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Poor performance in data refresh using multiple large CSV files

Power BI newbie here. I have large CSV files scattered on multiple directories. I specify datasource using Get Data > More > Folder. , Its taking too long when you hit refresh to get updated data. Does Power BI re-read all CSV files even if they are not updated? Is it better to have 1 large csv files compared to just incrementally adding new csv for every update?


Super User
Super User

Hi @jerald,


Having worked quite a lot with CSV's it would be ideal to put all the data into on CSV file, so it does not have to and read all the individual files.


Also currently there is no incremental refresh option as you have indicated.


You can refer to my blog post below, where I give some tips in terms of how to process CSV files as quickly as possible.


Power BI – Quick Tips working with multiple large CSV Files

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Community Support
Community Support

Hi @jerald,


You can turn off refresh function in query editor:


1. Open query editor.
2. Choose the query which you don't want to refresh.
3. Right-Click on it and turn off the "Include In Report Refresh" option.



Xiaoxin Sheng

Community Support Team _ Xiaoxin
If this post helps, please consider accept as solution to help other members find it more quickly.

Hi @v-shex-msft,


I forgot to mention that this multiple csv files are in only 1 query. I was hoping that Power BI supports incremental refresh but I recently found out that this is not supported.



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