Spring Boot MongoDB 聚合与 ReplaceRoot / 如何获取组中的最新项目

Question

我想在 Spring Boot 应用程序中获取此 MongoDB 查询的结果。

db.getCollection('contentSource').aggregate( [ { $sort: { "modified": -1 } }, 
{ $group: { _id: "$sourceId", cs: { $push: "$$ROOT" } }}, 
{ $replaceRoot: { newRoot: { $arrayElemAt: ['$cs', 0] } }} ] )

有人知道如何将 replaceRoot 添加到我的聚合中吗？

Answer 1

    SortOperation sortOperation = new SortOperation(new Sort(Sort.Direction.ASC,"modified"));

        GroupOperation groupOperation = group("sourceId").push("$$ROOT").as("cs");

        Aggregation aggregation = newAggregation( sortOperation , groupOperation);

AggregationOperation replaceRoot = Aggregation.replaceRoot().withValueOf(ArrayOperators.ArrayElemAt.arrayOf("cs").elementAt(0));

        AggregationResults<Document> result = mongoTemplate.aggregate(aggregation,"contentSource", replaceRoot,  Document.class);


        return result.getMappedResults();