"Markus Wollny" <[EMAIL PROTECTED]> writes:
>> ... What I find interesting though is
>> that the plain index scan in 8.0 is so enormously cheaper
>> than it's estimated to be. Perhaps the answer table in your
>> 8.0 installation is almost perfectly ordered by session_id?
> Not quite - there may be several concurrent sessions at any one time, but
> ordinarily the answers for one session-id would be quite close together, in a
> lot of cases even in perfect sequence, so "almost perfectly" might be a fair
> description, depending on the exact definition of "almost" :)
Could we see the pg_stats row for answer.session_id in both 8.0 and 8.1?
> I had set random_page_cost to 1.4 already, so I doubt that it would do much
> good to further reduce the value - reading the docs and the suggestions for
> tuning I would have thought that I should actually consider increasing this
> value a bit, as not all of my data will fit in memory any more. Do you
> nevertheless want me to try what happens if I reduce random_page_cost even
> further?
No, that's probably quite low enough already ...
regards, tom lane
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