不支持 Django datetime.datetime 到 Decimal 的迁移

Question

以下是我尝试迁移时出现的模型和错误。我正在使用 django 1.10，当我尝试迁移时，我的数据库是空的。

型号：

from django.db import models

class OrderEntry(models.Model):
    quote_num = models.CharField(max_length=50, primary_key=True)
    customer = models.CharField(max_length=100)
    cust_po = models.CharField(max_length=50)
    pdf = models.CharField(max_length=500)
    datetime = models.DateTimeField(auto_now=True, editable=True, null=True)

class Items(models.Model):
    quote_num = models.CharField(max_length=50, primary_key=True)
    item_1 = models.CharField(max_length=100)
    item_2 = models.CharField(max_length=100)
    item_3 = models.CharField(max_length=100)
    item_4 = models.CharField(max_length=100)
    item_5 = models.CharField(max_length=100)
    item_6 = models.CharField(max_length=100)
    item_7 = models.CharField(max_length=100)
    item_8 = models.CharField(max_length=100)
    item_9 = models.CharField(max_length=100)
    item_10 = models.CharField(max_length=100)

class ItemDetails(models.Model):
    item = models.CharField(max_length=100, primary_key=True)
    quote_num = models.CharField(max_length=50)
    quan = models.CharField(max_length=100)
    desc = models.TextField(max_length=1000)
    price = models.DecimalField(max_digits=10, decimal_places=2, default=0, null=True)

错误：

C:\Users\Evan\Desktop\webapp>py manage.py migrate 
Operations to perform:
Apply all migrations: admin, auth, contenttypes, orders, sessions

Running migrations:
  Applying orders.0013_itemdetails_price...Traceback (most recent call last):
  File "manage.py", line 22, in <module>
    execute_from_command_line(sys.argv)
  File "C:\Users\Evan\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\core\management\__init__.py", line 367, in execute_from_command_line
    utility.execute()
  File "C:\Users\Evan\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\core\management\__init__.py", line 359, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "C:\Users\Evan\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\core\management\base.py", line 294, in run_from_argv
    self.execute(*args, **cmd_options)
  File "C:\Users\Evan\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\core\management\base.py", line 345, in execute
    output = self.handle(*args, **options)
  File "C:\Users\Evan\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\core\management\commands\migrate.py", line 204, in handle
    fake_initial=fake_initial,
  File "C:\Users\Evan\AppData\Local\Programs\Python\Python35-32\lib\site-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 "C:\Users\Evan\AppData\Local\Programs\Python\Python35-32\lib\site-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 "C:\Users\Evan\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\migrations\executor.py", line 244, in apply_migration
    state = migration.apply(state, schema_editor)
  File "C:\Users\Evan\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\migrations\migration.py", line 129, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "C:\Users\Evan\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\migrations\operations\fields.py", line 84, in database_forwards
    field,
  File "C:\Users\Evan\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\postgresql\schema.py", line 21, in add_field
    super(DatabaseSchemaEditor, self).add_field(model, field)
  File "C:\Users\Evan\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\base\schema.py", line 395, in add_field
    definition, params = self.column_sql(model, field, include_default=True)
  File "C:\Users\Evan\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\base\schema.py", line 147, in column_sql
    default_value = self.effective_default(field)
  File "C:\Users\Evan\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\backends\base\schema.py", line 221, in effective_default
    default = field.get_db_prep_save(default, self.connection)
  File "C:\Users\Evan\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\models\fields\__init__.py", line 1583, in get_db_prep_save
    return connection.ops.adapt_decimalfield_value(self.to_python(value), self.max_digits, self.decimal_places)
  File "C:\Users\Evan\AppData\Local\Programs\Python\Python35-32\lib\site-packages\django\db\models\fields\__init__.py", line 1554, in to_python
    return decimal.Decimal(value)
TypeError: conversion from datetime.datetime to Decimal is not supported

我设置了一些默认值和空值来尝试迁移到 postgre 数据库。感谢您的帮助。

Answer 1

您的错误消息让我相信您错误地将价格字段设置为 DateTimeField，现在您正试图更改它。如果您尝试在 psql 控制台中执行这样的语句，这与您得到的错误一致。

ALTER TABLE item_details ALTER COLUMN price SET TYPE DECIMAL

为了修复它，请删除新创建的迁移。然后删除价格列（保存为日期时间的价格，如果有的话肯定不会有用）。然后 ./manage.py makemigrations 然后 ./manage.py migrate。

成功完成后，重新添加价格字段，但这次是十进制。