MongoDB filter by array of objectIds

Question

I have a document that has a array of ObjectIDs for reference. That array is not an associative array, it's just the ObjectIDS:

{
  ...
  "tags" : [ 
    ObjectId("54744662ae8a0be602568c4f")
  ]
}

Now I'm trying to filter based on that array, like this:

db.expenses.find({
  tags:{
    $elemMatch:{ObjectId("547469bb0bde915a05f74299")}
  }
})

I know that the projection on the $elemMatch is wrong, but I just don't know how to do it, and Google isn't helping must because most of the examples are for and array of json objects with defined properties.

Does anyone know how to do this?

user3473830 · Accepted Answer · 2014-11-28 05:11:37Z

6

If I got your problem correctly, this would be the answer

db.expenses.find(
{
  tags: {$in : [ObjectId("54744662ae8a0be602568c4f")]}  
})

edited Nov 28, 2014 at 5:11

user3473830

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answered Nov 27, 2014 at 17:25

Disposer

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3 Comments

JohnnyHK Over a year ago

You don't need the $in though since it's just a single value, so it can just be tags: ObjectId("54744662ae8a0be602568c4f")

Disposer Over a year ago

@JohnnyHK is right, but I used $in for searching multiple ObjectIds if its needed

Ricardo Gomes Over a year ago

I feel really dumb right now, your right, I have no clue why I didn't try this. I think the array thing made me think it should be different. Thanks

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