flask 迁移 "ValueError: Constraint must have a name"

Question

我创建了一个 flask 迁移脚本，但是，当我运行升级功能时，出现以下错误:

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###

Answer 1

这是正常的，因为 SQLite3 不支持 ALTER 表。
您可以通过 render_as_batch=True在像这样的 Flask-Migrate 实例化过程中:migrate = Migrate(app,db,render_as_batch=True)不需要修改env Flask-Migrate 的文件。
此外，为了完全避免您的 future 迁移问题，您可以为 SQLAlchemy 元数据的所有类型的约束创建一个约束命名模板，然后我认为您将获得一致的名称。
在 Flask-SQLAlchemy 中查看如何执行此操作文档。为方便起见，我正在从以下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)