How to handle Ruby on Rails error: "Please install the postgresql adapter: `gem install activerecord-postgresql-adapter'"

Question

Running a Ruby on Rails (RoR) app or Ruby code which uses the ActiveRecord framework, you get the error message:

Please install the postgresql adapter: gem install activerecord-postgresql-adapter

Trying to run:

gem install activerecord-postgresql-adapter 

also fails, leaving you at a loss.

Answer 1

The problem is not what anyone wrote. The problem is that the name of the postgresql database adapter is "postgresql", not "postgres", though the name of the GEM is "pg".

The definition in the database.yml file should include

  adapter: postgresql