how to fix postgres after updating/upgrading brew

Question

I upgraded to mavericks and had some trouble installing/compiling new gems so I reinstalled xcode and did a brew update and upgrade. Gems work now, and even postgres continued to work for a while until a recent reboot. Now postgres seems to be having issues.

postgres:

postgres does not know where to find the server configuration file.
You must specify the --config-file or -D invocation option or set the PGDATA environment variable.


brew info postgres:

postgresql: stable 9.3.2 (bottled)
http://www.postgresql.org/
Conflicts with: postgres-xc
/usr/local/Cellar/postgresql/9.2.4 (2842 files, 39M)
  Built from source
/usr/local/Cellar/postgresql/9.3.2 (2924 files, 39M) *
  Poured from bottle

postgres -D /usr/local/var/postgres:

FATAL:  database files are incompatible with server
DETAIL:  The data directory was initialized by PostgreSQL version 9.2, which is not compatible with this version 9.3.2.

What should I do now to get my database working again?

Answer 1

$ brew tap homebrew/versions
$ brew install postgresql92
$ brew switch postgresql 9.2.8 # might need to check this one, could be newer by the time you read this
$ pg_dumpall > ninedottwo-dump
$ brew uninstall postgresql92
$ brew switch postgresql 9.3.4 # again, check version
$ pg_ctl -D /usr/local/var/postgres -l /usr/local/var/postgres/server.log start
$ createdb # i got an error about my database not existing, so i had to run this
$ psql < ninedottwo-dump
$ bundle exec rails s

Thanks to Peter for getting me started in the right direction.

edit: this'll teach me to upgrade everything all at once...