what is the proper way to use $nin operator with mongoDB-CodePudding

I want to find entries in my MongoDB collection that match some filters. Each entry in my mongo collection looks like this data:

{
    type: "admin"
    senderId: "6131e7c597f50700160703fe"
    read_by: [
        {
        Object_id: 614dbbf83ad51412f16c0757
        readerId: "60b968dc5150a20015d6fcae"
        }
    ]
},
{
    type: "admin"
    senderId: "6131e7c597f50700160703fe"
    read_by: [
        {}
    ]
}

What I want to achieve properly, is to filter on the collection and get only the entries that match 'admin' as type and that don't have the current user's ID in the read_by array (that is an array of objects)

I wrote this (and tried some other combinations with errors :) ) but it is not working, I get 0 entries on the end, but I expect to get one of the two as the second have it's read_by array empty.

Thank you very much!

CodePudding user response：

I validated my solution using cloud.mongodb.com interface and the simplest following filter seems to do the job:

{ "read_by.readerId": {$ne:"60b968dc5150a20015d6fcae"}}

Only the record with empty array is being returned.

$nin operator works fine as well but if there is only single value for comparision then $ne should be enough.

{ "read_by.readerId": {$nin: ["60b968dc5150a20015d6fcae"]}}

CodePudding user response：

{ "read_by.readerId": {$ne:req.user._id}} worked like a charm thank you i didn't knew we can access the field with "read_by.readerId" :)