Update MongoDB field using value of another field

参考资料：https://stackoverflow.com/questions/3974985/update-mongodb-field-using-value-of-another-field/28460030

mongo 4.2

类似，update table set filed = other-filed where filter ....

db.collection.<update method>(

    {},

    [

        {"$set": {"name": { "$concat": ["$firstName", " ", "$lastName"]}}}

    ]

)

mongo3.4+

db.collection.aggregate(

    [

        { "$addFields": { 

            "name": { "$concat": [ "$firstName", " ", "$lastName" ] } 

        }},

        { "$out": "collection" }

    ]

)

mongo 3.2 and 3.0

var cursor = db.collection.aggregate([ 

    { "$project":  { 

        "name": { "$concat": [ "$firstName", " ", "$lastName" ] } 

    }}

])

​

var requests = [];

cursor.forEach(document => { 

    requests.push( { 

        'updateOne': {

            'filter': { '_id': document._id },

            'update': { '$set': { 'name': document.name } }

        }

    });

    if (requests.length === 500) {

        //Execute per 500 operations and re-init

        db.collection.bulkWrite(requests);

        requests = [];

    }

});

​

if(requests.length > 0) {

     db.collection.bulkWrite(requests);

}

 

mongo 2.6 and 3.0

var bulk = db.collection.initializeUnorderedBulkOp();

var count = 0;

​

cursor.snapshot().forEach(function(document) { 

    bulk.find({ '_id': document._id }).updateOne( {

        '$set': { 'name': document.name }

    });

    count++;

    if(count%500 === 0) {

        // Excecute per 500 operations and re-init

        bulk.execute();

        bulk = db.collection.initializeUnorderedBulkOp();

    }

})

​

// clean up queues

if(count > 0) {

    bulk.execute();

}

 

 

mongo 2.4

 

cursor["result"].forEach(function(document) {

    db.collection.update(

        { "_id": document._id }, 

        { "$set": { "name": document.name } }

    );

})