if absfilename && File.exist?(key)
# db already exists, use it
@db = DBTree.open_db(key)
elsif absfilename
# create empty db
@db = DBTree.create_db(key)
if absfilename && File.exist?(key)
# db already exists, use it
@db = DBTree.open_db(key)
elsif absfilename
# create empty db
@db = DBTree.create_db(key)