Update Mongo array: remove dynamic key

Question

Mongo newb. I'm trying to remove a tag based on the key which is an ObjectID:

{
  "_id": ObjectId("53ccff9bbb25567911f208a8"),

  "tags": {
    "53ccff9bbb25567911f208a4": "tag1",
    "53ccff9bbb25567911f208a5": "tag2",
    "53ccff9bbb25567911f208a6": "tag3"
  }
}

I think I know how to remove it from the array in javascript and update the document, but I'm trying to do this within a query.

score 1 · Accepted Answer · answered Dec 03 '14 at 17:08

1

You're looking for $unset:

collection.update(
    {"_id": ObjectId("53ccff9bbb25567911f208a8")},
    {"$unset": {"tags.53ccff9bbb25567911f208a6": ""}}
)

This will remove the "53ccff9bbb25567911f208a6": "tag3" entry from tags.

More info at http://docs.mongodb.org/manual/reference/operator/update/unset/#up._S_unset

answered Dec 03 '14 at 17:08

Max Noel

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The issue I'm having is adding the ObjectID: {"$unset": {"tags."+tag: ""}} doesn't seem to work. – Stephane Dec 03 '14 at 17:32
1

@Stephane See http://stackoverflow.com/questions/12393351/using-a-variable-in-mongodb-update/12393480#12393480 – JohnnyHK Dec 03 '14 at 17:56
@Stephane We can't help you further without seeing your actual code. – Max Noel Dec 03 '14 at 18:51

Update Mongo array: remove dynamic key

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