On Mon, Jan 22, 2018 at 8:24 AM, Michael Krüger <michael@kruegers.email> wrote:
> Dear community, > > I'm using PG10.1 on CentOS Linux release 7.4.1708 (Core) after upgrading > it from PG9.6.6. My application heavily uses sequences and requires > different increments of sequence numbers, e.g. a range of 100, 1000 or 5000 > numbers, so it is not possible to set a fixed increment on a sequence that > can be used by my application. > > With PG10.1 the performance has dropped seriously so that my application > becomes unusable. After investigating different aspects, I was able to > isolate the issue to be related to the sequences in Postgres 10.1. > > Below shows a simple test script showing the problem: > > [...] > > On my computer I tried this code on PG9.6.6 and it executed in roughly 3 > seconds. > When running it on PG10.1 it takes over 7 minutes. > > Further investigation showed that the problem is related to ALTER > SEQUENCE... > > I can't believe that PG10.1 was changed that dramatically without > providing a workaround or a way to switch to the old PG9.6 performance, at > least I can't find anything in the documentation. > > Is this a bug? > Without testing/confirming I'd be inclined to agree that this is a regression for an unusual usage of sequences. Work was done to make typical use cases of sequences more feature-full and it is quite possible the added effort involved hurts your specific scenario. I'd expect a hacker to eventually pick this up, confirm the observation, and provide feedback. This seems like sufficient amount of detail to get the ball rolling. David J.
