Django模型字段无法在数据库创建的问题排查求助

问题描述 #

开发项目管理应用时，创建ProjectComment模型并添加自定义字段后，数据库仅生成默认ID字段；删除迁移记录和数据库表重建后问题依旧。新建Comment模型执行迁移，仍只生成ID字段，无自定义字段。

相关代码 #

Project模型 #

class Project(models.Model):
    project_id = models.CharField(
        primary_key=True,
        max_length=50,
        null=False,
        blank=False,
    )

    project_owner2 = models.ForeignKey(Entity, 
        on_delete=models.CASCADE,
        default='916 075 855', #dette er bruker sin organisasjon
        )

    direction = models.CharField(
        max_length=50,
        null=True,
        blank=True,
    )

    title = models.CharField(
        unique=True,
        max_length=50,
        null=False,
        blank=False,
    )

    scope = models.TextField(
        verbose_name='Scope', # denne må få nytt navn
        help_text='Her skal du beskrive prosjektets omfang',
        max_length=2000,
        null=True,
        blank=True,
    )

    project_status_choices = (
        ('PLANNED', 'Planned'),
        ('ACTIVE', 'Active'),
        ('ON_HOLD', 'On hold'),
        ('COMPLETED', 'Completed'),
        ('CANCELLED', 'Cancelled'),
    )

    project_create = models.DateField(
        verbose_name='Project creation date',
        help_text='When the project was initiated',
        null=True,
        blank=True,
    )

    project_start = models.DateField(
        verbose_name='Project start date',
        help_text='Her skal du beskrive prosjektet',
        null=True,
        blank=True,
    )

    project_end = models.DateField(
        verbose_name='Project end date',
        help_text='Originaly end date',
        null=True,
        blank=True,
    )

    class Meta:
        pass

    def __str__(self):
        return self.title

ProjectComment模型（问题版本） #

class ProjectComment(models.Model):
project = models.ForeignKey(Project, on_delete=models.CASCADE),
pub_date = models.DateTimeField(auto_created=True, editable=False),
comment = models.TextField(max_length=2000, null=False, blank=False),
user = models.ForeignKey(User, on_delete=models.CASCADE)

    def __str__(self):
        template = '{0.project} {0.pub_date} {0.user}'
        return template.format(self)

初始迁移文件 #

# Generated by Django 4.0.6 on 2023-03-19 08:35

from django.conf import settings
from django.db import migrations, models
import django.db.models.deletion


class Migration(migrations.Migration):

    initial = True

    dependencies = [
        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
    ]

    operations = [
        migrations.CreateModel(
            name='Project',
            fields=[
                ('project_id', models.CharField(max_length=50, primary_key=True, serialize=False)),
                ('title', models.CharField(max_length=50, unique=True)),
                ('purpose', models.TextField(max_length=2000, null=True, verbose_name='Purpose')),
                ('scope', models.TextField(blank=True, max_length=2000, null=True, verbose_name='Scope')),
                ('project_start', models.DateField(blank=True, null=True, verbose_name='Project start date')),
                ('project_end', models.DateField(blank=True, null=True, verbose_name='Project end date')),
            ],
        ),
        migrations.CreateModel(
            name='ProjectComment',
            fields=[
                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
                ('user', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to=settings.AUTH_USER_MODEL)),
            ],
        ),
    ]

新建Comment模型（问题版本） #

class Comment(models.Model):
    project = models.ForeignKey(Project, on_delete=models.CASCADE),
    publication_date =  models.DateTimeField(auto_created=True, editable=False),
    comment_field = models.TextField(max_length=2000, null=False, blank=False),
    user = models.TextField(max_length=2000, null=False, blank=False),

    def __str__(self):
        template = '{0.project} {0.pub_date} {0.user}'
        return template.format(self)

新建Comment模型后的迁移文件 #

from django.db import migrations, models


class Migration(migrations.Migration):

    dependencies = [
        ('projects', '0008_alter_departementalroles_options_and_more'),
    ]

    operations = [
        migrations.CreateModel(
            name='Comment',
            fields=[
                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
            ],
        ),
    ]

问题根源 #

1. 字段末尾多余逗号：ProjectComment和Comment模型的每个字段末尾都加了逗号，导致这些字段被解析为单元素元组，而非Django可识别的模型字段实例，迁移时只会生成默认ID字段。
2. 缩进错误：ProjectComment模型的字段没有缩进，会导致模型解析异常。
3. 字段类型错误：Comment模型的user字段误用TextField，不符合关联用户的需求。

解决方案 #

1. 修正模型代码 #

去掉字段末尾的逗号，修正缩进，调整错误字段类型：

修正后的ProjectComment模型

class ProjectComment(models.Model):
    project = models.ForeignKey(Project, on_delete=models.CASCADE)
    pub_date = models.DateTimeField(auto_created=True, editable=False)
    comment = models.TextField(max_length=2000, null=False, blank=False)
    user = models.ForeignKey(User, on_delete=models.CASCADE)

    def __str__(self):
        template = '{0.project} {0.pub_date} {0.user}'
        return template.format(self)

修正后的Comment模型

class Comment(models.Model):
    project = models.ForeignKey(Project, on_delete=models.CASCADE)
    publication_date = models.DateTimeField(auto_created=True, editable=False)
    comment_field = models.TextField(max_length=2000, null=False, blank=False)
    user = models.ForeignKey(User, on_delete=models.CASCADE)

    def __str__(self):
        template = '{0.project} {0.publication_date} {0.user}'
        return template.format(self)

2. 重新执行迁移 #

• 删除之前为Comment模型生成的错误迁移文件
• 生成新迁移：

  python manage.py makemigrations
  

• 同步数据库：

  python manage.py migrate
  

3. 验证结果 #

查看数据库对应表，确认自定义字段已正常生成。

内容的提问来源于stack exchange，提问作者LegalGeek