Tom,
> Let's see the pg_stats rows for case_clients in both databases. The
> entries for trial_groups might be relevant too.
My reading is that the case is "borderline"; that is, becuase the correlation
is about 10-20% higher on the test database (since it was restored "clean"
from backup) the planner is resorting to a seq scan.
At which point the spectre of random_page_cost less than 1.0 rears its ugly
head again. Because the planner seems to regard this as a borderline case,
but it's far from borderline ... index scan takes 260ms, seq scan takes
244,000ms. Yet my random_page_cost is set pretty low already, at 1.5.
It seems like I'd have to set random_page_cost to less than 1.0 to make sure
that the planner never used a seq scan. Which kinda defies the meaning of
the setting.
*sigh* wish the client would pay for an upgrade ....
--
-Josh Berkus
Aglio Database Solutions
San Francisco