Upgrade PostgreSQL using Homebrew (macOS)

upgrade.sh

# Install the latest version of postgresql via Homebrew
brew upgrade postgresql

# After doing that, I needed to upgrade my existing database

# Need to have both the old and new version of postgresql installed. The example here uses 9.6.1 and 10.3.
brew unlink postgresql
brew switch postgresql 10.3
brew link postgresql

# init new database using 10.0
initdb /usr/local/var/postgres10.3 -E utf8

# finally the actual upgrade
# -b is the old binary dir, -B is the new binary dir
# -d is the old data dir, -D is the new data dir
pg_upgrade -b /usr/local/Cellar/postgresql/9.6.1/bin -B /usr/local/Cellar/postgresql/10.3/bin -d /usr/local/var/postgres9.6 -D /usr/local/var/postgres10.3

# Then link the new postgres instance
rm /usr/local/bin/postgresql
ln -s /usr/local/var/postgres10.3 /usr/local/bin/postgres

# start 10.3 to check that upgrade works
pg_ctl -D /usr/local/bin/postgres -l logfile start

# cleanup if upgrade was successful
brew uninstall postgresql@9.6
rm -rf /usr/local/var/postgres9.6