I'd stay away from little metal brackets etc... If countersunk carefully and toe screwed with (I'd use stainless fasteners) I'd say good to go.
I've seen plenty of them that just sat in place without issue but if it was up to me I'd want even a little attachment just in case crazy cousin Mary gets drunk and wants to pole dance.
Larger advise I'd have for any columns is to let them ventilate through the bottom base portion and not caulk them to the decking. Many years ago I started in woodworking by turning columns and making bases/capitals by hand. They'd rot on the bottom because they didn't get a chance to air out on the base. And trust me, custom turned to match parts were stupid expensive. Coopering together a 20' long blank would easily take a day before getting to turn it. Do not, however, leave openings in the top where it connects to the porch support beam. Wasps/bees will move it. Ask Vash about bee driven sprints
