Query in MongoDB (Pymongo) with operator $in using with ObjectId

Question

I have a list of ID's and I want to query a collection based on that list. The field I'm filtering is id_, it is an ObjectID.

Example:

list = ['abcd','mnop','qrst']

I want to search documents that the _id is in that list:

cursor = db.find( {"_id": { "$in": list} }   )
cursor = db.find( {"_id": { "$in": ObjectId(list)} }   )

I tried both options above and none of them worked. The first one returned empty, and the second one throws a type error: TypeError: id must be an instance of (bytes, str, ObjectId), not <class 'list'>

How can I correct my code?

Have you tried something like this for a list of ObjectIds: [ ObjectId('61bde475a216f8027c1379d1'), ...] — prasad_
– prasad_, Commented Dec 22, 2021 at 13:16
It Works. list = [ObjectId(x) for x in list]. Thanks. Feel free to awnser the question — mateusvl
– mateusvl, Commented Dec 22, 2021 at 13:29

mateusvl · Accepted Answer · 2021-12-23 00:56:18Z

1

As @prasad_ said, it is needed to generate the ObjectId from the string.

list_ = ['abcd','mnop','qrst']
list_ = [ObjectId(x) for x in list_]
cursor = db.find( {"_id": { "$in": list_} } )

So the "$in" operator of MongoDB refers to the list that has ObjectId's as its content.

answered Dec 23, 2021 at 0:56

mateusvl

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