如何通过Ruby的pg gem连接到Postgres数据库（Rails外部）

Question

I've been using Postgres without issue within Rails and have also been running psql without issue. However, I'm running into a problem trying to connect to the database with the pg gem.

The following code:

PG.connect

generates the error/output:

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

The result is the same whether I specify various dbname: values or not or just let this default.

When I click on the little elephant icon at the top of my screen, it says "Running on port 5432" and, as I said, I can connect with psql without a problem.

I found the very similar cannot connect to Postgres (pg) database from my Ruby Script using gem "pg"(This is not rails, just pure ruby) , but the answer simply said Rails works fine.

Any guidance would be appreciated. (Note: I realize I haven't entered any name/password info, but I don't have to enter than when I run psql and I gather it's not getting to the point of authentication).

Answer 1

You need to specify a host. It's trying to connect on a unix domain socket. The PG app doesn't listen on a unix socket (unless you configure it to) but runs on localhost:5432.

 conn = PG.connect( host: 'localhost' )

Answer 2

It is quite likely that the actual problem is that your 'pg' gem has linked to an older version of a libpq dynamic library. See this post for more details and a possible solution.