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From: Danut Soare <[email protected]>
To: Laurenz Albe <[email protected]>
Cc: [email protected]
Subject: Re: Sequence values change during upgrade
Date: Wed, 15 May 2024 15:17:27 +0300
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>

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 <[email protected]> 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

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