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.
v2-0001-Fix-apply-worker-busy-loop-when-subscription-max_ret.patch
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