Grouping

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

Default group

java

Mono<Map<String, GroupResult>> grouped = dsl
    .executeEntity(Order.class, MongoTemplateName.FRONT)
    .fields(pair("status", "DONE"))
    .end()
    .findAll()
    .group(String.class, GroupResult.class)
    .by("userId")
    .count()
    .sum("amount", "totalAmount")
    .execute();

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

.group(String.class, GroupResult.class)
.keyConverter(document -> ...)
.valueConverter(document -> ...)
.execute();

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.