> One objection to this is that after moving "off the gold standard" of
> 1.0 = one page fetch, there is no longer any clear meaning to the
> cost estimate units; you're faced with the fact that they're just an
> arbitrary scale. I'm not sure that's such a bad thing, though. For
> instance, some people might want to try to tune their settings so that
> the estimates are actually comparable to milliseconds of real time.
Any chance that the correspondence to time could be made a part of the
design on purpose and generally advise people to follow that rule? If we
could tell people to run *benchmark* and use those numbers directly as a
first approximation tuning, it could help quite a bit for people new to
PostgreSQL experiencing poor performance.
effective_cache_size then becomes essentially the last hand-set variable
for medium sized installations.
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TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
