migrations.py 文件源码

def get_current_version_from_table():
    """
    Return the current version of the database, from sql_version table.
    Return None if the table does not exist (schema not inited).
    """
    with connection.cursor() as cursor:
        try:
            cursor.execute("SELECT version_num FROM sql_version;")
        except ProgrammingError:
            # table does not exist ?
            return None

        rows = cursor.fetchall()

    versions = [row[0] for row in rows if is_version(row[0])]
    if not versions:
        return None

    # sort versions
    versions.sort(key=StrictVersion)

    # return the last one
    return versions[-1]