analyzer statistics, see this video.