Suggestion for shorter code

[vdboor]

Hi,

I came across your example, and it helped me understand app renamed a lot more. Thanks a lot :-)

I have a few suggestions for the project. Instead of sending a pull request, I can imagine you'd like to rebase / force push a new history instead. Hence, this ticket.

The second data migration for content-types can be merged into the first, by using:

    if not db.dry_run:
        ContentType.objects.filter(app_label='old_app').update(app_label='new_app')

(the only difference between a SchemaMigration and DataMigration is the fact that data migrations don't go through a dry-run)

The was_applied code can also be shortened:

def was_applied(migration_file_path, app_name):
    """true if migration with a given file name ``migration_file`` was applied to app with name ``app_name``"""
    migration_name = os.path.basename(migration_file_path).split('.')[0]
    return MigrationHistory.objects.exists(app_name=app_name, migration=migration_name)

I also found it useful to check for existing table names, not sure if it applies here. (code is if 'messages_message' in connection.introspection.table_names())

Hope this helps :-)

[evgenyfadeev]

Awesome, glad it was useful.

Why is if not db.dry_run necessary?

Yeah, the shorter version of was_applied() is better. Not sure when I find the time to rebase this though:)...

[vdboor]

Good to know, thanks :-)

About the dry_run: South distinguishes between a SchemaMigration and DataMigration, but the main difference is that a SchemaMigration is executed twice. The first time it's a "dry run", to see what the code would execute. The second time it does the actual execution. This feature is also used for commands like ./manage.py migrate --changes. Just grep through the South code, and you'll see that the difference is remarkably thin; the only difference is a property at one of the classes.

Hence, if you want to alter data in a SchemaMigration, or merge both together, it needs to check whether this is the first dry run, or second final run.