How to Fix the \'Incorrect String Value\' Error When Saving Unicode Strings in Django?

Incorrect String Value Error when Saving Unicode Strings in Django

When attempting to save unicode strings to Django's auth_user model, you may encounter a "incorrect string value" error. This error is typically caused by the MySQL character set and collation settings.

MySQL Character Set and Collation

MySQL supports the UTF-8 character set, but it has a 3-byte limit on characters. This means that it is not possible to store 4-byte unicode characters in MySQL with the standard UTF-8 character set.

Problem Explanation

When Django attempts to save unicode strings to the auth_user model, MySQL tries to convert them to the UTF-8 character set. However, if the strings contain 4-byte characters, the conversion fails and results in the "incorrect string value" error.

Solution

To resolve this issue, you can:

1. Change MySQL Character Set to utf8mb4: MySQL 5.5 onwards supports the utf8mb4 character set, which allows for 4-byte characters. Recreate your database, tables, and columns using utf8mb4.
2. Specify Character Set in Django Settings: Add the following to your Django settings file (settings.py) to specify the character set for the database connection:

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        ...
        'OPTIONS': {'charset': 'utf8mb4'},
    }
}

Additional Considerations

• If you cannot reduce the size of your VARCHAR field to 191 characters, you can consider switching to PostgreSQL, which supports 4-byte unicode characters by default.
• If you wish to keep using MySQL with utf8mb4, you may need to apply hacks to Django to increase the allowed VARCHAR size.
• In rare cases, this issue can also be caused by a database configuration that limits key sizes. Check your MySQL configuration and adjust it if necessary.

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