Re: prevent immature WAL streaming
От | alvherre@alvh.no-ip.org |
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Тема | Re: prevent immature WAL streaming |
Дата | |
Msg-id | 202108251232.aaxpgvj3rcvw@alvherre.pgsql обсуждение исходный текст |
Ответ на | Re: prevent immature WAL streaming ("Bossart, Nathan" <bossartn@amazon.com>) |
Список | pgsql-hackers |
On 2021-Aug-24, Bossart, Nathan wrote: > If moving RegisterSegmentBoundary() is sufficient to prevent the flush > pointer from advancing before we register the boundary, I bet we could > also remove the WAL writer nudge. Can you elaborate on this? I'm not sure I see the connection. > Another interesting thing I see is that the boundary stored in > earliestSegBoundary is not necessarily the earliest one. It's just > the first one that has been registered. I did this for simplicity for > the .ready file fix, but I can see it causing problems here. Hmm, is there really a problem here? Surely the flush point cannot go past whatever has been written. If somebody is writing an earlier section of WAL, then we cannot move the flush pointer to a later position. So it doesn't matter if the earliest point we have registered is the true earliest -- we only care for it to be the earliest that is past the flush point. -- Álvaro Herrera Valdivia, Chile — https://www.EnterpriseDB.com/
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