Terrible performance when normalizing a flat table in Power Query

Anonymous - Yes, I would expect the same outcome through SSAS Tabular as I've had through Power BI when using Power Query for my normalizing process. However, I'm still going to implement the SSAS Tabular version and view the result. I'll also post the result here, once I get round to it, so others will know too.

ImkeF - Yes, with the power/speed of the in-memory vertipaq engine I can see a single large flat table as acceptable when only working with a single fact table, however the requirements may start out with a single fact table but down-the-line there could be the requirement for another fact table, thus meaning you would need dimensions. I guess it's a toss-up between creating a Star Schema up front or creating when you know you will be working with multiple fact tables (I know you know this - just saying it in case it prompts you to point anything else out).

Also, in my scenario, there are additional transformations in my fact/dimension tables (removing columns/changing types, etc..) so I guess this is preventing the 'pay once' approach when referencing the original, single flat table.

For the suggestion of creating the fact and dimensions tables up-stream and maybe saving them on the source server, it's quite often the case that I do not have credentials to save the any objects (i.e. tables) on the source server. So the approach of using the SQL Statement window in the SQL Server Connection is a good idea. It will at least prompt to practice my sql.

Thanks for your responses.