Update specific values in a nested array within mongo through mongoose

Question

I have somewhat the following schema(without _id) -

 {uid: String,
 inbox:[{msgid:String, someval:String}]
 }

Now, in the request I get the msgid and I use it in the following mongoose query like this-

 my_model.findOne({'inbox.msgid':'msgidvaluexyz'}
  , function(err, doc) {           
    console.log(doc);
    return !0; })

Now, the problem is that I get the whole document which has the specific message along with the other messages in inbox -

   Output-
   {uid:'xyz',
    inbox:[
     {msgid:,someval},
     {msgid:'our queried msgid',someval}, //required sub array
     {msgid:,someval},
      ]
       }

Now what query can i use to get the specific sub array only as the document inbox is too large to be looped through.

JohnnyHK · Accepted Answer · 2013-04-05 12:01:18Z

3

Use the $ positional selection operator to have the returned doc only include the matched inbox element:

my_model.findOne({'inbox.msgid':'msgidvaluexyz'}
  , {'inbox.$': 1}
  , function(err, doc) {           
    console.log(doc);
    return !0; })

answered Apr 5, 2013 at 12:01

JohnnyHK

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6 Comments

digster Over a year ago

thx man..sure does look like it will get the work done.. will save some serious processing time.. :)

digster Over a year ago

one quick quesn...the callback does return the specific sub array..but whn i try to change something and save the callback variable... say callback_doc.inbox[0].changed_var=something;callback_doc.save() .. it updates the changes to the first index of the array(index 0)..how do we refer to the specific index in the callback.. something like callback_doc.inbox[$] ?

JohnnyHK Over a year ago

@user597272 You don't have the whole object, so I think you'll want to update it via update rather than save and use the $ positional update operator which serves the same purpose on the update side.

digster Over a year ago

...actually i was using save because in the mongoose documentation it said that save follows the routine integrity checks which update skips.. however i dont inderstand the behavior of save for the sub array... function(err, doc) { doc.save(function(err1, doc1) {})} .. here i change 'doc' and outputting 'doc1' does shows it as changed..but in mongo it updates the element at the '0th' position.. i change doc.inbox[0].changed_var bcoz doc only returns the '0th' inbox array..cant i use '$' in place of '0' ?

digster Over a year ago

srry for the big post.. in short can I get the numeric index of the returned sub array?

|

andrei · Accepted Answer · 2013-04-05 08:41:03Z

0

If I understood your question correctly:

// find each person with a last name matching 'Ghost'
var query = Person.findOne({ 'name.last': 'Ghost' });

// selecting the `name` and `occupation` fields
query.select('name occupation');

http://mongoosejs.com/docs/queries.html

You can select which fields you want to get back. You could get only the inbox array or everything except that.

answered Apr 5, 2013 at 8:41

andrei

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1 Comment

digster Over a year ago

srry..but i think you didn't get my question properly...the 'inbox' field is an array, it will still have all the msg sub arrays..

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