Create Postgresql database in Heroku with Ruby (without Rails) - ruby

Question

I'm currently hosting a simple Ruby script that stores URLs and Scores and saving them to YAML. However, I'd like to save to a Postgresql database instead since the yaml file is deleted every time I restart the app. Here's the error I'm getting in Heroku:
could not connect to server: No such file or directory (PG::ConnectionBad)
Here's an example script that works locally, but throws me the above error in Heroku:
require 'pg'
conn = PG.connect( dbname: 'template1' )
res1 = conn.exec('SELECT * from pg_database where datname = $1', ['words'])
if res1.ntuples == 1 # db exists
# do nothing
else
conn.exec('CREATE DATABASE words')
words_conn = PGconn.connect( :dbname => 'words')
words_conn.exec("create table top (url varchar, score integer);")
words_conn.exec("INSERT INTO top (url, score) VALUES ('http://apple.com', 1);")
end
Thanks in advance for any help or suggestions!

Answer 1

Assuming you have created a Postgres database using the Heroku toolchain via heroku addons:add heroku-postgresql:dev (or the plan of your choice) you should have a DATABASE_URL environmental variable that contains your connection string. You can check that locally through heroku pg:config.
Using the pg gem (docs: http://deveiate.org/code/pg/PG/Connection.html) - and modifying the example from there to suit -
require 'pg'
# source the connection string from the DATABASE_URL environmental variable
conn = PG::Connection.new(ENV['DATABASE_URL'])
res = conn.exec_params('create table top (url varchar, score integer;")
Update: A slightly more complete example for the purposes of error handling:
conn = PG::Connection.new(ENV['TEST_DATABASE_URL'])
begin
# Ensures the table is created if it doesn't exist
res = conn.exec("CREATE TABLE IF NOT EXISTS top (url varchar, score integer);")
res.result_status
rescue PG::Error => pg_error
puts "Table creation failed: #{pg_error.message}"
end