create table chats(
    id uuid primary key,
    created timestamp with time zone not null default now()
);

create table chat_messages(
    id uuid primary key,
    chat uuid not null,
    sender uuid not null references users(id),
    timestamp timestamp with time zone not null default now(),
    text text not null,
    extra jsonb
);

create index chat_messages_chat_index on chat_messages(chat);

create table chat_members(
    chat uuid not null,
    "user" uuid not null,
    read_until uuid references chat_messages(id),
    primary key(chat, "user")
);

create index chat_members_user_index on chat_members("user");
create index chat_members_chat_user_index ON chat_members(chat, "user");