Autogeneration

Note: this section discusses the internal API of Alembic as regards the autogeneration feature of the alembic revision command. This section is only useful for developers who wish to extend the capabilities of Alembic. For general documentation on the autogenerate feature, please see Auto Generating Migrations.

The autogeneration system has a wide degree of public API, including the following areas:

  1. The ability to do a “diff” of a MetaData object against a database, and receive a data structure back. This structure is available either as a rudimentary list of changes, or as a MigrateOperation structure.
  2. The ability to alter how the alembic revision command generates revision scripts, including support for multiple revision scripts generated in one pass.
  3. The ability to add new operation directives to autogeneration, including custom schema/model comparison functions and revision script rendering.

注意： 本节讨论 Alembic 的内部 API 关于 alembic 修订命令的自动生成功能。 本节仅对希望扩展 Alembic 功能的开发人员有用。 有关自动生成功能的一般文档，请参阅自动生成迁移。

自动生成系统具有广泛的公共API，包括以下领域：

  1. 能够根据数据库对 MetaData 对象进行“比较”，并接收返回的数据结构。 此结构可用作基本更改列表或 MigrateOperation 结构。
  2. 更改 alembic revision 命令生成修订脚本的方式的能力，包括支持一次生成的多个修订脚本。
  3. 向自动生成添加新操作指令的能力，包括自定义模式/模型比较功能和修订脚本渲染。