database.yml collection

example.database.mysql.extra

pool:                    number indicating size of connection pool (default 5)
checkout_timeout:        number of seconds to block and wait for a connection before giving up and raising a timeout error (default 5 seconds).
reaping_frequency:       frequency in seconds to periodically run the Reaper, which attempts to find and close dead connections, which can occur if a programmer forgets to close a connection at the end of a thread or a thread dies unexpectedly. (Default nil, which means don't run the Reaper).
dead_connection_timeout: number of seconds from last checkout after which the Reaper will consider a connection reapable. (default 5 seconds).
encoding:                (Optional) Sets the client encoding by executing "SET NAMES <encoding>" after connection.
reconnect:               Defaults to false (See MySQL documentation: dev.mysql.com/doc/refman/5.0/en/auto-reconnect.html).
strict:                  Defaults to true. Enable STRICT_ALL_TABLES. (See MySQL documentation: dev.mysql.com/doc/refman/5.0/en/server-sql-mode.html)
variables:               (Optional) A hash session variables to send as `SET @@SESSION.key = value` on each database connection. Use the value `:default` to set a variable to its DEFAULT value. (See MySQL documentation: dev.mysql.com/doc/refman/5.0/en/set-statement.html).
sslca:                   Necessary to use MySQL with an SSL connection.
sslkey:                  Necessary to use MySQL with an SSL connection.
sslcert:                 Necessary to use MySQL with an SSL connection.
sslcapath:               Necessary to use MySQL with an SSL connection.
sslcipher:               Necessary to use MySQL with an SSL connection.

example.database.mysql.host.yml

development:
  adapter: mysql2
  encoding: utf8
  reconnect: false
  database: databasename_development
  pool: 5
  username: databaseuser
  password: databasepassword
  host: 127.0.0.1
  port: 3306

test:
  adapter: mysql2
  encoding: utf8
  reconnect: false
  database: databasename_test
  pool: 5
  username: databaseuser
  password: databasepassword
  host: 127.0.0.1
  port: 3306

production:
  adapter: mysql2
  encoding: utf8
  reconnect: false
  database: databasename_production
  pool: 5
  username: databaseuser
  password: databasepassword
  host: 127.0.0.1
  port: 3306

example.database.mysql.socket.yml

development:
  adapter: mysql2
  encoding: utf8
  reconnect: false
  database: databasename_development
  pool: 5
  username: databaseuser
  password: databasepassword
  socket: /tmp/mysql.sock
  #socket: /var/run/mysqld/mysqld.sock # arch linux & ubuntu
  #socket: /var/lib/mysql/mysql.sock # redhat & centos

test:
  adapter: mysql2
  encoding: utf8
  reconnect: false
  database: databasename_test
  pool: 5
  username: databaseuser
  password: databasepassword
  socket: /tmp/mysql.sock
  #socket: /var/run/mysqld/mysqld.sock # arch linux & ubuntu
  #socket: /var/lib/mysql/mysql.sock # redhat & centos

production:
  adapter: mysql2
  encoding: utf8
  reconnect: false
  database: databasename_production
  pool: 5
  username: databaseuser
  password: databasepassword
  socket: /tmp/mysql.sock
  #socket: /var/run/mysqld/mysqld.sock # arch linux & ubuntu
  #socket: /var/lib/mysql/mysql.sock # redhat & centos

example.database.postgres.extra

schema_search_path: An optional schema search path for the connection given as a string of comma-separated schema names. This is backward-compatible with the :schema_order option.
encoding:           An optional client encoding that is used in a SET client_encoding TO <encoding> call on the connection.
min_messages:       An optional client min messages that is used in a SET client_min_messages TO <min_messages> call on the connection.
variables:          An optional hash of additional parameters that will be used in SET SESSION key = val calls on the connection.
insert_returning:   An optional boolean to control the use or RETURNING for INSERT statements defaults to true.

Any further options are used as connection parameters to libpq. See www.postgresql.org/docs/9.1/static/libpq-connect.html for the list of parameters.
In addition, default connection parameters of libpq can be set per environment variables. See www.postgresql.org/docs/9.1/static/libpq-envars.html .

example.database.postgres.yml

# PostgreSQL. Versions 7.4, 8.x, and 9.x are supported.
#
# Install the pg driver:
#   gem install pg
# On Mac 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.
development:
  adapter: postgresql
  encoding: unicode
  database: database_development
  pool: 5
  username: databaseuser
  password: databasepassword

  # 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
  #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
  # The server defaults to notice.
  #min_messages: warning

# 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:
  adapter: postgresql
  encoding: unicode
  database: database_test
  pool: 5
  username: databaseuser
  password: databasepassword

production:
  adapter: postgresql
  encoding: unicode
  database: database_production
  pool: 5
  username: databaseuser
  password: databasepassword

example.database.sqlite3.yml

# SQLite version 3.x
#   gem install sqlite3
development:
  adapter: sqlite3
  database: db/development.sqlite3
  pool: 5
  timeout: 5000

# 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:
  adapter: sqlite3
  database: db/test.sqlite3
  pool: 5
  timeout: 5000

production:
  adapter: sqlite3
  database: db/production.sqlite3
  pool: 5
  timeout: 5000