What is query folding and why is it critical for performance?

< 1 min read

Query folding means Power BI pushes transformation steps back to the source database instead of processing them locally.
In one project, filtering and aggregation steps in Power Query were folded into the SQL query automatically.
This allowed the database engine to handle heavy processing using its optimization capabilities.
When query folding breaks, Power BI loads full data and processes transformations in memory.
That significantly increases refresh time and memory usage.
We always checked “View Native Query” to ensure folding was happening.
Applying filters early helped maintain query folding.
So query folding is critical because it improves refresh speed and reduces resource consumption.

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