Vojtěch ŠímaData Bender
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Power Query & M

13 posts on Power Query & M: benchmarks, internals and workarounds for the Microsoft data stack.

  1. 13
    Fix Slow Refreshes: Faster Way to Load SharePoint Files in Power BI

    Optimize Power BI SharePoint data retrieval. Learn technical differences between connectors and implement a custom REST API strategy for faster dataset refreshes.

  2. 12
    How to Fix Slow SharePoint List Refresh in Power BI

    Boost Power BI SharePoint refresh speed. Fix RenderListDataAsStream errors and use a custom M script to cut load times from minutes to seconds.

  3. 11
    Why Power BI Says a Value Is a Duplicate When It’s Not

    Power Query is case sensitive, the model is not, and that mismatch quietly breaks relationship keys. Why it happens, and three ways to fix it.

  4. 10
    Why Is Power Query List.Contains Slow? Faster Lookup Alternatives

    Power Query lookup benchmarks. Learn why List.Contains is slow at scale, when buffering helps, and how joins or Record.FieldOrDefault beat list contains.

  5. 09
    How to Connect GraphQL APIs as a Data Source in Power BI

    Learn how to connect GraphQL APIs to Power BI effortlessly. Discover key GraphQL concepts and integrate GraphQL with Power BI for seamless data analysis.

  6. 08
    How Power Query (M) evaluates your queries, and why the performance gets weird

    Lazy versus eager evaluation in Power Query M, what buffering actually changes, and why the same query can return different numbers on each run.

  7. 07
    While Loop in M Language

    Discover how to mimic a while loop in M Language using List.Generate(). Learn to implement while loop logic effectively in Power Query M.

  8. 06
    Make Your Power Query Dynamic with Parameters

    Discover how to make your Power Query dynamic with parameters. Learn practical ways to use parameters in Power BI, enhancing flexibility and control.

  9. 05
    Ultimate intro to Power Query M Language

    What M actually is, how Power Query writes it for you, and how to start editing it yourself. A beginner introduction built on working examples.

  10. 04
    Combine Files Quickly in Power Query

    Power Query's built-in file combiner generates a folder of helper queries. Two simpler ways to combine files, in roughly one line of M.

  11. 03
    API Authentication in Power Query

    The five authentication methods Power Query supports: Anonymous, API Key, Bearer Token, Basic and OAuth 2.0, with working M for each.

  12. 02
    Pagination in Power Query

    How to page through an API from Power Query: offset, cursor and link-header styles, with M that keeps asking until the last page comes back.

  13. 01
    Introduction to API in Power Query

    Calling a REST API from Power Query with Web.Contents and Json.Document: the request, the response, and turning JSON into a usable table.

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