Updated MySQL documentation link to MySQL latest version 5.7 everywhere [ci skip]

Bumps from `5.6` to `5.7`

activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb

@@ -137,7 +137,7 @@ def supports_statement_cache?
       #
       # In order to get around this problem, #transaction will emulate the effect
       # of nested transactions, by using savepoints:
-      # http://dev.mysql.com/doc/refman/5.6/en/savepoint.html
+      # http://dev.mysql.com/doc/refman/5.7/en/savepoint.html
       # Savepoints are supported by MySQL and PostgreSQL. SQLite3 version >= '3.6.8'
       # supports savepoints.
       #
@@ -190,7 +190,7 @@ def supports_statement_cache?
       # semantics of these different levels:
       #
       # * http://www.postgresql.org/docs/current/static/transaction-iso.html
-      # * https://dev.mysql.com/doc/refman/5.6/en/set-transaction.html
+      # * https://dev.mysql.com/doc/refman/5.7/en/set-transaction.html
       #
       # An <tt>ActiveRecord::TransactionIsolationError</tt> will be raised if:
       #

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -980,14 +980,14 @@ def configure_connection
         defaults = [':default', :default].to_set
 
         # Make MySQL reject illegal values rather than truncating or blanking them, see
-        # http://dev.mysql.com/doc/refman/5.6/en/sql-mode.html#sqlmode_strict_all_tables
+        # http://dev.mysql.com/doc/refman/5.7/en/sql-mode.html#sqlmode_strict_all_tables
         # If the user has provided another value for sql_mode, don't replace it.
         unless variables.has_key?('sql_mode') || defaults.include?(@config[:strict])
           variables['sql_mode'] = strict_mode? ? 'STRICT_ALL_TABLES' : ''
         end
 
         # NAMES does not have an equals sign, see
-        # http://dev.mysql.com/doc/refman/5.6/en/set-statement.html#id944430
+        # http://dev.mysql.com/doc/refman/5.7/en/set-statement.html#id944430
         # (trailing comma because variable_assignments will always have content)
         if @config[:encoding]
           encoding = "NAMES #{@config[:encoding]}"

activerecord/lib/active_record/connection_adapters/mysql_adapter.rb

@@ -58,9 +58,9 @@ module ConnectionAdapters
     # * <tt>:password</tt> - Defaults to nothing.
     # * <tt>:database</tt> - The name of the database. No default, must be provided.
     # * <tt>:encoding</tt> - (Optional) Sets the client encoding by executing "SET NAMES <encoding>" after connection.
-    # * <tt>:reconnect</tt> - Defaults to false (See MySQL documentation: http://dev.mysql.com/doc/refman/5.6/en/auto-reconnect.html).
-    # * <tt>:strict</tt> - Defaults to true. Enable STRICT_ALL_TABLES. (See MySQL documentation: http://dev.mysql.com/doc/refman/5.6/en/sql-mode.html)
-    # * <tt>:variables</tt> - (Optional) A hash session variables to send as <tt>SET @@SESSION.key = value</tt> on each database connection. Use the value +:default+ to set a variable to its DEFAULT value. (See MySQL documentation: http://dev.mysql.com/doc/refman/5.6/en/set-statement.html).
+    # * <tt>:reconnect</tt> - Defaults to false (See MySQL documentation: http://dev.mysql.com/doc/refman/5.7/en/auto-reconnect.html).
+    # * <tt>:strict</tt> - Defaults to true. Enable STRICT_ALL_TABLES. (See MySQL documentation: http://dev.mysql.com/doc/refman/5.7/en/sql-mode.html)
+    # * <tt>:variables</tt> - (Optional) A hash session variables to send as <tt>SET @@SESSION.key = value</tt> on each database connection. Use the value +:default+ to set a variable to its DEFAULT value. (See MySQL documentation: http://dev.mysql.com/doc/refman/5.7/en/set-statement.html).
     # * <tt>:sslca</tt> - Necessary to use MySQL with an SSL connection.
     # * <tt>:sslkey</tt> - Necessary to use MySQL with an SSL connection.
     # * <tt>:sslcert</tt> - Necessary to use MySQL with an SSL connection.

activerecord/lib/active_record/locking/pessimistic.rb

@@ -51,7 +51,7 @@ module Locking
     #   end
     #
     # Database-specific information on row locking:
-    #   MySQL: http://dev.mysql.com/doc/refman/5.6/en/innodb-locking-reads.html
+    #   MySQL: http://dev.mysql.com/doc/refman/5.7/en/innodb-locking-reads.html
     #   PostgreSQL: http://www.postgresql.org/docs/current/interactive/sql-select.html#SQL-FOR-UPDATE-SHARE
     module Pessimistic
       # Obtain a row lock on this record. Reloads the record to obtain the requested

activerecord/lib/active_record/transactions.rb

@@ -167,7 +167,7 @@ module Transactions
     # writing, the only database that we're aware of that supports true nested
     # transactions, is MS-SQL. Because of this, Active Record emulates nested
     # transactions by using savepoints on MySQL and PostgreSQL. See
-    # http://dev.mysql.com/doc/refman/5.6/en/savepoint.html
+    # http://dev.mysql.com/doc/refman/5.7/en/savepoint.html
     # for more information about savepoints.
     #
     # === Callbacks

guides/source/active_record_validations.md

@@ -636,7 +636,7 @@ class Holiday < ActiveRecord::Base
     message: "should happen once per year" }
 end
 ```
-Should you wish to create a database constraint to prevent possible violations of a uniqueness validation using the `:scope` option, you must create a unique index on both columns in your database. See [the MySQL manual](http://dev.mysql.com/doc/refman/5.6/en/multiple-column-indexes.html) for more details about multiple column indexes or [the PostgreSQL manual](http://www.postgresql.org/docs/current/static/ddl-constraints.html) for examples of unique constraints that refer to a group of columns.
+Should you wish to create a database constraint to prevent possible violations of a uniqueness validation using the `:scope` option, you must create a unique index on both columns in your database. See [the MySQL manual](http://dev.mysql.com/doc/refman/5.7/en/multiple-column-indexes.html) for more details about multiple column indexes or [the PostgreSQL manual](http://www.postgresql.org/docs/current/static/ddl-constraints.html) for examples of unique constraints that refer to a group of columns.
 
 There is also a `:case_sensitive` option that you can use to define whether the
 uniqueness constraint will be case sensitive or not. This option defaults to

railties/lib/rails/generators/rails/app/templates/config/databases/jdbcmysql.yml

@@ -7,7 +7,7 @@
 # gem 'activerecord-jdbcmysql-adapter'
 #
 # And be sure to use new-style password hashing:
-#   http://dev.mysql.com/doc/refman/5.6/en/old-client.html
+#   http://dev.mysql.com/doc/refman/5.7/en/old-client.html
 #
 default: &default
   adapter: mysql

railties/lib/rails/generators/rails/app/templates/config/databases/mysql.yml

@@ -7,7 +7,7 @@
 #   gem 'mysql2'
 #
 # And be sure to use new-style password hashing:
-#   http://dev.mysql.com/doc/refman/5.6/en/old-client.html
+#   http://dev.mysql.com/doc/refman/5.7/en/old-client.html
 #
 default: &default
   adapter: mysql2