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GJA
Helper II
Helper II

Dax & Direct Query Performances

Hi, 

 

I noticed that there are performances issues when I create measure when I am connected to date source (sql server) in direct query mode.

 

For sample if I put a column from a fact table and use the native sum of power bi table the result is less than 1 or 2 seconds.

 

But If I create a measure it's everytime longer. For sample a simple calculate with a filter on one column it will be longer.

 

One other example Is the round function. If I use a dynamic round digits it will be longer (more than 10 secs) than putting the value in variable making a switch on the variable (Switch (roundDigits, 1, round(value,1) .....) it will take maybe 3 secs

 

Can someone explain me why ? 

 

And it seems that the calculation in direct query mode is supported mostly by the database ? Do you have a good documentation please ?

 

Many thanks

1 REPLY 1
HotChilli
Super User
Super User

Direct Query does it's processing on the source database. Use Import mode as your first option unless you have good reasons not to.

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