@Rasmus Stokholm​ : Please let me know if this helps!

It's good that you set the log level to debug, but it's important to know where the logs are written to so you can check them. Usually, the logs will be written to a file on the server where the query is executed, or they may be sent to a centralized logging system.

Regarding forcing the access plan to use partitions, you can use the

EXPLAIN statement to see the query plan generated by the database engine. This will give you insight into how the engine is processing your query and whether it's using partitioning as expected.

When you created the table in SQL with the PARTITIONED BY clause, did you also specify the partitioning column in the query? For example, if you partitioned the table by year and month, did you include those columns in your WHERE clause when querying the table?

It's good to hear that switching to Delta Lake in Azure Storage and using Synapse via OpenRowset helped with the partitioning issue. It's important to optimize your queries and data storage to avoid unnecessary scans, as you mentioned, to reduce both time and cost.