8.2 and 8.3 postgresql.conf oddity

From: "Guillaume Smet" <guillaume(dot)smet(at)gmail(dot)com>
To: pgsql-bugs <pgsql-bugs(at)postgresql(dot)org>
Subject: 8.2 and 8.3 postgresql.conf oddity
Date: 2008-01-23 10:50:38
Message-ID: 1d4e0c10801230250w8bf439cp81897f65857ef1a5@mail.gmail.com
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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

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