MongoDB remove object from array deletes complete array

Question

I have a document like this one:

{
        "_id" : 0,
        "name" : "aimee Zank",
        "scores" : [
                {
                        "type" : "exam",
                        "score" : 1.463179736705023
                },
                {
                        "type" : "quiz",
                        "score" : 11.78273309957772
                },
                {
                        "type" : "homework",
                        "score" : 6.676176060654615
                },
                {
                        "type" : "homework",
                        "score" : 35.8740349954354
                }
        ]
}

On that document I want to delete the score that has the lowest score of type homework. First, I'm trying to do it on the mongo shell, so I put the values manually.

 db.students.update({ _id:0}, {$unset: {"scores.score":6.676176060654615} })

That query does nothing, so I tried to search on Google and I found here a question about removing an object from an array and I tried this other query:

db.students.update({ _id:0 }, { $unset: 
                                   { "scores": { 
                                        "homework": 6.676176060654615 } } }, false, true);

The second query worked, but not as I expected because the result was

{ "_id" : 0, "name" : "aimee Zank" }

To check that the lowest value of type homework exists I find with this query:

db.students.find({"scores.score":6.676176060654615}).pretty();

Community · Accepted Answer · 2017-05-23 12:15:48Z

1

If you want to delete/pull only score = 6.676176060654615, you need to simply use following query :

db.collection.update({"_id":0},{"$pull":{"scores":{score: 6.676176060654615}}})

If you want to find minimum value and remove it from your collection. You need to do this is two steps. For more details refer this

edited May 23, 2017 at 12:15

CommunityBot

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answered Jun 13, 2015 at 14:19

Vishwas

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3 Comments

Vishwas Over a year ago

This should work to pull score = 6.676176060654615 . can you check using find query whether score = 6.676176060654615 exists or not?

abaracedo Over a year ago

I edited my question and I added the find that I used to check if exists. Using $min can I get the minimum score of type homework?

abaracedo Over a year ago

I tried again with the query you provied, because it is similar to one from the link you posted.

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