This is simple steps to upgrade puppet.

systemctl stop puppetserver
systemctl stop puppetdb

Download New repo puppet-release

yum install puppetserver

Install New postgres pgdg-redhat9.6

systemctl stop postgresql-9.5
yum install postgresql96-server
yum install postgresql96-contrib

Do it as user `postgres`

/usr/pgsql-9.6/bin/initdb /var/lib/pgsql/9.6/data/
/usr/pgsql-9.6/bin/pg_upgrade -b /usr/pgsql-9.5/bin/ -B /usr/pgsql-9.6/bin/ -d /var/lib/pgsql/9.5/data/ -D /var/lib/pgsql/9.6/data/ -v
 
systemctl start postgresql-9.6

Upgrade puppetdb

yum install puppetdb
yum install puppetdb-termini
 
puppet resource service puppetdb ensure=stopped
puppet resource package puppetdb ensure=latest
puppet resource service puppetdb ensure=running

Optimize postgresql puppetdb.
run as `postgres` user.

./analyze_new_cluster.sh
./delete_old_cluster.sh

Run as `postgres` user

Only if you do not care for the data

drop database 'puppetdb'

createdb -E UTF8 -O puppetdb puppetdb
psql puppetdb -c 'create extension pg_trgm'