DockerでPostgresの操作に失敗する

DockerでRubyの環境構築をしています。

docker-compose run --rm back rails db:create

を実行すると以下のエラーが出ます。

could not connect to server: Connection refused
        Is the server running on host "db" (172.19.0.2) and accepting
        TCP/IP connections on port 5432?
Couldn't create 'app_development' database. Please check your configuration.
rails aborted!
PG::ConnectionBad: could not connect to server: Connection refused
        Is the server running on host "db" (172.19.0.2) and accepting
        TCP/IP connections on port 5432?
/usr/local/bundle/gems/pg-1.2.2/lib/pg.rb:58:in `initialize'
/usr/local/bundle/gems/pg-1.2.2/lib/pg.rb:58:in `new'
/usr/local/bundle/gems/pg-1.2.2/lib/pg.rb:58:in `connect'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/connection_adapters/postgresql_adapter.rb:692:in `connect'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/connection_adapters/postgresql_adapter.rb:223:in `initialize'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/connection_adapters/postgresql_adapter.rb:48:in `new'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/connection_adapters/postgresql_adapter.rb:48:in `postgresql_connection'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:830:in `new_connection'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:874:in `checkout_new_connection'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:853:in `try_to_checkout_new_connection'      
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:814:in `acquire_connection'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:538:in `checkout'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:382:in `connection'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:1033:in `retrieve_connection'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/connection_handling.rb:118:in `retrieve_connection'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/connection_handling.rb:90:in `connection'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/tasks/postgresql_database_tasks.rb:12:in `connection'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/tasks/postgresql_database_tasks.rb:21:in `create'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/tasks/database_tasks.rb:119:in `create'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/tasks/database_tasks.rb:139:in `block in create_current'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/tasks/database_tasks.rb:316:in `block in each_current_configuration'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/tasks/database_tasks.rb:313:in `each'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/tasks/database_tasks.rb:313:in `each_current_configuration'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/tasks/database_tasks.rb:138:in `create_current'
/usr/local/bundle/gems/activerecord-5.2.4.1/lib/active_record/railties/databases.rake:29:in `block (2 levels) in <main>'
/usr/local/bundle/gems/railties-5.2.4.1/lib/rails/commands/rake/rake_command.rb:23:in `block in perform'
/usr/local/bundle/gems/railties-5.2.4.1/lib/rails/command.rb:48:in `invoke'
/usr/local/bundle/gems/railties-5.2.4.1/lib/rails/commands.rb:18:in `<main>'
/usr/local/bundle/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require'
/usr/local/bundle/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `block in require_with_bootsnap_lfi'
/usr/local/bundle/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/loaded_features_index.rb:92:in `register'
/usr/local/bundle/gems/bootsnap-1.4.5/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:30:in `require'
/usr/local/bundle/gems/activesupport-5.2.4.1/lib/active_support/dependencies.rb:291:in `block in require'
/usr/local/bundle/gems/activesupport-5.2.4.1/lib/active_support/dependencies.rb:257:in `load_dependency'
/usr/local/bundle/gems/activesupport-5.2.4.1/lib/active_support/dependencies.rb:291:in `require'
/app/bin/rails:9:in `<top (required)>'
/usr/local/bundle/gems/spring-2.1.0/lib/spring/client/rails.rb:28:in `call'
/usr/local/bundle/gems/spring-2.1.0/lib/spring/client/command.rb:7:in `call'
/usr/local/bundle/gems/spring-2.1.0/lib/spring/client.rb:30:in `run'
/usr/local/bundle/gems/spring-2.1.0/bin/spring:49:in `<top (required)>'
/usr/local/bundle/gems/spring-2.1.0/lib/spring/binstub.rb:11:in `load'
/usr/local/bundle/gems/spring-2.1.0/lib/spring/binstub.rb:11:in `<top (required)>'
/app/bin/spring:15:in `<top (required)>'
bin/rails:3:in `load'
bin/rails:3:in `<main>'
Tasks: TOP => db:create
(See full trace by running task with --trace)

datanase.ymlとdocker-compose.ymlは以下の通りです

datanase.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
  host: db            # add
  username: postgres  # add
  password:           # add
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %> 

development:
  <<: *default
  database: app_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: app

  # 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: app_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: app_production
  username: app
  password: <%= ENV['APP_DATABASE_PASSWORD'] %>

docker-compose.yml
version: "3"

services:
  db:
    container_name: sample_db
    image: postgres:11.4-alpine
    environment:
      - TZ=Asia/Tokyo
    volumes:
      - ./back/tmp/db:/var/lib/postgresql/data

  back:
    container_name: sample_back
    build: back/
    volumes:
      - ./back:/app
    depends_on:
      - db
    ports:
      - 3000:3000

  front:
    container_name: sample_front
    build: front/
    command: npm run dev
    volumes:
      - ./front:/app
    ports:
      - 8080:3000

いろいろ試してみたのですがよくわかりませんでした。
すでに動いているのかと思い、db:createしても同様の結果でした。
ご教授いただければ幸いです。