How to delete a persistent message

Hi all,

Regarding persistent messages, I discovered an undesired behavior I would
like to confirm here:

- I know persistent messages will be saved on disk as they are received in
the broker. That's fine.
- However, I thought that those messages would be automatically deleted
once all the subscribers confirm the reception of the message. However, it
seems to me that they still saved on disk forever and ever.
- I thought I could solve this by setting a time ti expire. However, it
doesn't seems to work for me.

So, here are my questions:
- Are persistent messages meant to live forever in the BBDD? In such case,
my BBDD will keep growing and growing...
- Do I have any mean to delete those messages programatically (via Java)?

Many thanks in advance,
Francisco