migration.py 文件源码

def get_current_revision(self):
        """Return the current revision, usually that which is present
        in the ``alembic_version`` table in the database.

        If this :class:`.MigrationContext` was configured in "offline"
        mode, that is with ``as_sql=True``, the ``starting_rev``
        parameter is returned instead, if any.

        """
        if self.as_sql:
            return self._start_from_rev
        else:
            if self._start_from_rev:
                raise util.CommandError(
                    "Can't specify current_rev to context "
                    "when using a database connection")
            self._version.create(self.connection, checkfirst=True)
        return self.connection.scalar(self._version.select())