Setting value of a specific child element mongodb -


i have following database:

> db.test.find().pretty() {     "_id" : objectid("56b4c13d7db9acd913ce6e08"),     "state" : "helloworld",     "items" : [         {             "guid" : 123,             "uniqueid" : 0         },         {             "guid" : 124,             "uniqueid" : 1         }     ] }

and want set guid of items.uniqueid = 1 field 125, result be: 

{     "_id" : objectid("56b4c13d7db9acd913ce6e08"),     "state" : "helloworld",     "items" : [         {             "guid" : 123,             "uniqueid" : 0         },         {             "guid" : 125,             "uniqueid" : 1         }     ] }

i tried: 

> db.test.update( {'items.uniqueid' : 1} , { $set : { 'items.guid' : 125 }} ) writeresult({     "nmatched" : 0,     "nupserted" : 0,     "nmodified" : 0,     "writeerror" : {         "code" : 16837,         "errmsg" : "cannot use part (items of items.guid) traverse element ({items: [ { guid: 123.0, uniqueid: 0.0 }, { guid: 124.0, uniqueid: 1.0 } ]})"     } })

what doing wrong?

apply $set operator $ positional operator in update change guid field. $ positional operator identify correct element in array update without explicitly specifying position of element in array, final update statement should like:

db.collection.update({ "items.uniqueid": 1 },      {         "$set": {             "items.$.guid": 125         }     } )

if want increment value 1, use $inc update operator

db.collection.update({ "items.uniqueid": 1 },      {         "$inc": {             "items.$.guid": 1         }     } )

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