If builds of PostgreSQL 9 are failing and you have version 8.x installed,
you may need to remove the previous version first. See:
https://github.com/Homebrew/legacy-homebrew/issues/2510
To migrate existing data from a previous major version (pre-9.3) of PostgreSQL, see:
https://www.postgresql.org/docs/9.3/static/upgrading.html
When installing the postgres gem, including ARCHFLAGS is recommended:
ARCHFLAGS="-arch x86_64" gem install pg
To install gems without sudo, see the Homebrew documentation:
https://docs.brew.sh/Gems,-Eggs-and-Perl-Modules
This formula has created a default database cluster with:
initdb $(brew --prefix)/var/postgres
For more details, read:
https://www.postgresql.org/docs/9/app-initdb.html
