Django+MongoDB mysql改写

一个文档管理系统，本来数据库用的是mysql，但是现在需要改为mongodb数据库，对mongodb不熟悉，求求大佬们指导一下小弟都需要改写什么，我只在settings.py里面连接了数据库，具体在models.py里怎么改写。

settings.py

DATABASES = {
    'default': {
        'ENGINE': None,
        # 'ENGINE': 'django.db.backends.mysql',
        # 'NAME': 'test1',
        # 'USER': 'root',
        # 'PASSWORD': 'root',
        # 'HOST': '127.0.0.1',
    }
}
from mongoengine import connect
connect('test')

models.py(files)

from datetime import datetime
from mongoengine import *
from django.db import models


# 文件model
class File(models.Model):
    fileno = models.CharField(max_length=18, verbose_name='文件编号')
    filename = models.CharField(max_length=200, verbose_name='文件名称')
    filepath = models.CharField(max_length=200, verbose_name='文件路径')
    owner = models.CharField(max_length=30, verbose_name='文件所属用户')
    add_time = models.DateTimeField(default=datetime.now, verbose_name='上传时间')
    first_check = models.CharField(max_length=1, choices=(('0', '未审批'), ('1', '已审批')), verbose_name='初审', default='0')
    second_check = models.CharField(max_length=1, choices=(('0', '未审批'), ('1', '已审批')), verbose_name='二审', default='0')
    isapprove = models.CharField(max_length=1, choices=(('0', '未审批'), ('1', '已审批'), ('2', '已驳回')), verbose_name='终审', default='0')

    class Meta:
        verbose_name = '文件'
        verbose_name_plural = verbose_name

    def __str__(self):
        return self.filename


# 文件审批日志model
class ApproveLog(models.Model):
    fileno = models.CharField(max_length=18, verbose_name='文件编号')
    filename = models.CharField(max_length=200, verbose_name='文件名称')
    owner = models.CharField(max_length=30, verbose_name='文件所属用户')
    add_time = models.DateTimeField(verbose_name='上传时间')
    isapprove = models.CharField(max_length=1, choices=(('1', '已审批'), ('2', '已驳回')), verbose_name='终审')
    approve_time = models.DateTimeField(default=datetime.now, verbose_name='审批时间')

    class Meta:
        verbose_name = '文件审批日志'
        verbose_name_plural = verbose_name

    def __str__(self):
        return self.filename


# 公用电脑ip地址model
class PublicIp(models.Model):
    host_ip = models.CharField(max_length=300, verbose_name='公用电脑ip地址', blank=True)

    class Meta:
        verbose_name = '公用电脑ip地址'
        verbose_name_plural = verbose_name

    def __str__(self):
        return self.host_ip

models.py(users)

from datetime import datetime

from django.db import models
from django.contrib.auth.models import AbstractUser

# 定义用户模型，添加额外的字段
class UserProfile(AbstractUser):
    userno = models.CharField(max_length=15, verbose_name='工号')
    department = models.CharField(max_length=15, verbose_name='部门', blank=True)
    role = models.CharField(max_length=1, choices=(('3', '监察稽核员'), ('2', '系统管理员'),
                                                   ('1', '普通员工'), ('0', '离职员工')),
                            verbose_name='用户角色', default='1')
    sub_role = models.CharField(max_length=1, choices=(('2', '二审员'), ('1', '初审员'), ('0', '')),
                                verbose_name='子角色', default='0')
    is_superuser = models.IntegerField(verbose_name='超级管理员', default=0)
    add_time = models.DateTimeField(default=datetime.now, verbose_name='添加时间')

    class Meta:
        verbose_name = '用户信息'
        verbose_name_plural = verbose_name

    def __str__(self):
        return self.username


# 定义用户操作日志模型
class UserOperateLog(models.Model):
    userno = models.CharField(max_length=15, verbose_name='工号')
    username = models.CharField(max_length=20, verbose_name='姓名')
    type = models.CharField(max_length=20, verbose_name='操作类型')
    comment = models.CharField(max_length=20, verbose_name='备注')
    fileno = models.CharField(max_length=18, verbose_name='文件编号')
    filename = models.CharField(max_length=200, verbose_name='文件名称')
    modify_time = models.DateTimeField(default=datetime.now, verbose_name='操作时间')

    class Meta:
        verbose_name = '用户操作日志'
        verbose_name_plural = verbose_name

    def __str__(self):
        return self.username + '.' + self.type