Dict issue with PostgreSQL for last_login plugin (duplicate key)

Hello,

I am trying to setup the last_login plugin on Dovecot 2.3 in order to log a user's last IMAP login into a separate PostgreSQL table called last_login. I am actually following that guide: https://docs.iredmail.org/track.user.last.login.html with the exception that I use PostgreSQL instead of MySQL.

So far it works at least for the very first login of a user but it looks like Dict always want to add a new record into my last_login table instead of updating the existing record for a specific user. Here is the error message from Dovecot:

May 19 12:45:14-mbox1 dovecot: imap(user@domain.tld)<51915>: Error: last_login_dict: Failed to write value: dict-server returned failure: sql dict: commit failed: ERROR: duplicate key value violates unique constraint "last_logins_pkey"

It looks like Dict with PostgreSQL does not support UPDATEing an already existing record in the table. Or am I missing something? or it does not work with PostgreSQL? Which does not make much sense to me...

Regards, Mabi