> If I’d written out the query, I might have seen that I didn’t need the JOIN (or never written it in the first place). Whereas the view hides that complexity. So they can make things easier, but that can lead to performance pitfalls if we’re not careful.

you can avoid this particular pitfall by using left joins for views like this (that join stuff in for convenience that you might not select) - postgres will eliminate a left join but not an inner join since the inner join could filter rows (eg symbols in stocks_real_time that don't exist in company (commercial engines will use the presence of fk constraints to know that's impossible and go ahead and eliminate inner joins as well))