Forum Discussion

MS_fn's avatar
MS_fn
Frequent Visitor
3 years ago
Solved

Dataflow - different results between preview and later access

Hello community,   how could it be that the results of a dataflow is different to the results if this dataflow is loaded within another dataflow or within the Power BI desktop? The dataflow based o...
Dataflow
  • v-yueyunzh-msft's avatar
    v-yueyunzh-msft
    3 years ago

    Hi ,  MS_fn 

    Thanks for your quick response! According to your description, this may cause by the ehance compute engine.

    As searched, this function is mainly used to create a SQL cache to implement Query folding to increase the performance of dataflow. 

     

    Once the enhanced compute engine is enabled in the Power BI Premium capacity settings, and the dataflow settings and configuration (as illustrated above) dictate that the engine is used for a given dataflow, this is what happens:

    （1）When the dataflow is refreshed, the Power Query for each entity is executed, and the output of the query is persisted in the dataflow’s CDM folder as CSV data and JSON metadata
    （2）For any entity for which the enhanced compute engine is enabled, the output of the entity’s Power Query is also loaded into a table in a SQL database instance managed by the Power BI service

     

    And there is differnce about ""what exactly do you mean by supported queries?"":

     And for more information, you can refer to if can help you :
    Dataflows enhanced compute engine – will it fold? – BI Polar (ssbipolar.com)
    Power BI dataflows enhanced compute engine - YouTube
     

    Thank you for your time and sharing, and thank you for your support and understanding of PowerBI! 

     

    Best Regards,

    Aniya Zhang

    If this post helps, then please consider Accept it as the solution to help the other members find it more quickly

     

bk2001050's avatar
bk2001050
Regular Visitor
2 years ago

Hey MS_fn,
Thanks for your post. I am facing the exact same issue and my enhanced compute engine is misbehaving, changing some seemingly random values in a specific column. It took me a while to troubleshoot the problem but turning it off since to have fixed it for now. Did you ever find out why this happens and how to avoid it?

MS_fn's avatar
MS_fn
Frequent Visitor
2 years ago

No it's not solved - neither this specific case nor the more general issue that a data-update to a dataflow (just clicking on the update-button within the workspace) results reliable in updated and correct data. It worked instead by opening the dataflow and saving it again and performing then directly afterwards the update.

 

I think this behaviour is related to the implemented caching-logic - which might need to be configurred in some way (maybe activating an incremental refresh would also trigger a real update) or maybe just completely disabled.

 

Currently I didn't dive deeper into the matter because it's only a side-project to evaluate if Power BI is an alternatively for our other reporting. At the moment it didn't look like as if Power BI as environment has enough capabilities in regard to a multi-layer ETL and analytics in the UI - at least for our current requirements.