Re: Sequence values change during upgrade

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!
Dănuț Soare

> On 15 May 2024, at 14:01, Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> wrote:
>
> On Wed, 2024-05-15 at 11:03 +0300, Danut Soare wrote:
>> I’m upgrading the PostgreSQL version from 12 to 16 using pg_upgrade utility
>> with -k option. After upgrading the database, before starting any application
>> processing, on checking the last value of some sequences, the value has been
>> changed to a value different from the original value. Not all but some of the
>> sequences have modified value. I’ve repeated the upgrade several times and
>> each time the same sequences have changed with the same values. I’ve expected
>> that the upgrade would not interfere with the application data …
>> This is the upgrade command:
>>
>> /usr/pgsql-16/bin/pg_upgrade \
>> —old-datadir=/u01/pgrdb/12/app \
>> —new-data for=/u01/pgrdb/16/app \
>> —old-bindir=/usr/pgsql-12/bin \
>> —new-bindir=/usr/pgsql-16/bin \
>> -k
>
> 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 an
> influence, and the difference could be bigger.
>
> If the sequence moved backward, that would be a bug. If it moves forward,
> that is to be expected and OK.
>
> Yours,
> Laurenz Albe