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From: Danut Soare <danut_soare@yahoo.com>
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Subject: Re: Sequence values change during upgrade
Date: Wed, 15 May 2024 15:17:27 +0300
Message-Id: <7BA33FCE-0EC0-4843-B945-8A4CA13DF426@yahoo.com>
References: <16b971b62eb5c4219184084ddaa6e91797030297.camel@cybertec.at>
Cc: pgsql-general@lists.postgresql.org
In-Reply-To: <16b971b62eb5c4219184084ddaa6e91797030297.camel@cybertec.at>
To: Laurenz Albe <laurenz.albe@cybertec.at>
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Archived-At: <https://www.postgresql.org/message-id/7BA33FCE-0EC0-4843-B945-8A4CA13DF426%40yahoo.com>
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Hi,

Thank you for your answer. Here is the requested information.

select last_value from seq_name;

The difference was less than 32 except one sequence with difference equal to=
 32

The cache used for sequence creation was 1.

Thank you once again!
D=C4=83nu=C8=9B Soare

> On 15 May 2024, at 14:01, Laurenz Albe <laurenz.albe@cybertec.at> wrote:
>=20
> =EF=BB=BFOn Wed, 2024-05-15 at 11:03 +0300, Danut Soare wrote:
>>  I=E2=80=99m upgrading the PostgreSQL version from 12 to 16 using pg_upgr=
ade utility
>> with -k option. After upgrading the database, before starting any applica=
tion
>> processing, on checking the last value of some sequences, the value has b=
een
>> changed to a value different from the original value. Not all but some of=
 the
>> sequences have modified value. I=E2=80=99ve repeated the upgrade several t=
imes and
>> each time the same sequences have changed with the same values. I=E2=80=99=
ve expected
>> that the upgrade would not interfere with the application data =E2=80=A6
>> This is the upgrade command:
>>=20
>> /usr/pgsql-16/bin/pg_upgrade \
>> =E2=80=94old-datadir=3D/u01/pgrdb/12/app \
>> =E2=80=94new-data for=3D/u01/pgrdb/16/app \
>> =E2=80=94old-bindir=3D/usr/pgsql-12/bin \
>> =E2=80=94new-bindir=3D/usr/pgsql-16/bin \
>> -k
>=20
> How exactly did you determine the current sequence value before and after
> the upgrade?  Was the difference less than 32?  If yes, that is normal,
> because sequences don't WAL log every single nextval() call.
> Also, what CACHE setting did you use in CREATE SEQUENCE?  That will have a=
n
> influence, and the difference could be bigger.
>=20
> If the sequence moved backward, that would be a bug.  If it moves forward,=

> that is to be expected and OK.
>=20
> Yours,
> Laurenz Albe