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

Hi,

I don't understand about this problem, but
it seems this problem is still remaining in 93_STABLE(*).
(*)f1e522696fbc01b5c8a41dbd45d6cbae229be425

9.3.2   : 4.225(s)
93_STABE: 2.819(s)
9.2.6   : 0.135(s)

93_STABLE is faster than 9.3.2, but it's apparently
slower than 9.2.6.

9.3.3 is going to be released in next week.
Will any fixes be included in 9.3.3?

regards,
-----------
Tomonari Katsumata

(2014/01/14 22:09), Alvaro Herrera wrote:
 > Oskari Saarenmaa wrote:
 >> 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?
 >
 > Well, I gave this patch a long, careful look and eventually noticed that
 > there was a rather subtle but serious design bug in it, and I had to
 > ditch it.  I have the intention to come back to this problem again
 > later, but right now I cannot.
 >
 > I'm not sure whether I will have something for 9.3.3, but it's not
 > likely because that'll happen only in a week or two.
 >