Rails PostgreSQL 如何在教程和 Heroku 中自动创建用户访问权限，即使未在 database.yml 中明确定义
How does Rails PostgreSQL automatically creates user access in tutorials and in Heroku even though not explicitly defined in 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: shoutr_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: shoutr
# 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: shoutr_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: shoutr_production
username: shoutr
password: <%= ENV['SHOUTR_DATABASE_PASSWORD'] %>
正如您在 config/database.yml 文件中看到的那样，开发和生产环境的密码都没有定义，这些用户也没有在 PostgreSQL 中创建，但是我仍然可以推送到 Heroku 并且 Heroku 可以以某种方式仍然提供应用程序使用的 PostgreSQL 生产环境数据库。
我正在努力学习 ruby rails 开发和 tutorial 以及
从 3:50 标记，作者做了 bundle install 并立即成功地做了 db:create 这意味着他可以在开发环境中连接到 PostgreSQL，而无需配置用户并随后更改 config/database.yml 中的值进行开发env，虽然如果我做同样的事情会导致错误，这当然可以通过在 PostgreSQL 中创建用户并更改 yml 文件中的凭据来解决，但是我偶然发现的每个教程都没有显示用户的创建：
/home/webmaster/gems/gems/activesupport-5.2.2/lib/active_support/dependencies.rb:291:in `require'
bin/rails:4:in `<main>'
Caused by:
PG::InsufficientPrivilege: ERROR: permission denied to create database
访问本地 postgresql 数据库主要有两种方式。一种是在 database.yml 文件中使用特定的 user/password 组合。另一个是设置本地 postgres 以信任您的用户身份。
对于后一种情况，您需要编辑 pg_hba.conf 文件以包含 trust 行（允许任何人连接，只需传递用户名）或 peer 或 ident（取决于连接 - socket 或 tcp - 只允许一个与连接用户同名的 postgres 角色，在你的情况下可能 webmaster）
例如：
# Allow any user on the local system to connect to any database with
# any database user name using Unix-domain sockets (the default for local
# connections).
#
# TYPE DATABASE USER ADDRESS METHOD
local all all trust
# The same using local loopback TCP/IP connections.
#
# TYPE DATABASE USER ADDRESS METHOD
host all all 127.0.0.1/32 trust
您可以在此处找到更多示例：
https://www.postgresql.org/docs/devel/auth-pg-hba-conf.html
警告请勿在生产服务器上使用此配置！
# 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: shoutr_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: shoutr
# 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: shoutr_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: shoutr_production
username: shoutr
password: <%= ENV['SHOUTR_DATABASE_PASSWORD'] %>
正如您在 config/database.yml 文件中看到的那样，开发和生产环境的密码都没有定义，这些用户也没有在 PostgreSQL 中创建，但是我仍然可以推送到 Heroku 并且 Heroku 可以以某种方式仍然提供应用程序使用的 PostgreSQL 生产环境数据库。
我正在努力学习 ruby rails 开发和 tutorial 以及
从 3:50 标记，作者做了 bundle install 并立即成功地做了 db:create 这意味着他可以在开发环境中连接到 PostgreSQL，而无需配置用户并随后更改 config/database.yml 中的值进行开发env，虽然如果我做同样的事情会导致错误，这当然可以通过在 PostgreSQL 中创建用户并更改 yml 文件中的凭据来解决，但是我偶然发现的每个教程都没有显示用户的创建：
/home/webmaster/gems/gems/activesupport-5.2.2/lib/active_support/dependencies.rb:291:in `require'
bin/rails:4:in `<main>'
Caused by:
PG::InsufficientPrivilege: ERROR: permission denied to create database
访问本地 postgresql 数据库主要有两种方式。一种是在 database.yml 文件中使用特定的 user/password 组合。另一个是设置本地 postgres 以信任您的用户身份。
对于后一种情况，您需要编辑 pg_hba.conf 文件以包含 trust 行（允许任何人连接，只需传递用户名）或 peer 或 ident（取决于连接 - socket 或 tcp - 只允许一个与连接用户同名的 postgres 角色，在你的情况下可能 webmaster）
例如：
# Allow any user on the local system to connect to any database with
# any database user name using Unix-domain sockets (the default for local
# connections).
#
# TYPE DATABASE USER ADDRESS METHOD
local all all trust
# The same using local loopback TCP/IP connections.
#
# TYPE DATABASE USER ADDRESS METHOD
host all all 127.0.0.1/32 trust
您可以在此处找到更多示例： https://www.postgresql.org/docs/devel/auth-pg-hba-conf.html
警告请勿在生产服务器上使用此配置！