Using $nin in $cond using aggregate() function.

[Nisrina Luthfiyati]

Hi all,
I'm trying to write a query that count the number of document that pass a condition using the aggregate function.
Is there any way to use $nin or something of its equivalent in the condition? Like:

db.collectionName.aggregate({
  $group: {
    _id: "$field1",
    ...,
    count: {
      $sum: {
        $cond: [ { "$field2": {$nin: ["possibleValue1", "possibleValue2"]} }, 1, 0 ]
      }
    },
    ...
  }
})

According to http://docs.mongodb.org/manual/meta/aggregation-quick-reference/#comparison-expressions $nin is not one of the comparison expressions defined in aggregation framework.

If so is there anything that I can do to accomplish the same thing while still using aggregate?
I can't put the condition in $match because I might use the documents not passing the condition in other stages.

Thank you,
Nisrina.

[Will Berkeley]

$nin means "not having any of these values", which is the same as $and'ing together $ne expressions. Try

db.collectionName.aggregate([
  { "$group" : {
    "_id" : "$field1",

    "count" : {
      "$sum" : {
        "$cond" : [ { "$and" : [{ "$ne" : [ "$field2", "possibleValue1" ] }, { "$ne" : [ "$field2", "possibleValue2" ] } ] }, 1, 0 ]
      }
    }
  } }
])

There were also some syntax errors in the pipeline. I fixed them.

-Will

[Nisrina Luthfiyati]

Hi Will,
ah that sounds so obvious now why didn't I think of that.

Thank you!
Nisrina