Vlad <marchenko@gmail.com> writes:
> 2. We ran several tests and found 8.3 generally 10% slower than 8.2.6.
The particular case you are showing here seems to be all about the speed
of hash aggregation --- at least the time differential is mostly in the
HashAggregate step. What is the data type of a_id? I speculate that
you're noticing the slightly slower/more complicated hash function that
8.3 uses for integers. On a case where the data was well distributed
you'd not see any countervailing efficiency gain from those extra
cycles.
regards, tom lane