RE: Subscription statistics are not dropped at DROP SUBSCRIPTION in some cases
От | Zhijie Hou (Fujitsu) |
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Тема | RE: Subscription statistics are not dropped at DROP SUBSCRIPTION in some cases |
Дата | |
Msg-id | OS0PR01MB5716671E946C1C0AA48C05F794E8A@OS0PR01MB5716.jpnprd01.prod.outlook.com обсуждение исходный текст |
Ответ на | Re: Subscription statistics are not dropped at DROP SUBSCRIPTION in some cases (Masahiko Sawada <sawada.mshk@gmail.com>) |
Ответы |
Re: Subscription statistics are not dropped at DROP SUBSCRIPTION in some cases
(Masahiko Sawada <sawada.mshk@gmail.com>)
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Список | pgsql-hackers |
On Monday, September 4, 2023 10:42 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote: Hi, > On Mon, Sep 4, 2023 at 9:38 PM Zhijie Hou (Fujitsu) <houzj.fnst@fujitsu.com> > wrote: > > > > On Wednesday, July 5, 2023 2:53 PM Masahiko Sawada > <sawada.mshk@gmail.com> wrote: > > > > > Thanks for reviewing the patch. Pushed. > > > > My colleague Vignesh noticed that the newly added test cases were failing in > BF animal sungazer[1]. > > Thank you for reporting! > > > > > The test failed to drop the slot which is active on publisher. > > > > --error-log-- > > This failure is because pg_drop_replication_slot fails with "replication slot > "test_tab2_sub" is active for PID 55771638": > > 2023-09-02 09:00:04.806 UTC [12910732:4] 026_stats.pl LOG: statement: > > SELECT pg_drop_replication_slot('test_tab2_sub') > > 2023-09-02 09:00:04.807 UTC [12910732:5] 026_stats.pl ERROR: > > replication slot "test_tab2_sub" is active for PID 55771638 > > 2023-09-02 09:00:04.807 UTC [12910732:6] 026_stats.pl STATEMENT: > > SELECT pg_drop_replication_slot('test_tab2_sub') > > ------------- > > > > I the reason is that the test DISABLEd the subscription before > > dropping the slot, while "ALTER SUBSCRIPTION DISABLE" doesn't wait for > > the walsender to release the slot, so it's possible that the walsender > > is still alive when calling > > pg_drop_replication_slot() to drop the slot on > > publisher(pg_drop_xxxslot() doesn't wait for slot to be released). > > I agree with your analysis. > > > > > I think we can wait for the slot to become inactive before dropping like: > > $node_primary->poll_query_until('otherdb', > > "SELECT NOT EXISTS (SELECT 1 FROM pg_replication_slots > WHERE active_pid IS NOT NULL)" > > ) > > > > I prefer this approach but it would be better to specify the slot name in the > query. > > > Or we can just don't drop the slot as it’s the last testcase. > > Since we might add other tests after that in the future, I think it's better to drop > the replication slot (and subscription). > > > > > Another thing might be worth considering is we can add one parameter > > in > > pg_drop_replication_slot() to let user control whether to wait or not, > > and the test can be fixed as well by passing nowait=false to the func. > > While it could be useful in general we cannot use this approach for this issue > since it cannot be backpatched to older branches. We might want to discuss it > on a new thread. > > I've attached a draft patch to fix this issue. Feedback is very welcome. Thanks, it looks good to me. Best Regards, Hou zj
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