Configure database with sqlite3 for Rails and postgreSQL for Heroku - ruby-on-rails

Question

I looked for hours on the web but none of my attempts to adapt my database.yml work out. I just started with Rails and the exercise is to use sqlite3 for development, and postgreSQL for production. I am using rvm 2.4.1 and rails 5.3.1.
I added this to my gemfile:
group :production do
gem 'pg'
end
And this is my database.yml
# SQLite version 3.x
# gem install sqlite3
#
# Ensure the SQLite 3 gem is defined in your Gemfile
# gem 'sqlite3'
#
default: &default
adapter: sqlite3
pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
timeout: 5000
development:
<<: *default
database: db/development.sqlite3
# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
<<: *default
database: db/test.sqlite3
production:
<<: *default
database: db/production.sqlite3
So that does not work out and I get the following error when I try to deploy to heroku:
Specified 'postgresql' for database adapter, but the gem is not loaded. Add
`gem 'pg'` to your Gemfile (and ensure its version is at the minimum required
by ActiveRecord).
I am assuming I need to somehow let the production part lead to postgreSQL but the manuals on the heruko website and other posts on stackOverflow and elsewhere are not helping me. How can I get it work? I can add :default to the groups, gem 'pg' is in within my Gemfile but then other things like scaffolding produce errors later on. I would really be thankful to get specific help on this as a spend about 12 hours on this single issue already..

Answer 1

first, since you informed in your production using postgresql then you must change setting in database.yml (see production part)
default: &default
adapter: sqlite3
pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
timeout: 5000
development:
<<: *default
database: db/development.sqlite3
# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
<<: *default
database: db/test.sqlite3
production:
adapter: postgresql
encoding: unicode
database: project_name_production
pool: 5
host: localhost
username: your_username
password: your_database_password
and then you can follow this rake command in heroku
second about your gem file, if the problem still persist then you can put out from production environtment and push to heroku, and then do bundle install to install the adapter
GEMFILE
gem 'pg'
here is good for your to read to solve your problem link information for heroku with postgresql