Grouping

Construct group key and accumulator after general criteria, and extend with Driver-native accumulators or custom mapping.

Default group

java

Accumulator

• count() / countAs(alias)

• sum(field, alias) / avg(field, alias)

• min(field, alias) / max(field, alias)

• addToSet(field, alias) / push(field, alias)

• Driver-native accumulator: accumulator(BsonField)

Group result mapping

java

If a different result shape is needed from the default key/value mapping, a converter can be specified directly. You can also connect executeLookup(rightBuilder, spec) to the grouping results.