Django Wagtail 1.8.1迁移问题

正在尝试将Wagtail从1.7升级到1.8.1，但在运行迁移时出现以下错误。我们正在使用Postgres数据库

Applying wagtailimages.0016_deprecate_rendition_filter_relation...Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 367, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 359, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 294, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 345, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/migrate.py", line 204, in handle
    fake_initial=fake_initial,
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 115, in migrate
    state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 145, in _migrate_all_forwards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 244, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/migration.py", line 129, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/operations/fields.py", line 204, in database_forwards
    schema_editor.alter_field(from_model, from_field, to_field)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/base/schema.py", line 495, in alter_field
    old_db_params, new_db_params, strict)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/postgresql/schema.py", line 117, in _alter_field
    new_db_params, strict,
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/base/schema.py", line 649, in _alter_field
    params,
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/base/schema.py", line 112, in execute
    cursor.execute(sql, params)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 79, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "/usr/local/lib/python2.7/dist-packages/django/db/utils.py", line 94, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
django.db.utils.IntegrityError: could not create unique index "wagtailimages_rendition_image_id_742f4fe4119535f1_uniq"
DETAIL:  Key (image_id, filter_id, focal_point_key)=(507, 4, 2617-1240-3472x35) is duplicated.

sql导入的错误为psql:foxtail.sql:68823:

ERROR:  constraint    "wagtailcore__content_type_id_c28424df_fk_django_content_type_id" for  relation "wagtailcore_page" already exists
psql:foxtail.sql:68831: ERROR:  constraint   "wagtailcore_collection_id_5423575a_fk_wagtailcore_collection_id" for   relation "wagtailcore_groupcollectionpermission" already exists
ALTER TABLE
psql:foxtail.sql:68847: ERROR:  constraint   "wagtailcore_groupc_permission_id_1b626275_fk_auth_permission_id" for   relation "wagtailcore_groupcollectionpermission" already exists
psql:foxtail.sql:68855: ERROR:  constraint   "wagtailcore_groupcollectionp_group_id_05d61460_fk_auth_group_id" for   relation "wagtailcore_groupcollectionpermission" already exists
ALTER TABLE
ALTER TABLE
ALTER TABLE
ALTER TABLE
ALTER TABLE
psql:foxtail.sql:68903: ERROR:  constraint  "wagtaildocs_collection_id_23881625_fk_wagtailcore_collection_id" for  relation "wagtaildocs_document" already exists
psql:foxtail.sql:68911: ERROR:  constraint  "wagtaildocs_docume_uploaded_by_user_id_17258b41_fk_auth_user_id" for   relation "wagtaildocs_document" already exists
ALTER TABLE
psql:foxtail.sql:68927: ERROR:  constraint   "wagtailimag_collection_id_c2f8af7e_fk_wagtailcore_collection_id" for    relation "wagtailimages_image" already exists

新导入后但运行迁移前的输出

Table "public.wagtailimages_rendition"
Column      |          Type          |                                 Modifiers
-----------------+------------------------+--------------------------   --------------------------------------------
id              | integer                | not null default   nextval('wagtailimages_rendition_id_seq'::regclass)
filter_id       | integer                | not null
file            | character varying(100) | not null
width           | integer                | not null
height          | integer                | not null
image_id        | integer                | not null
focal_point_key | character varying(255) | not null
Indexes:
"wagtailimages_rendition_pkey" PRIMARY KEY, btree (id)
"wagtailimages_rendition_image_id_742f4fe4119535f1_uniq" UNIQUE  CONSTRAINT, btree (image_id, filter_id, focal_point_key)
"wagtailimages_rendition_filter_id" btree (filter_id)
"wagtailimages_rendition_image_id" btree (image_id)
Foreign-key constraints:
"filter_id_refs_id_6909da8c" FOREIGN KEY (filter_id) REFERENCES   wagtailimages_filter(id) DEFERRABLE INITIALLY DEFERRED
"image_id_refs_id_e221c01d" FOREIGN KEY (image_id) REFERENCES   wagtailimages_image(id) DEFERRA:

---

由于我无法理解上述情况是如何产生的，我只能建议“核心选项”：通过运行

DELETE FROM wagtailimages_rendition;

在Postgresql命令行上。这将允许剩余的迁移顺利完成。这不会导致持久的数据丢失，因为Wagtail会在需要时重新生成格式副本-尽管页面请求会慢一段时间，因为它必须重新呈现缺少格式副本条目的每个图像

更新：与删除所有记录相比，更保守的方法是查找并删除重复记录：

DELETE FROM wagtailimages_rendition
WHERE image_id || '-' || filter_id || '-' || focal_point_key IN (
    SELECT image_id || '-' || filter_id || '-' || focal_point_key
    FROM (
        SELECT image_id, filter_id, focal_point_key, COUNT(*) AS count
        FROM wagtailimages_rendition GROUP BY image_id, filter_id, focal_point_key
    ) AS renditions
    WHERE count > 1
);

---

我可以确认乔斯在这边看到了什么

我猜，由于某种原因，我们比其他人有更长的焦点关键值，否则每个人在迁移时都会看到这个问题

这可能是因为你过去为我们做的一些定制工作吗

---

现在不确定解决方案是什么，非常感谢任何帮助。

我对这个错误有点困惑，因为所讨论的迁移应该是删除有问题的唯一索引，而不是创建它。。。请在Postgresql命令行上运行

\d wagtailimages\u rendition

并将输出粘贴到此处，以便我可以看到数据库表当前处于何种状态？我们正在使用docker for local dev，当我在移除容器后再次尝试时，迁移运行正常。当我试图导入一些sql以用一些数据填充db时，我得到了一些错误，我的管理中只有默认的欢迎使用wagtail站点页面。尽管它已经导入了用户等。如果数据已经存在，迁移似乎会失败。SQL导入文件似乎包含一些架构更改/创建命令，这些命令肯定不会很好地用于迁移，因为它依赖于从一个特定的初始数据库状态开始。我猜它应该是从一个空数据库开始运行的-这是否完成而没有错误？如果是这样的话，如果在此之后运行Wagtail 1.8.1迁移会发生什么情况？它会在没有错误的情况下完成从头开始的导入，但随后发生了迁移错误。请在导入运行之后，但在运行迁移之前，显示

\d wagtailimages\u rendition

的输出？（我假设上面显示的输出是在新数据库上成功运行迁移的结果，对吗？）在生产中，我们不确定是否要取消格式副本表，这不仅是因为性能，还因为外部系统调用wagtail来生成在django模板外使用的设置大小的图像，它们再也不会像页面上使用的图像那样被调用。（如果这有意义的话？）我发现了Karl不久前在本期中发布的这段SQL，它删除了重复的格式副本。我在本地尝试过，它允许迁移继续进行。你认为这是一种选择吗？谢谢Joss@joss是的，应该行。我认为您可能需要修改Karl的SQL，以便在唯一性条件中包含

focal\u point\u key

，使其与当前模式保持最新-我已更新我的答案，以包含（未测试的）固定SQL。我测试了更新的查询，但没有返回要删除的结果。这是因为复制品有一个焦点键值，该值在所有情况下都是相同的，除了最后一个值比另一个值小之外，例如，“4010-1722-4208x4230”和“4010-1722-4208x4231”在错误中表示细节：键（图像id，过滤器id，焦点键）=（788，4321-1430-5472x28）被复制。当我返回图像788的所有格式副本时，这三条记录都有焦点，如“3231-1430-5472x2874”，因此它切断了最后两个字符，并且认为我们已经复制了此迁移似乎为焦点设置了max_length=16，这与忽略最后两个字符有关

DELETE FROM wagtailimages_rendition
WHERE image_id || '-' || filter_id || '-' || focal_point_key IN (
    SELECT image_id || '-' || filter_id || '-' || focal_point_key
    FROM (
        SELECT image_id, filter_id, focal_point_key, COUNT(*) AS count
        FROM wagtailimages_rendition GROUP BY image_id, filter_id, focal_point_key
    ) AS renditions
    WHERE count > 1
);