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Django-DB-Migrations：无法更改表，因为它具有未决的触发事件

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问题：Django-DB-Migrations：无法更改表，因为它具有未决的触发事件
回答 0
回答 1
回答 2
回答 3
回答 4

问题：Django-DB-Migrations：无法更改表，因为它具有未决的触发事件

我想从TextField中删除null = True：

-    footer=models.TextField(null=True, blank=True)
+    footer=models.TextField(blank=True, default='')

我创建了一个架构迁移：

manage.py schemamigration fooapp --auto

由于某些页脚列包含，NULL因此error在运行迁移时会得到以下信息：

django.db.utils.IntegrityError：“页脚”列包含空值

我将其添加到架构迁移中：

    for sender in orm['fooapp.EmailSender'].objects.filter(footer=None):
        sender.footer=''
        sender.save()

现在我得到：

django.db.utils.DatabaseError: cannot ALTER TABLE "fooapp_emailsender" because it has pending trigger events

怎么了？

点击查看英文原文

I want to remove null=True from a TextField:

-    footer=models.TextField(null=True, blank=True)
+    footer=models.TextField(blank=True, default='')

I created a schema migration:

manage.py schemamigration fooapp --auto

Since some footer columns contain NULL I get this error if I run the migration:

django.db.utils.IntegrityError: column “footer” contains null values

I added this to the schema migration:

    for sender in orm['fooapp.EmailSender'].objects.filter(footer=None):
        sender.footer=''
        sender.save()

Now I get:

django.db.utils.DatabaseError: cannot ALTER TABLE "fooapp_emailsender" because it has pending trigger events

What is wrong?

回答 0

造成这种情况的另一个原因可能是因为您尝试将一列设置为NOT NULL实际上已经具有NULL值的时间。

点击查看英文原文

Another reason for this maybe because you try to set a column to NOT NULL when it actually already has NULL values.

回答 1

每次迁移都在事务内部。在PostgreSQL中，您不得在一个事务中更新表然后更改表模式。

您需要拆分数据迁移和架构迁移。首先使用以下代码创建数据迁移：

 for sender in orm['fooapp.EmailSender'].objects.filter(footer=None):
    sender.footer=''
    sender.save()

然后创建架构迁移：

manage.py schemamigration fooapp --auto

现在，您有两个事务，并且应该在两个步骤中进行迁移。

点击查看英文原文

Every migration is inside a transaction. In PostgreSQL you must not update the table and then alter the table schema in one transaction.

You need to split the data migration and the schema migration. First create the data migration with this code:

 for sender in orm['fooapp.EmailSender'].objects.filter(footer=None):
    sender.footer=''
    sender.save()

Then create the schema migration:

manage.py schemamigration fooapp --auto

Now you have two transactions and the migration in two steps should work.

回答 2

刚刚遇到这个问题。您还可以在模式迁移中使用db.start_transaction（）和db.commit_transaction（）将数据更改与模式更改分开。可能不那么干净，无法进行单独的数据迁移，但是在我的情况下，我需要架构，数据，然后再进行另一种架构迁移，因此我决定一次完成所有操作。

点击查看英文原文

Have just hit this problem. You can also use db.start_transaction() and db.commit_transaction() in the schema migration to separate data changes from schema changes. Probably not so clean as to have a separate data migration but in my case I would need schema, data, and then another schema migration so I decided to do it all at once.

回答 3

在操作中，我将SET约束：

operations = [
    migrations.RunSQL('SET CONSTRAINTS ALL IMMEDIATE;'),
    migrations.RunPython(migration_func),
    migrations.RunSQL('SET CONSTRAINTS ALL DEFERRED;'),
]
点击查看英文原文

At the operations I put SET CONSTRAINTS:

operations = [
    migrations.RunSQL('SET CONSTRAINTS ALL IMMEDIATE;'),
    migrations.RunPython(migration_func),
    migrations.RunSQL('SET CONSTRAINTS ALL DEFERRED;'),
]

回答 4

您正在更改列架构。该页脚列不能再包含空白值。该列中很可能已经有空白值存储在数据库中。Django将使用migration命令将数据库中的空白行从空白更新为现在的默认值。Django尝试更新页脚列为空值的行，并在看起来相同的同时更改架构（我不确定）。

问题是您无法更改试图同时更新其值的列模式。

一种解决方案是删除迁移文件以更新架构。然后，运行脚本以将所有这些值更新为默认值。然后重新运行迁移以更新架构。这样，更新已完成。Django迁移仅更改架构。

点击查看英文原文

You are altering the column schema. That footer column can no longer contain a blank value. There are most likely blank values already stored in the DB for that column. Django is going to update those blank rows in your DB from blank to the now default value with the migrate command. Django tries to update the rows where footer column has a blank value and change the schema at the same time it seems (I’m not sure).

The problem is you can’t alter the same column schema you are trying to update the values for at the same time.

One solution would be to delete the migrations file updating the schema. Then, run a script to update all those values to your default value. Then re-run the migration to update the schema. This way, the update is already done. Django migration is only altering the schema.