Re: _page_cost parameter with values < 1

Thomas Kellerer <spam_eater(at)gmx(dot)net> writes:
> recently I have seen a Postgres configuration with the following values:
> seq_page_cost = 0.5
> random_page_cost = 0.6
> Is there any advantage (or maybe disadvantage) compared to using e.g. 1.0 and 1.2?

That reduces these costs relative to the cpu_xxx_cost ones. You'd get the
same plans if you scaled *all* the planner cost parameters by the same
amount, but changing only these two is the easiest way to reduce the
significance of I/O relative to CPU costs.

regression=# select name,setting from pg_settings where name like '%cost';
name | setting
----------------------+---------
cpu_index_tuple_cost | 0.005
cpu_operator_cost | 0.0025
cpu_tuple_cost | 0.01
parallel_setup_cost | 1000
parallel_tuple_cost | 0.1
random_page_cost | 4
seq_page_cost | 1
(7 rows)

regards, tom lane