Hi -bugs,
I just noticed something odd in the Planner constants part of the 8.2
and 8.3 postgresql.conf:
# - Planner Cost Constants -
#seq_page_cost = 1.0 # measured on an arbitrary scale
#random_page_cost = 4 # same scale as above
#cpu_tuple_cost = 0.01 # same scale as above
#cpu_index_tuple_cost = 0.005 # same scale as above
#cpu_operator_cost = 0.0025 # same scale as above
The "same scale as above" while we have an "arbitrary scale" on the
first line is a bit weird.
8.1 was:
random_page_cost = 2 # units are one sequential page fetch
# cost
cpu_tuple_cost = 0.01 # (same)
cpu_index_tuple_cost = 0.001 # (same)
cpu_operator_cost = 0.0025 # (same)
Which seems better.
AFAIK, the unit of random_page_cost and cpu_*_cost is now seq_page_cost.
--
Guillaume
