8 files changed, 36 insertions, 20 deletions
diff --git a/guides/source/4_0_release_notes.md b/guides/source/4_0_release_notes.md
index b9444510ea..4615cf18e6 100644
--- a/guides/source/4_0_release_notes.md
+++ b/guides/source/4_0_release_notes.md
@@ -108,7 +108,7 @@ In Rails 4.0, several features have been extracted into gems. You can simply add
 * Mass assignment protection in Active Record models ([GitHub](https://github.com/rails/protected_attributes), [Pull Request](https://github.com/rails/rails/pull/7251))
 * ActiveRecord::SessionStore ([GitHub](https://github.com/rails/activerecord-session_store), [Pull Request](https://github.com/rails/rails/pull/7436))
 * Active Record Observers ([GitHub](https://github.com/rails/rails-observers), [Commit](https://github.com/rails/rails/commit/39e85b3b90c58449164673909a6f1893cba290b2))
-* Active Resource ([GitHub](https://github.com/rails/activeresource), [Pull Request](https://github.com/rails/rails/pull/572), [Blog](http://yetimedia.tumblr.com/post/35233051627/activeresource-is-dead-long-live-activeresource))
+* Active Resource ([GitHub](https://github.com/rails/activeresource), [Pull Request](https://github.com/rails/rails/pull/572), [Blog](http://yetimedia-blog-blog.tumblr.com/post/35233051627/activeresource-is-dead-long-live-activeresource))
 * Action Caching ([GitHub](https://github.com/rails/actionpack-action_caching), [Pull Request](https://github.com/rails/rails/pull/7833))
 * Page Caching ([GitHub](https://github.com/rails/actionpack-page_caching), [Pull Request](https://github.com/rails/rails/pull/7833))
 * Sprockets ([GitHub](https://github.com/rails/sprockets-rails))
diff --git a/guides/source/5_0_release_notes.md b/guides/source/5_0_release_notes.md
index 6351ff57c1..9078e91923 100644
--- a/guides/source/5_0_release_notes.md
+++ b/guides/source/5_0_release_notes.md
@@ -585,6 +585,9 @@ Please refer to the [Changelog][active-record] for detailed changes.
 *   Added ActiveRecord `#second_to_last` and `#third_to_last` methods.
     ([Pull Request](https://github.com/rails/rails/pull/23583))
 
+*  Added ability to annotate database objects (tables, columns, indexes)
+   with comments stored in database metadata for PostgreSQL & MySQL.
+   ([Pull Request](https://github.com/rails/rails/pull/22911))
 
 Active Model
 ------------
diff --git a/guides/source/action_cable_overview.md b/guides/source/action_cable_overview.md
index d1f17fdce5..0c486bb96c 100644
--- a/guides/source/action_cable_overview.md
+++ b/guides/source/action_cable_overview.md
@@ -549,12 +549,13 @@ You can change that in `config/database.yml` through the `pool` attribute.
 ### In App
 
 Action Cable can run alongside your Rails application. For example, to
-listen for WebSocket requests on `/websocket`, mount the server at that path:
+listen for WebSocket requests on `/websocket`, specify that path to
+`config.action_cable.mount_path`:
 
 ```ruby
-# config/routes.rb
-Example::Application.routes.draw do
-  mount ActionCable.server => '/cable'
+# config/application.rb
+class Application < Rails::Application
+  config.action_cable.mount_path = '/websocket'
 end
 ```
 
diff --git a/guides/source/active_record_migrations.md b/guides/source/active_record_migrations.md
index cd6b7fdd67..f914122242 100644
--- a/guides/source/active_record_migrations.md
+++ b/guides/source/active_record_migrations.md
@@ -247,6 +247,7 @@ end
 ```
 
 This migration will create a `user_id` column and appropriate index.
+For more `add_reference` options, visit the [API documentation](http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html#method-i-add_reference).
 
 There is also a generator which will produce join tables if `JoinTable` is part of the name:
 
@@ -353,7 +354,14 @@ end
 ```
 
 will append `ENGINE=BLACKHOLE` to the SQL statement used to create the table
-(when using MySQL, the default is `ENGINE=InnoDB`).
+(when using MySQL or MariaDB, the default is `ENGINE=InnoDB`).
+
+Also you can pass the `:comment` option with any description for the table
+that will be stored in database itself and can be viewed with database administration
+tools, such as MySQL Workbench or PgAdmin III. It's highly recommended to specify
+comments in migrations for applications with large databases as it helps people
+to understand data model and generate documentation.
+Currently only the MySQL and PostgreSQL adapters support comments.
 
 ### Creating a Join Table
 
@@ -454,6 +462,7 @@ number of digits after the decimal point.
 are using a dynamic value (such as a date), the default will only be calculated
 the first time (i.e. on the date the migration is applied).
 * `index`        Adds an index for the column.
+* `comment`      Adds a comment for the column.
 
 Some adapters may support additional options; see the adapter specific API docs
 for further information.
@@ -970,7 +979,7 @@ this, then you should set the schema format to `:sql`.
 Instead of using Active Record's schema dumper, the database's structure will
 be dumped using a tool specific to the database (via the `db:structure:dump`
 rails task) into `db/structure.sql`. For example, for PostgreSQL, the `pg_dump`
-utility is used. For MySQL, this file will contain the output of
+utility is used. For MySQL and MariaDB, this file will contain the output of
 `SHOW CREATE TABLE` for the various tables.
 
 Loading these schemas is simply a question of executing the SQL statements they
diff --git a/guides/source/active_record_querying.md b/guides/source/active_record_querying.md
index 9d349691b4..e9f6275e55 100644
--- a/guides/source/active_record_querying.md
+++ b/guides/source/active_record_querying.md
@@ -50,7 +50,7 @@ class Role < ApplicationRecord
 end
 ```
 
-Active Record will perform queries on the database for you and is compatible with most database systems (MySQL, PostgreSQL and SQLite to name a few). Regardless of which database system you're using, the Active Record method format will always be the same.
+Active Record will perform queries on the database for you and is compatible with most database systems, including MySQL, MariaDB, PostgreSQL and SQLite. Regardless of which database system you're using, the Active Record method format will always be the same.
 
 Retrieving Objects from the Database
 ------------------------------------
@@ -1915,7 +1915,7 @@ EXPLAIN for: SELECT `users`.* FROM `users` INNER JOIN `articles` ON `articles`.`
 2 rows in set (0.00 sec)
 ```
 
-under MySQL.
+under MySQL and MariaDB.
 
 Active Record performs a pretty printing that emulates that of the
 corresponding database shell. So, the same query running with the
@@ -1975,7 +1975,7 @@ EXPLAIN for: SELECT `articles`.* FROM `articles`  WHERE `articles`.`user_id` IN
 1 row in set (0.00 sec)
 ```
 
-under MySQL.
+under MySQL and MariaDB.
 
 ### Interpreting EXPLAIN
 
@@ -1986,4 +1986,6 @@ following pointers may be helpful:
 
 * MySQL: [EXPLAIN Output Format](http://dev.mysql.com/doc/refman/5.7/en/explain-output.html)
 
+* MariaDB: [EXPLAIN](https://mariadb.com/kb/en/mariadb/explain/)
+
 * PostgreSQL: [Using EXPLAIN](http://www.postgresql.org/docs/current/static/using-explain.html)
diff --git a/guides/source/command_line.md b/guides/source/command_line.md
index 62d742fc28..0905c4bd16 100644
--- a/guides/source/command_line.md
+++ b/guides/source/command_line.md
@@ -326,7 +326,7 @@ With the `helper` method it is possible to access Rails and your application's h
 
 ### `rails dbconsole`
 
-`rails dbconsole` figures out which database you're using and drops you into whichever command line interface you would use with it (and figures out the command line parameters to give to it, too!). It supports MySQL, PostgreSQL and SQLite3.
+`rails dbconsole` figures out which database you're using and drops you into whichever command line interface you would use with it (and figures out the command line parameters to give to it, too!). It supports MySQL (including MariaDB), PostgreSQL and SQLite3.
 
 INFO: You can also use the alias "db" to invoke the dbconsole: `rails db`.
 
diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index 6b9b95f1ab..582b14e25f 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -336,7 +336,7 @@ All these configuration options are delegated to the `I18n` library.
 
 The MySQL adapter adds one additional configuration option:
 
-* `ActiveRecord::ConnectionAdapters::Mysql2Adapter.emulate_booleans` controls whether Active Record will consider all `tinyint(1)` columns in a MySQL database to be booleans and is true by default.
+* `ActiveRecord::ConnectionAdapters::Mysql2Adapter.emulate_booleans` controls whether Active Record will consider all `tinyint(1)` columns as booleans. True by default.
 
 The schema dumper adds one additional configuration option:
 
@@ -784,11 +784,11 @@ development:
   timeout: 5000
 ```
 
-NOTE: Rails uses an SQLite3 database for data storage by default because it is a zero configuration database that just works. Rails also supports MySQL and PostgreSQL "out of the box", and has plugins for many database systems. If you are using a database in a production environment Rails most likely has an adapter for it.
+NOTE: Rails uses an SQLite3 database for data storage by default because it is a zero configuration database that just works. Rails also supports MySQL (including MariaDB) and PostgreSQL "out of the box", and has plugins for many database systems. If you are using a database in a production environment Rails most likely has an adapter for it.
 
-#### Configuring a MySQL Database
+#### Configuring a MySQL or MariaDB Database
 
-If you choose to use MySQL instead of the shipped SQLite3 database, your `config/database.yml` will look a little different. Here's the development section:
+If you choose to use MySQL or MariaDB instead of the shipped SQLite3 database, your `config/database.yml` will look a little different. Here's the development section:
 
 ```yaml
 development:
@@ -801,7 +801,7 @@ development:
   socket: /tmp/mysql.sock
 ```
 
-If your development computer's MySQL installation includes a root user with an empty password, this configuration should work for you. Otherwise, change the username and password in the `development` section as appropriate.
+If your development database has a root user with an empty password, this configuration should work for you. Otherwise, change the username and password in the `development` section as appropriate.
 
 #### Configuring a PostgreSQL Database
 
@@ -843,9 +843,9 @@ development:
   database: db/development.sqlite3
 ```
 
-#### Configuring a MySQL Database for JRuby Platform
+#### Configuring a MySQL or MariaDB Database for JRuby Platform
 
-If you choose to use MySQL and are using JRuby, your `config/database.yml` will look a little different. Here's the development section:
+If you choose to use MySQL or MariaDB and are using JRuby, your `config/database.yml` will look a little different. Here's the development section:
 
 ```yaml
 development:
diff --git a/guides/source/upgrading_ruby_on_rails.md b/guides/source/upgrading_ruby_on_rails.md
index 0c1e00100b..34cfb742a4 100644
--- a/guides/source/upgrading_ruby_on_rails.md
+++ b/guides/source/upgrading_ruby_on_rails.md
@@ -44,7 +44,7 @@ TIP: Ruby 1.8.7 p248 and p249 have marshaling bugs that crash Rails. Ruby Enterp
 
 ### The Task
 
-Rails provides the `app:update` task. After updating the Rails version
+Rails provides the `app:update` task (`rails:update` on 4.2 and earlier). After updating the Rails version
 in the Gemfile, run this task.
 This will help you with the creation of new files and changes of old files in an
 interactive session.
@@ -70,7 +70,8 @@ Upgrading from Rails 4.2 to Rails 5.0
 
 ### Ruby 2.2.2+
 
-ToDo...
+From Ruby on Rails 5.0 onwards, Ruby 2.2.2+ is the only supported version. 
+Make sure you are on Ruby 2.2.2 version or greater, before you proceed. 
 
 ### Active Record models now inherit from ApplicationRecord by default