Re: BUG #8470: 9.3 locking/subtransaction performance regression

Thanks for looking at this and sorry about the late reply, I finally got
around to testing your latest patch.

20.12.2013 22:47, Alvaro Herrera kirjoitti:
>> Removing the BEGIN/EXCEPTION/END block and just doing a 'SELECT FOR
>> UPDATE' for a suitable row is significantly slower in 9.3.0 (314.765 ms
>> vs 118.894 ms on 9.2.4).  A 'SELECT' without a FOR UPDATE and
>> BEGIN/EXCEPTION/END has the same performance on 9.2.4 and 9.3.0.
>
> I have come up with the attached patch.  As far as I can tell it
> restores performance roughly to the level of 9.2 for this test case;
> could you please try it out and see if it fixes things for you?  It'd be
> particularly good if you can check not only the test case you submitted
> but also the one that made you explore this in the first place.

I didn't try this patch, but I built today's REL9_3_STABLE with the patch
from your mail on the 31st of Dec
(http://github.com/saaros/postgres/tree/alvaro-multixact-optimize-9.3) and
ran the older version of my appliaction's test suite which has a case that
times out after 3 minutes with unpatched 9.3.  With the current patch the
test case successfully completes in ~20 seconds which is a major improvement
although it's still slower than 9.2  It also passes all other test cases in
my test suite.

Do you think it'll make it to 9.3.3?

Thanks,
Oskari