stupid but working updating postgresql to 9.5.0 with homebrew on OSX

update_postgres_db.sh

# stupid but working updating postgresql to 9.5.0 with homebrew on OSX

brew update

# if you already updated and have your old databases inacessible, just do
#   ls /usr/local/Cellar/postgresql
# for versions, then
#   brew switch postgresql 9.4.5
# or whatever version you had before

# create giant backup for all your databases:
pg_dumpall > tempdump.sql
# ...5 minutes later...
launchctl unload ~/Library/LaunchAgents/homebrew.mxcl.postgresql.plist
# I suggest you to check your postgres db is shut down
ps axu | grep postgres
brew upgrade postgresql
# ...5 minutes...
# save your older database
mv /usr/local/var/postgres /usr/local/var/postgres.old
# create empty database
mkdir /usr/local/var/postgres
chown ${USER}:admin /usr/local/var/postgres
initdb -D /usr/local/var/postgres
launchctl load ~/Library/LaunchAgents/homebrew.mxcl.postgresql.plist

# check if postgres started ok
#   psql postgres
# check logs if not started:
#   tail /usr/local/var/postgres/server.log
time psql < tempdump.sql
# ...it could take a lot of time. 1.5hours in my case...
# check everything's working... then:
# rm -rf /usr/local/var/postgres.old
# rm temdump.sql