MongoDB - Unset an attribute from a single array element

Question

How can I unset an attribute from a single array element from the Mongo console. For example, how do I unset the junk attribute from time[1]

{
  "_id" : ObjectId("4d525ab2924f0000000022ad"), 
  "name" : "hello", 
  "time" : [
      {
          "stamp" : "2010-07-01T12:01:03.75+02:00",
          "reason" : "new"
      },
      {
          "stamp" : "2010-07-02T16:03:48.187+03:00",
          "reason" : "update",
          "junk"  : "yes"
      },
      {
          "stamp" : "2010-07-02T16:03:48.187+04:00",
          "reason" : "update"
      },

   ]
}

Sergio Tulentsev · Accepted Answer · 2016-01-09 22:09:09Z

12

This should do the trick:

db.coll.update({"time.junk": "yes"}, {$unset: {"time.$.junk": 1}});

Read on dot notation.

edited Jan 9, 2016 at 22:09

answered Jan 16, 2012 at 11:57

Sergio Tulentsev

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1 Comment

Patrycja K Over a year ago

Actually it will remove the value, BUT only from the first occurrence of the subdocument, because "the positional $ operator acts as a placeholder for the first element that matches the query document" (docs.mongodb.org/manual/reference/operator/update/positional/…) Also: see Hassek's hack here: stackoverflow.com/questions/19945924/…

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