Atomically move object by ID from one array to another in same document [duplicate]

Answer 1

Here's an example:

> db.baz.find()
> db.baz.insert({
...   "_id": ObjectId("4d525ab2924f0000000022ad"),
...   "arrayField": [
...     { id: 1, other: 23 },
...     { id: 2, other: 21 },
...     { id: 0, other: 235 },
...     { id: 3, other: 765 }
...   ],
...   "someOtherArrayField": []
... })
WriteResult({ "nInserted" : 1 })

function extractIdZero(arrayFieldName) {
    return {$arrayElemAt: [
        {$filter: {input: arrayFieldName, cond: {$eq: ["$$this.id", 0]}}}, 
        0
    ]};
}

extractIdZero("$arrayField")
{
    "$arrayElemAt" : [
        {
            "$filter" : {
                "input" : "$arrayField",
                "cond" : {
                    "$eq" : [
                        "$$this.id",
                        0
                    ]
                }
            }
        },
        0
    ]
}

db.baz.updateOne(
    {_id: ObjectId("4d525ab2924f0000000022ad")},
    [{$set: {
         arrayField: {$filter: {
             input: "$arrayField",
             cond: {$ne: ["$$this.id", 0]}
         }},
         someOtherArrayField: {$concatArrays: [
             "$someOtherArrayField",
             [extractIdZero("$arrayField")]
         ]}
     }}
    ])
{ "acknowledged" : true, "matchedCount" : 1, "modifiedCount" : 1 }
> db.baz.findOne()
{
    "_id" : ObjectId("4d525ab2924f0000000022ad"),
    "arrayField" : [
        {
            "id" : 1,
            "other" : 23
        },
        {
            "id" : 2,
            "other" : 21
        },
        {
            "id" : 3,
            "other" : 765
        }
    ],
    "someOtherArrayField" : [
        {
            "id" : 0,
            "other" : 235
        }
    ]
}