rails app默认为sqlite3.我想将postgresql作为默认_如何更改

gem 'pg'

default: &default
  adapter: postgresql
  encoding: unicode
  pool: 5
  username: your_username
  password: your_password
  host: your_host
  port: your_port

gem 'sqlite3', group: :development
gem 'pg', group: :production

config.database_configuration_for_development = {
  'adapter' => 'postgresql',
  'encoding' => 'unicode',
  'pool' => 5,
  'username' => 'your_username',
  'password' => 'your_password',
  'host' => 'your_host',
  'port' => your_port
}

config.database_configuration_for_production = {
  'adapter' => 'postgresql',
  'encoding' => 'unicode',
  'pool' => 5,
  'username' => 'your_username',
  'password' => 'your_password',
  'host' => 'your_host',
  'port' => your_port
}