Extended $lookup

[Stennie_X (Stennie)]

@Javier_Blanco

The db.collection.distinct() method provides a wrapper around the distinct command.

But it doesn’t work.

Hi @Javier_Blanco,

To try to clarify this: distinct is a Database Command. The aggregation framework uses an aggregate database command, which supports Aggregation Pipeline Stages which use Aggregation Pipeline Operators. Aggregation stages and operators are prefixed with $ (for example: $group).

You cannot call the distinct command from within the aggregate command. If you add distinct in an aggregation pipeline, it is just a value:

@Asya_Kamsky

The syntax ["distinct": "devices", "key": "_id", "query": {"group.$id": 11}] may be legal JSON but it does not represent running a distinct command, it’s just an array with a bunch of values in it.

You can perform the equivalent processing of a distinct command in the aggregation framework using a $group aggregation stage, but I would consider the recommendations you’ve been given such as adjusting the data model to support your common queries or upgrading to MongoDB 5.0+ to take advantage of performance improvements.

Regards,
Stennie