MySQL utf8mb4 encoding quirk fix

config/initializers/mysqlpls.rb

@@ -0,0 +1,13 @@
+# see https://github.com/rails/rails/issues/9855#issuecomment-28874587
+# circumvents the default InnoDB limitation for index prefix bytes maximum when using proper 4byte UTF8 (utf8mb4)
+# (for server-side workaround see http://dev.mysql.com/doc/refman/5.7/en/innodb-parameters.html#sysvar_innodb_large_prefix)
+
+require 'active_record/connection_adapters/abstract_mysql_adapter'
+
+module ActiveRecord
+  module ConnectionAdapters
+    class AbstractMysqlAdapter
+      NATIVE_DATABASE_TYPES[:string] = { :name => "varchar", :limit => 191 }
+    end
+  end
+end