Re: Using CTID system column as a "temporary" primary key

Ok... sounds not good all in all.
Appreciate your help!
Thanks!
________________________________
From: Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>
Sent: Wednesday, March 29, 2023 5:53 PM
To: Sebastien Flaesch <sebastien(dot)flaesch(at)4js(dot)com>; Kirk Wolak <wolakk(at)gmail(dot)com>
Cc: Geoff Winkless <pgsqladmin(at)geoff(dot)dj>; pgsql-general <pgsql-general(at)lists(dot)postgresql(dot)org>
Subject: Re: Using CTID system column as a "temporary" primary key

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On Wed, 2023-03-29 at 14:23 +0000, Sebastien Flaesch wrote:
> From: Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>
> > It is safe to assume that the CTID is stable within a single transaction
> > only if you use REPEATABLE READ or better transaction isolation level.
> >
> > With READ COMMITTED, you see updated rows (and consequently changed CTID)
> > within a single transaction. And if you use SELECT ... FOR UPDATE, you
> > could even see a changed CTID within a single statement.
> >
> > So don't use CTID to identify rows unless you use REPEATABLE READ or better.
>
> Thanks for the advice about REPEATABLE READ isolation level!

... but that is only useful in a read-only scenario.

If you try to UPDATE the row in a REPEATABLE READ transaction, you
will get a serialization error if there was a concurrent update.

In short: don't use the CTID to identify a row.

Yours,
Laurenz Albe