MongoDB How to remove value from array if exist otherwise add

Question

I have document

 {
    "_id" : ObjectId("5aebf141a805cd28433c414c"),
    "forumId" : ObjectId("5ae9f82989f7834df037cc90"),
    "userName" : "Name",
    "usersLike" : [ 
        "1","2"
    ],
    "comment" : "Comment",
}

I want to remove value from usersLike array if the value exists, or add if the value does not exist.

Eg:

If I try to push 1 into usersLike, it should return

{
    "_id" : ObjectId("5aebf141a805cd28433c414c"),
    "forumId" : ObjectId("5ae9f82989f7834df037cc90"),
    "userName" : "Name",
    "usersLike" : [ 
        "2"
    ],
    "comment" : "Comment",
}

How can I query it..??

Value exists as in? The array usersLike exists or a particular value should exist in usersLike? — Sivaprasanna Sethuraman
– Sivaprasanna Sethuraman, Commented May 4, 2018 at 7:04
If the value 1 exists in the array usersLike it should be removed. Otherwise, the value 1 should be added to the array usersLike. — sudhin
– sudhin, Commented May 4, 2018 at 7:45
I think more to the point here is why would you not know it exists? If you are trying to build something like "this site" or "likes" on facebook for example, then the data in the page actually knows the current user already has a vote. So if I "upvote" this question, and then come back to this page later, part of the page data includes the record of "my vote", so before I even send a request to vote again I can already tell I have voted, hence no need to send the request. — Neil Lunn
– Neil Lunn, Commented May 4, 2018 at 7:51
I think you're trying to "blind toggle" such values under just those circumstances, but it's not really the correct approach. As stated, your "client" should already know if a user has voted/liked. For a bit more detail, see How to Model a “likes” voting system with MongoDB. — Neil Lunn
– Neil Lunn, Commented May 4, 2018 at 7:52

Tom Slabbaert · Accepted Answer · 2020-06-19 09:58:09Z

6

MongoDB version 4.2+ introduces pipelined update. Which means we can now use aggregation operators while updating. this gives us a lot of power.

db.collection.updateOne(
    {
        _id: ObjectId("597afd8200758504d314b534")
    },
    [
        {
            $set: {
                usersLike: {
                    $cond: [
                        {
                            $in: ["1", "$usersLike"]
                        },
                        {
                            $setDifference: ["$usersLike", ["1"]]
                        },
                        {
                            $concatArrays: ["$usersLike", ["1"]]
                        }
                    ]
                }
            }
        }
    ]
)

edited Jun 19, 2020 at 9:58

answered Jun 19, 2020 at 9:41

Tom Slabbaert

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Comments

whoami - fakeFaceTrueSoul · Accepted Answer · 2019-12-30 16:36:26Z

0

Mongodb doesn't support conditional push or pull update. However you can still do it by using find:

 db.collectionName.find({_id:ObjectId("597afd8200758504d314b534"),usersLike:{$in:["1"]}}).pretty()

if id exist in usersLike than pull else push.

Or you use the update query to pull as:

db.collectionName.update({
    _id: ObjectId("597afd8200758504d314b534"),
    usersLike: {
        $in: ["1"]
    }
    }, {
        $pull: { 'usersLike': "1" }
    }, { multi: true })

And to push you can use:

db.collectionName.update({
   _id:ObjectId("597afd8200758504d314b534"), 
   usersLike:{$nin:["1"]
}},{
   $push:{'usersLike':"1"}
}, {multi: true})

edited Dec 30, 2019 at 16:36

whoami - fakeFaceTrueSoul

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answered May 5, 2018 at 7:05

Bhagyashree Sarkar

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Comments

whoami - fakeFaceTrueSoul · Accepted Answer · 2019-12-30 16:38:13Z

0

Try this :

db.collectionName.update({_id:ObjectId("597afd8200758504d314b534")},{$pull:{'usersLike':"1"}}, {multi: true})

edited Dec 30, 2019 at 16:38

whoami - fakeFaceTrueSoul

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answered May 4, 2018 at 13:13

Bhagyashree Sarkar

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3 Comments

Ashh Over a year ago

Can't be done using this query... This query will only extract($pull) the id, can't add($push) and as the question says $push and $pull should be done simultaneously...

Bhagyashree Sarkar Over a year ago

Mongodb doesn't support conditional push or pull update. However you can still do it by using find (db.collectionName.find({_id:ObjectId("597afd8200758504d314b534"),usersLike:{$in:["1"]}}).pretty()) , if id exist in usersLike than pull else push.

Ashh Over a year ago

yes it can be done... but he wants it in a single query, which is not possible

keikai · Accepted Answer · 2020-05-05 09:55:06Z

0

Try this

if db.collectionName.find({'_id':ObjectId("5aebf141a805cd28433c414c"),'usersLike:{'$in:['1']}}).count() > 0:

    db.collectionName.update({'_id':ObjectId("5aebf141a805cd28433c414c")},{'$pull':{'usersLike':'1'}})

else:
    db.collectionName.update({'_id':ObjectId("5aebf141a805cd28433c414c")},{'$addToSet':{'usersLike':'1'}})

edited May 5, 2020 at 9:55

keikai

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answered May 5, 2020 at 9:32

Sarathkumar Shrinivasa

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