Buffer a Table for Performance in Power Query M

Loads a table into memory once with Table.Buffer so it isn't re-evaluated every time it's referenced.

Performance OptimizationIntermediateperformancebuffercache

Power Query M code

let
    Source = YourTable,
    BufferedTable = Table.Buffer(Source)
in
    BufferedTable

Notes

Only buffer tables small enough to comfortably fit in memory - buffering a large table can slow the query down instead of speeding it up.

Requirements

A table that's referenced multiple times downstream, such as inside a loop or repeated lookup.

How to use this snippet

In Power BI Desktop, choose Transform data to open Power Query, then open the Advanced Editor on a query (or start from a blank query).
Paste the snippet and replace the placeholder names (tables, columns, file paths) with your own. Check the requirements above first.
Run it through the Power Query M Formatter to tidy the layout.

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