Forum Discussion
Error While Refreshing Dataflow with Lakehouse Delta Tables - Stack Overflow Error-Mashup Exception
Hi Bhargava05 ,
From the content of your error report there are two error messages: Stack Overflow Error and Out of Memory Error.
For your first error: Stack Overflow Error, I think this is usually the case if there is too much recursion or too deep call stack. So you may need to simplify the query or break it into smaller, more manageable parts.
For your second reported error, Out of Memory Error, this happens when the data stream runs out of memory during evaluation. So I think you can reduce the amount of data you process at each step. Filter out unnecessary columns and rows early in the query. Break the data transformation process into smaller steps and stage the intermediate results. If possible, allocate more memory for the data flow process.
In addition to this, I think you can do the following:
1. make sure the schema of the Delta table matches the expected schema in Dataflow.
2. make sure your Data Gateway is up to date.
Best Regards
Yilong Zhou
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.
Anonymous Thank you for the response. I understand the possible reasons you’ve mentioned for the errors, such as Stack Overflow and Out of Memory issues. However, I still have some concerns and questions:
- The Dataflow works perfectly when the data source is either ADLS flat files or Lakehouse flat files. Why does the process fail specifically when switching to Lakehouse Delta tables as the source?
- The query complexity and the schema remain the same across these scenarios. Does Delta introduce additional overhead or incompatibility in Dataflow Gen2 compared to flat file sources?
- Also, the Delta table schema is already aligned with the expected schema in Dataflow, and my Data Gateway is up-to-date, so these factors shouldn’t be contributing to the errors.
I’m still curious why such issues occur only with Delta tables in Lakehouse, despite other sources working smoothly. Could this be a specific limitation or a compatibility issue between Dataflow Gen2 and Lakehouse Delta tables?
Looking forward to your insights on this!