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[英]difference between objects.create() and object.save() in django orm
[英]orm['model'].objects.create(attr=some_value) causes IntegrityError
我的模型Backlog和Entity之間存在一對一的正向關系。 每個積壓都有一個實體。 如果積壓的東西缺少一個(在數據庫中不存在),我的代碼將嘗試創建一個實體,並將其鏈接到缺失該實體的積壓。
new_entity = orm['entities.entity'].objects.create(long_name=entity_name)
if entity_short_name is not None and entity_short_name != '':
new_entity.name = entity_short_name
if entity_url is not None:
new_entity.primary_url = entity_url
new_entity.save()
backlog.entity = new_entity
backlog.save()
每個實體對象都有一個稱為guid的唯一ID。 這是我在上面的代碼上得到的錯誤:
django.db.utils.IntegrityError: duplicate key value violates unique constraint "entities_entity_guid_uniq"
DETAIL: Key (guid)=(2f49223d-8732-4582-b8a1-7015f515134a) already exists.
實體模型只有一個唯一的鍵:
guid = models.CharField('A globally unique identifier', default = lambda: str(uuid.uuid4()), unique = True, db_index = True)
是什么導致此完整性錯誤? 檢查數據庫中是否存在具有此GUID的實體,返回None
** orm是從db獲取對象的標准Django orm
File "./manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 399, in execute_from_command_line
utility.execute()
File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 392, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 242, in run_from_argv
self.execute(*args, **options.__dict__)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 285, in execute
output = self.handle(*args, **options)
File "/usr/local/lib/python2.7/dist-packages/south/management/commands/migrate.py", line 111, in handle
ignore_ghosts = ignore_ghosts,
File "/usr/local/lib/python2.7/dist-packages/south/migration/__init__.py", line 220, in migrate_app
success = migrator.migrate_many(target, workplan, database)
File "/usr/local/lib/python2.7/dist-packages/south/migration/migrators.py", line 254, in migrate_many
result = migrator.__class__.migrate_many(migrator, target, migrations, database)
File "/usr/local/lib/python2.7/dist-packages/south/migration/migrators.py", line 329, in migrate_many
result = self.migrate(migration, database)
File "/usr/local/lib/python2.7/dist-packages/south/migration/migrators.py", line 133, in migrate
result = self.run(migration, database)
File "/usr/local/lib/python2.7/dist-packages/south/migration/migrators.py", line 114, in run
return self.run_migration(migration, database)
File "/usr/local/lib/python2.7/dist-packages/south/migration/migrators.py", line 84, in run_migration
migration_function()
File "/usr/local/lib/python2.7/dist-packages/south/migration/migrators.py", line 60, in <lambda>
return (lambda: direction(orm))
File "/usr/local/PATH/0123__.py", line 69, in forwards
new_entity = orm['entities.entity'].objects.create(long_name=entity_name)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/manager.py", line 157, in create
return self.get_queryset().create(**kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 322, in create
obj.save(force_insert=True, using=self.db)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/base.py", line 545, in save
force_update=force_update, update_fields=update_fields)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/base.py", line 573, in save_base
updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/base.py", line 654, in _save_table
result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/base.py", line 687, in _do_insert
using=using, raw=raw)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/manager.py", line 232, in _insert
return insert_query(self.model, objs, fields, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 1514, in insert_query
return query.get_compiler(using=using).execute_sql(return_id)
File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/compiler.py", line 903, in execute_sql
cursor.execute(sql, params)
File "/usr/local/lib/python2.7/dist-packages/django/db/backends/util.py", line 69, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
File "/usr/local/lib/python2.7/dist-packages/django/db/backends/util.py", line 53, in execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python2.7/dist-packages/django/db/utils.py", line 99, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/usr/local/lib/python2.7/dist-packages/django/db/backends/util.py", line 53, in execute
return self.cursor.execute(sql, params)
django.db.utils.IntegrityError: duplicate key value violates unique constraint "entities_entity_guid_uniq"
DETAIL: Key (guid)=(2f49223d-8732-4582-b8a1-7015f515134a) already exists.
guid
字段的問題在於,您將可調用uuid.uuid4()
的結果設置為默認值,而不是僅設置每次創建新對象時都會調用的可調用項,以修復:
def get_unique_id():
return str(uuid.uuid4())
guid = models.CharField('A globally unique identifier', default=get_unique_id, unique=True, db_index=True)
不要忘記運行makemigrations
並在此更改后進行migrate
。
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