The simplest way to select all distinct values of a column is, somewhat unintuitively:
this runs the query
select distinct project from visits, and returns an array of strings. Exactly what you need, except ... I want it to be paginated. So we
... and that completely bombs: we now get an array of numbers?
So we try something else, and write:
which runs the good query, but returns an array of
Visit's with only the project filled in. I can live with that. And then pagination (using the kaminari gem) is again as expected: