- Query folding means Power Query pushes transformation steps back to the source database instead of processing locally.
So SQL Server performs filtering, joins, and aggregations before data reaches Power BI.
This reduces data volume and improves refresh performance significantly.
Example: I filtered last 2 years sales — only those rows were fetched from database.
Without folding, entire table downloads then filtering happens in Power BI (slow).
I usually keep filtering and column selection early to preserve folding.
Complex custom columns or certain functions can break folding.
I check it using “View Native Query” option in Power Query.
Goal is faster refresh and less gateway/server load.
What is query folding during transformation?
Updated on February 11, 2026
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