Upgrade to 8.3.1 causing errors retrieving data - Executing query with old implementation due to detected difference

Hi all Got a real headscratcher on our hands We’re trying to upgrade from 8.3, to 8.3.1. In this app, we have a page with 3 data views nested and in the third is a list view of “Cover” (using an association data source) When we load this page, none of the data loads in – we can see the data is all populated from the debugger, but the page seems to think all the data views and lists are empty. But if you go on to browser refresh the page (We have the object ID in the URL), it retrieves all the data. We have ruled out it being a security issue. When this page loads initially and fails, we see this warning logged: Executing query with old implementation due to detected difference:    Please provide the following information to Mendix Support. We have detected an issue during the validation of a future product improvement. This did not impact the execution of your request, but may impact execution in future versions of the Mendix product.  and Executing query with old implementation due to detected exception in new implementation: Unsupported type cast from st (Coverwise_UK) to not Through a painful process of elimination, we’ve narrowed it down to the Cover list view causing the problem, or any list view at that level using an association data source. The page has other listviews, using Microflow associations. These do not seem to cause issues. If we retrieve a listview association of another object, we get the same issue If we remove the listview of Cover, we do not get the issue (Page loads fine) If we replace the Cover data source from association to Microflow (and set the flow to be a simple retrieve from association) we do not get the issue (Page loads fine) In the microflow that calls this page, if we commit the second data view object (Quote) before showing the page, we do not get the issue   This has only been an issue in 8.3.1 onwards (Found in 8.4 and so on), but we are eager to upgrade due to other fixes to document templates. Can anyone advise as to what might be going on? We’re completely stumped as to why this would be falling over considering it’s such a relatively simple page, and that so many odd workarounds seem to resolve the issue Cheers
1 answers

Amended my answer based on Patrick’s comment (thanks for the comment, my attention was caught by the bold text :( ).

It seems the warning and the behavior are unrelated: your data is missing, even though the warning says everything is fine. I would follow these steps:

  • Submit the warning to Mendix support,
  • Create a test project for the retrieval in 8.3.1 and submit that to Mendix in a separate ticket; I would say the fact that your page does not load anymore is a bug,
  • Upgrade to 8.4.2 and see if the page works there


In the future, you probably should not use such recent versions of Mendix: I still recommend my colleagues to start projects in 7.23.8, which seems like a fairly stable release. Furthermore, you should perform upgrades in a new branch and test extensively before merging to the main line to avoid these situations.