@Gerhard Brueckl
we have seen near 80k-120k file deletions in Azure per hour while doing a VACUUM on delta tables, it's just that the vacuum is slower in azure and S3. It might take some time as you said when deleting the files from the delta path.
In order to minimize the cost associated with DBUs while doing a vacuum, you can use autoscaling 0-2 workers on the cheapest instances.
The reason why we recommend auto-scaling with the minimum node as 1, is because, the first step of vacuum, where we read the delta logs and identify the files to be deleted can be very slow if there is only one node for large tables. To avoid this, use cluster resources wisely in step 1 and then in step 2 where we start the deletion from the driver, scale down the executor resources.
How to get estimated # of files deleted in an hour:
You can get a high-level estimate of how many files are getting deleted in an hour by checking for FS_OP_DELETE emitter in the driver logs.
Another way is to run a dry-run command after an hour and see what count it's showing.
the second approach won't give the exact rate of deletion, because, there could be new files identified to be vacuumed when u run the command after an hour. but good to get an estimate
