Not in document field array mongodb with $expr

Question

I'm trying to get all documents that don't have an _id in the array excluded.

db.sites.find({ "$expr": { '_id': { "$not": { "$in": "$excluded"} } } });

I'm not using $nin because it's not allowed under $expr.

I'm getting the following error message:

Error: error: {
    "ok" : 0,
    "errmsg" : "Expression $in takes exactly 2 arguments. 1 were passed in.",
    "code" : 16020,
    "codeName" : "Location16020"
}

Can I use $where for this instead?

mickl · Accepted Answer · 2019-03-20 13:04:01Z

6

The $in operator requires two arguments:

db.sites.find({ $expr: { $not: { $in: [ "$_id", "$excluded" ] } } })

Working example here

answered Mar 20, 2019 at 13:04

mickl

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2 Comments

mickl Over a year ago

@psykx please don't, there are just two $in operators in MongoDB and you tried to use the one for queries but you needed the one for aggregations

psykx Over a year ago

Aaahhhh. Ok. That makes sense.

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