Re: xmin increasing within a transaction block?

On Mon, Nov 6, 2017 at 3:26 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> writes:
>> Luca Ferrari wrote:
>>> Why is xmin greater than the current transaction id (and most notably
>>> not "fixed")?
>
>> Something is using subtransactions there. My first guess would be that
>> there are triggers with EXCEPTION blocks, but your example doesn't show
>> any. Or maybe you have event triggers.
>
> I can reproduce the example if I "\set ON_ERROR_ROLLBACK on" in psql.
>

Shame on me, I did forgot to have enabled that in my ~/.psqlrc file
(and did not hit an error within the transaction block to see it was
aborting). And in fact, the manual page for psql reports that
ON_ERROR_ROLLBACK:

The error rollback mode works by issuing an implicit SAVEPOINT for you,
just before each command that is in a transaction block, and
then rolling back to the savepoint if the command fails.

Sorry for the noise.
Thanks,
Luca