> 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

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