On Mon, Apr 27, 2026 at 10:32 PM SATYANARAYANA NARLAPURAM <[email protected]> wrote: > > Hi, > > On Mon, Apr 27, 2026 at 2:48 AM shveta malik <[email protected]> wrote: >> >> On Mon, Apr 27, 2026 at 2:11 PM SATYANARAYANA NARLAPURAM >> <[email protected]> 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): >> >> error: corrupt patch at line 22 > > > Thanks! Please find the updated v2 patch.
Thanks. The patch looks good. thanks Shveta
