Manfred Koizar <[EMAIL PROTECTED]> writes: > The comment describing cost_nonsequential_access() says that the two > functions "meet in the middle". They meet at random_page_cost/2, > however, not in the middle between 1 and random_page_cost. For > random_page_cost < 2 the result can be less than 1 for relpages near > effective_cache_size. I don't think that this was intended.
You're right, I failed to consider that random_page_cost might be less than 2. > This patch makes sure that cost_nonsequential_access() is always between > 1 and randon_page_cost and the functions meet a (1+random_page_cost)/2. This patch seems to do considerably more violence to the equations than is needed to cover that oversight, though. The old behavior was intentionally nonlinear in relsize; this is not. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 7: don't forget to increase your free space map settings