Making Django migrations that work with MySQL 5.5 and utf8mb4

[bd808]

Reader comments on Making Django migrations that work with MySQL 5.5 and utf8mb4

[bd808]

My method has a problem if you are going to apply the migration on any backend other than MySQL. The ROW_FORMAT argument will probably make your database engine barf. This can be fixed by wrapping the RunSQL call in a function that checks the database type:

def fix_unicodehack_row_format(apps, schema_editor):
    if not schema_editor.connection.vendor == 'mysql':
        return
    migrations.RunSQL('ALTER TABLE unicodehack ROW_FORMAT = DYNAMIC;')

and calling that using RunPython:

migrations.RunPython(fix_unicodehack_row_format),

[volans-]

I've achieved the same goal using a custom MySQL backend that extends the Django's one, just overriding the sql_create_table template to add the ROW_FORMAT=DYNAMIC at the end of the query (I've tested it with Django 2.0.x). The advantages of this approach IMHO are that:

• It doesn't have any side effect on other database engines, so an application could still support multiple backends just changing the database's settings, as long as the other engines support the schema.
• Doesn't require to manually modify the migration files autogenerated by Django's makemigrations.

You can check the code in wikimedia/operations-software-debmonitor@6219784

It should also be mentioned that this requires that the MySQL server is configured with:

innodb_file_per_table = 1
innodb_file_format    = barracuda
innodb_large_prefix   = 1

[bd808]

I've achieved the same goal using a custom MySQL backend that extends the Django's one

That's a nice approach @volans-. Had you considered extracting that and publishing it as a pypi package? I know its a very small amount of code, but I'm sure it would be useful to others. I know I would drop it into Striker to replace my migration hack.