To find the _id of document other than during insertion

Question

I have created several documents and inserted into Mongo DB.I am using python for the same . Is there a way where in I can get the _id of a particular record? I know that we get the _id during insertion. But if i need to use it at a lateral interval is there a way I can get it by say using the find() command?

what are you trying to do? Each document has an _id, of course you can search for a document and display its _id. — sergiuz, Oct 14 '15 at 23:31
`_id` will be returned as part of the document when you use `find`. — dirn, Oct 14 '15 at 23:31
http://stackoverflow.com/questions/25589113/how-to-select-a-single-field-in-mongodb This link provides the option to return selective fields. Is there any option to retrieve only the id field? @dirn — TheFallenOne, Oct 14 '15 at 23:55
`Collection.findOne(query,{fields: {_id: 1}})` will get you just the `_id` — Michel Floyd, Oct 15 '15 at 02:02

score 0 · Answer 1 · answered Oct 15 '15 at 02:17

0

You can user the projection to get particular field from the document like this

db.collection.find({query},{_id:1}) this will return only _id

http://docs.mongodb.org/manual/reference/method/db.collection.find/

answered Oct 15 '15 at 02:17

Rohit Jain

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score 0 · Answer 2 · answered Oct 28 '15 at 11:11

In python, you can use the find_one() method to get the document and access the _id property as following:

def get_id(value):
    # Get the document with the record:
    document = client.db.collection.find_one({'field': value}, {'_id': True})
    return document['_id']

score 0 · Answer 3 · answered Oct 28 '15 at 12:15

When you insert the record, you can specify the _id value. This has added benefits for when you're using ReplicaSets as well.

from pymongo.objectid import ObjectId

client.db.collection.insert({'_id': ObjectId(), 'key1': value....})

You could store those Ids in a list and use it later on if your requirement for needing the _id occurs immediately after insert.

To find the _id of document other than during insertion

3 Answers3