From: | "alvherre(at)alvh(dot)no-ip(dot)org" <alvherre(at)alvh(dot)no-ip(dot)org> |
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To: | "Bossart, Nathan" <bossartn(at)amazon(dot)com> |
Cc: | Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, "x4mmm(at)yandex-team(dot)ru" <x4mmm(at)yandex-team(dot)ru>, "a(dot)lubennikova(at)postgrespro(dot)ru" <a(dot)lubennikova(at)postgrespro(dot)ru>, "hlinnaka(at)iki(dot)fi" <hlinnaka(at)iki(dot)fi>, "matsumura(dot)ryo(at)fujitsu(dot)com" <matsumura(dot)ryo(at)fujitsu(dot)com>, "masao(dot)fujii(at)gmail(dot)com" <masao(dot)fujii(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: archive status ".ready" files may be created too early |
Date: | 2021-08-17 20:23:03 |
Message-ID: | 202108172023.b52p6convvvd@alvherre.pgsql |
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Lists: | pgsql-hackers |
The thing I still don't understand about this patch is why we call
RegisterSegmentBoundaryEntry and NotifySegmentsReadyForArchive in
XLogInsertRecord.
My model concept of this would have these routines called only in
XLogFlush / XLogWrite, which are conceptually about transferring data
from in-memory WAL buffers into the on-disk WAL store (pg_xlog files).
As I understand, XLogInsertRecord is about copying bytes from the
high-level operation (heap insert etc) into WAL buffers. So doing the
register/notify dance in both places should be redundant and
unnecessary.
In the NotifySegmentsReadyForArchive() call at the bottom of XLogWrite,
we use flushed=InvalidXLogRecPtr. Why is that? Surely we can use
LogwrtResult.Flush, just like in the other callsite there? (If we're
covering for somebody advancing FlushRecPtr concurrently, I think we
add a comment to explain that. But why do we need to do that in the
first place?)
--
Álvaro Herrera PostgreSQL Developer — https://www.EnterpriseDB.com/
"The eagle never lost so much time, as
when he submitted to learn of the crow." (William Blake)
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