From: alvherre@alvh.no-ip.org <alvherre@alvh.no-ip.org>
To: Bossart, Nathan <bossartn@amazon.com>
Cc: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: x4mmm@yandex-team.ru <x4mmm@yandex-team.ru>
Cc: a.lubennikova@postgrespro.ru <a.lubennikova@postgrespro.ru>
Cc: hlinnaka@iki.fi <hlinnaka@iki.fi>
Cc: matsumura.ryo@fujitsu.com <matsumura.ryo@fujitsu.com>
Cc: masao.fujii@gmail.com <masao.fujii@gmail.com>
Cc: pgsql-hackers@postgresql.org <pgsql-hackers@postgresql.org>
Subject: Re: archive status ".ready" files may be created too early
Date: Tue, 17 Aug 2021 13:44:05 -0400
Message-ID: <202108171744.wzeymligc6e2@alvherre.pgsql> (raw)
In-Reply-To: <1264128B-5757-4A56-974E-45447FC09433@amazon.com>
On 2021-Aug-17, Bossart, Nathan wrote:
> On 8/16/21, 5:09 PM, "alvherre@alvh.no-ip.org" <alvherre@alvh.no-ip.org> wrote:
> > The reason for the latter is that I suspect the segment boundary map
> > will also have a use to fix the streaming replication issue I mentioned
> > earlier in the thread. This also makes me think that we'll want the wal
> > record *start* address to be in the hash table too, not just its *end*
> > address. So we'll use the start-1 as position to send, rather than the
> > end-of-segment when GetFlushRecPtr() returns that.
>
> I've been thinking about the next steps for this one, too. ISTM we'll
> need to basically assume that the flush pointer jumps along record
> boundaries except for the cross-segment records. I don't know if that
> is the safest assumption, but I think the alternative involves
> recording every record boundary in the map.
I'm not sure I understand your idea correctly. Perhaps another solution
is to assume that the flush pointer jumps along record boundaries
*including* for cross-segment records. The problem stems precisely from
the fact that we set the flush pointer at segment boundaries, even when
they aren't record boundary.
--
Álvaro Herrera 39°49'30"S 73°17'W — https://www.EnterpriseDB.com/
Bob [Floyd] used to say that he was planning to get a Ph.D. by the "green
stamp method," namely by saving envelopes addressed to him as 'Dr. Floyd'.
After collecting 500 such letters, he mused, a university somewhere in
Arizona would probably grant him a degree. (Don Knuth)
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To: pgsql-hackers@postgresql.org
Cc: alvherre@alvh.no-ip.org, bossartn@amazon.com, horikyota.ntt@gmail.com, x4mmm@yandex-team.ru, a.lubennikova@postgrespro.ru, hlinnaka@iki.fi, matsumura.ryo@fujitsu.com, masao.fujii@gmail.com
Subject: Re: archive status ".ready" files may be created too early
In-Reply-To: <202108171744.wzeymligc6e2@alvherre.pgsql>
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