如何判断迁移是否可逆?

几天没人接电话,我就想办法解决了。 This SO answer 是一个很好的起点。

from django.db.migrations.executor import MigrationExecutor
from django.db import connections, DEFAULT_DB_ALIAS

def are_migrations_reversible(target_migrations, database=DEFAULT_DB_ALIAS):
    """check if all migrations required to reach the target migrations are reversible

    `target_migrations` is an iterable of (app_label, migration_name) 2-tuples.
    """
    connection = connections[database]
    connection.prepare_database()
    executor = MigrationExecutor(connection)
    migration_plan = executor.migration_plan(list(target_migrations))

    return all(
        operation.reversible
        for (migration, is_backwards) in migration_plan
        for operation in migration.operations
    )

上述操作需要确定目标迁移,可以从 showmigrations 管理命令,或者进一步使用内部django迁移代码。