Flask Migrate "ValueError: Constraint must have a name"
Flask Migrate "ValueError: Constraint must have a name"
我已经创建了一个 flask 迁移脚本，但是，当我 运行 升级功能时，我得到以下错误：
INFO [alembic.runtime.migration] Context impl SQLiteImpl.
INFO [alembic.runtime.migration] Will assume non-transactional DDL.
INFO [alembic.runtime.migration] Running upgrade -> 6378428b838a, empty message
Traceback (most recent call last):
File "migrate.py", line 22, in <module>
manager.run()
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/flask_script/__init__.py", line 417, in run
result = self.handle(argv[0], argv[1:])
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/flask_script/__init__.py", line 386, in handle
res = handle(*args, **config)
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/flask_script/commands.py", line 216, in __call__
return self.run(*args, **kwargs)
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/flask_migrate/__init__.py", line 95, in wrapped
f(*args, **kwargs)
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/flask_migrate/__init__.py", line 280, in upgrade
command.upgrade(config, revision, sql=sql, tag=tag)
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/alembic/command.py", line 298, in upgrade
script.run_env()
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/alembic/script/base.py", line 489, in run_env
util.load_python_file(self.dir, "env.py")
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/alembic/util/pyfiles.py", line 98, in load_python_file
module = load_module_py(module_id, path)
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/alembic/util/compat.py", line 173, in load_module_py
spec.loader.exec_module(module)
File "<frozen importlib._bootstrap_external>", line 728, in exec_module
File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
File "migrations/env.py", line 96, in <module>
run_migrations_online()
File "migrations/env.py", line 90, in run_migrations_online
context.run_migrations()
File "<string>", line 8, in run_migrations
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/alembic/runtime/environment.py", line 846, in run_migrations
self.get_context().run_migrations(**kw)
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/alembic/runtime/migration.py", line 518, in run_migrations
step.migration_fn(**kw)
File "/Users/slatifi/git/StaffTrainingLog/migrations/versions/6378428b838a_.py", line 23, in upgrade
batch_op.create_foreign_key(None, 'organisation', ['organisation'], ['id'])
File "/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.7/lib/python3.7/contextlib.py", line 119, in __exit__
next(self.gen)
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/alembic/operations/base.py", line 325, in batch_alter_table
impl.flush()
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/alembic/operations/batch.py", line 106, in flush
fn(*arg, **kw)
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/alembic/operations/batch.py", line 390, in add_constraint
raise ValueError("Constraint must have a name")
ValueError: Constraint must have a name
我见过其他人有同样的错误，他们只是将 render_as_batch 添加到 env.py 文件中。我这样做了，但我仍然遇到同样的错误。有什么想法吗？
注意：这是我在env.py文件中所做的修改：
with connectable.connect() as connection:
context.configure(
connection=connection,
target_metadata=target_metadata,
process_revision_directives=process_revision_directives,
**current_app.extensions['migrate'].configure_args,
render_as_batch=True
)
这是迁移创建的升级脚本
from alembic import op
import sqlalchemy as sa
# revision identifiers, used by Alembic.
revision = '2838e3e96536'
down_revision = None
branch_labels = None
depends_on = None
def upgrade():
# ### commands auto generated by Alembic - please adjust! ###
with op.batch_alter_table('user', schema=None) as batch_op:
batch_op.add_column(sa.Column('organisation', sa.String(length=5), nullable=False))
batch_op.create_foreign_key(None, 'organisation', ['organisation'], ['id'])
# ### end Alembic commands ###
def downgrade():
# ### commands auto generated by Alembic - please adjust! ###
with op.batch_alter_table('user', schema=None) as batch_op:
batch_op.drop_constraint(None, type_='foreignkey')
batch_op.drop_column('organisation')
# ### en
d Alembic 命令###
这很正常，因为 SQLite3 不支持 ALTER 表。
您可以像这样在 Flask-Migrate 实例化期间传递 render_as_batch=True :
migrate = Migrate(app,db,render_as_batch=True)
不需要修改 Flask-Migrate 的 env 文件。
此外，为了完全避免未来迁移的问题，您可以为 SQLAlchemy 元数据的所有类型的约束创建约束命名模板，然后我认为您将获得一致的名称。
在 Flask-SQLAlchemy 文档中查看如何执行此操作。为了您的方便，我正在从下面的文档中复制代码示例：
from sqlalchemy import MetaData
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
convention = {
"ix": 'ix_%(column_0_label)s',
"uq": "uq_%(table_name)s_%(column_0_name)s",
"ck": "ck_%(table_name)s_%(constraint_name)s",
"fk": "fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s",
"pk": "pk_%(table_name)s"
}
metadata = MetaData(naming_convention=convention)
db = SQLAlchemy(app, metadata=metadata)
安装 Flask-Migrate 有助于避免代码引用 declarative_base 或修改 env.py 文件。
对于带有应用工厂的应用，在 extensions.py 和 __init__.py 文件之间拆分元数据分配和 db 启动。
extensions.py:
from sqlalchemy import MetaData
from flask_sqlalchemy import SQLAlchemy
metadata = MetaData(
naming_convention={
"ix": 'ix_%(column_0_label)s',
"uq": "uq_%(table_name)s_%(column_0_name)s",
"ck": "ck_%(table_name)s_%(constraint_name)s",
"fk": "fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s",
"pk": "pk_%(table_name)s"
}
)
db=SQLAlchemy(metadata=metadata)
__init__.py:
from flask import Flask, Blueprint
from config import ...
from flask_migrate import Migrate
from extensions import db
...
def create_app():
app = Flask(__name__,
template_folder='../app/templates')
app.config.from_object(config[...])
config[...].init_app(app)
db.init_app(app)
with app.app_context():
db.create_all()
migrate = Migrate(app, db)
...
from .templates.main import main
app.register_blueprint(main)
return app
其他答案显示了如何配置 Flask 以在将来使用命名约束，但这并没有解决 的问题在 Alembic 迁移中删除 现有未命名约束。要处理任何现有的未命名约束，您还需要在迁移脚本中定义命名约定，如 Alembic docs.
中所述
例如，假设您正在尝试执行将 ON DELETE CASCADE 添加到 test table 中现有外键的迁移。如果您遵循其他答案之一（例如 https://whosebug.com/a/62651160/470844）并将 naming_convention 添加到 Flask 初始化脚本，那么 flask db upgrade 将生成如下内容：
def upgrade():
with op.batch_alter_table('test', schema=None) as batch_op:
batch_op.drop_constraint(None, type_='foreignkey')
batch_op.create_foreign_key(batch_op.f('fk_test_user_id_user'), 'user', ['user_id'], ['id'], ondelete='CASCADE')
请注意，虽然 create_foreign_key 调用使用约束名称（即 fk_test_user_id_user），但 drop_constraint 调用仍使用 None 作为约束名称，这将导致ValueError: Constraint must have a name 这个问题的标题有误。
要解决此问题，您需要编辑迁移以使用 naming_convention，并将 None 替换为生成的约束名称。例如，您可以将上面的 upgrade 更改为：
naming_convention = {
"ix": 'ix_%(column_0_label)s',
"uq": "uq_%(table_name)s_%(column_0_name)s",
"ck": "ck_%(table_name)s_%(column_0_name)s",
"fk": "fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s",
"pk": "pk_%(table_name)s"
}
def upgrade():
with op.batch_alter_table('test', schema=None, naming_convention=naming_convention) as batch_op:
batch_op.drop_constraint('fk_test_user_id_user', type_='foreignkey')
batch_op.create_foreign_key(batch_op.f('fk_test_user_id_user'), 'user', ['user_id'], ['id'], ondelete='CASCADE')
（在此示例中，您还需要在 运行 迁移脚本时禁用 SQLite 外键支持，例如使用技术 here, to avoid the batch migration itself triggering a cacading delete. The problem is documented here。）
我已经创建了一个 flask 迁移脚本，但是，当我 运行 升级功能时，我得到以下错误：
INFO [alembic.runtime.migration] Context impl SQLiteImpl.
INFO [alembic.runtime.migration] Will assume non-transactional DDL.
INFO [alembic.runtime.migration] Running upgrade -> 6378428b838a, empty message
Traceback (most recent call last):
File "migrate.py", line 22, in <module>
manager.run()
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/flask_script/__init__.py", line 417, in run
result = self.handle(argv[0], argv[1:])
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/flask_script/__init__.py", line 386, in handle
res = handle(*args, **config)
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/flask_script/commands.py", line 216, in __call__
return self.run(*args, **kwargs)
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/flask_migrate/__init__.py", line 95, in wrapped
f(*args, **kwargs)
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/flask_migrate/__init__.py", line 280, in upgrade
command.upgrade(config, revision, sql=sql, tag=tag)
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/alembic/command.py", line 298, in upgrade
script.run_env()
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/alembic/script/base.py", line 489, in run_env
util.load_python_file(self.dir, "env.py")
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/alembic/util/pyfiles.py", line 98, in load_python_file
module = load_module_py(module_id, path)
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/alembic/util/compat.py", line 173, in load_module_py
spec.loader.exec_module(module)
File "<frozen importlib._bootstrap_external>", line 728, in exec_module
File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
File "migrations/env.py", line 96, in <module>
run_migrations_online()
File "migrations/env.py", line 90, in run_migrations_online
context.run_migrations()
File "<string>", line 8, in run_migrations
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/alembic/runtime/environment.py", line 846, in run_migrations
self.get_context().run_migrations(**kw)
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/alembic/runtime/migration.py", line 518, in run_migrations
step.migration_fn(**kw)
File "/Users/slatifi/git/StaffTrainingLog/migrations/versions/6378428b838a_.py", line 23, in upgrade
batch_op.create_foreign_key(None, 'organisation', ['organisation'], ['id'])
File "/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.7/lib/python3.7/contextlib.py", line 119, in __exit__
next(self.gen)
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/alembic/operations/base.py", line 325, in batch_alter_table
impl.flush()
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/alembic/operations/batch.py", line 106, in flush
fn(*arg, **kw)
File "/Users/slatifi/git/StaffTrainingLog/venv/lib/python3.7/site-packages/alembic/operations/batch.py", line 390, in add_constraint
raise ValueError("Constraint must have a name")
ValueError: Constraint must have a name
我见过其他人有同样的错误，他们只是将 render_as_batch 添加到 env.py 文件中。我这样做了，但我仍然遇到同样的错误。有什么想法吗？
注意：这是我在env.py文件中所做的修改：
with connectable.connect() as connection:
context.configure(
connection=connection,
target_metadata=target_metadata,
process_revision_directives=process_revision_directives,
**current_app.extensions['migrate'].configure_args,
render_as_batch=True
)
这是迁移创建的升级脚本
from alembic import op
import sqlalchemy as sa
# revision identifiers, used by Alembic.
revision = '2838e3e96536'
down_revision = None
branch_labels = None
depends_on = None
def upgrade():
# ### commands auto generated by Alembic - please adjust! ###
with op.batch_alter_table('user', schema=None) as batch_op:
batch_op.add_column(sa.Column('organisation', sa.String(length=5), nullable=False))
batch_op.create_foreign_key(None, 'organisation', ['organisation'], ['id'])
# ### end Alembic commands ###
def downgrade():
# ### commands auto generated by Alembic - please adjust! ###
with op.batch_alter_table('user', schema=None) as batch_op:
batch_op.drop_constraint(None, type_='foreignkey')
batch_op.drop_column('organisation')
# ### en
d Alembic 命令###
这很正常，因为 SQLite3 不支持 ALTER 表。
您可以像这样在 Flask-Migrate 实例化期间传递 render_as_batch=True :
migrate = Migrate(app,db,render_as_batch=True)
不需要修改 Flask-Migrate 的 env 文件。
此外，为了完全避免未来迁移的问题，您可以为 SQLAlchemy 元数据的所有类型的约束创建约束命名模板，然后我认为您将获得一致的名称。
在 Flask-SQLAlchemy 文档中查看如何执行此操作。为了您的方便，我正在从下面的文档中复制代码示例：
from sqlalchemy import MetaData
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
convention = {
"ix": 'ix_%(column_0_label)s',
"uq": "uq_%(table_name)s_%(column_0_name)s",
"ck": "ck_%(table_name)s_%(constraint_name)s",
"fk": "fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s",
"pk": "pk_%(table_name)s"
}
metadata = MetaData(naming_convention=convention)
db = SQLAlchemy(app, metadata=metadata)
安装 Flask-Migrate 有助于避免代码引用 declarative_base 或修改 env.py 文件。
对于带有应用工厂的应用，在 extensions.py 和 __init__.py 文件之间拆分元数据分配和 db 启动。
extensions.py:
from sqlalchemy import MetaData
from flask_sqlalchemy import SQLAlchemy
metadata = MetaData(
naming_convention={
"ix": 'ix_%(column_0_label)s',
"uq": "uq_%(table_name)s_%(column_0_name)s",
"ck": "ck_%(table_name)s_%(constraint_name)s",
"fk": "fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s",
"pk": "pk_%(table_name)s"
}
)
db=SQLAlchemy(metadata=metadata)
__init__.py:
from flask import Flask, Blueprint
from config import ...
from flask_migrate import Migrate
from extensions import db
...
def create_app():
app = Flask(__name__,
template_folder='../app/templates')
app.config.from_object(config[...])
config[...].init_app(app)
db.init_app(app)
with app.app_context():
db.create_all()
migrate = Migrate(app, db)
...
from .templates.main import main
app.register_blueprint(main)
return app
其他答案显示了如何配置 Flask 以在将来使用命名约束，但这并没有解决 的问题在 Alembic 迁移中删除 现有未命名约束。要处理任何现有的未命名约束，您还需要在迁移脚本中定义命名约定，如 Alembic docs.
中所述例如，假设您正在尝试执行将 ON DELETE CASCADE 添加到 test table 中现有外键的迁移。如果您遵循其他答案之一（例如 https://whosebug.com/a/62651160/470844）并将 naming_convention 添加到 Flask 初始化脚本，那么 flask db upgrade 将生成如下内容：
def upgrade():
with op.batch_alter_table('test', schema=None) as batch_op:
batch_op.drop_constraint(None, type_='foreignkey')
batch_op.create_foreign_key(batch_op.f('fk_test_user_id_user'), 'user', ['user_id'], ['id'], ondelete='CASCADE')
请注意，虽然 create_foreign_key 调用使用约束名称（即 fk_test_user_id_user），但 drop_constraint 调用仍使用 None 作为约束名称，这将导致ValueError: Constraint must have a name 这个问题的标题有误。
要解决此问题，您需要编辑迁移以使用 naming_convention，并将 None 替换为生成的约束名称。例如，您可以将上面的 upgrade 更改为：
naming_convention = {
"ix": 'ix_%(column_0_label)s',
"uq": "uq_%(table_name)s_%(column_0_name)s",
"ck": "ck_%(table_name)s_%(column_0_name)s",
"fk": "fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s",
"pk": "pk_%(table_name)s"
}
def upgrade():
with op.batch_alter_table('test', schema=None, naming_convention=naming_convention) as batch_op:
batch_op.drop_constraint('fk_test_user_id_user', type_='foreignkey')
batch_op.create_foreign_key(batch_op.f('fk_test_user_id_user'), 'user', ['user_id'], ['id'], ondelete='CASCADE')
（在此示例中，您还需要在 运行 迁移脚本时禁用 SQLite 外键支持，例如使用技术 here, to avoid the batch migration itself triggering a cacading delete. The problem is documented here。）