Django 1.8 迁移无法将列 ID 转换为整数
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【中文标题】Django 1.8 迁移无法将列 ID 转换为整数【英文标题】：Django 1.8 migration unable to cast column id to integer 【发布时间】：2015-09-06 01:00:07 【问题描述】：我正在将我的网站从 SQLite 后端迁移到 Postgres 后端。从项目一开始，我们就一直在运行原生 Django 风格的迁移（即不是 South）。大多数迁移运行良好，但我们的应用程序出现了问题。
我们在 Postgres 迁移中走到了这一步。 （所有其他应用程序已完全迁移。）所有迁移都在 SQLite3 上顺利运行。
processes
[X] 0001_initial
[X] 0002_auto_20150508_2149
[ ] 0003_auto_20150511_1543
[ ] 0004_auto_20150528_1739
[ ] 0005_process_upstream
[ ] 0006_auto_20150605_1436
[ ] 0007_auto_20150605_1706
[ ] 0008_milestone_prevailing_process
这两个迁移运行正确：
0001_initial.py：
class Migration(migrations.Migration):
dependencies = [
]
operations = [
migrations.CreateModel(
name='DateReason',
fields=[
('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
('name', models.CharField(unique=True, max_length=50)),
('active', models.BooleanField(default=True)),
('final', models.BooleanField(default=False)),
],
),
migrations.CreateModel(
name='EventType',
fields=[
('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
('name', models.CharField(unique=True, max_length=50)),
('active', models.BooleanField(default=True)),
],
),
migrations.CreateModel(
name='Metric',
fields=[
('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
('name', models.CharField(unique=True, max_length=50)),
('active', models.BooleanField(default=True)),
],
),
migrations.CreateModel(
name='Process',
fields=[
('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
('name', models.CharField(max_length=50)),
('sequence', models.PositiveIntegerField()),
('sla', models.PositiveSmallIntegerField(null=True, blank=True)),
('milestone', models.BooleanField(default=False)),
],
options=
'ordering': ['workflow', 'sequence'],
,
),
migrations.CreateModel(
name='Workflow',
fields=[
('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
('name', models.CharField(unique=True, max_length=20)),
('active', models.BooleanField(default=True)),
],
),
migrations.AddField(
model_name='process',
name='workflow',
field=models.ForeignKey(to='processes.Workflow'),
),
migrations.AlterUniqueTogether(
name='process',
unique_together=set([('workflow', 'name'), ('workflow', 'sequence')]),
),
]
0002_auto_20150508_2149.py：
class Migration(migrations.Migration):
dependencies = [
('processes', '0001_initial'),
]
operations = [
migrations.CreateModel(
name='Milestone',
fields=[
('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
('name', models.CharField(max_length=50)),
('sequence', models.PositiveIntegerField()),
('workflow', models.ForeignKey(to='processes.Workflow')),
],
options=
'ordering': ['workflow', 'sequence'],
,
),
migrations.AlterModelOptions(
name='process',
options='ordering': ['milestone', 'sequence'],
),
migrations.AlterUniqueTogether(
name='process',
unique_together=set([('milestone', 'name'), ('milestone', 'sequence')]),
),
migrations.RemoveField(
model_name='process',
name='workflow',
),
migrations.AlterUniqueTogether(
name='milestone',
unique_together=set([('workflow', 'name'), ('workflow', 'sequence')]),
),
]
此迁移不会运行： 0003_auto_20150511_1543.py
class Migration(migrations.Migration):
dependencies = [
('processes', '0002_auto_20150508_2149'),
]
operations = [
migrations.AlterModelOptions(
name='process',
options='ordering': ['milestone', 'sequence'], 'verbose_name_plural': 'processes',
),
migrations.AlterField(
model_name='process',
name='milestone',
field=models.ForeignKey(to='processes.Milestone'),
),
]
尝试运行此迁移会导致：
django.db.utils.ProgrammingError: column "milestone_id" cannot be cast automatically to type integer
HINT: Specify a USING expression to perform the conversion.
相关模型表的当前完全迁移状态是：
class Milestone(models.Model):
"""A collection of steps in a workflow"""
workflow = models.ForeignKey(Workflow, blank=False, null=False)
name = models.CharField(max_length=50, blank=False, null=False)
sequence = models.PositiveIntegerField(blank=False, null=False)
prevailing_process = models.ForeignKey('Process', blank=False, null=True, related_name='controls_milestone')
class Meta:
ordering = ['workflow', 'sequence']
unique_together = (("workflow", "sequence"), ("workflow", "name"))
def __unicode__(self):
return u"0: 1".format(self.workflow.name, self.name)
class Process(models.Model):
"""A step in a workflow"""
milestone = models.ForeignKey(Milestone, blank=False, null=False)
name = models.CharField(max_length=50, blank=False, null=False)
sequence = models.PositiveIntegerField(blank=False, null=False)
sla = models.PositiveSmallIntegerField(blank=True, null=True)
upstream = models.ForeignKey('self', blank=True, null=True, on_delete=models.SET_NULL, related_name='downstream_set')
class Meta:
ordering = ['milestone', 'sequence']
unique_together = (("milestone", "sequence"), ("milestone", "name"))
verbose_name_plural = "processes"
def __unicode__(self):
return u"0 1: 2".format(self.milestone.workflow.name, self.milestone.name, self.name)
压缩迁移没有帮助。 Postgres 数据库是干净的，除了表定义。其卡住形式的相关 Postgres 表定义是：
scorecard=# \d processes_milestone
Table "public.processes_milestone"
Column | Type | Modifiers
-------------+-----------------------+------------------------------------------------------------------
id | integer | not null default nextval('processes_milestone_id_seq'::regclass)
name | character varying(50) | not null
sequence | integer | not null
workflow_id | integer | not null
Indexes:
"processes_milestone_pkey" PRIMARY KEY, btree (id)
"processes_milestone_workflow_id_21e7e70ae59594a8_uniq" UNIQUE CONSTRAINT, btree (workflow_id, sequence)
"processes_milestone_workflow_id_363216929a08f11e_uniq" UNIQUE CONSTRAINT, btree (workflow_id, name)
"processes_milestone_846c77cf" btree (workflow_id)
Check constraints:
"processes_milestone_sequence_check" CHECK (sequence >= 0)
Foreign-key constraints:
"processes_workflow_id_53b7557aa3f3378e_fk_processes_workflow_id" FOREIGN KEY (workflow_id) REFERENCES processes_workflow(id) DEFERRABLE INITIALLY DEFERRED
scorecard=# \d processes_process
Table "public.processes_process"
Column | Type | Modifiers
-----------+-----------------------+----------------------------------------------------------------
id | integer | not null default nextval('processes_process_id_seq'::regclass)
name | character varying(50) | not null
sequence | integer | not null
sla | smallint |
milestone | boolean | not null
Indexes:
"processes_process_pkey" PRIMARY KEY, btree (id)
"processes_process_milestone_20dc77c2825fcc38_uniq" UNIQUE CONSTRAINT, btree (milestone, name)
"processes_process_milestone_5bb869985140bf86_uniq" UNIQUE CONSTRAINT, btree (milestone, sequence)
Check constraints:
"processes_process_sequence_check" CHECK (sequence >= 0)
"processes_process_sla_check" CHECK (sla >= 0)
Referenced by:
TABLE "collection_implementation" CONSTRAINT "collection__process_id_6461d2ef37b3f126_fk_processes_process_id" FOREIGN KEY (process_id) REFERENCES processes_process(id) DEFERRABLE INITIALLY DEFERRED
我基本上没有想法。看起来它已经是一个整数了，实际上，Django 指定的主键还能是什么？
【问题讨论】：
fwiw，在某些情况下，我必须先删除一个字段，然后在后续迁移中添加不同类型的字段。 这不是一个干净的解决方案，但是有罪的迁移似乎很小，也许您可以手动更改数据库，然后伪造迁移？ 继 Brandon 的评论之后，我通过删除该字段然后在后续迁移中再次添加相同的字段来修复它。 【参考方案1】：问题是从作为布尔字段的 Process.milestone 迁移到作为外键的 Process.milestone。 Postgres 不会等待迁移在不可转换的数据上失败。它想要一个规则来提前改变表格。
如果您不打算在两个字段之间进行任何类型的数据迁移，最简单的选择是简单地删除并添加该字段。在这种特定情况下，这意味着将操作更改如下：
operations = [
migrations.RemoveField(
model_name='process',
name='milestone'
),
migrations.AddField(
model_name='process',
name='milestone',
field=models.ForeignKey(to='processes.Milestone'),
),
migrations.AlterModelOptions(
name='process',
options='ordering': ['milestone', 'sequence'], 'verbose_name_plural': 'processes',
)
]
【讨论】：
【参考方案2】：Postgres 不知道如何将布尔字段转换为整数，即使表是空的。你需要用 using 子句告诉它。在转换为外键之前，您可以使用 SQL 迁移进行整数转换。我不认为没有任何 SQL 就可以做到这一点，django 不知道该怎么做。
ALTER_SQL = '''
ALTER TABLE processes_process ALTER COLUMN milestone TYPE integer USING (
CASE milestone
when TRUE then ...
when FALSE then ...
END
);
'''
class Migration(migrations.Migration):
dependencies = [
('processes', '0002_auto_20150508_2149'),
]
operations = [
migrations.AlterModelOptions(
name='process',
options='ordering': ['milestone', 'sequence'], 'verbose_name_plural': 'processes',
),
migrations.RunSQL(ALTER_SQL, None, [
migrations.AlterField(
model_name='process',
name='milestone',
field=models.IntegerField(),
preserve_default=True,
),
]),
migrations.AlterField(
model_name='process',
name='milestone',
field=models.ForeignKey(to='processes.Milestone'),
),
]
如果表是空的，你也许可以用一个空的 using 子句或一个空的 case 来逃避。
【讨论】：
将 USING 子句添加到 RunSQL 操作并没有解决问题（它仍然抛出相同的错误），但试图找出它出错的地方至少让我更好地了解Django 文档自己解决问题。非常感谢！ 错误是什么？你的 USING 子句是什么？ 错误是完全一样的。我尝试了一个空的 USING 子句并将其设置为 null 为真和假。 @AlexH。什么是“django 文档中更好的部分”：S 谢谢以上是关于Django 1.8 迁移无法将列 ID 转换为整数的主要内容，如果未能解决你的问题，请参考以下文章