database.yml

default: &default
  adapter: mysql2
  encoding: utf8mb4
  username: root
  password:
  host: localhost
  variables:
    sql_mode: TRADITIONAL,NO_AUTO_VALUE_ON_ZERO,ONLY_FULL_GROUP_BY

development:
  <<: *default
  database: myna_development

mysql_migration_ext.rb

ActiveSupport.on_load(:active_record) do
require 'active_record/connection_adapters/mysql2_adapter'

module ActiveRecord
  module ConnectionAdapters

    module MysqlMigrationExt
      def create_table(table_name, options = {})
        if %w(development test).include?(Rails.env)
          innodb_variables = []
          unless show_variable('innodb_file_per_table') == 1
            innodb_variables << 'innodb_file_per_table = 1'
          end
          unless show_variable('innodb_file_format') == 'Barracuda'
            innodb_variables << 'innodb_file_format = Barracuda'
          end
          unless show_variable('innodb_large_prefix') == 1
            innodb_variables << 'innodb_large_prefix = 1'
          end
          unless innodb_variables.empty?
            innodb_variables << 'innodb_strict_mode = 1'
            execute("SET GLOBAL #{innodb_variables.join(',')}".tap { |sql| puts "NOTICE: #{sql}" })
            required_innodb_file_format_barracuda_message
          end
        end
        super(table_name, options.reverse_merge(options: "ROW_FORMAT=DYNAMIC"))
      end

      def required_innodb_file_format_barracuda_message
        puts "This application required MySQL 5.6 and innodb_file_format = Barracuda."
        puts "Please add the following setting in your my.cnf."
        puts ""
        puts "```my.cnf"
        puts "[mysqld]"
        puts "innodb_strict_mode = 1"
        puts "innodb_file_format = Barracuda"
        puts "innodb_large_prefix = 1"
        puts "innodb_file_per_table = 1"
        puts "```"
        puts ""
      end
    end

    class Mysql2Adapter
      include MysqlMigrationExt
    end
  end
end

end