Switch collection in mongoengine for find query

Question

I've read mongoengine documentation about switching collection to save document. And test this code and it worked successfully:

from mongoengine.context_managers import switch_db

class Group(Document):
    name = StringField()

Group(name="test").save()  # Saves in the default db

with switch_collection(Group, 'group2000') as Group:
    Group(name="hello Group 2000 collection!").save()  # Saves in group2000 collection

But the problem is when I want to find saved document in switch collection switch_collection doesn't work at all.

with switch_collection(Group, 'group2000') as GroupT:
    GroupT.objects.get(name="hello Group 2000 collection!")  # Finds in group2000 collection

Can you try specifying the db you are querying that record from? GroupT.objects.using(dbname).filter(name="hello Group 2000 collection!") — Syed Mauze Rehan, Nov 02 '14 at 10:55

score 9 · Answer 1 · edited Sep 21 '15 at 11:03

9

As of mongoengine==0.10.0 mongoengine.context_managers.switch_collection(cls, collection_name) used as "with switch_collection(Group, 'group1') as Group:" in the example doesn't work inside functions. It gives unboundlocalerror. A simple get around with existing resources is :

To get:

new_group = Group.switch_collection(Group(),'group1')
from mongoengine.queryset import QuerySet
new_objects = QuerySet(Group,new_group._get_collection())

Use new_objects.all() to get all objects etc.

To save:

group_obj = Group()
group_obj.switch_collection('group2')
group_obj.save()

edited Sep 21 '15 at 11:03

NoobEditor

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answered Sep 21 '15 at 10:50

Prachetos Sadhukhan

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great, was looking for this. – noPE Sep 21 '15 at 11:29

score 0 · Answer 2 · answered Oct 01 '18 at 09:22

Although Prachetos Sadhukhan answer works for me, I prefer to get the collection directly, not relying on private _get_collection method:

from mongoengine import connection
new_group_collection = connection.get_db()['group1']
from mongoengine.queryset import QuerySet
new_objects = QuerySet(Group, new_group_collection)

Switch collection in mongoengine for find query

2 Answers2

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