Postgres Server error -> PGError: could not connect to server

Question

I get the error below when trying to start my rails app on the localhost:

PGError (could not connect to server: No such file or directory Is the server running locally and accepting connections on Unix domain socket "/tmp/.s.PGSQL.5432"?

From what I have read it sounds like this is most likely a problem in connecting to the Postgres server, and may indicate that it is not started?

It all started when I was attempting my first (yay noobs!) merge using git. There was a conflict (having to do with the Rubymine workspace.xml file), and I started to open up a conflict resolution program. It then seemed that there was really no need to track workspace.xml at all and so I quit from the resolution program, intending to run "git rm --cached" on the file. I think in quitting the program something went foul, and I ended up restarting, before untracking the file, and then completing the merge. Further evidence that something was gummed up is that my terminal shell didn't open up correctly until I restarted the machine.

Now, as far as I can tell, everything in the merge went fine (there were trivial differences in the two branches anyway), but for the life of me I can't seem to get rid of this PGError. If it is as simple as starting the server, then I'd love help on how to do that.

(other context: OSx, rails 3, posgresql83 installed via macports, pg gem).

EDIT - I have been trying to start up the server, but am not succeeding. eg, I tried:

pg_ctl start -D /opt/local/var/db/postgresql83/defaultdb

This seems to be the right path for the data (it finds the postgresql.conf file) but the response I get is "cannot execute binary file."

Answer 1

and may indicate that it is not started?

Yes, sounds like the server is not running on your local machine.

See the description of this error in the PostgreSQL manual:
http://www.postgresql.org/docs/8.3/static/server-start.html#CLIENT-CONNECTION-PROBLEMS

Answer 2

Try sudo port load postgresql83-server - this should work with the latest 8.3 port from macports.

If this doesn't work, try sudo port selfupdate; sudo port upgrade outdated sudo port selfupdate; sudo port upgrade outdated and then try again.

Note - this may take absolutely ages.

Answer 3

To start the server, try something along the following lines (adjust for pgsql version # and logfile):

sudo su postgres -c '/opt/local/lib/postgresql84/bin/pg_ctl -D /opt/local/var/db/postgresql8/defaultdb -l /opt/local/var/log/postgresql84/postgres.log start'

To stop the server,

sudo su postgres -c '/opt/local/lib/postgresql84/bin/pg_ctl -D /opt/local/var/db/postgresql84/defaultdb stop'