@Rasmus Stokholm​ :

Based on what you've mentioned, it seems that the partition filters are not being utilized by the optimizer, even though the necessary partition columns are defined and the query is using the underlying base column of a generation expression. This could be due to a number of factors, including the specific syntax of the query or the structure of the data.

One potential solution you could try is to use the EXPLAIN command to get more information about how the query is being executed. This can help identify any issues with the query syntax or data structure that may be preventing the optimizer from using partition filters. Additionally, you could try reorganizing the data or reformatting the query to see if this makes a difference in how the partition filters are being used.