Re: pg_upgrading to 10.1 corrupts (varchar,varchar) UNIQUE indices

What platform are you on

FreeBSD 10.3-RELEASE-p26 amd64

, how was PostgreSQL installed

pkg install.
Additionally, 10.1 needed for pg_upgrade to run was installed using portmaster -m PREFIX=/10.1, because FreeBSD doesn't allow more than one major version to be installed simultaneously.
After the upgrade took place, 9.6.6 was pkg deleted and 10.1 was pkg installed.

and exactly how was pg_upgrade executed? (or is, since it's reproducible)

sudo -u postgres /10.1/bin/pg_upgrade -j2 --link -r -b /usr/local/bin -B /10.1/bin/ -d /var/db/postgres/data96/ -D /var/db/postgres/data10/