How Much Are You Really Saving?

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I helped an ISV a while back with their BI model design. They purchased a data transformation tool for $5,200/year because it’s “simple to use” (the tool was designed for self-service data transformation tasks by business analysists) and “relatively inexpensive”. The idea was to run the tool manually every time they have new data, import data from text files, transform, and output the data in another set of files, and then load the transformed data in Power BI. However, as it typically happens, the data transformation complexity quickly outgrew this approach. What did the ISV learn along the way?

  1. Stage the data – Although it’s tempting to do transformations on the fly, data typically must be staged so you can query and manipulate it. This is also required to compare the input dataset with the target dataset and take care of things like Type 2 slowly changing dimensions that may sneak in unexpected.
  2. Get a relational database – At much lower price point of purchasing a “user-friendly” ETL tool that does transforms only, the ISV could have bought a scalable SQL Server Standard Edition priced at $1,859 per core (or $7,500 for four cores). Mind you that this is a perpetual license that will typically last you 2-3 years until it’s time for upgrade. And they must pay only for production use (remember that on-prem SQL Server is free for dev and test). Or, they could have opted for an Azure SQL Database and pay as they go (Microsoft gives away $120,000 as Azure Cloud credits for qualifying startups for two years). Or, if they are really under budget and don’t have large data volumes, they could have gone with the free SQL Server Express edition.
  3. Use the ELT pattern – What happens when you outgrow the capabilities of the “user-friendly” tool and you must migrate to a professional tool, like SSIS or ADF? Start over. You don’t want to do this, trust me, because more than 60% of the effort to build a BI solution typically goes into data prep. Personally, I’m a big fan of the ELT pattern (see my blog “3 Techniques to Save BI Implementation Effort” for more info on this pattern) that relies heavily on T-SQL and stored procedures. If you go ELT, the tool choice becomes irrelevant as you use it only to orchestrate data tasks. For example, you use Control Flow and very simple Data Flow (just a simple source-destination data flow to stage data) in SSIS. And as a bonus, if one day you migrate to Azure Synapse, you’ll find that it recommends ELT too. Since they wanted to run ETL occasionally, they could have used Visual Studio Community Edition and the SSIS extension. Or, they could have gone completely free by using an open-source ETL tool, like Talend.

When evaluating tools, cost is not the only factor. Your design must be flexible and capable of accommodating changes which are sure to happen.

Tracking COVID

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I’ve seen various reports designed to track COVID-19. I personally like the Microsoft Bing tracker (https://www.bing.com/covid). Not only does the report track the current counts, but it also shows a trend over time. It even goes down to a county level (the trend is not available at that level)! And it’s very fast. As good as it is, this is one report I hope I don’t have to use for long… Stay healthy!

Here is another more advanced dashboard that a data geek will appreciate.

Getting to Power Apps Source Code

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As it stands, Power Apps doesn’t offer an easy way to get to the app source code. Yet, there are scenarios where this could be useful, including:

  1. Putting the app source under source control when the Power Apps version history is not enough. Currently, Power Apps doesn’t integrate with source code repos, such as GitHub.
  2. Finding references to an item. For example, I’ve referenced a collection in the wrong property, and I couldn’t find what triggered the collection load on the app startup. Since Power Apps doesn’t currently include dependency analysis for collections, I wanted to search the source code to find all references to it.

Here is the fastest way to get to the app source code:

  1. Open the app in edit mode and click Save As.
  2. Choose “This computer” and click Download to download the app as a *.msapp file
  3. Rename the extension of the downloaded file to zip. Double click the zip file.

In my case, the exported app has three *.json files in the Controls folder. The interesting code is in the largest json file: 3.json.

Open this file in your favorite JSON editor and this is how we get to the app source code.

Getting Lineage Across Power BI Tenant

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Power BI Service (powerbi.com) packs a graphical lineage view with the caveat that it only works within a workspace. As a Power BI admin, you may need a utility to inventory all Power BI artifacts published to all workspaces (including My Workspaces) in your Power BI tenant. Fortunately, the Admin – Groups GetGroupsAsAdmin can do the job in one call without any coding! Don’t be misled by “groups” in the API name as groups are equivalent to workspaces (the original V1 workspaces were joined by the hip with O365 groups so Microsoft got carried away here, which I’m sure they regret by now given than V2 workspaces decoupled from groups :-).

  1. Go to the API page and click the “Try it” button (isn’t great that you can test any Power BI API without writing a single line of code?). Sign in with your Power BI credentials when prompted.
  2. Enter a value for the $top parameter to limit the number of workspaces returned. It must be withing the 1-5000 range.
  3. Add a $expand parameter and specify what artifacts you’re interested in. Make sure to click the plus next to the parameter to add it to the API call. In the example below, I request all Power BI artifacts: datasets, reports, dashboards, and dataflows

Next run the API and get the results as JSON. You can use one of the online JSON viewers, such as the Code Beautify JSON Viewer, to get a user-friendly view of the data. The Tree Viewer is particularly useful to drill down a workspace to items.

Power BI Embedded, Service Principals, and AAS

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In my previous post “Power BI Embedded, Service Principals, and SSAS“, I discussed how you can integrate Power BI Embedded (App Owns Data) configured for service principal authentication with SSAS to pass the effective user identity. One important observation is that you can use this approach with both internal and external users. For internal users, the Power BI gateway (running under an account that has admin rights to the SSAS instance) passes the effective user identity under the EffectiveUserName connection string setting. For internal users, the effective user identity maps to the user UPN, such as john.doe@prologika.com, so that AAS can map it to the corresponding AAS account. For external users, you can configure the gateway for CustomData, and pass whatever you want as an effective user identity.

Suppose that one day you migrate your code to Azure Analysis Services (AAS)? AAS. Will it work? Unfortunately, not. Since there is no gateway between Power BI and AAS, there isn’t a layer to authenticate using a trusted account. So, the Power BI team has decided to go only with CustomData instead and Power BI Embedded supports a special parameter which only works for AAS . Although the documentation doesn’t emphasize this difference, it has an important paragraph “The only way to have dynamic RLS (which uses dynamic values for filter evaluation) in Azure Analysis Services, is using the CUSTOMDATA() function”. Let’s break this down.

  1. You must use the Object ID of the service principal account when you construct your effective identity. See my previous blog of how to obtain that identifier. Attempting to pass anything other than the Object ID will result in a Forbidden error when the code attempts to obtain the embed token by calling client.Reports.GenerateTokenInGroup().
    var identity = new EffectiveIdentity(“<Object ID GUID>”, new List<string> { report.DatasetId }, customData:“someuser@acme.com”);
  2. You must use the customData parameter to pass whatever identifier your AAS row-level security will use to authorize the interactive user. DAX can obtain this identifier from the CUSTOMDATA() function.
  3. You must add the service principal Object ID to each AAS security role in which the user needs to be evaluated.

Your Power BI Embedded App Owns Data implementation will need different code for SSAS and AAS. The AAS version relies on CUSTOMDATA for handling row-level security.

Although this implementation path is fundamentally different from SSAS, it will work with external users that are not part of your Azure AD. But users registered in Azure AD cannot be just added to AAS roles. This will be pointless because you won’t be able to pass their identity under EffectiveUserName and AAS won’t be able to evaluate them as AAD users. So, both internal and external users must go somehow through CUSTOMDATA.

NullToZero in Power BI and Tabular

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Null and zero typically have different semantics, where null indicates an unknown or missing value while zero is an explicit value. Sometimes, however, you want to show nulls as zeros. For example, an insurance company might want to show 0 claims instead of a blank value. By default, when a DAX filter doesn’t find any rows, the formula returns null (BLANK in DAX). For example, this Claims Count measure will return null when no claims match the report filters.

Claims Count = DISTINCTCOUNT(FactClaims[UniqueClaimNumber])

How do we show nulls as zeros?

The easiest and fastest way is to simply append zero.

Claims Count = DISTINCTCOUNT(FactClaims[UniqueClaimNumber]) + 0

Note that the storage engine is optimized to eliminate empty spaces so converting measures to zero can impact performance negatively. In addition, by default, reports remove dimension members with empty measures. This won’t happen if measures return zero.

Power BI Report Books

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Scenario: Management has requested an easy way to view a subset of strategic reports located in different Power BI workspaces. You can ask the users to mark reports and dashboards as favorites so they can access pertinent content in the Favorites menu, but you’re looking for an easier configuration, such as to create a book of reports with a built-in navigation that organizes reports in groups (like a table of contents), such as the screenshot below demonstrates.

021520_1921_PowerBIRepo1.png

Workaround: Creating a Power BI app might be your best option. However, a long-standing limitation of apps is that there is 1:1 relationship between an app and a workspace. Therefore, by default all included content must come from the same workspace and you can’t create multiple apps in a workspace, such as to distribute content to different audiences.

But thanks to the upgraded navigation experience, an app can include links to reports in other workspaces if consumers have at least Viewer permission to these workspaces.

  1. Start by deploying the core set of reports that you want to distribute to a workspace, such as an Executive Reports workspace. This workspace will serve as a base for the app.
  2. Create an app. In the Navigation tab, the app will already include sections for each distributed report. Add links to reports in other workspaces and organize them in group.
  3. To prevent external reports “losing” the navigation experience, specify the report embed URL which you can obtain by opening the report in Power BI Service, and clicking the Embed , “Website or portal” menu. Then, copy the URL (not the iframe element) and use it as the link.
  4. Grant permission to the appropriate users or groups.
  5. (Optional) Upload an image for the app logo so end users can tell the app apart from other apps.

Here is a configuration for a report residing in a different workspace. Notice that to preserve the navigation experience, the report is configured to open in the page content.

021520_1921_PowerBIRepo2.png

There are two main caveats of this approach:

  1. Users must have permissions to the workspaces (except the app workspace) where the distributed reports reside. The app permissions you set up don’t propagate to content outside the app workspace.
  2. App consumers are not isolated from changes to the external reports. By default, an app propagates content changes to included content only when the app is updated. End users will see changes to external content even if the app is not updated.

Power BI Report Slide Show

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Scenario: You plan to display a Power BI report on a monitor. You want the report to automatically cycle through report pages, showing each after a configurable time delay, like a photo slide show.

Solution: There are at least two solutions to accomplish this:

  1. The Microsoft-supported way is to install the Power BI Mobile for Windows and use its presentation mode feature, which is shown in the screenshot below.
  2. The open-source Chrome “Power BI Real Time Slideshow” extension.

021320_2308_PowerBIRepo1.png

Power BI Slicers and Filters

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Besides the built-in cross-filtering and cross-highlighting among visuals, Power BI supports two explicit filtering options: slicers and filters. Which one to use? Traditionally, you would use a slicer when you want the user to easily see what’s filtered on the report page. But with the introduction of the new filter pane and slicer enhancements, the choice becomes more difficult. Let’s compare the two options:

CriteriaSlicerFilter
PlacementReport page (requires space on the page as other visuals)Report pane
Filter targetVisual, page, reportVisual, page, report
ConfigurationDrop-down, list, slider (numbers and dates), “buttons”Basic and advanced
TopN/BottomN filteringNoYes
Can be hiddenYesYes
Can be visible but read-only NoYes
SearchingYes (must be enabled)Yes (automatically enabled for larger lists)
Relative datesYesYes
Can be filtered by measureYesNo
Geo location filteringNoYes
Cross-filtering fields in same tableAutomatically cross-filters other slicers with fields from the same tableAutomatically cross-filters other slicers with fields from the same table
Cross-filtering fields in other tablesCan be accomplished with a filter on a measureNo
Support hierarchiesYesNo
Selecting default value programmaticallyNoOnly with Power BI Embedded JavaScript APIs
Persistent filtersYesYes
Power BI Mobile considerationsUsers find it difficult to select values in listsBetter user experience
Power BI Embedded considerationsPassing a filter via JavaScript APIs to set default values cross-filters the slicer but doesn’t pre-select the slicer default valueSets the filter as expected

A glaring gap for both filters and slicers is that you can’t currently set the default value programmatically, such as to default a date filter to the last date with data. As a workaround, you can add a field to the Date table, such as IsToday, that is set to Yes for the last date and prefilter on this field, but users must be educated to know how to remove the filter if they want to select another date. This is especially cumbersome with slicers, which don’t even support a single date selection, unless configured as a drop-down or Before/After.

Based on experience, people tend to rely mostly on slicers. But because it’s not uncommon to create reports that must be visually appealing on desktops and mobile devices, here are some recommendations to accommodate both large and small displays.

  1. Use slicers judiciously because they take space on the report page. This could be an issue with mobile devices. Besides taking space, mobile users find it difficult to select values in slicers. I typically use slicers only for common filters, such as Date. Another scenario where slicers could be useful is when you need to visualize the items in a special way, such as a slider or to show a hierarchy of items.
  2. Use filters for the rest of the filtering needs, especially if you plan to optimize reports for mobile viewing in portrait mode and/or use Power BI Embedded to embed reports.

how-we-filter

Power BI Embedded, Service Principals, and SSAS

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Power BI Embedded supports two ways that your custom app can authenticate to Power BI using a trusted account: master account (the original option) and more recently service principle. Service principal authentication is preferred because it doesn’t require storing and using credentials of a Power BI Pro account. Configuring the service principal and embedding reports with imported data is easy. Not so much with embedding reports connected to on-prem Analysis Services models, mainly because of documentation gaps. Here are some notes you might find useful that I harvested from a recent engagement.

  1. Unlike what the documentation states that only SSAS models with RLS requires it, you must grant the service principal ReadOverrideEffectiveIdentity permission. Otherwise, the service principal can’t delegate the user identity to the gateway. So, the gateway admin must call the Gateways – Add Datasource User API.

    TIP: Don’t write code but use the documentation page to call the API (isn’t this nice!). Construct the body to look like this:
    {

“identifier”: “3d9b93c6-7b6d-4801-a491-1738910904fd“,

“datasourceAccessRight”: “ReadOverrideEffectiveIdentity”,

“principalType”: “App”

}

What the API page doesn’t tell you is what you need to use for the identifier in the request body. Your first attempt might be to use ApplicationID, but you’ll get greeted with error ” DMTS_PrincipalsAreInvalidError”. Instead, you must use the object id (in Azure portal, go to the app registration, and then click the app name in the “Managed Application in local directory” property).

Then, on the next page, copy Object ID.

  1. Once the permission is granted, your custom app must construct an effective identity, such as by using this code. Notice you need to get to the report dataset to check how it’s configured. The GetDatasetByIdInGroup API requires the workspace identifier. The code assumes that the dataset is in the report’s workspace. If you need to embed reports connected to shared datasets which reside in other workspaces, you have a problem because the workspace id is not available in the report object. The best way your app can address this might be to maintain a reference map for these reports (reportId, workspaceId). I hope Microsoft changes the GetDatasetByIdInGroup to not require a workspace (not sure why is needed at all with guids).
  2. var dataset = client.Datasets.GetDatasetByIdInGroup(WorkspaceId, report.DatasetId);
  3. var IsEffectiveIdentityRequired = dataset.IsEffectiveIdentityRequired;
  4. var IsEffectiveIdentityRolesRequired = dataset.IsEffectiveIdentityRolesRequired;
  5. GenerateTokenRequest generateTokenRequestParameters = null;
  7. if (!(bool)IsEffectiveIdentityRequired)
  8. // reports with imported data that don’t require RLS
  9. {
  10. // Generate Embed Token for reports without effective identities.
  11. generateTokenRequestParameters = new GenerateTokenRequest(accessLevel: “view”);
  12. }
  13. else
  14. // reports connecting to RLS datasets and Analysis Services
  15. {
  16. var identity = new EffectiveIdentity(“<replace with the interactive user email, e.g. john@acme.com>”,
  17.     new List<string> { report.DatasetId });
  19. var roles = “”; // if you want the user to evaluated as a member of a certain RLS role, replace with a comma-delimited list of roles
  20. if (!string.IsNullOrWhiteSpace(roles))
  21. {
  22. var rolesList = new List<string>();
  23. rolesList.AddRange(roles.Split(‘,’));
  24. identity.Roles = rolesList;
  25. }
  26. // Generate Embed Token with effective identities.
  27. generateTokenRequestParameters = new GenerateTokenRequest(accessLevel: “view”,
  28.     identities: new List<EffectiveIdentity> { identity });
  29. }

    Notice that in line 16, your app must pass a valid Windows login to Analysis Services because behind the scenes the gateway will be append EffectiveUserName to the connection string.