Q: Upgrade postgres 10.6 a 12.3 I upgraded a postgres cluster from version 10.6 to 12.3 with the pg_upgrade command, it was fine, but when I connect with psql they appear:
> psql
psql (12.3, server 10.6)

# select version ();
                                                  version
-------------------------------------------------- -------------------------------------------------- -----
  PostgreSQL 10.6 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-28), 64 bit
(1 row)

What did I do wrong?

A: Let me guess: You ran pg_upgrade without -k, so that the data from the old cluster were copied to the new cluster.
But the old cluster is still there. So your problem is probably just that you started and used the old cluster by mistake.
Try with the new cluster (the one you specified with the -D option of pg_upgrade).
