标签: aggregation-framework

我是 MongoDB 的新手，所以如果我错过了文档中的某些内容，请原谅我。我有一个这样的收藏

[date: "2015-12-01", status: "resolved", parentId: 1]
[date: "2015-12-01", status: "resolved", parentId: 2]
[date: "2015-12-01", status: "resolved", parentId: 2]
[date: "2015-12-01", status: "waiting", parentId: 2]
[date: "2015-12-02", status: "resolved", parentId: 1]
[date: "2015-12-02", status: "waiting", parentId: 2]
[date: "2015-12-02", status: "waiting", parentId: 2]
[date: "2015-12-03", status: "resolved", parentId: 1]

我期望对按以下分组的输出求和

日期 -> 父 ID -> 状态

所以那就是

{
    "2015-12-01": {
        "1": {
            "resolved": 1
        },
        "2": {
            "resolved": 2,
            "waiting": 1
        }
    }
    "2015-12-02": {
        "1": {
            "resolved": …

嘿，

我需要一些帮助将以下 MongoDB 查询转换为 MongoDB Java 驱动程序查询。

请注意，查询有效。

db.days.aggregate([
    { $match: { 'day' : 'March_1'}},
    { $project: {
        _id : 0,
        day: 1,
        events: {$filter: {
            input: '$events',
            as: 'event',
            cond: {$eq: ['$$event.year', '2002']}
        }}
    }}
])

我的尝试是这样的，但失败了，我需要你的帮助。

Document query = new Document("$match", new Document("day", day)).
    append("$project", new Document("_id", 0).
            append("day", 1).
            append("events", new Document("$filter", new Document(
                    "input", "$" + category).
                    append("as", "event").
                    append("cond", new Document("$eq", Arrays.asList("$$event.year", year))))));

我得到的错误是

"{ "ok" : 0.0, "errmsg" : "A pipeline stage specification object …

我有两个模式users和Lessons。我必须按每个用户获取课程组。我还将用户的参考 ID 存储在课程模式中。

为了获得结果，我按照以下格式完成了聚合查询

db.lessons.aggregate([{
  $lookup: {
    from: "users",
    localField: "user",
    foreignField: "_id",
    as: "user"
  }
}, {
  "$project": {
    "user": "$user.email",
    "title": "$title",
    "scheduled_at": "$scheduled_at"
  }
}, {
  $group: {
    _id: "$user",
    num_lessons: {
      $sum: 1
    },
    lessons: {
      $push: {
        title: "$title",
        schedule: "$scheduled_at"
      }
    }
  }
}])

从上面的查询我能够得到如下的输出，

{
    "_id" : [ 
        "harry.quill@gmail.com"
    ],
    "num_lessons" : 1.0,
    "lessons" : [ 
        {
            "title" : "welcome to Mongoose",
            "schedule" : { …

这是订单实体：

public class Order 
{
    @Id
    private String id;
    private String internalId;
    private String externalId;
    private String status;
}

public class OrderAssigned 
{
    @Id
    private String id;
    private String internalId;
    private String externalId;
    private String stationId;
    private String rejectStatus;
}

我想加入这两个集合。

• 首先我想找到stationId
• 然后加入Orders.internalId和OrderAssigned.internalId和status = "OrderCreated"

就像这个 SQL 查询：

select orders.* 
from PARTNER_RESTAURANT_ORDER orders 
inner join PARTNER_RESTAURANT_ORDER_ASSIGNED_STATION assigned_station on orders.internalId = assigned_station.internalId 
where assigned_station.stationId = "5e2968e2763e750001c8ba5f" 
  and orders.status = "OrderCreated"

我有一个类似的 mongodb 集合：

{ "_id" : 1, "item" : "item1", "quantity" : 2, "date" : ISODate("2014-01-01T08:00:00Z") }
{ "_id" : 2, "item" : "item2", "quantity" : 1, "date" : ISODate("2014-02-03T09:00:00Z") }
{ "_id" : 3, "item" : "item2", "quantity" : 5, "date" : ISODate("2014-02-03T09:05:00Z") }
{ "_id" : 4, "item" : "item1", "quantity" : 10, "date" : ISODate("2014-02-15T08:00:00Z") }
{ "_id" : 5, "item" : "item2", "quantity" : 10, "date" : ISODate("2014-02-15T09:05:00Z") }

我想获取每个项目的最新文档（基于日期值）

{ …