Integration of Naming Conventions into Operations, Autogenerate

As of Alembic 0.6.4, the naming convention feature is integrated into the Operations object, so that the convention takes effect for any constraint that is otherwise unnamed. The naming convention is passed to Operations using the MigrationsContext.configure.target_metadata parameter in env.py, which is normally configured when autogenerate is used:

从 Alembic 0.6.4 开始，命名约定功能集成到 Operations 对象中，因此约定对任何未命名的约束生效。 命名约定使用 env.py 中的 MigrationsContext.configure.target_metadata 参数传递给 Operations ，通常在使用 autogenerate 时配置：

# in your application's model:

meta = 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"
      })
Base = declarative_base(metadata=meta)

# .. in your Alembic env.py:

# add your model's MetaData object here
# for 'autogenerate' support
from myapp import mymodel
target_metadata = mymodel.Base.metadata

# ...

def run_migrations_online():

    # ...

    context.configure(
                connection=connection,
                target_metadata=target_metadata
                )

Above, when we render a directive like the following:

以上，当我们渲染一个指令时：

op.add_column('sometable', Column('q', Boolean(name='q_bool')))

The Boolean type will render a CHECK constraint with the name "ck_sometable_q_bool", assuming the backend in use does not support native boolean types.

假设使用的后端不支持原生布尔类型，布尔类型将呈现名为 “ck_sometable_q_bool” 的 CHECK 约束。

We can also use op directives with constraints and not give them a name at all, if the naming convention doesn’t require one. The value of None will be converted into a name that follows the appropriate naming conventions:

如果命名约定不需要，我们也可以使用带有约束的 op 指令而不给它们命名。 None 的值将转换为遵循适当命名约定的名称：

def upgrade():
    op.create_unique_constraint(None, 'some_table', 'x')

When autogenerate renders constraints in a migration script, it renders them typically with their completed name. If using at least Alembic 0.6.4 as well as SQLAlchemy 0.9.4, these will be rendered with a special directive Operations.f() which denotes that the string has already been tokenized:

当自动生成在迁移脚本中呈现约束时，它通常使用完整的名称呈现它们。 如果至少使用 Alembic 0.6.4 和 SQLAlchemy 0.9.4，这些将使用特殊指令 Operations.f() 呈现，表示字符串已经被标记：

def upgrade():
    op.create_unique_constraint(op.f('uq_const_x'), 'some_table', 'x')

For more detail on the naming convention feature, see Configuring Constraint Naming Conventions.

有关命名约定功能的更多详细信息，请参阅配置约束命名约定。