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Data & Analytics · Advanced

Query Folding

Power Query's ability to translate transformation steps into a single native source query, such as SQL, so the source does the work.

Definition

Folding improves refresh performance and is required for incremental refresh to filter efficiently and for DirectQuery. Some steps, such as adding an index column or certain custom M functions, break folding for all later steps. Right-click 'View Native Query' checks folding.

Exam tip

Put folding-friendly steps (filters, column removal) before steps that break folding.

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