Power Query - How to identify slow steps in query.

[NAOS]

Hi all,

I would like to know if there is a way to identify which query steps are slowing down the overall refresh time of my queries. I've been doing some reading and suggestions vary a lot, with no clear guidance on how to actually measure and identify slow query steps.

I know join/merge operations will slow down things. I also know from experience that comparing lists with the default List.Difference and similar operations are a burden too. I avoid all of this operations and try to sort the dependencies of the queries so it doesn't call the data source multiple times for different queries. I've tried table / list buffering but Im not sure I fully understand what they do...and I think neiter does the people that recomends their use haha.

Still, some of the queries are really slow. Any suggestions?

Thanks!

[Stachu · Accepted solution]

using Table.Buffer or List.Buffer may help in the scenarios you mentioned
@ImkeF has created nice summary of different M performance tips:
https://www.thebiccountant.com/speedperformance-aspects/

[NAOS]

Excellent collection of articles. Thanks @Stachu!