On Mon, Apr 27, 2026 at 2:11 PM SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com> wrote: > > Hi Hackers, > > When a subscription has retain_dead_tuples enabled with maxretention set > to zero (unlimited retention), adjust_xid_advance_interval() caps > xid_advance_interval to Min(interval, maxretention). Since maxretention > is zero, this always collapses the interval to zero milliseconds. > > A zero makes TimestampDifferenceExceeds(last_time, now, 0) always > true in get_candidate_xid(). This causes the apply worker to call > GetOldestActiveTransactionId() on every single WAL message. This results in > a huge number of ProcArrayLock acquisitions under moderate write load. > > Fix by adding a maxretention > 0 guard to the cap. When maxretention is zero , > the exponential back-off in adjust_xid_advance_interval() > now works correctly, growing the interval from 100 ms toward the 180 s > ceiling. > > Measured with perf uprobe counting GetOldestActiveTransactionId calls > at ~39K TPS (pgbench, 5 clients): > > Before fix: 25,104 calls / 5 s (~5,021/s) > After fix: 31 calls / 5 s (~6/s) >
Thanks for reporting it. I am reveiwing the problem sattement. Meanwhile can you please look at it, I am getting the following error while applying the patch on my Ubuntu setup (git am):
