Pavel Luzanov <p.luzanov@xxxxxxxxxxxxxx> writes: > One thing remains unclear. > Why, if a scalar subquery is used to materialize the function value(even > constant), then an inefficient index scan is chosen: The scalar subquery prevents the planner from seeing the actual comparison value, so it falls back to a default selectivity estimate (notice the fairly bad rowcount estimate). I'm a bit surprised that that would end in choosing an indexscan over a seqscan, but that might be a consequence of the small random_page_cost you're using. regards, tom lane
