$lookup

Configures simple join and let/pipeline based LookupSpec, Driver-native raw stage, unwind and lookup count flow.

localField / foreignField

java

let + pipeline + $expr

java

• bindConditionFields(leftField, condition, rightField)

• bindConditionFieldsLeftToObjectId(...)

• bindConditionConst, bindConditionBetween, bindConditionLike

• bindConditionExists, bindConditionIsNull, bindConditionIsNotNull

• rawStage(Bson) for Driver-native lookup pipeline stages

• unwind(preserveNullAndEmptyArrays)

• outerStage(Bson) / outerStages(...) for stages after $lookup

Execute Lookup

java

unwind(...)를 사용하지 않은 기본 findAll lookup은 right 결과를 List<R>로 반환합니다. 단건 left/right가 필요하면 find().executeLookup(...) 경로를 사용합니다.

Lookup + count / exists

java

executeLookupAndCount(...) returns data and totalCount together in the form of $facet(data, count). The count/exists builder can also receive lookup results as left/right tuples.