Power BI performance - DAX queries vs MDX queries

[arcellie]

Hi all,

we're investigating some performance issues on reporting, which is showing in heavy delays of Power BI updates.

The issues started about a month ago, affecting at first Time Intelligence KPIs, but then also some reports without any complex calculations. Reporting is based on SSAS Direct Connection data sources.

We investigated also if the excel version of the reports (same filters and report elements) showed the same performance issues and they didn't. The difference is of seconds against minutes, so we're thinking about some issue in the Power Bi Service/Gateway.

Anyone else is experiencing some issues with Power BI reporting performance?

Can the last Power BI mash-up engine updates affects in some ways the report behaviour in retrieving?

Is there any other test we can try to point out the source of the performance issue?

thank you in advance and best regards,

[v-deddai1-msft · Accepted solution]

Hi @arcellie ,

It could be some dax query can't make use of the Analysis Services Storage Engine cache.  What's the version of your SSAS.  This problem has finally been fixed as part of the general SuperDAX performance improvements in Analysis Services 2019 CU5. For more details, please refer to https://blog.crossjoin.co.uk/2016/09/26/ssas-multidimensional-caching-related-performance-problems-w...

For the performance in Power BI service.  Most likely due to the network. You can use Fiddler  to see the back and forth with the Power BI service from the client machine. This traffic list might show errors and other related information.

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.

Best Regards,

Dedmon Dai

[arcellie]

hi @v-deddai1-msft ,

Actually using Performance analyzer we've already seen that some queries are slower, but still better thank the power bi service portal. We also perform the same extractions from excel pivot tables and the performance are very good rather than PBI (where delays are caused by DAX queries and not by report elements rendering).

Since this should exclude bad MDX, could it be a conversion behavour?

best regards,

[v-deddai1-msft]

Hi @arcellie ,

I suggest you use Performance Analyzer in Power BI Desktop to rule out whether it is the cause of power bi service or gateway. Please refer to https://docs.microsoft.com/en-us/power-bi/create-reports/desktop-performance-analyzer

I also suggest you try to update your gateway to the latest version and please ensure that the gateway is close enough to the data source, and whether the performance of the server where the gateway is installed is excessively invaded by other software.

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.

Best Regards,

Dedmon Dai