"Guillaume Smet" <guillaume(dot)smet(at)gmail(dot)com> writes:
> So a total of: 16 minutes for 8.2 compared to 53 minutes for 8.3 to
> have the database in the same state.
Please try that experiment with all three configurations on both
versions:
* autovacuum off
* autovacuum on, autovacuum_vacuum_cost_delay = 0
* autovacuum on, autovacuum_vacuum_cost_delay = 20
Comparing apples and oranges isn't real helpful in determining
what's happening.
regards, tom lane