PyMongo：在 arrays 数组中拉取一个 object

Question

Let's say I have a collection that looks like this (essentially a double-nested array holding objects):

{ 
  'customer': 'bob',
  'products': [
   {
     'id': 5,
     'variants': [
       {'name': 'blue',
       'id': 23},
       {'name': 'orange',
       'id': 13},
       {'name': 'green',
       'id': 53},
      ]    
   }
  ]
},
{ 
  'customer': 'dylan',
  'products': [
   {
     'id': 5,
     'variants': [
       {'name': 'blue',
       'id': 23},
       {'name': 'green',
       'id': 53},
      ]    
   }
  ]
}

I would like to remove all variants whose id is in the following: [23, 53] for only bob

{ 
  'customer': 'bob',
  'products': [
   {
     'id': 5,
     'variants': [ 
       {'name': 'orange',
       'id': 13}, 
      ]    
   }
  ]
},
{ 
  'customer': 'dylan',
  'products': [
   {
     'id': 5,
     'variants': [
       {'name': 'blue',
       'id': 23},
       {'name': 'green',
       'id': 53},
      ]    
   }
  ]
}

I have the following, however it also removes all variants for dylan :

db.update({'$and': [{'user': 'bob'}, {'products': {'$elemMatch': {'id': 5}}}]}, {'$pull': {'products.$[].variants': {'id': {'$in': [23, 53]}}}}, False, True)

Any ideas on how to approach this?

Answer 1

It's not clear if you are dealing with one or two records here; I've assumed two. Don't use update() - it's deprected - use update_one() or update_many() ; and you're querying on a user field that doesn't exist.

Given all that, try:

db.mycollection.update_one({'customer': 'bob', 'products.variants.id': {'$in': [23, 53]}},
                           {'$pull': {'products.$.variants': {'id': {'$in': [23, 53]}}}})

Full example:

from pymongo import MongoClient
import json

db = MongoClient()['mydatabase']

db.mycollection.insert_many([
    {
        'customer': 'bob',
        'products': [
            {
                'id': 5,
                'variants': [
                    {'name': 'blue',
                     'id': 23},
                    {'name': 'orange',
                     'id': 13},
                    {'name': 'green',
                     'id': 53},
                ]
            }
        ]
    },
    {
        'customer': 'dylan',
        'products': [
            {
                'id': 5,
                'variants': [
                    {'name': 'blue',
                     'id': 23},
                    {'name': 'green',
                     'id': 53},
                ]
            }
        ]
    }]
)

db.mycollection.update_one({'customer': 'bob', 'products.variants.id': {'$in': [23, 53]}},
                           {'$pull': {'products.$.variants': {'id': {'$in': [23, 53]}}}})

for item in db.mycollection.find({'customer': 'bob'}, {'_id': 0}):
    print(json.dumps(item, indent=4))

prints:

{
    "customer": "bob",
    "products": [
        {
            "id": 5,
            "variants": [
                {
                    "name": "orange",
                    "id": 13
                }
            ]
        }
    ]
}