How to migrate attachment storage?

Hi Hyperkitty developers,

As per docs,

By default, HyperKitty stores the email attachments in the database. If you would rather have them stored on the filesystem, you can set the HYPERKITTY_ATTACHMENT_FOLDER configuration value to a directory.

After we achieved some uncomfortable size of the attachments table in the database, we want to migrate them to the filesystem.

Could you please bring some light on who they stored in the database? Any insight on how to accomplish the migration would be highly appreciated...