Dataflow throws "Evaluation failure" after 1-2 minutes only

[FireFighter1017]

We are trying to convert power query transformations from pbix to dataflows and multiple queries are throwing "Evaluation failure" error.

It looks like any "foldable" source will throw this error if the remote system is not able to return a resultset within a minute or so.

When using a non-foldable source, or a connector like Odbc.Query, the query is able to show a resultset event after 10-15 minutes refresh.

This is a big issue for us as it prevents us from being able to use any wizard to generate new steps and sometimes, won't even allow us to save the dataflow because it is not able to validate the schema.  Since Value.NativeQuery is executing on the remote host, it is considered as "executed remotely", it feels like there is some sort of timeout occuring if the remote host is unable to return a resultset within 60 seconds after it has accepted the remote query.

Any idea why?

Our queries are very simple and are in fact, just a SQL query in a Value.NativeQuery step.

Datasources wher we are experiencing this issue are Google Big Query and SAP HANADB.

GBQ is connected through cloud connector.

SAP HANADB is connected through our on-premise Power BI gateway.

Thanks

[Scott_A_Griffi1]

I just started getting this same issue on Dataflows where I had not before maybe January or February of this year (2025). The dataflows actually refresh fine, but it makes it difficult to edit a query when I get

 in the UI when in "Data View". I do not get this error on the query in the UI when I am in Schema View. 
But that isn't helpful when I need to actually see the data. 

I have tried limiting the number of rows and still get the error. Not sure if anyone has found a solution. 

[FireFighter1017]

Hi @Scott_A_Griffi1 ,

Trial and error, that's all I could find to circumvent this problem.  We even had to split some SQL queries to optimize execution on the backend and finish the work in Power Query, forcing it to avoid query folding by adding EnableFolding = false parameter in the Value.NativeQuery step or the database connection step you are using.

So far, we have not found how to avoid it other than optimizing the back end by creating compiled tables that are built and filled with the same structure and data we would get with our SQL query, so the query we now have is a simple Select * From ...., which takes only a few second to return data.

That means we can't access live data anymore and have to make sure those tables are refreshed frequently enough for our Power BI artefacts.

[Akash_Varuna]

Hi @FireFighter1017 , It might be related to time out limits from foldable sources could you please try these

• Optimize Queries: Simplify SQL queries and use indexing to speed up execution.
• Batch Queries: Fetch smaller datasets using filters or ranges.
• Adjust Gateway Settings: Increase timeout for the on-premises gateway in SAP HANA.
• Try to reduce the Data size during validations 
  If this post helped please do give a kudos and accept this as a solution
  Thanks In Advance

[FireFighter1017]

Hi @Akash_Varuna ,

The dataset is already shrunk down to ~1200 lines.

I have tried to split all CTEs in the SQL query into separate power query and then merge them (because I need to) and sometimes the separate tables would still return an evaluation failure.  Especially the one that has 1200 lines.

From all the testing I have done since yesterday, everything points toward some timeout somewhere down the pipeline between PQO and HANA.  Something is causing Power BI to lose connection or drop the request.

The funny thing is that sometimes, I would edit a SQL query in advanced editor, and upon saving my changes, it would run the refresh until it gets to an evaluation failure.  I then refresh again and now I get an SQL error.

So it might have something to do with the delay of opening the connection and receiving a status from the remote host.

Gateway settings would probably apply during data refresh as well.

In our case, the same query in a desktop pbix was working.

It is only when PQO is querying the data that it throws the evaluation failure message.

And the error would also come up when querying Google BigQuery, which is not going through our on-premise gateway

[v-sgandrathi]

Hi @FireFighter1017,

If you continue to experience the issue after following the recommended steps mentioned by @Akash_Varuna, please consider raising a support ticket for further assistance.

To raise a support ticket for Fabric and Power BI, kindly follow the steps outlined in the following guide:

How to create a Fabric and Power BI Support ticket - Power BI | Microsoft Learn

If this post helps, please give us Kudos and consider marking it Accept as solution to assist other members in finding it more easily.

Thank you for being a part of Microsoft Fabric Community Forum!

[FireFighter1017]

Hi @v-sgandrathi ,

I'm currently working with our team to ensure we have done everything we could to optimize the SQL query.

If all fails, we will open a support ticket and hope it will lead to something

In the meantime, can someone explain to me why we had no issues with those queries while working in Power BI Desktop, and they were actually pretty fast.  But when we wanted to transfer those queries in a dataflow gen1 (because gen2 is not supported with deployment pipelines), we started having these evaluation failures?

[v-sgandrathi]

Hi @FireFighter1017,

Based on my analysis, the following factors are likely contributing to the evaluation error:

Power BI Desktop executes queries locally, allowing more flexibility with timeouts, while Power BI Service (dataflows) enforces execution time limits. This can cause longer queries to fail in the service but succeed locally.

Dataflow Gen 1 may have performance limitations, including timeouts and inefficiencies with complex queries or large datasets.

Gateway performance issues, or resource contention on the on-premise Power BI Gateway can cause connection drops. If the gateway doesn't return results in time, Power BI throws an "Evaluation failure."

Thanks for connecting with the Microsoft Fabric Community Forum.

[v-sgandrathi]

Hi @FireFighter1017,

Thanks for reaching out to the Microsoft Fabric Community forum.

May I ask if you have gotten this issue resolved?

If it is solved, please mark the helpful reply or share your solution and accept it as solution, it will be helpful for other members of the community who have similar problems as yours to solve it faster.

Thankyou.

[v-sgandrathi]

Hi @FireFighter1017,

We haven’t heard from you on the last response and was just checking back to see if your query was answered. Also could you please confirm if you raised the support ticket or else If a solution has been found from your end, it would be greatly appreciated if you could share your insights with the community.
This would be helpful for other members who may encounter similar issues.

Thank you for your understanding and assistance.