Django“ValueError：找不到 {migrations} 的共同祖先”答案

【问题标题】：Django "ValueErrror: could not find common ancestor of {migrations}"Django“ValueError：找不到 {migrations} 的共同祖先”
【发布时间】：2018-07-18 04:40:39
【问题描述】：

我正在尝试按照https://docs.djangoproject.com/en/2.0/ref/contrib/postgres/operations/ 中的文档创建一个迁移，该迁移基本上将在数据库上执行CREATE EXTENSION IF NOT EXISTS hstore; 的SQL 语句。我尝试将名为create_extension_hstore.py 的以下文件添加到migrations 目录：

from django.db import migrations
from django.contrib.postgres.operations import CreateExtension


class Migration(migrations.Migration):
    operations = [CreateExtension(name='hstore')]

我的“心理模型”是，由于 Django 从他们的dependencies 推断迁移的顺序，而这个没有，它应该首先运行。但是，当我尝试运行 python manage.py makemigrations --merge 时出现错误：

(venv) Kurts-MacBook-Pro:lucy-web kurtpeek$ python manage.py makemigrations --merge
(0.000) SELECT typarray FROM pg_type WHERE typname = 'citext'; args=None
(0.003) 
            SELECT c.relname, c.relkind
            FROM pg_catalog.pg_class c
            LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
            WHERE c.relkind IN ('r', 'v')
                AND n.nspname NOT IN ('pg_catalog', 'pg_toast')
                AND pg_catalog.pg_table_is_visible(c.oid); args=None
(0.001) SELECT "django_migrations"."app", "django_migrations"."name" FROM "django_migrations"; args=()
Traceback (most recent call last):
  File "manage.py", line 29, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/kurtpeek/Documents/Dev/lucy/lucy-web/venv/lib/python3.6/site-packages/django/core/management/__init__.py", line 364, in execute_from_command_line
    utility.execute()
  File "/Users/kurtpeek/Documents/Dev/lucy/lucy-web/venv/lib/python3.6/site-packages/django/core/management/__init__.py", line 356, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/kurtpeek/Documents/Dev/lucy/lucy-web/venv/lib/python3.6/site-packages/django/core/management/base.py", line 283, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/Users/kurtpeek/Documents/Dev/lucy/lucy-web/venv/lib/python3.6/site-packages/django/core/management/base.py", line 330, in execute
    output = self.handle(*args, **options)
  File "/Users/kurtpeek/Documents/Dev/lucy/lucy-web/venv/lib/python3.6/site-packages/django/core/management/commands/makemigrations.py", line 142, in handle
    return self.handle_merge(loader, conflicts)
  File "/Users/kurtpeek/Documents/Dev/lucy/lucy-web/venv/lib/python3.6/site-packages/django/core/management/commands/makemigrations.py", line 272, in handle_merge
    raise ValueError("Could not find common ancestor of %s" % migration_names)
ValueError: Could not find common ancestor of {'0091_family_adopting_or_surrogate', 'create_extension_hstore'}

我该如何解决这个问题？我可以尝试将dependencies=['0001_initial'] 添加到Migration 类中，但这似乎有点武断，因为我真正想要的是先运行此迁移。

【问题讨论】：

标签： python django postgresql database-migration hstore

【解决方案1】：

如果您希望它在第一次生成的迁移之前运行，我认为您希望将此迁移添加到 0001 中的依赖项中。

如果您现在才需要 hstore 并且不需要先运行它，您可以很容易地像往常一样添加为 data migration。

【讨论】：

【解决方案2】：

我最终解决了更大的问题，使用HStoreField 无需在数据库上手动运行CREATE EXTENSION hstore;，方法是将HStoreExtension() 操作添加到0001_initial.py 迁移的operations；另见https://docs.djangoproject.com/en/2.0/ref/contrib/postgres/operations/#create-postgresql-extensions。

【讨论】：