Bringing Version Control to Power BI: A Gentle Introduction to Git and TMDL

[marcelsmaglhaes]

Yes, you could store .pbix files in Git, but any change — even a small DAX tweak — would rewrite the entire binary. Merging was nearly impossible, and collaboration often meant overwriting someone else's work.

That changed with the introduction of TMDL (Tabular Model Definition Language).

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What is TMDL

TMDL is a text-based representation of a Power BI semantic model.
It expresses the same model you design in Power BI Desktop or Service, but now in a human-readable structure.

It exposes:

• Tables

• Columns

• Measures

• Relationships

• Roles

• Calculation groups

All stored as editable .tmdl files.

With that, your data model finally behaves like code: versionable, traceable, and mergeable.

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Why Git Matters for Power BI

With TMDL, Git becomes more than a backup repository — it becomes a collaboration layer.

You can:

• Track every change in your model with commit history

• Compare versions of measures and understand why they changed

• Review pull requests before merging changes into production

• Maintain a single, consistent baseline model across multiple environments or clients

This is not just about control. It’s about confidence in every deployment.

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A Simple Workflow Example

1. Baseline model (Main branch):
   Your reference model — stable, reviewed, and validated.

2. Feature branch (Client or Project):
   Developers create branches to add or adjust measures, relationships, or parameters.

3. Merge and review:
   Once approved, changes are merged back into main, ensuring synchronization and traceability.

4. Automation ready:
   The model can integrate into CI/CD pipelines, trigger dataset deployments, or regenerate .pbip packages automatically.

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Start Small

You don’t need to build a full DevOps pipeline on day one.

Start by storing your .pbip project in Git, commit your changes regularly, and review them like any other codebase.

Once version control becomes part of the habit, evolve toward automation — CI/CD, deployment pipelines, and all the bells and whistles.

Start simple. Grow with structure.

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Final Thoughts

Git and TMDL redefine how Power BI development teams collaborate.

We move from isolated .pbix files to semantic models that live under version control, from manual syncs to structured, reviewable changes, and from uncertainty to governance.

This shift marks the beginning of something bigger: Power BI as code.