MongoDB - Update or Insert object in array

Question

I have the following collection

{
    "_id" : ObjectId("57315ba4846dd82425ca2408"),
    "myarray" : [ 
        {
            userId : ObjectId("570ca5e48dbe673802c2d035"),
            point : 5
        },
        {
            userId : ObjectId("613ca5e48dbe673802c2d521"),
            point : 2
        },        
     ]
}

These are my questions

I want to push into myarray if userId doesn't exist, it should be appended to myarray. If userId exists, it should be updated to point.

I found this

db.collection.update({
    _id : ObjectId("57315ba4846dd82425ca2408"),
    "myarray.userId" :  ObjectId("570ca5e48dbe673802c2d035")
}, {
    $set: { "myarray.$.point": 10 }
})

But if userId doesn't exist, nothing happens.

and

db.collection.update({
    _id : ObjectId("57315ba4846dd82425ca2408")
}, {
  $push: {
      "myarray": {
          userId: ObjectId("570ca5e48dbe673802c2d035"),
          point: 10
      }
  }
})

But if userId object already exists, it will push again.

What is the best way to do this in MongoDB?

For reference, I added my verbose solution to the answer at the following link that covers the same scenario, ie how to add a new object to an array of objects unless a specific object value (eg userId) exists, in which case update the object: stackoverflow.com/a/52671119 — user1063287
– user1063287, Commented Nov 3, 2018 at 12:31

asquirous · Accepted Answer · 2024-05-12 04:49:09Z

36

Try this

db.collection.update(
    { _id : ObjectId("57315ba4846dd82425ca2408")},
    { $pull: {"myarray.userId": ObjectId("570ca5e48dbe673802c2d035")}}
)
db.collection.update(
    { _id : ObjectId("57315ba4846dd82425ca2408")},
    { $push: {"myarray": {
        userId:ObjectId("570ca5e48dbe673802c2d035"),
        point: 10
    }}
)

Explanation:
In the first statement $pull removes the element with userId= ObjectId("570ca5e48dbe673802c2d035") from the array on the document where _id = ObjectId("57315ba4846dd82425ca2408").

In the second one, $push inserts this object { userId:ObjectId("570ca5e48dbe673802c2d035"), point: 10 } in the same array.

edited May 12, 2024 at 4:49

asquirous

53 bronze badges

answered May 25, 2016 at 8:06

Flying Fisher

1,9522 gold badges13 silver badges13 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Diagathe Josué Over a year ago

would be great to explicit what your code does for future readers

Saddam Mohsen Over a year ago

ok , that is greate but in MongoDb the id should inserted automatically whereas you added it manually

Gabriel Lupu Over a year ago

two different cals, a great ideea but expensive.

Yeti · Accepted Answer · 2018-02-28 18:58:06Z

35

The accepted answer by Flying Fisher is that the existing record will first be deleted, and then it will be pushed again.

A safer approach (common sense) would be to try to update the record first, and if that did not find a match, insert it, like so:

// first try to overwrite existing value
var result = db.collection.update(
   {
       _id : ObjectId("57315ba4846dd82425ca2408"),
       "myarray.userId": ObjectId("570ca5e48dbe673802c2d035")
   },
   {
       $set: {"myarray.$.point": {point: 10}}
   }
);
// you probably need to modify the following if-statement to some async callback
// checking depending on your server-side code and mongodb-driver
if(!result.nMatched)
{
    // record not found, so create a new entry
    // this can be done using $addToSet:
    db.collection.update(
        {
            _id: ObjectId("57315ba4846dd82425ca2408")
        },
        {
            $addToSet: {
                myarray: {
                    userId: ObjectId("570ca5e48dbe673802c2d035"),
                    point: 10
                }
            }
        }
    );
    // OR (the equivalent) using $push:
    db.collection.update(
        {
            _id: ObjectId("57315ba4846dd82425ca2408"),
            "myarray.userId": {$ne: ObjectId("570ca5e48dbe673802c2d035"}}
        },
        {
            $push: {
                myarray: {
                    userId: ObjectId("570ca5e48dbe673802c2d035"),
                    point: 10
                }
            }
        }
    );
}

This should also give (common sense, untested) an increase in performance, if in most cases the record already exists, only the first query will be executed.

answered Feb 28, 2018 at 18:58

Yeti

2,8752 gold badges39 silver badges41 bronze badges

2 Comments

Fabio Formosa Over a year ago

What happens if two concurrent requests enter simultaneously into the if-statements? only one of two $addToSet has effect, hasn't it?

Yeti Over a year ago

@FabioFormosa Yeah, but you're right, this is still unsafe. What if meanwhile, not only $addToSet is executed, but also the points are updated... This code should definitely be in a transaction.

tmptplayer · Accepted Answer · 2022-12-30 03:37:40Z

23

There is a option called update documents with aggregation pipeline starting from MongoDB v4.2,

check condition $cond if userId in myarray.userId or not
if yes then $map to iterate loop of myarray array and check condition if userId match then merge with new document using $mergeObjects
if no then $concatArrays to concat new object and myarray

let _id = ObjectId("57315ba4846dd82425ca2408");
let updateDoc = {
  userId: ObjectId("570ca5e48dbe673802c2d035"),
  point: 10
};

db.collection.update(
  { _id: _id },
  [{
    $set: {
      myarray: {
        $cond: [
          { $in: [updateDoc.userId, "$myarray.userId"] },
          {
            $map: {
              input: "$myarray",
              in: {
                $mergeObjects: [
                  "$$this",
                  {
                    $cond: [
                      { $eq: ["$$this.userId", updateDoc.userId] },
                      updateDoc,
                      {}
                    ]
                  }
                ]
              }
            }
          },
          { $concatArrays: ["$myarray", [updateDoc]] }
        ]
      }
    }
  }]
)

Playground

edited Dec 30, 2022 at 3:37

tmptplayer

5091 gold badge7 silver badges22 bronze badges

answered Jan 30, 2021 at 11:48

turivishal

36.4k7 gold badges48 silver badges69 bronze badges

2 Comments

gdollardollar Over a year ago

That's a great way to solve that. I tried to "improve" it by first setting the index of the element to be updated and using that avoid going through the array multiple times. But I can't figure out how to use that index to only update the right element like here. So I'll go with your solution!

MartianMartian Over a year ago

crazy lengthy, is it necessary?...

Fabio Formosa · Accepted Answer · 2020-06-19 21:00:46Z

4

I haven't found any solutions based on a one atomic query. Instead there are 3 ways based on a sequence of two queries:

always $pull (to remove the item from array), then $push (to add the updated item to array)

db.collection.update(
               { _id : ObjectId("57315ba4846dd82425ca2408")},
               { $pull: {"myarray.userId": ObjectId("570ca5e48dbe673802c2d035")}}
)

db.collection.update(
               { _id : ObjectId("57315ba4846dd82425ca2408")},
               {
                 $push: {
                          "myarray": {
                                      userId:ObjectId("570ca5e48dbe673802c2d035"),
                                      point: 10
                                     }
                         }
                }
)

try to $set (to update the item in array if exists), then get the result and check if the updating operation successed or if a $push needs (to insert the item)

var result = db.collection.update(
    {
       _id : ObjectId("57315ba4846dd82425ca2408"),
      "myarray.userId": ObjectId("570ca5e48dbe673802c2d035")
    },
    {
       $set: {"myarray.$.point": {point: 10}}
    }
 );

if(!result.nMatched){
       db.collection.update({_id: ObjectId("57315ba4846dd82425ca2408")},
                            {
                              $addToSet: {
                                           myarray: {
                                              userId: ObjectId("570ca5e48dbe673802c2d035"),
                                              point: 10
                                          }
                            }
       );

always $addToSet (to add the item if not exists), then always $set to update the item in array

   db.collection.update({_id: ObjectId("57315ba4846dd82425ca2408")},
                         myarray: { $not: { $elemMatch: {userId: ObjectId("570ca5e48dbe673802c2d035")} } } },
                        { 
                           $addToSet : {
                                         myarray: {
                                                    userId: ObjectId("570ca5e48dbe673802c2d035"),
                                                    point: 10
                                                   }
                                        }
                         },
                        { multi: false, upsert: false});

   db.collection.update({
                          _id: ObjectId("57315ba4846dd82425ca2408"),
                           "myArray.userId": ObjectId("570ca5e48dbe673802c2d035")
                        },
                        { $set : { myArray.$.point: 10 } },
                        { multi: false, upsert: false});

1st and 2nd way are unsafe, so transaction must be established to avoid two concurrent requests could push the same item generating a duplicate.

3rd way is safer. the $addToSet adds only if the item doesn't exist, otherwise nothing happens. In case of two concurrent requests, only one of them adds the missing item to the array.

edited Jun 19, 2020 at 21:00

answered Sep 25, 2019 at 13:13

Fabio Formosa

1,11410 silver badges31 bronze badges

8 Comments

fluidsonic Over a year ago

How is approach #3 safe? If a concurrent request has modified the array element so that points is no longer 10 then the first call will add a second element for the same userId to the array.

Fabio Formosa Over a year ago

The only race condition would be: the element is not in the array, the first request completes the $addToSet, now the second request runs both updates and finally the first request runs the $set. There will be always one only element (never two!) because only one $addToSet hits! The value of the point field will be the value of the last request that executes the $set. You shouldn't interested to which request executes the $addToSet . So it's a safer way because it doesn't fall in a double insert.

fluidsonic Over a year ago

If an array element exists for the same userId but with a different point value, then a second element for the same userId would be added to the array. The $addToSet approach would only work if 10 is forever the only possible value for point which is unlikely.

fluidsonic Over a year ago

Ah, now I understand what you mean. I have missed the $elemMatch because I didn't scroll far enough. In that case you're right - it should work. You can even use $push instead of $addToSet because you've basically covered the set behavior by the $elemMatch filter.

Fabio Formosa Over a year ago

I've just re-edited that line to avoid the horinzontal scroll that caused the misunderstanding. It could be useful to other people. Thank you a lot for the feedback.

|

Sandesh · Accepted Answer · 2016-05-25 04:49:39Z

3

Unfortunately "upsert" operation is not possible on embedded array. Operators simply do not exist so that this is not possible in a single statement.Hence you must perform two update operations in order to do what you want. Also the order of application for these two updates is important to get desired result.

answered May 25, 2016 at 4:49

Sandesh

1,0445 silver badges13 bronze badges

Comments

Vova Ilemskiy · Accepted Answer · 2022-05-30 12:45:55Z

Possible solution with aggregation pipeline:

db.collection.update(
      { _id },
      [
        {
          $set: {
            myarray: { $filter: {
              input: '$myarray',
              as: 'myarray',
              cond: { $ne: ['$$myarray.userId', ObjectId('570ca5e48dbe673802c2d035')] },
            } },
          },
        },
        {
          $set: {
            myarray: {
              $concatArrays: [
                '$myarray',
                [{ userId: ObjectId('570ca5e48dbe673802c2d035'), point: 10 },
                ],
              ],
            },
          },
        },
      ],
    );

We use 2 stages:

filter myarray (= remove element if userId exist)
concat filtered myarray with new element;

Роман Зыков · Accepted Answer · 2019-03-07 14:55:20Z

0

When you want update or insert value in array try it

Object in db

key:name,
key1:name1,
arr:[
    {
        val:1,
        val2:1
    }
]

Query

var query = {
    $inc:{
        "arr.0.val": 2,
        "arr.0.val2": 2
    }
}
.updateOne( { "key": name }, query, { upsert: true }

key:name,
key1:name1,
arr:[
    {
        val:3,
        val2:3
    }
]

answered Mar 7, 2019 at 14:55

Роман Зыков

6036 silver badges7 bronze badges

Comments

Gagandeep Kalra · Accepted Answer · 2019-11-13 09:43:09Z

-1

array update and create don't mix in under one query, if you care much about atomicity then there's this solution:

normalise your schema to,

{
    "_id" : ObjectId("57315ba4846dd82425ca2408"),
    userId : ObjectId("570ca5e48dbe673802c2d035"),
    point : 5
}

answered Nov 13, 2019 at 9:43

Gagandeep Kalra

1,06514 silver badges13 bronze badges

1 Comment

Gagandeep Kalra Over a year ago

creating or updating this schema document is possible in one query

amota · Accepted Answer · 2021-11-09 03:13:41Z

-2

You could use a variation of the .forEach/.updateOne method I currently use in mongosh CLI to do things like that. In the .forEach, you might be able to set all of your if/then conditions that you mentioned.

Example of .forEach/.updateOne:

let medications = db.medications.aggregate([
  {$match: {patient_id: {$exists: true}}}
]).toArray();

medications.forEach(med => {
  try {
    db.patients.updateOne({patient_id: med.patient_id}, 
      {$push: {medications: med}}
    )
  } catch {
    console.log("Didn't find match for patient_id.  Could not add this med to a patient.")
  }  
})

This may not be the most "MongoDB way" to do it, but it definitely works and gives you the freedom of javascript to do things within the .forEach.

edited Nov 9, 2021 at 3:13

answered Nov 9, 2021 at 3:03

amota

3513 silver badges14 bronze badges

2 Comments

ephemer Over a year ago

This doesn't answer the question, and is very non-idiomatic (why use an aggregation for a simple query in the first lines?). If you're going to use an aggregation, it'd be better to aggregate over the entire collection, perform your updates inline, and then $merge the output with the original collection. But as others have mentioned, the best solution is probably the update + aggregation pipeline syntax from MongoDB 4.2+. Also, it'd be better to use .forEach instead of .toArray on the initial query if you did it this way.

amota Over a year ago

Thanks for the info. Definitely had and still do have a lot to learn with MongoDB operations.

Collectives™ on Stack Overflow

MongoDB - Update or Insert object in array

These are my questions

I found this

and

9 Answers 9

3 Comments

2 Comments

2 Comments

8 Comments

Comments

Comments

Comments

1 Comment

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

These are my questions

I found this

and

9 Answers 9

3 Comments

2 Comments

2 Comments

8 Comments

Comments

Comments

Comments

1 Comment

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related