Spring data mongoDB: Get the distinct fields with pagination - spring

Question

I want to implement method for getting distict values with pagination using spring MongoDb.
For exaple here I want to get just 2 distinct userMailBoxAddresses. But in result I received list of all distict values. So pagination does not work
Pageable pageable = PageRequest.of(0, 2);
Query query = new Query().with(pageable);
Page<String> page;
List<String> distinct = mongoTemplate.findDistinct(query, "userMailBoxAddress",
Entity.class, String.class);
I found that "The current Distinct() implementation only allows for bringing back ALL distinct values in the collection or matching a query, but there is no way to limit these results. "
Is it true? and maybe is some another way to implement getting distinct values with pagination?

Answer 1

for small collections, this could be an option:
Pageable pageable = PageRequest.of(0, 2);
GroupOperation groupOp = Aggregation.group("userMailBoxAddress");
SortOperation sortOp = Aggregation.sort(Direction.ASC, "_id");
SkipOperation skipOp = Aggregation.skip(pageable.getPageNumber() * pageable.getPageSize() * 1L);
LimitOperation limitOp = Aggregation.limit(pageable.getPageSize());
Aggregation aggregation = Aggregation.newAggregation(groupOp, sortOp, skipOp, limitOp);
List<String> distinct = mongoTemplate.aggregate(aggregation, Entity.class, Document.class)
.getMappedResults()
.stream()
.map(result -> (String)result.get("_id"))
.collect(Collectors.toList());