Merge pull request #48 from pmourlanne/add-k4nar-answer-regarding-iterator-to-readme

Add a FAQ section to the README

Author: Joachim Jablon

README.rst

@@ -54,6 +54,7 @@ You can also use ``values()``:
     you'll have several small queries. This will save your RAM instead, because
     you'll not load a huge queryset result before looping on it.
 
+
 If you want to manipulate the pages directly, you can use `chunkator_page`:
 
 .. code:: python
@@ -63,6 +64,21 @@ If you want to manipulate the pages directly, you can use `chunkator_page`:
     for page in chunkator_page(queryset, 200):
         launch_some_task([item['pk'] for item in page])
 
+
+FAQ
+===
+
+- How is django-chunkator different from Django's `iterator <https://docs.djangoproject.com/en/2.2/ref/models/querysets/#django.db.models.query.QuerySet.iterator>`_?
+
+If you have server-side cursors (using Postgres or Oracle & not setting `DISABLE_SERVER_SIDE_CURSORS`), then the main difference is that the cursor is in the hands of the application instead of the server. It really depends on your constraints, but sometimes server side cursors can put too much strains on your DB.
+
+If you don't have server-side cursors, then chunkator will allow you to iterate over your queryset by batch, without relying on LIMIT/OFFSET. The problem with LIMIT/OFFSET is that computing a large offset (when you're at the end of your queryset) requires the DB to go through all the previous entries. With large tables this can be a huge issue.
+
+- Will django-chunkator preserve the ordering on my querysets?
+
+No, it orders the queryset by pk. However you could do the same thing than chunkator with another field, given that it's unique and not nullable, see `here <https://github.com/peopledoc/django-chunkator/blob/master/chunkator/__init__.py#L27-L33>`_ for more details.
+
+
 License
 =======