create table message (
	id text
		not null
		primary key,
	channel text
		not null
		references channel (id),
	sender text
		not null
		references login (id),
	sent_sequence bigint
		unique
		not null,
	sent_at text
		not null,
	body text
		not null
);

create index message_sent_at
on message (sent_at);