Setting up Multiple Version Directories

设置多版本目录

While optional, it is often the case that when working with multiple bases, we’d like different sets of version files to exist within their own directories; typically, if an application is organized into several sub-modules, each one would have a version directory containing migrations pertinent to that module. So to start out, we can edit alembic.ini to refer to multiple directories; we’ll also state the current versions directory as one of them:

虽然是可选的，但通常情况下，在使用多个基础时，我们希望不同的版本文件集存在于它们自己的目录中； 通常，如果一个应用程序被组织成几个子模块，每个子模块都会有一个版本目录，其中包含与该模块相关的迁移。 因此，首先，我们可以编辑 alembic.ini 来引用多个目录； 我们还将当前的 versions 目录声明为其中之一：

# A separator for the location paths must be defined first.
version_path_separator = os  # Use os.pathsep.
# version location specification; this defaults
# to foo/versions.  When using multiple version
# directories, initial revisions must be specified with --version-path
version_locations = %(here)s/model/networking:%(here)s/alembic/versions

The new directory %(here)s/model/networking is in terms of where the alembic.ini file is, as we are using the symbol %(here)s which resolves to this location. When we create our first new revision targeted at this directory, model/networking will be created automatically if it does not exist yet. Once we’ve created a revision here, the path is used automatically when generating subsequent revision files that refer to this revision tree.

新目录 %(here)s/model/networking 与 alembic.ini 文件的位置有关，因为我们使用符号 %(here)s 来解析该位置。 当我们针对这个目录创建第一个新版本时，如果 model/networking 尚不存在，它将自动创建。 一旦我们在此处创建了修订，在生成引用此修订树的后续修订文件时，将自动使用该路径。