Do you really can diff Power BI files?

While working with some customers a few times this question came up: “How can I diff my current file with a older one? I really want to compare my files, to know what changed from one to another."

Many many people working with Power BI end up with a directory full of files looking like: “myPowerBIFileV1.pbix”, “myPowerbifilev2.pbix”… “myPowerbifilevN.pbix”. The scenario wull get worse if we have two or more people working in the same file, and until recently my answer was always the same: “You can’t”.

Once again PowerShell to the rescue

Using a library that’s open sourced by DevScope we can diff the files by using the function to migrate a Power BI file to an Analysis Services tabular model for each of the files and in the end compare them with any text comparing software.

A full example

You can install the library by running in a elevated PowerShell console the following command:

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Install-Module PowerBIPS.Tools

If you have already installed to make sure you have the latest version run:

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Update-Module PowerBIPS.Tools

And then you run this script replacing with your own files:

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# Load the Module
Import-Module PowerBIPS.Tools

# Get script current path
$currentPath = (Split-Path $MyInvocation.MyCommand.Definition -Parent)

# Extract the model to the folder SSAS. Make sure you have your Power BI file open
Convert-PowerBIDesktopToASTabular -pbiDesktopWindowName "DemoFile -*" -outputPath "$currentPath\SSAS\" -removeInternalPBITables -Verbose

################################################################################
# Diffing
# Extract the altered model to the folder SSASV2. Make sure you have your Power BI file open
Convert-PowerBIDesktopToASTabular -pbiDesktopWindowName "DemoFile2 -*" -outputPath "$currentPath\SSASV2\" -removeInternalPBITables -Verbose

# Call the diff viewer
$fileV1 = "$currentPath\SSAS\model.bim"
$fileV2 = "$currentPath\SSASV2\model.bim" 

#Invoke-Command  -ScriptBlock {& 'C:\Program Files (x86)\KDiff3\kdiff3.exe' $fileV1 $fileV2}  #Kdiff3
Compare-Object (Get-Content $fileV1) (Get-Content $fileV2) -SyncWindow 10                  # Powershell Way

You should get this kind of output showing the differences between the two files:

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InputObject                                                                                                  SideIndicator
-----------                                                                                                  -------------
  "name": "cf391530-7ccc-48d2-a86b-f14e16122e89",                                                            =>
            "name": "Adventure Works Sales",                                                                 =>
            "expression": "CALCULATE(sum(Sales[ReturnAmount]), 'Product'[BrandName] = \"Adventure Works\")", =>
  "name": "b9f7b199-f8a7-4ca4-83a4-35b5f6724554",                                                            <=
            "name": "Teste",                                                                                 <=
            "expression": "sum(Sales[ReturnAmount])",                                                        <=

Or if you use a tool like kdiff3, uncommenting line 19 of the script:

Have fun!!

Diffing Power BI files

Do you really can diff Power BI files?

Once again PowerShell to the rescue

A full example

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