Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl> writes:
> One thing I've wondered is if one can trust the "conversion" to keep
> roughly the same from one query to another,
If the planner's units don't bear some reasonably linear relationship
to the real world, then its cost estimation process doesn't work at all.
So yeah, on any given machine there ought to be a fairly consistent
conversion.
regards, tom lane