Mongodb: $pull operator is not removing given value from array

Question

edit:

Structure of document:

{"tags" : ["a"], "name" : "a", "creator" : "Nick here", "users" : [ "Nick here"], "connected" : 1, "ra" : 0.3967885102611035, "_id" : ObjectId("513c3e42071a103c09000003")}

I have problem with MongoDB $pull operator. It doesn't remove value from an array. Here's my query:

db.rooms.update({users: ["Nick here"]},{$pull: {users: ["Nick here"]}})

Here's how users field looks like:

(...),"users" : [ "Nick here" ],(...)

if I write it like this:

db.rooms.update({users: "Nick here"},{$pull: {users: ["Nick here"]}})

or

db.rooms.update({users: "Nick here"},{$pull: {users: "Nick here"}})

an error is returned:

Cannot apply $pull/$pullAll modifier to non-array

What is wrong in those queries? I want to pull/push users' nicks and remove document when 'users' field is empty.

Thanks in advance, Michał

Can you show the structure of the document? There is nothing wrong with this query db.rooms.update({users: "Nick here"},{$pull: {users: "Nick here"}}) — user20140268
– user20140268, Commented Mar 10, 2013 at 9:35
I've added document's structure edit: it seems that nick is being pulled properly now, I don't know what was wrong with this — kardysm
– kardysm, Commented Mar 10, 2013 at 10:52

Vladimir Korshunov · Accepted Answer · 2013-03-10 11:30:50Z

1

I wrote test… Check you syntax. Query:

db.rooms.update({'users': 'Nick here'}, {$pull: {'users': 'Nick here'}})

May be in your query need use { multi: true }. For example:

db.rooms.update({'users': 'Nick here'}, {$pull: {'users': 'Nick here'}}, { multi: true })

Full log:

MongoDB shell version: 2.2.3
connecting to: so
> db.rooms.insert({"tags" : ["a"], "name" : "a", "creator" : "Nick here", "users" : [ "Nick here"], "connected" : 1, "ra" : 0.3967885102611035, "_id" : ObjectId("513c3e42071a103c09000003")} )
> db.rooms.findOne()
{
    "_id" : ObjectId("513c3e42071a103c09000003"),
    "tags" : [
        "a"
    ],
    "name" : "a",
    "creator" : "Nick here",
    "users" : [
        "Nick here"
    ],
    "connected" : 1,
    "ra" : 0.3967885102611035
}
> db.rooms.update({'users': 'Nick here'}, {$pull: {'users': 'Nick here'}})
> db.rooms.findOne()
{
    "_id" : ObjectId("513c3e42071a103c09000003"),
    "connected" : 1,
    "creator" : "Nick here",
    "name" : "a",
    "ra" : 0.3967885102611035,
    "tags" : [
        "a"
    ],
    "users" : [ ]
}
>

edited Mar 10, 2013 at 11:30

answered Mar 10, 2013 at 11:19

Vladimir Korshunov

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1 Comment

kardysm Over a year ago

That was not syntax problem. I just changed 'users' structure from single value field to array and forgot to remove documents from earlier tests with non-array here. Thanks anyway for your time!

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