Running our First Migration

运行我们的第一次迁移

We now want to run our migration. Assuming our database is totally clean, it’s as yet unversioned. The alembic upgrade command will run upgrade operations, proceeding from the current database revision, in this example None, to the given target revision. We can specify 1975ea83b712 as the revision we’d like to upgrade to, but it’s easier in most cases just to tell it “the most recent”, in this case head:

我们现在想要运行我们的迁移。 假设我们的数据库完全干净，它还没有版本化。 alembic upgrade 命令将运行升级操作，从当前数据库修订版（在本例中为“None”）到给定的目标修订版。 我们可以指定 1975ea83b712 作为我们想要升级到的修订版，但在大多数情况下，告诉它“最新的”更容易，在这种情况下是 head：

$ alembic upgrade head
INFO  [alembic.context] Context class PostgresqlContext.
INFO  [alembic.context] Will assume transactional DDL.
INFO  [alembic.context] Running upgrade None -> 1975ea83b712

Wow that rocked! Note that the information we see on the screen is the result of the logging configuration set up in alembic.ini - logging the alembic stream to the console (standard error, specifically).

哇，震撼！ 请注意，我们在屏幕上看到的信息是在 alembic.ini 中设置的日志配置的结果 - 将 alembic 流记录到控制台（特别是标准错误）。

The process which occurred here included that Alembic first checked if the database had a table called alembic_version, and if not, created it. It looks in this table for the current version, if any, and then calculates the path from this version to the version requested, in this case head, which is known to be 1975ea83b712. It then invokes the upgrade() method in each file to get to the target revision.

此处发生的过程包括 Alembic 首先检查数据库是否有名为“alembic_version”的表，如果没有，则创建它。 它在此表中查找当前版本（如果有），然后计算从该版本到请求版本的路径，在本例中为 head，已知为 1975ea83b712。 然后它调用每个文件中的 upgrade() 方法以获取目标修订版。