如何使用投影和过滤器区分 MongoDB 中的查询？

Question

I have list of attributes in mongo and I am querying some nested field. Here is my code,

public List<Brand> searchBrands(Request request) {
    final MongoCollection<Document> collection = mongoDatabase.getCollection("shop");
    final Document query = new Document();
    final Document projection = new Document();
    final List<Brand> brandList = new ArrayList<>();


    query.append("_id", request.getId());
    query.append("isActive", true);
    if (request.Year() != null) {
        query.append("attributes.name", "myYear");
        query.append("attributes.value", request.getYear());
    }

    projection.append("brand.code", 1.0);
    projection.append("brand.description", 1.0);
    projection.append("_id", 0.0);



    Block<Document> processBlock = document -> brandList.
            add(Brand.builder().code(document.get("brand",Document.class).getString("code"))
                    .description(document.get("brand",Document.class).getString("description"))
                    .build());


    collection.find(query).projection(projection).forEach(processBlock);

    return brandList;}

Above code return results correctly, 72 item with same brand.code. But I want to fetch distinct according to brand.code How can I do that?

Answer 1

I'm not sure which mongodb client library you're using to create queries for mongodb; I'm sharing the query that you can run in mongodb console to get the results you want. I hope you know how to create this query using your mongodb client library

db.shop.distinct('brand.code', myQuery)
//Replace myQuery with your query e.g. {isActive: true}