Mysql2::Error: Incorrect string value

Question

I have a rails application running on production mode, but all of the sudden this error came up today when a user tried to save a record.

Answer 1

I managed to store emojis (which take up 4 bytes) by following this blog post:

Rails 4, MySQL, and Emoji (Mysql2::Error: Incorrect string value error.)

You might think that you’re safe inserting most utf8 data in to mysql when you’ve specified that the charset is utf-8. Sadly, however, you’d be wrong. The problem is that the utf8 character set takes up 3 bytes when stored in a VARCHAR column. Emoji characters, on the other hand, take up 4 bytes.

The solution is in 2 parts:

Change the encoding of your table and fields:

ALTER TABLE `[table]` 
  CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_bin,
MODIFY [column] VARCHAR(250)
    CHARACTER SET utf8mb4 COLLATE utf8mb4_bin

Tell the mysql2 adapter about it:

development:
  adapter: mysql2
  database: db
  username: 
  password:
  encoding: utf8mb4
  collation: utf8mb4_unicode_ci

Hope this helps someone!

Then I had to restart my app and it worked. Please note that some emojis will work without this fix, while some won't:

• ➡️ Did work

Answer 2

You can use a migration like this to convert your tables to utf8:

class ConvertTablesToUtf8 < ActiveRecord::Migration
  def change_encoding(encoding,collation)
    connection = ActiveRecord::Base.connection
    tables = connection.tables
    dbname =connection.current_database
    execute <<-SQL
      ALTER DATABASE #{dbname} CHARACTER SET #{encoding} COLLATE #{collation};
    SQL
    tables.each do |tablename|
      execute <<-SQL
        ALTER TABLE #{dbname}.#{tablename} CONVERT TO CHARACTER SET #{encoding} COLLATE #{collation};
      SQL
    end
  end

  def change
    reversible do |dir|
      dir.up do
        change_encoding('utf8','utf8_general_ci')
      end
      dir.down do
        change_encoding('latin1','latin1_swedish_ci')
      end
    end
  end
end

Answer 3

Need to change CHARACTER SET and COLLATE for already created database:

ALTER DATABASE databasename CHARACTER SET utf8 COLLATE utf8_unicode_ci;

Or it was necessary to create a database with pre-set parameters:

CREATE DATABASE databasename CHARACTER SET utf8 COLLATE utf8_general_ci;

Answer 4

Also, if you don't want to do changes in your database structure, you could opt by serializing the field in question.

class MyModel < ActiveRecord::Base
  serialize :content

  attr_accessible :content, :title
end

Answer 5

If you want to the store emoji, you need to do the following:

1. Create a migration (thanks @mfazekas)

   class ConvertTablesToUtf8 < ActiveRecord::Migration def change_encoding(encoding,collation) connection = ActiveRecord::Base.connection tables = connection.tables dbname =connection.current_database execute <<-SQL ALTER DATABASE #{dbname} CHARACTER SET #{encoding} COLLATE #{collation}; SQL tables.each do |tablename| execute <<-SQL ALTER TABLE #{dbname}.#{tablename} CONVERT TO CHARACTER SET #{encoding} COLLATE #{collation}; SQL end end

   def change reversible do |dir| dir.up do change_encoding('utf8mb4','utf8mb4_bin') end dir.down do change_encoding('latin1','latin1_swedish_ci') end end end end

2. Change rails charset to utf8mb4 (thanks @selvamani-p)

   production: encoding: utf8mb4

References:

https://stackoverflow.com/a/39465494/1058096

https://stackoverflow.com/a/26273185/1058096

Answer 6

It seems like an encoding problem while getting data from database. Try adding the below to your database.yml file

   encoding: utf8 

Hope this solves your issue