Slow refresh of SharePoint list data

[jenb1]

I have a report that currently retreives data from a large Sharepoint list, and two Sharepoint folders.  The refresh time was fine until two days ago, when it grew from a few minutes to more than few hours.  The pulls are direct, I'm not having to unpivot data or anything.  I've had to open the Query Editor and refresh the tables individually and even that takes an absurd amount of time, for very little data. When I trace back thru my Applied Steps, the issue seems to start after the data is imported, but as soon as I try to Invoke a Custom Function, which makes me think it has something to do with the transform binaries option?

I know that Power BI is showing issues with data refresh from Sharepoint, but I'm also having this issue when I try to refresh from SSAS cube. When I first open the Query Editor, it's showing errors for all my tables, even one I created myself. I have no idea what is going on and / or what steps to take.

[v-qiuyu-msft]

Hi @jenb1,

1. Where did you refresh data spend long time, desktop or service? From your description, it seems there is a custom function defined in query, can you share how did you define it? If you just get SharePoint list data without any custom function, is the refresh time normally? Please share detail steps how did you get data so that we can try to reproduce the issue on our side.

2. As you mentioned when you open Query Editor, the data source connects to SSAS throws out error, what's the error message?

Best Regards,
Qiuyun Yu