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wpf_
Post Prodigy
Post Prodigy

How does calculated columns work in directquery?

So if i understand correctly, for import mode, calculated columns are loaded into the model during a data refresh.  And once it's loaded any queries are to the calculated column stored within the local bi file. 

 

But what happens with calculated column in directqueries?  Are calculated columns persisted in the data source and when we refresh the visuals it queries the data source every time?  

 

I have created a custom column through power query vs calculated column for directquery and it seems like the calculated column is slower for the report. Any clarifications would help. Thanks. 

1 ACCEPTED SOLUTION

@wpf_ That is exactly what I think happens behind the scenes, yes.


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Greg_Deckler
Super User IV
Super User IV

@wpf_ I don't believe that the values are persisted in the data model or the data source. For example, I added a calculated column to a DirectQuery model and it added a total of about 600 bytes to the data model and added nothing to the data source. So, likely it just stores the formula for the calculated column in the PBIX file in the Data Model.


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@Greg_Deckler 

 

Thank you.  

So does that mean that every time I refresh a visual that contains a measure that references a calculated column, it queries the data source  and calculates the calculated column then the measure on demand?

@wpf_ That is exactly what I think happens behind the scenes, yes.


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@Greg_Deckler 

Makes sense.  I guess that’s why the calculated column version I had took longer then the custom column version. Thanks!

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