“postgresql gem is not loaded” error deploying a Ruby on Rails application on Heroku

Question

I am trying to use postgresql with Ruby on Rails on Heroku but got an error

Specified \'postgresql\' for          


        

Answer 1

Add pg in gemfile

 gem 'pg', '~> 0.20'

then bundle update & commit Gemfile & Gemfile.lock to heroku.
simple include like gem 'pg' will not work.