Hi Robert,
you send many questions so bear with us and slowly you will get answers:)
For this question, there is an internal partitioning schema in monetdb, and actually that is what you are seeing in the query with LIMIT in your other email (in that case of LIMIT it is wrongly triggered).
As for external partitioning from the user we are currently working on that. There is an experimental implementation for that, where you can define different merge tables but it is not yet stable enough to be included in the current release.