MongoDB组操作返回文档，而不是单个字段

Question

我正在根据我在Mongo中拥有的数据，根据文件的最后访问时间对文件集合进行分组。

但是我不确定如何从组操作中返回更多文档。

如何检索包含每个分组下所有信息的文档？

例如，我现在要返回：

[
  {
    "year": [
      2020
    ],
    "month": [
      2
    ],
    "week": [
      7
    ],
    "day": [
      2
    ],
    "results": [
      "filename-1",
      "filename-2"
    ]
  }
]

我只将文件名恢复到基本数组中。我想要的是文档，而不仅仅是名称。

我用来在上面创建结果的代码

  public void groupTest() {

    final String dateField = "lastAccessTime";

    final LocalDate now = LocalDate.now();
    final LocalDate firstDay = now.with(firstDayOfYear());
    final LocalDate lastDay = now.with(lastDayOfYear());

    final Criteria criteria =
        new Criteria().andOperator(where(dateField).gte(firstDay), where(dateField).lte(lastDay));

    final ProjectionOperation dateProjection =
        project()
            .and("_id")
            .as("id")
            .and("name")
            .as("name")
            .and("absolutePath")
            .as("absolutePath")
            .and(dateField)
            .extractYear()
            .as("year")
            .and(dateField)
            .extractMonth()
            .as("month")
            .and(dateField)
            .extractWeek()
            .as("week")
            .and(dateField)
            .extractDayOfWeek()
            .as("day");

    final GroupOperation groupBy =
        group("year", "month", "week", "day")
                .addToSet("name")
                .as("results");

    final Aggregation aggregation =
        newAggregation(
            match(criteria),
            dateProjection,
            groupBy,
            sort(Sort.Direction.ASC, "year", "month", "week", "day"));
  }

我希望我的结果值更像：

[
  {
    "year": [
      2020
    ],
    "month": [
      2
    ],
    "week": [
      7
    ],
    "day": [
      2
    ],
    "results": [
      {
        "id": "123",
        "filename": "filename-1",
        "size": 30000
      },
      {
        "id": "456",
        "filename": "filename-2",
        "size": 30000
      }
    ]
  }
]

非常感谢您的帮助

Answer 1

GroupOperation group = Aggregation
    .group("year", "month", "week", "day")
    .addToSet(new Document("id", "$id")
                   .append("filename", "$name")
                   .append("size", "$size"))
    .as("results");

注意：确保将size字段包括在dateProjection阶段中。