环境：flask+python+sqlite，我想给某个表里某个字段加unique属性
执行 python manage.py db migrate 没报错，执行 python manage.py db upgrade 的时候报错如下
Traceback (most recent call last):
File "manage.py", line , in <module>
manager.run()
File "/app/fusionwork_deployment/venv/lib/python3.6/site-packages/flask_script/__init__.py", line , in run
result = self.handle(argv[], argv[:])
File "/app/fusionwork_deployment/venv/lib/python3.6/site-packages/flask_script/__init__.py", line , in handle
res = handle(*args, **config)
File "/app/fusionwork_deployment/venv/lib/python3.6/site-packages/flask_script/commands.py", line , in __call__
return self.run(*args, **kwargs)
File "/app/fusionwork_deployment/venv/lib/python3.6/site-packages/flask_migrate/__init__.py", line , in wrapped
f(*args, **kwargs)
File "/app/fusionwork_deployment/venv/lib/python3.6/site-packages/flask_migrate/__init__.py", line , in upgrade
command.upgrade(config, revision, sql=sql, tag=tag)
File "/app/fusionwork_deployment/venv/lib/python3.6/site-packages/alembic/command.py", line , in upgrade
script.run_env()
File "/app/fusionwork_deployment/venv/lib/python3.6/site-packages/alembic/script/base.py", line , in run_env
util.load_python_file(self.dir, "env.py")
File "/app/fusionwork_deployment/venv/lib/python3.6/site-packages/alembic/util/pyfiles.py", line , in load_python_file
module = load_module_py(module_id, path)
File "/app/fusionwork_deployment/venv/lib/python3.6/site-packages/alembic/util/compat.py", line , in load_module_py
spec.loader.exec_module(module)
File "<frozen importlib._bootstrap_external>", line , in exec_module
File "<frozen importlib._bootstrap>", line , in _call_with_frames_removed
File "migrations/env.py", line , in <module>
run_migrations_online()
File "migrations/env.py", line , in run_migrations_online
context.run_migrations()
File "<string>", line , in run_migrations
File "/app/fusionwork_deployment/venv/lib/python3.6/site-packages/alembic/runtime/environment.py", line , in run_migrations
self.get_context().run_migrations(**kw)
File "/app/fusionwork_deployment/venv/lib/python3.6/site-packages/alembic/runtime/migration.py", line , in run_migrations
step.migration_fn(**kw)
File "/app/fusionwork_deployment/api/migrations/versions/ce7abee10440_.py", line , in upgrade
batch_op.create_unique_constraint(None, ['ip'])
File "/app/fusionwork_deployment/venv/lib/python3.6/contextlib.py", line , in __exit__
next(self.gen)
File "/app/fusionwork_deployment/venv/lib/python3.6/site-packages/alembic/operations/base.py", line , in batch_alter_table
impl.flush()
File "/app/fusionwork_deployment/venv/lib/python3.6/site-packages/alembic/operations/batch.py", line , in flush
fn(*arg, **kw)
File "/app/fusionwork_deployment/venv/lib/python3.6/site-packages/alembic/operations/batch.py", line , in add_constraint
raise ValueError("Constraint must have a name")
ValueError: Constraint must have a name
解决方案：
在app/__init__.py文件
增加代码
from sqlalchemy import MetaData # 定义命名惯例
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"
}
# db = SQLAlchemy()
db = SQLAlchemy(metadata=MetaData(naming_convention=naming_convention))
检查 migrations/env.py是否有 render_as_batch=True 配置
context.configure(
connection=connection,
target_metadata=target_metadata,
process_revision_directives=process_revision_directives,
compare_type=True, # 检查字段类型
compare_server_default=True, # 比较默认值
render_as_batch=True, # this is new feature,for sqlite alter table
**current_app.extensions['migrate'].configure_args
)
然后把之前迁移产生的版本文件删掉，重新迁移一次，成功。