java - 按降序对数组进行排序并仅返回数组中匹配的元素

Question

/* 1 */
{
    "_id" : ObjectId("5c4ff961d4404a0dccec4f71"),
    "tier" : "3",
    "agentName" : "Dial2Travel1",
    "meeting" : [ 
        {
            "meetingDate" : ISODate("2019-01-23T00:00:00.000Z"),
            "comment" : "call back after 4 days",
            "meetingDoneBy" : {
                "$ref" : "salesExecutive",
                "$id" : ObjectId("5c6b9dc9d56dbad67a951786")
            }
        }, 
        {
            "meetingDate" : ISODate("2019-02-23T00:00:00.000Z"),
            "comment" : "wrong number",
            "meetingDoneBy" : {
                "$ref" : "salesExecutive",
                "$id" : ObjectId("5c6b9dc9d56dbad67a951786")
            }
        }, 
        {
            "meetingDate" : ISODate("2019-03-12T00:00:00.000Z"),
            "comment" : "packages request",
            "meetingDoneBy" : {
                "$ref" : "salesExecutive",
                "$id" : ObjectId("5c6b9dc9d56dbad67a951786")
            }
        }
    ]
}

/* 2 */
{
    "_id" : ObjectId("5c4ff961d4404a0dccec4f72"),
    "tier" : "3",
    "agentName" : "Dial2Travel2",
    "meeting" : [ 
        {
            "meetingDate" : ISODate("2019-01-23T00:00:00.000Z"),
            "comment" : "call back after 4 days",
            "meetingDoneBy" : {
                "$ref" : "salesExecutive",
                "$id" : ObjectId("5c6b9dc9d56dbad67a951786")
            }
        }, 
        {
            "meetingDate" : ISODate("2019-02-23T00:00:00.000Z"),
            "comment" : "wrong number",
            "meetingDoneBy" : {
                "$ref" : "salesExecutive",
                "$id" : ObjectId("5c6b9dc9d56dbad67a951786")
            }
        }, 
        {
            "meetingDate" : ISODate("2019-03-12T00:00:00.000Z"),
            "comment" : "packages request",
            "meetingDoneBy" : {
                "$ref" : "salesExecutive",
                "$id" : ObjectId("5c6b9dc9d56dbad67a951786")
            }
        }
    ]
}

/* 3 */
{
    "_id" : ObjectId("5c4ff961d4404a0dccec4f73"),
    "tier" : "3",
    "agentName" : "Dial2Travel3-",
    "meeting" : [ 
        {
            "meetingDate" : ISODate("2019-01-23T00:00:00.000Z"),
            "comment" : "call back after 4 days",
            "meetingDoneBy" : {
                "$ref" : "salesExecutive",
                "$id" : ObjectId("5c6b9dc9d56dbad67a951786")
            }
        }, 
        {
            "meetingDate" : ISODate("2019-02-23T00:00:00.000Z"),
            "comment" : "wrong number",
            "meetingDoneBy" : {
                "$ref" : "salesExecutive",
                "$id" : ObjectId("5c6b9dc9d56dbad67a951786")
            }
        }, 
        {
            "meetingDate" : ISODate("2019-03-12T00:00:00.000Z"),
            "comment" : "packages request",
            "meetingDoneBy" : {
                "$ref" : "salesExecutive",
                "$id" : ObjectId("5c6b9dc9d56dbad67a951786")
            }
        }
    ]
}

/* 4 */
{
    "_id" : ObjectId("5c4ff961d4404a0dccec4f74"),
    "tier" : "3",
    "agentName" : "Dial2Travel4",
    "meeting" : [ 
        {
            "meetingDate" : ISODate("2019-01-23T00:00:00.000Z"),
            "comment" : "call back after 4 days",
            "meetingDoneBy" : {
                "$ref" : "salesExecutive",
                "$id" : ObjectId("5c6b9dc9d56dbad67a951786")
            }
        }, 
        {
            "meetingDate" : ISODate("2019-02-23T00:00:00.000Z"),
            "comment" : "wrong number",
            "meetingDoneBy" : {
                "$ref" : "salesExecutive",
                "$id" : ObjectId("5c6b9dc9d56dbad67a951786")
            }
        }, 
        {
            "meetingDate" : ISODate("2019-03-12T00:00:00.000Z"),
            "comment" : "packages request",
            "meetingDoneBy" : {
                "$ref" : "salesExecutive",
                "$id" : ObjectId("5c6b9dc9d56dbad67a951786")
            }
        }
    ]
}

我想按降序对 session 数组进行排序，然后应用分页以仅检索响应中匹配的 session ，而不是完整的数组。因此，对于第一页，我想请求 5 次 session ，那么只会返回/预计 5 次 session 。在第 2 页请求下 5 页等。目前我得到的是一系列完整的 session 。这不是我想要的。

Answer 1

尝试一下这个聚合查询:

var pageNum = 1;
var resPerPage = 5;
var skipAmt = pageNum * resPerPage;

db.Test.aggregate([
    {
        $unwind: "$meeting"
    },
    {
        $project: {
            "_id": 0,
            "meeting": "$meeting"
        }
    },
    {
        $sort: {
            "meeting.meetingDate": - 1
        }
    },
    {
        $skip: skipAmt
    },
    {
        $limit: resPerPage
    }
]);