Read data from other postgres database

Question

I have a Rails app A with a postgres database. I also have another Rails app B with a postgres database. Now I want to reuse some of the data of app B in app A. What is the best way to import that data? I assume a rake task can be used for this, but how would you do this?

Do you need to add the connection details of the database of app B in the database.yml of app A? And how do I actually get the data?

do you want to keep them synced? or is it a time connection to just bulk import? — Doon
– Doon, Commented Jun 24, 2013 at 12:34
@Denis That's pretty much an answer as it stands; consider posting it as such. — Craig Ringer
– Craig Ringer, Commented Jun 24, 2013 at 12:43

Luiz E. · Accepted Answer · 2013-06-24 13:07:24Z

1

You can do a manual connection via activerecord

require 'active_record' 
ActiveRecord::Base.establish_connection(
  :adapter => "mysql", 
  :host => "localhost", 
  :username => "root", 
  :password => "abcd", 
  :database => "funonrails")

or do something like this

dbconfig = YAML::load(File.open('database.yml')) 
ActiveRecord::Base.establish_connection( dbconfig[:students_development] )

answered Jun 24, 2013 at 13:07

Luiz E.

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2 Comments

John Over a year ago

This looks interesting, but how would I actually make a request to this database, like "people = People.all"? How does it know it should get this from database B and not from database A?

Luiz E. Over a year ago

You have to pass the database B address to the connection. Actually, I think you'll need to instantiate 2 activerecord connections, connectionA and connectionB. Take a look at this link: railskey.wordpress.com/2012/07/20/… it may help you

Denis de Bernardy · Accepted Answer · 2013-06-24 12:47:15Z

1

Depending on what you actually mean by import, you could use dblink to query the other DB directly:

http://postgresql.org/docs/current/static/dblink.html

When PostgreSQL 9.3 gets released, be sure to also look into the new foreign data wrapper:

http://postgresql.org/docs/9.3/static/postgres-fdw.html

answered Jun 24, 2013 at 12:47

Denis de Bernardy

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