MIME-Version: 1.0
References: <1d12d2-67235980-35-19a406a0@63439497>
 <CAPpHfdtp61pSt72KxxOnnV_Oj4OTAiKYCSTek0Pm87hVDod4Bg@mail.gmail.com>
 <CAA4eK1Lmd-stXWrNqX9iXugjY=ahhe7zRfyq+-vN512xvF4G2w@mail.gmail.com>
 <CAPpHfdsTiYQPywr4yeqVhUtA+eFdqisqcAOiTb+kiYhi9EVEvw@mail.gmail.com>
 <CAPpHfdvk-nfu5xzJyPArxWctofWPR+1L9uJ+yyWFA34n6b5rGQ@mail.gmail.com>
 <CAA4eK1Ladnm40UO-YC+c7eBYqjyFQSwg0dn1w_CiaMoBTsJUDA@mail.gmail.com>
 <CAPpHfduX--KKX853UwaJ8Cjo5bxbh19V_+McKQ3p9aS6b8T1Wg@mail.gmail.com>
 <CAA4eK1+VbBxYY-rG4B7Jq6TsYvdjt3d2nbUrs7p9-1sP5mH+sw@mail.gmail.com>
 <CAPpHfdvxqjE+RZdoOODQZAmQip6NpvSH40DuvVFWuf_00ek-yQ@mail.gmail.com>
 <1d97ec-6841b600-3-b7b4780@40747246>
 <CAA4eK1LvssAcp61qg957xRF0=K4xF0hfJQjQ6c9V7EGHSqraPg@mail.gmail.com>
 <28c8bf-68470780-3-51b29480@89454035>
 <CAPpHfdt77k3BqD=anh4b7UiRevfPOu2Hcf3rvSZXntxH+4G=Ug@mail.gmail.com>
 <fbc5d94e-6fbd-4a64-85d4-c9e284a58eb2@gmail.com>
 <CAPpHfdvPpg5VUTNOqfKSNx66ij3ZJNZbf4kn6SDcPkdq9FTvng@mail.gmail.com>
 <0a617d34-abc3-4090-92a5-ea15d45e36f6@gmail.com>
 <228607.1750003556@sss.pgh.pa.us>
 <CAPpHfdvJMe4i0_wp1tq2ZGSDKqUHKPwkfD_Y6KyJ3XQRFvc0cQ@mail.gmail.com>
 <OSCPR01MB1496667BEA93302F8903EE512F570A@OSCPR01MB14966.jpnprd01.prod.outlook.com>
 <CAPpHfdsdJ4YPTzH=cnany5_LjCNb_Z9e+Oucv53qYQHaHzJhag@mail.gmail.com>
 <CALDaNm3s-jpQTe1MshsvQ8GO=TLj233JCdkQ7uZ6pwqRVpxAdw@mail.gmail.com>
 <3f242e-68518380-11-78125f00@134027639>
 <OSCPR01MB14966F3D6F2E8B6C982890880F572A@OSCPR01MB14966.jpnprd01.prod.outlook.com>
 <14841-68528100-1f-5d76c480@266989578>
In-Reply-To: <14841-68528100-1f-5d76c480@266989578>
From: vignesh C <vignesh21@gmail.com>
Date: Wed, 18 Jun 2025 15:33:17 +0530
Message-ID: 
 <CALDaNm21=mTJLrXxKYZ_07S9tAWMGEfxSnRXu_+t-k7jb5Kcyw@mail.gmail.com>
Subject: Re: Slot's restart_lsn may point to removed WAL segment after hard
 restart unexpectedly
To: Vitaly Davydov <v.davydov@postgrespro.ru>
Cc: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>,
 Alexander Korotkov <aekorotkov@gmail.com>,
	Tom Lane <tgl@sss.pgh.pa.us>, Alexander Lakhin <exclusion@gmail.com>,
	Amit Kapila <amit.kapila16@gmail.com>,
 pgsql-hackers <pgsql-hackers@postgresql.org>,
	Masahiko Sawada <sawada.mshk@gmail.com>, "tomas@vondra.me" <tomas@vondra.me>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Archived-At: 
 <https://www.postgresql.org/message-id/CALDaNm21%3DmTJLrXxKYZ_07S9tAWMGEfxSnRXu_%2Bt-k7jb5Kcyw%40mail.gmail.com>
Precedence: bulk

On Wed, 18 Jun 2025 at 14:35, Vitaly Davydov <v.davydov@postgrespro.ru> wro=
te:
>
> Dear Hayato,
>
> > To confirm, can you tell me the theory why the walsender received old L=
SN?
> > It is sent by the walreceiver, so is there a case that LogstreamResult.=
Flush can go backward?
> > Not sure we can accept the situation.
>
> I can't say anything about the origin of the issue, but it can be easily =
reproduced
> on the master branch:
>
> 1. Add an assert in PhysicalConfirmReceivedLocation (apply the attached p=
atch)
> 2. Compile & install with tap tests and assertions enabled
> 3. cd src/bin/pg_basebackup/
> 3. PROVE_TESTS=3Dt/020_pg_receivewal.pl gmake check

Thanks for the steps, I was able to reproduce the issue with the
suggested steps.

> The test will fail because of the assertion. I plan to investigate the is=
sue
> but I need some more time for it. Once, it happens on the original master
> branch, I think, this problem already exists. The proposed patch seems
> to be not guilty.

This issue occurs even prior to this commit, I was able to reproduce
it on a version just before it. I=E2=80=99ll also look into analyzing the r=
oot
cause further.

> It may be the same problem as discussed in:
> https://www.postgresql.org/message-id/CALDaNm2uQbhEVJzvnja6rw7Q9AYu9FpVmE=
T%3DTbwLjV3DcPRhLw%40mail.gmail.com

This issue was related to confirmed_flush and was addressed in commit
d1ffcc7fa3c54de8b2a677a3e503fc808c7b419c. It is not related to
restart_lsn.

Regards,
Vignesh