pg_upgrade to 9.5.0

pg_upgrade

Assuming you've used home-brew to install and upgrade Postgres, you can perform the following steps.

Stop current Postgres server:

launchctl unload ~/Library/LaunchAgents/homebrew.mxcl.postgresql.plist

Initialize a new 9.5 database:

initdb /usr/local/var/postgres9.5 -E utf8

run pg_upgrade:

pg_upgrade -v \
  -d /usr/local/var/postgres \
  -D /usr/local/var/postgres9.5 \
  -b /usr/local/Cellar/postgresql/9.4.5_2/bin/ \
  -B /usr/local/Cellar/postgresql/9.5.0/bin
Move new data into place:

cd /usr/local/var
mv postgres postgres9.4
mv postgres9.5 postgres
Restart Postgres:

launchctl load ~/Library/LaunchAgents/homebrew.mxcl.postgresql.plist

Check /usr/local/var/postgres/server.log for details and to make sure the new server started properly.

Finally, re-install the rails pg gem

gem uninstall pg
gem install pg