On Mon, Jul 7, 2025 at 12:29 PM Hayato Kuroda (Fujitsu) <kuroda.hay...@fujitsu.com> wrote: > > Dear Sawada-san, > > > What does each duration mean in these results? Can we interpret the > > test case of max_conflict_retention_duration=120s that when 7 clients > > and 15 clients are working on the publisher and the subscriber > > respectively, the TPS on the subscriber was about one fourth (17835.3 > > vs. 4707)? > > Firstly, this workload is done to prove that users can tune their workload to > keep > enabling the update_deleted detections. Let me describe what happened there > with > the timetable since the test starts. > > 0-162s: > Number of clients on both publisher/subscriber was 15. TPS was 17835.3 on the > publisher and 4571.8 on the subscriber. This means that retained dead tuples > on > the subscriber may reduce the performance to around 1/4 compared with > publisher, > and the workload on the publisher is too heavy to keep working the > update_deleted > detection. > > 163-314s: > Number of clients was 7 on publisher, and 15 on subscriber. TPS was 9503.8 on > the publisher and 4707 on the subscriber. This means that N=7 on the publisher > was still too many thus conflict slot must be invalidated. > > 315-597s: > Number of clients was 3 on publisher, and 15 on subscriber. TPS was 4243.9 on > the publisher and 19568.4 on the subscriber. Here the conflict slot could > survive > during the benchmark because concurrency on the publisher was reduced. > Performance could be improved on the subscriber side because dead tuples can > be > reduced here.
Thank you for your explanation! Since this feature is designed to reliably detect conflicts on the subscriber side, this scenario, where both the publisher and subscriber are under load, represents a typical use case. The fact that the subscriber can withstand the case where N=7 on the publisher and N=15 on the subscriber with retain_conflict_info = false, but fails to do so when retain_conflict_info = true, might suggests a significant performance impact from enabling this feature. In these test cases, was autovacuum disabled? I'm curious whether users would experience permanently reduced transaction throughput, or if this performance drop is temporary and recovers after autovacuum runs. Regards, -- Masahiko Sawada Amazon Web Services: https://aws.amazon.com
