Speeding Up Power BI Aggregations With Primary Keys

Chris Webb has an interesting use case for adding primary keys on lookup tables:

As you can see, the Property Type column from the #”Price Paid” query contains single letter codes describing the type of property sold in each transaction; the Property Type column from #“Property Types” contains a distinct list of the same codes and acts as a dimension table. Again there’s nothing interesting going on in this query.

The problems start when you try to join data from these two queries using a Merge and then, for each row in #”Property Types”, show the sum of the Price Paid column from #”Price Paid”.

Although baseline performance is bad, Chris shows a way of improving that performance significantly.

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