mongodb $not _id

Question

I need a way to search but not include an _id which is already on the screen in front of the user. For example, I have 3 pet profiles one which the user is already viewing.

On that page I have a heading called My Family. I then run this search:

public function fetch_family($owner)
    {
        $collection = static::db()->mypet;
        $cursor = $collection->find(array('owner' => new MongoId($owner)));

        if ($cursor->count() > 0)
            {
                $family = array();
                // iterate through the results
                while( $cursor->hasNext() ) {   
                    $family[] = ($cursor->getNext());
                }
                return $family;
            }
    }

And it returns all the pets in my family even knowing I am already showing one. So I want to exclude that one _id from the search.

I thought something like this.

$cursor = $collection->find(array('owner' => new MongoId($owner), '$not'=>array('_id'=>new MongoId(INSERT ID HERE))));

However, that just stops the whole thing from running.

Forehanded

This is a good question, and I needed this info too, but you might consider doing this on the client side to save the server from the (very small) load of considering the object _id? – Martins

Answer 1

You need to do a $ne (not equal) to make sure the current pet you are viewing is excluded from the search by owner.

Example in the mongo shell:

var viewingPetId = ObjectId("515535b6760fe8735f5f6899");
var ownerId = ObjectId("515535ba760fe8735f5f689a");

db.mypet.find(
    {
        _id: { $ne: viewingPetId },
        owner: ownerId
    }
)

Martens

Answer 2

Use $ne as (notice no need to use ObjectId(), string will autocast to ObjectId):

db.organizations.find({"_id" : {$ne:"563c50e05cdb2be30391e873"}})

Withy

Thus is just the same as what the provided answer says, so there is no need to add another one. Also as long as the schema type is present ( and always is for _id ) then mongoose will autocast from string anyway, which means an explicit conversion is not required. – Orchitis

I added it because I was getting "ObjectId not resolved error". What do you mean by autocast? do you mean db.organizations.find({"_id" : {$ne:"563c50e05cdb2be30391e873"}}) is sufficient? – Withy

Yes. Mongoose will take that string and convert it to an ObjectId automatically. You can see how it does this and the query sent to the server by enabling debugging. mongoose.set('debug',true) – Orchitis

Thanks, thats the right suggestion, answer updated as per your suggestion. – Withy

how about using $nin with array of string? – Presume