| From: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
|---|---|
| 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: | 2021-07-28 01:04:58 |
| Message-ID: | 202107280104.ah3afb7d3grg@alvherre.pgsql |
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| Lists: | pgsql-hackers |
On 2021-Feb-19, Bossart, Nathan wrote:
> 0002 adds logic for persisting the last notified segment through
> crashes. This is needed because a poorly-timed crash could otherwise
> cause us to skip marking segments as ready-for-archival altogether.
> This file is only used for primary servers, as there exists a separate
> code path for marking segments as ready-for-archive for standbys.
I'm not sure I understand what's the reason not to store this value in
pg_control; I feel like I'm missing something. Can you please explain?
There were some comments earlier in the thread about the maximum size of
a record. As I recall, you can have records of arbitrary size if you
have COMMIT with a large number of relation invalidation messages being
included in the xlog record, or a large number of XIDs of
subtransactions in the transaction. Spanning several segments is
possible, AFAIU.
--
Álvaro Herrera 39°49'30"S 73°17'W — https://www.EnterpriseDB.com/
"La rebeldía es la virtud original del hombre" (Arthur Schopenhauer)
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