title: How to save ManyToMany field in second database
body: <p>I have two databases:</p>
  
  <pre><code>DATABASES = {
      'default': {
          'ENGINE': 'django.db.backends.sqlite3',
          'NAME': os.path.join(ROOT_PATH, 'db', 'sqlite.db'),
      },
  
      'slave': {
          'ENGINE': 'django.db.backends.sqlite3',
          'NAME': os.path.join(ROOT_PATH, 'db', 'slave.db'),
      }
  
  }
  </code></pre>
  
  <p>i have table with ManyToMany field:</p>
  
  <pre><code>from django.db import models
  from django.contrib.auth.models import User
  
  class Data(models.Model):
      xml     = models.TextField(max_length=90000)
      users   = models.ManyToManyField(User)
  </code></pre>
  
  <p>when i run code:</p>
  
  <pre><code>for i in Data.objects.all():
      i.save(using='slave')
  </code></pre>
  
  <p>all entry from 'default' database appear in 'slave' without ManyToMany field users.
  How can i explicitly copy users field to 'slave' database?</p>
  
  <p>EDITED:</p>
  
  <p>i try advice from Rohan:</p>
  
  <pre><code>for i in Data.objects.all():
      back_i = i
      # back_i.users.all().count() = 1
      i.save(using='slave')
      # back_i.users.all().count() = 0
      for u in back_i.users.all():
          i.users.add(u)
  </code></pre>
  
  <p>so i think solution is near, but not here</p>