Recently, I updated all of the packages I have installed via Homebrew and ran into some issues with the PostgreSQL package. I was getting this error:
The data directory was initialized by PostgreSQL version 9.0, which is not compatible with this version 9.1.4
A quick search took me to this page, however the docs left a lot to be desired to say the least. Here's a step-by-step to how I eventually fixed it using pg_upgrade.
First, change directories to your Postgres data directory.
$ cd /usr/local/var
Next, create a new directory for the new data directory.
$ mkdir postgres9
initdb to initialize the new Postgres cluster in the new data
directory you created above.
$ initdb /usr/local/var/postgres9
pg_upgrade with the following arguments:
$ pg_upgrade -d /usr/local/var/postgres/ -D /usr/local/var/postgres9 -b /usr/local/Cellar/postgresql/9.0.4/bin/ -B /usr/local/Cellar/postgresql/9.1.4/bin/ -v
If all goes without error, you can switch the data directories so Postgres will point to the right source.
$ mv postgres postgres9.0.1 $ mv postgres9 postgres
You can delete the script left behind by
$ rm delete_old_cluster.sh
I actually had my old Postgres instance running, so I had to stop it before restarting the new one:
$ pg_ctl -D /usr/local/var/postgres9.0.1 stop -m fast
Then I restarted the new Postgres instance:
$ launchctl unload -w homebrew.mxcl.postgresql.plist $ launchctl load -w homebrew.mxcl.postgresql.plist
And you're done - this should fix the PostgreSQL incompatible data directory issue.