Disruptive corruption of data during an update

A few minutes ago I wrote:
---- quote
update command:
--------
mydb=> update bibl set argomento='curatori', autore='DELLA VOLPE Galvano \
(con due capitoli aggiunti e note di) where n_prog=3285;
mydb'> ';

UPDATE 12845
mydb=>
--------

Having an adequate back-up I think I'll be able to recover the data, but
can someone explain what the hell happened?

-------- unquote

Having come out of the initial panic I reconsidered the thing with calm
and of course 'discovered' that the program has done exactly what I told
it to do, as the 'where' clause was incorporated within the two «'».

My question now is:
is there any possibility to recover such type of error while postgres is
still running and no other transacion has been committed?

Regards,
ennio

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