Query loads bigger file then saved on the disk

Hi, jacek_k 

It will depend on the number of times a source file (query) is duplicated or referenced and also the number of query transformations.  The same file can be loaded multiple times. 

Usually PQ would load the source data twice: First while retrieving the metadata to generate the evaluation plan and then to fetch the data itself.

You might considering using the M function Table.Buffer Table.Buffer - PowerQuery M | Microsoft Docs This can reduce the number of re-reading the base file.

You can find more performance tips on this blog here: Speed/Performance aspects – The BIccountant

 

Refer:

Why does Power BI "Load" much more data (volume) than what's in my source file?

XLSX file 10MB, but Power Query loads 100MB into Power Query

Speed/Performance aspects

 

 

Best Regards,
Community Support Team _ Zeon Zheng

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