Power Query - Query Folding (The key to faster query execution)

Understanding Query Folding: the process by which transformation steps are performed at the data source to improve query execution time. Examine strategies to repair "broken" queries, and techniques to turn partial-folded queries into fully-folded queries.

00:02 What is Query Folding?
00:46 Query Evaluation Process
01:43 Query Folding Levels
02:28 What makes Query Folding break?
03:17 Folding Indicators Explained
03:57 Example of a Hybrid Query
06:36 Breaking the Folding Chain
07:59 Fixing "Broken Chains"
08:42 Automatic Query Optimization
09:00 Viewing Step Folding in Excel / Power BI
11:40 Query Optimization

[nelsonrioux]

WOW. I had never heard about this before. I wish I could take such an advanced course.

[Quidisi]

Wow! I always thought query folding was some sort of witchcraft that was too complex for my meager brain to understand. But once again, your video cut through the fog of confusion and made it relatively simple to grasp.
Thanks so much!
PS - Yes I have a lot of dataflows that take many minutes to run - I will definitely go do some inspections, now.

[joelabacherli]

This is the best explanation of query folding I’ve seen yet. Freaking brilliant. Thank you so much. Makes perfect sense. I totally see why it’s bad to break the fold. Thanks for a great vid

[Rice]

Ohmy! I need to rescan all of my tens queries to search fold broken steps.😯
But since now I know how to write steps a bit efficiently. So, great thanks, sir!🤗

[douglasevans]

Oh my! I'm rating this video 6 out of 5 stars! So well done. Thanks for this!

[iankr]

Interesting video, many thanks! In my job, all our Power Queries take their data from Excel sources, so folding doesn't occur. This concept is useful to know, however, just in case things change.

[IvanCortinas_ES]

Great explanation!!! Thank you, Bryon!!!

[vitorviotti]

Finally someone gave nore details about query folding. Thank you for that. I got a question, and I hope someone can give me more details. You clearly mebtioned about the folsing happening when the step can be translated to SQL, is there a reference documentation that expand on this concept? Are there any clauses that won't work with folding?

[jessicajolly]

This is such a great explanation. I usually describe it as “outsourcing” back to the source. One thing I found interesting — you did a Changed Type step that didn’t break query folding. Usually they do.

[FsoOmar]

It's always good to be informed about anything in PQ; I don't deal or use SQL, but who knows! Query Folding. Thanks for the info. (I haven't watched the vid yet😊.)

[Vogeln]

Amazing tutorial. You rock!!! Thank you.

[johnjoannou]

Thanks so much for this video, I'd like to see the whole setup though, from the connection to the server through to the end result. Only to see if the steps I'd normally take in Power Query are the same or different if it's being actioned at the server level.
Really appreciate these vids.. :)

[Simon-vcwk]

Wow I definitely learnt something watching this video. Hopefully, these icons come to the desktop version

[pabeader]

Note: Just because you lose the folding indicator, you may still be folding. There is a tool that you can use to see the actual query that is being generated to KNOW for sure.

[kkravch]

Just wanted to revisit this video. I wonder whether it make any difference if one, instead of relaying on the folding function, simply sets the SQL query at the source dialogue. I have done it many times in the past to get more organized and overall less data to deal with on the power query side. Writing your own query disables the folding, as far as I remember, but at the time I felt like the native SQL query would take noticeably less time to run and refresh. Did anyone do any test comparing (properly working!) folding vs native SQL at the source? Thanks

[ziomekzedzielni]

Will it work with MS Access files as source? Or that doesn't matter if it's Excel or Access files?

[jessicajolly]

I always think of the Fleetwood Mac song “Never Break the Chain”—never break the fold!

[RichardJones]

I guess getting data from Microsoft access won't be speeded up either