Paginated Reports Rendering Extremely Slow

Similarly to https://community.powerbi.com/t5/Service/Extremely-slow-paginated-reports-due-to-high-connection-opening/m-p/1712251, I've been able to conclude that a Paginated Report connecting to a Power BI Dataset will open a new session for each dataset it needs to retrieve from the Power BI Dataset. So if you have 4 internal datasets in the Paginated Report, it will open at minimum 4 new sessions. Each session takes roughly 2 seconds to be opened.

Now, another issue we have observed is that some datasets will be retrieved from the Power BI Dataset more than once, which in turn means more new sessions being opened. We have seen datasets being retrieved even three times.

The cherry on the top is that datasets are retrieved sequentially and not concurrently from the Power BI Dataset, so all these sessions are one after another. A simple Paginated Report for us takes at 25 seconds to render, even though 3 out of 4 dataset queries finish in under 20 ms and the last query finishes in 1000 ms.

This is unacceptable... so I've raised a formal Critical ticket with Microsoft to explore why this happens and potential solutions.

For consideration:

- we use Power BI Embedded A4

- The Power BI Desktop model from which the Paginated Report reads is around 28 MB in size on disk, so technically a small dataset

- dataset queries have been tuned and tested in DAX Studio, so the performance added above is real and reproducible...