How to update multiple MongoDB subdocuments in one shot? -

i have created couple of documents in mongodb:

> db.mycollection.insert( {"bucket": [{"field1":"x"},{"field2":{"a":"b","c":"d","e":"f"}}]} )  > db.mycollection.insert( {"bucket": [{"field1":"y"},{"field2":{"g":"h","i":"j","k":"l"}}]} )  > db.mycollection.find() { "_id" : objectid("534102c492970f1b06b1edc8"), "bucket" : [    {   "field1" : "x" },   {   "field2" : {    "a" : "b",  "c" : "d",  "e" : "f" } } ] } { "_id" : objectid("5341054e92970f1b06b1edc9"), "bucket" : [    {   "field1" : "t" },   {   "field2" : {    "g" : "h",  "i" : "j",  "k" : "l" } } ] } 

now wold update such values of "bucket" set []

so try this:

db.mycollection.update({},{"bucket":[]}, false, false) 

this partially worked. changed first bucket []:

> db.mycollection.find() { "_id" : objectid("534102c492970f1b06b1edc8"), "bucket" : [ ] } { "_id" : objectid("5341054e92970f1b06b1edc9"), "bucket" : [    {   "field1" : "t" },   {   "field2" : {    "g" : "h",  "i" : "j",  "k" : "l" } } ] } 

so tried change "multi" field true , tried again. didn't work:

> db.mycollection.update({},{"bucket":[]}, false, true) multi update works $ operators 

how can update multiple subdocuments using update() method?

what need $set operator update query work. try this:

db.mycollection.update({},{$set:{"bucket":[]}}, false, true)