PowerBI DAX Optimization with PowerQuery

[Anonymous]

Hi

I was reading the Book "The Definitive Guide to DAX: Business intelligence with Microsoft Power BI..." of Marco Russo and Alberto Ferrari, and in the optimization section, I've got something that it's not clear to me.

According to what I understand, the compression of columns in DAX is performed first with data source columns and after multiple steps, with calculated columns, making that calculations columns are not compressed in the best way. Because of this, they recommend to create, if possible, this calculated columns in data source.

But I've as PowerBI has PowerQuery as ETL, I wonder if I create the calculated columns in PowerQuery are they going to be compressed so good as if they were created in the datasource, or not?

Hope you understand my question.. Thanks!

[d_gosbell · Accepted solution]

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@Anonymous wrote:

But I've as PowerBI has PowerQuery as ETL, I wonder if I create the calculated columns in PowerQuery are they going to be compressed so good as if they were created in the datasource, or not?

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Yes columns calculated in Power Query will be treated the same as ones created in the original data source. As far as the tabular engine is concerned it only sees the output from Power Query it can't tell the difference between a column from the original source or one derived within the query.