push item in sub document

问题

I have simple collection. I want to push item in question, but it gives an exception.How can I resolve it ?

/* 1 */ my collection data

{
    "_id" : ObjectId("557e8c93a6df1a22041e0879"),
    "QuestionCount" : 2.0000000000000000,
    "Questions" : [ 
        {
            "_id" : ObjectId("557e8c9ba6df1a22041e087a"),
            "DataSource" : [],
            "DataSourceItemCount" : NumberLong(0)
        }, 
        {
            "_id" : ObjectId("557e8c9fa6df1a22041e087b"),
            "DataSource" : [],
            "DataSourceItemCount" : NumberLong(0)
        }
    ],
    "Name" : "er"
}

( id =557e8c93a6df1a22041e0879 and question id = 557e8c9fa6df1a22041e087b)

db.getCollection('forms').update({
    "_id": ObjectId("557e8c93a6df1a22041e0879"),
    "Questions._id": ObjectId("557e8c9fa6df1a22041e087b")
}, {
    "$push": {
    "Questions.DataSource": {
        "_id": ObjectId("557e8e5ea6df1a27b403ff6b"),
        "CreationDate": ISODate("2015-06-15T08:35:42.923Z"),
        "IsActive": true,
        "Text": "op",
        "Value": "op"
    }
    }
})

cannot use the part (Questions of Questions.DataSource) to traverse the element ({Questions: [ { _id: ObjectId('557e8c9ba6df1a22041e087a'), CreationDate: new Date(1434356891784), IsActive: true, Name: "uıo", IsRequired: false, QuestionType: 1, AnswerInputType: 1, AnswerValidationPattern: null, AnswerValidationMessage: null, QuestionOrder: 1, DataSource: [], DataSourceItemCount: 0 }, { _id: ObjectId('557e8c9fa6df1a22041e087b'), CreationDate: new Date(1434356895695), IsActive: true, Name: "ıu", IsRequired: false, QuestionType: 2, AnswerInputType: 1, AnswerValidationPattern: null, AnswerValidationMessage: null, QuestionOrder: 2, DataSource: [], DataSourceItemCount: 0 } ]})

回答1:

You need the positional $ operator in your update portion of the statement:

db.getCollection('forms').update(
    { 
        "_id" : ObjectId("557e8c93a6df1a22041e0879"),
        "Questions._id" : ObjectId("557e8c9fa6df1a22041e087b")
    },
    { 
        "$push" : { 
            "Questions.$.DataSource" : { 
                "_id" : ObjectId("557e8e5ea6df1a27b403ff6b"),
                "CreationDate" : ISODate("2015-06-15T08:35:42.923Z"), 
                "IsActive" : true, 
                "Text" : "op", 
                "Value" : "op" 
            }
        }
    }
)

It identifies the index of the found item you want to update.

Whilst this is okay for $push operations with a nested array structure, you will quickly find that "nested arrays" are not good for updating. The main problem here is that the "positional operator" can only match the index of the "first" or "outer" array only. So it is not possible to match the position of an inner array element and update it.

I would strongly recommend changing your structure to "flatten" as a single array which is more suited to these operations.

来源：https://stackoverflow.com/questions/30840945/push-item-in-sub-document

标签

mongodb

mongodb-query