如何开始在Rails应用程序中使用Postgresql数据库？

Question

I have spend several hours looking for solutions to this on the web. Postgresql installation guides do not help since i am not familiar with interacting with databases only with ruby on rails and dealing with them this way.

I have made several simple rails application by following tutorials and am still learning rails. I am using Windows 10 and I have deployed some of these to Heroku for which i had to use the pg gem becasue Heroku doesnt use sqlite3. But I have read in several places that it is necessary to install postgresql locally. So i have installed it, i think, but now i am lost. I have a software called pgAdmin4 and now i have absolutely no idea what to do in order to use postgresql through rails. I started a new app just to test it by using the following command:

rails new postgresapp --database=postgresql

This has given me the basic starting point for a new app set up to use postgresql. the first error that I get when i try to connecct to the localhost3000 is:

PG::ConnectionBad
fe_sendauth: no password supplied

Extracted source (around line #56):

    ### Convenience alias for PG::Connection.new.
    def self::connect( *args )
        return PG::Connection.new( *args )
    end

bearing in mind that i am not sure if the installation was a success. i went through the process of installation and entered a password and all the information so i assume that it did install somewhere.

also there are no servers showing on pgAdmin so i added one called localhost. i am not sure if this was the right thing to do or not.

gem file:

source 'https://rubygems.org'

git_source(:github) do |repo_name|
  repo_name = "#{repo_name}/#{repo_name}" unless repo_name.include?("/")
  "https://github.com/#{repo_name}.git"
end


# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '~> 5.0.6'
# Use postgresql as the database for Active Record
gem 'pg', '~> 0.18'
# Use Puma as the app server
gem 'puma', '~> 3.0'
# Use SCSS for stylesheets
gem 'sass-rails', '~> 5.0'
# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'
# Use CoffeeScript for .coffee assets and views
gem 'coffee-rails', '~> 4.2'
# See https://github.com/rails/execjs#readme for more supported runtimes
# gem 'therubyracer', platforms: :ruby

# Use jquery as the JavaScript library
gem 'jquery-rails'
# Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks
gem 'turbolinks', '~> 5'
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~> 2.5'
# Use Redis adapter to run Action Cable in production
# gem 'redis', '~> 3.0'
# Use ActiveModel has_secure_password
# gem 'bcrypt', '~> 3.1.7'

# Use Capistrano for deployment
# gem 'capistrano-rails', group: :development

group :development, :test do
  # Call 'byebug' anywhere in the code to stop execution and get a debugger console
  gem 'byebug', platform: :mri
end

group :development do
  # Access an IRB console on exception pages or by using <%= console %> anywhere in the code.
  gem 'web-console', '>= 3.3.0'
end

# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]

database.yml

# PostgreSQL. Versions 9.1 and up are supported.
#
# Install the pg driver:
#   gem install pg
# On OS X with Homebrew:
#   gem install pg -- --with-pg-config=/usr/local/bin/pg_config
# On OS X with MacPorts:
#   gem install pg -- --with-pg-config=/opt/local/lib/postgresql84/bin/pg_config
# On Windows:
#   gem install pg
#       Choose the win32 build.
#       Install PostgreSQL and put its /bin directory on your path.
#
# Configure Using Gemfile
# gem 'pg'
#
default: &default
  adapter: postgresql
  encoding: unicode
  # For details on connection pooling, see rails configuration guide
  # http://guides.rubyonrails.org/configuring.html#database-pooling
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>

development:
  <<: *default
  database: postgresapp_development

  # The specified database role being used to connect to postgres.
  # To create additional roles in postgres see `$ createuser --help`.
  # When left blank, postgres will use the default role. This is
  # the same name as the operating system user that initialized the database.
  #username: postgresapp

  # The password associated with the postgres role (username).
  #password:

  # Connect on a TCP socket. Omitted by default since the client uses a
  # domain socket that doesn't need configuration. Windows does not have
  # domain sockets, so uncomment these lines.
  #host: localhost

  # The TCP port the server listens on. Defaults to 5432.
  # If your server runs on a different port number, change accordingly.
  #port: 5432

  # Schema search path. The server defaults to $user,public
  #schema_search_path: myapp,sharedapp,public

  # Minimum log levels, in increasing order:
  #   debug5, debug4, debug3, debug2, debug1,
  #   log, notice, warning, error, fatal, and panic
  # Defaults to warning.
  #min_messages: notice

# 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: postgresapp_test

# As with config/secrets.yml, you never want to store sensitive information,
# like your database password, in your source code. If your source code is
# ever seen by anyone, they now have access to your database.
#
# Instead, provide the password as a unix environment variable when you boot
# the app. Read http://guides.rubyonrails.org/configuring.html#configuring-a-database
# for a full rundown on how to provide these environment variables in a
# production deployment.
#
# On Heroku and other platform providers, you may have a full connection URL
# available as an environment variable. For example:
#
#   DATABASE_URL="postgres://myuser:mypass@localhost/somedatabase"
#
# You can use this database configuration with:
#
#   production:
#     url: <%= ENV['DATABASE_URL'] %>
#
production:
  <<: *default
  database: postgresapp_production
  username: postgresapp
  password: post#<%= ENV['POSTGRESAPP_DATABASE_PASSWORD'] %>

Answer 1

When you check what is in your database.yml file you need user and password configuration.

You have password as blank value.

I would suggest create a postgreSql user with password and use those credentials

You will need psql for accessing postgreSql from terminal, to create new user with permissions.

one of the links , you can find a lot more about this on the web.

But you problem is user and his password

After fixing you user and password problems, you will need to create the DB with the name from database.yml .

In you database.yml DB name is postgresapp_development . You will ne to create it. Find a client for windows to connect to you postgreSql with user and password you defined when installing and create the DB.

Check this for accessing you postgresSql server