mysql - How to validate string attributes avoiding "ActiveRecord::StatementInvalid: Mysql2::Error: Data too long for column [...]" exception? -

i'm facing problem mysql text columns related string attributes containing utf-8 characters. let's suppose have migration one:

class createitems < activerecord::migration   def change     create :items |t|       t.text "description", null: false     end   end end 

as know maximum length of mysql text column 65535 bytes, , adding validation 1 below should prevent such mysql exception:

class item < activerecord::base   validates :description, length: { maximum: 65535 } end 

and of course works moment when user puts long text containing characters more 1 byte long. how difference? see example:

> s = "a text national characters ĄąĘę"           => "a text national characters ĄąĘę" > s.length => 41 > s.bytesize => 45 

so e.g. if puts long description 65500 character long lots of such characters, validation passes mysql not forgive...

temporarily i've created bytesize validation:

class bytesizevalidator < activemodel::eachvalidator   def validate_each(record, attribute, value)     record.errors.add(attribute, :too_long, count: options[:maximum]) if value.bytesize > options[:maximum]   end end 

which used in model follows:

validates :description, bytesize: { maximum: 65535 } 

solves problem believe, there simple solution. maybe missed , possible make regular rails length validation covering multibyte characters expected here?

i use rails 4.2.5.1, ruby 2.2.4 , mariadb 15.1 on linux.