我将我的网站从SQLite后端迁移到Postgres后端。我们从项目开始就开始运行本地Django风格的迁移(即不是南方)。大多数迁移运行良好,但我们的应用程序出现了打嗝。
我们在Postgres迁移中得到了这么多。 (所有其他应用程序都已完全迁移。)所有迁移都在SQLite3上无故障运行。
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
这两次迁移正确运行:
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为:
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)
压缩迁移并没有帮助。除表定义外,Postgres数据库是干净的。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。它看起来已经是一个整数,真的,它还有什么期望Django指定的主键?
答案 0 :(得分:21)
问题是从Process.milestone作为布尔字段迁移到Process.milestone作为外键。 Postgres不会等待无法播放数据的迁移失败。它希望规则提前更改表格。
如果您不想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字段。在这种特定情况下,这意味着改变操作如下:
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'},
)
]
答案 1 :(得分:4)
Postgres不知道如何将布尔字段转换为整数,即使该表为空。你需要用using子句告诉它。在转换为外键之前,可以使用SQL迁移进行整数转换。我认为没有任何SQL就有办法做到这一点,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,您可以使用空的using子句或空的case来逃避。