On Thu, Feb 25, 2016 at 1:43 PM, Bruce Momjian <bruce@momjian.us> wrote:
> On Thu, Feb 25, 2016 at 12:50:06PM +1300, Thomas Munro wrote:
>> On Thu, Feb 25, 2016 at 12:26 PM, Bruce Momjian <bruce@momjian.us> wrote:
>> > On Thu, Feb 25, 2016 at 10:06:34AM +1100, James Sewell wrote:
>> >> Now when I run the following SQL (multiple times to allow for getting
>> >> everything into shared buffers, which is 4GB on my machine):
>> >>
>> >>
>> >> select sum(count_n) from base group by view_time_day;
>> >>
>> >>
>> >> I get the following results:
>> >>
>> >>
>> >> PSQL 9.5 - ~21 seconds
>> >> PSQL 9.6 devel - ~8.5 seconds
>> >>
>> >>
>> >> I think that's pretty good!
>> >>
>> >> I know this is a devel release, things may change, blah blah. But still,
>> >> something has changed for the better here!
>> >
>> > Wow, that is cool. Can anyone suggest which commit improved this?
>>
>> Since it sums numerics, maybe integer transition functions from commit
>> 959277a4f579da5243968c750069570a58e92b38 helped?
>
> Seems it was a wrong report, but anyway, this commit was in 9.5, while
> the user reported a speedup in 9.6.
Oops, right, and as David said it's also irrelevant.
FWIW I couldn't reproduce this comparing 9.5 with 9.6, but the numbers
reported just happen to match nearly exactly what I get comparing -O2
and -O0 builds here...
--
Thomas Munro
http://www.enterprisedb.com