It is now possible to specify schema in database definition for postgres. for example:
db.select table=viapri driver=pg database="dbname=mydb,schema=myschema"
The value set byt db.connect schema= cannot be used directly by driver, because it can collide with connection of vector. I am not sure how to handle schemas in general.
The same should be done for mysql, I don't have mysql running.
Radim