Performance Tip: Partition your tables at crossjoins where possible – PowerQuery PowerBI

Recently I’ve distributed some techniques for partial matches or relative joins between tables using PowerQuery or the query editor in PowerBI. They are very flexible and powerful – yet slow.

To improve performance you can check if there is a chance to “partition” your table using a Table.Group. If you have an equality expression in your statement like we had in our rolling-12-months-exercise here for example:

You can boost performance into a different dimension by grouping your table on the “Associate”-table instead like this:

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Is it time to remove detail fields from our cubes?

During my evaluation of Power Query as a reporting engine I wondered why we should keep detail fields in our cube at all if the preferred output is a flat table anyway. Cubes are meant for aggregation, aren’t they?

Especially in the Finance- & Accounting area you will come across many cubes with detail fields because sometimes you simply need to perform analysis on ledger entry level. But this seems like a loose/loose scenario in my eyes: Not only do these detail reports often perform badly, their biggest negative impact might lie in the fact that they cause the fact tables to be x-times bigger than the next aggregation level, thereby decreasing the overall performance of the cube.

So how about this approach then: Use Power Query for your reports on detail level: Directly connect to your fact table in the DWH and merge to your SSAS-data in order to retrieve the attributes/filters only. Or keep your fact tables in a dedicated DB if your DWH serves other purposes as well and you fear the performance impacts of those queries.

So this would leave the cubes’ fact tables with much less data -> improving performance.

I tried some scenarios that worked fine. But putting the fact tables into a separate tabular model instead of a relational DB performed quite badly.

Does anyone have experience with this approach? If you know someone who might, please forward.

What do you think about this approach, any other obstacles I’ve missed?