Alexandre,
> If the plans for both queries are exactly the same, should I assume
> that the cost will also be the same?
Nope. A seq scan over 1,000,000,000 rows is going to cost a LOT more than a
seq scan over 1000 rows, even though it's the same plan.
When you have the data sorted out, post explain analyzes and we'll take a shot
at it.
--
Josh Berkus
Aglio Database Solutions
San Francisco