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help / color / mirror / Atom feedFrom: Alexander Korotkov <[email protected]>
To: Amit Kapila <[email protected]>
Cc: Vitaly Davydov <[email protected]>
Cc: pgsql-hackers <[email protected]>
Cc: Masahiko Sawada <[email protected]>
Cc: [email protected]
Subject: Re: Slot's restart_lsn may point to removed WAL segment after hard restart unexpectedly
Date: Thu, 29 May 2025 14:59:39 +0300
Message-ID: <CAPpHfduX--KKX853UwaJ8Cjo5bxbh19V_+McKQ3p9aS6b8T1Wg@mail.gmail.com> (raw)
In-Reply-To: <CAA4eK1Ladnm40UO-YC+c7eBYqjyFQSwg0dn1w_CiaMoBTsJUDA@mail.gmail.com>
References: <1d12d2-67235980-35-19a406a0@63439497>
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On Tue, May 27, 2025 at 2:26 PM Amit Kapila <[email protected]> wrote:
> Yeah, we should be able to change ABI during beta, but I can't comment
> on the idea of effective_restart_lsn without seeing the patch or a
> detailed explanation of this idea.
Could you, please, check the patch [1]. It implements this idea
except it names new field restart_lsn_flushed instead of
effective_restart_lsn.
> Now, you see my point related to restart_lsn computation for logical
> slots, it is better to also do some analysis of the problem related to
> xmin I have highlighted in one of my previous emails [1]. I see your
> response to it, but I feel someone needs to give it a try by writing a
> test and see the behavior. I am saying because logical slots took
> precaution of flushing to disk before updating shared values of xmin
> for a reason, whereas similar precautions are not taken for physical
> slots, so there could be a problem with that computation as well.
I see LogicalConfirmReceivedLocation() performs correctly while
updating effective_catalog_xmin only after syncing the slot to the
disk. I don't see how effective_xmin gets updates with the logical
replication progress though. Could you get me some clue on this,
please?
Links.
1. https://www.postgresql.org/message-id/1538a2-67c5c700-7-77ec5a80%40179382871
------
Regards,
Alexander Korotkov
Supabase
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Subject: Re: Slot's restart_lsn may point to removed WAL segment after hard restart unexpectedly
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