Example migrate script for Django

gistfile1.py

'''
Created on Oct 29, 2012

@author: jacobg
'''

from django.contrib.auth.decorators import login_required
from django.shortcuts import render_to_response
from django.template import RequestContext
from django.views.decorators.http import require_GET
from myapp.models import Employee
from myapp.decorators import app_admin_required
import logging

def _get_task_name():
    return 'index-employees' #__name__

def _get_model():
    return Employee

def _get_first_item():
    return _get_model().objects.all().order_by('id')[0]

def _get_item_filter_from_id(item_id):
    return _get_model().objects.filter(id__gte=item_id).order_by('id')

def _process_item(item):

    employee = item

    employee.save()

@require_GET
@login_required
@app_admin_required
def migrate_handler(request):
    
    items_per_task = 100 # default
    task_name = _get_task_name()
    
    item_id = request.GET.get('id')
    if item_id is not None:
        item_id = int(item_id)
    else:
        # First request, just get the first item out of the datastore.
        item = _get_first_item()
        item_id = item.id

    # check whether user only wants one task
    stop = request.GET.get('stop', 'no') == 'yes'
    if stop:
        
        # check if query string sets different limit to items for this task.
        # as the code demonstrates, this is only supported when we are using
        # one task
        limit = request.GET.get('limit')
        if limit is not None:
            items_per_task = int(limit)
        
    # process items_per_task at a time, plus look ahead 1 entity to get next id to process
    items = _get_item_filter_from_id(item_id)[:items_per_task+1]
    item_count = items.count()

    if item_count == items_per_task+1:
        next_id = items[items_per_task-1].id if not stop else None
        item_count = items_per_task
    else:
        next_id = None
                
    for item in items:
        _process_item(item)

    next_url = None
    if next_id is not None:
        next_url = '/migrate/%s?id=%d' % (task_name, next_id)

    context = {
        'task_name': task_name,
        'item_id': item_id,
        'item_count': item_count,
        'next_item_id': next_id,
        'next_url': next_url
    }
    
    logging.info('%s.migrate_handler: started at id %d, queued task containing %d item(s), next id is %s' % (task_name, item_id, item_count, str(next_id)))
    
    return render_to_response('migrate/redirecting_migrator.html', context, context_instance=RequestContext(request))