使用 mongodb Aggregate 对嵌套对象进行排序？
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【中文标题】使用 mongodb Aggregate 对嵌套对象进行排序？【英文标题】：Sort in nasted Object using mongo db Aggregate? 【发布时间】：2021-02-26 05:34:35 【问题描述】：我有故事数据，我想通过基于 createdDate 的 desc 内部对象对其进行排序。 y代码在下面
Story.aggregate(
[
"$project" :
"_id" : 0,
"stories" : "$$ROOT"
,
"$lookup" :
"localField" : "stories.user",
"from" : "users",
"foreignField" : "_id",
"as" : "users"
,
"$unwind" :
"path" : "$users",
"preserveNullAndEmptyArrays" : false
,
"$lookup" :
"localField" : "stories.place",
"from" : "places",
"foreignField" : "_id",
"as" : "places"
,
"$unwind" :
"path" : "$places",
"preserveNullAndEmptyArrays" : true
,
"$lookup" :
"localField" : "places.categories",
"from" : "categories",
"foreignField" : "_id",
"as" : "categories"
,
"$unwind" :
"path" : "$categories",
"preserveNullAndEmptyArrays" : false
,
$match: "stories._id": mongoose.Types.ObjectId(req.params.id) ,
"$sort":"stories.comments.createdDate":-1
,
"$project" :
"stories._id" : "$stories._id",
"stories.title" : "$stories.title",
"stories.createdDate" : "$stories.createdDate",
"stories.image" : "$stories.image",
"stories.likeCount" : "$stories.likeCount",
"stories.commentCount" : "$stories.commentCount",
"stories.likes" : "$stories.likes",
"stories.comments" : "$stories.comments",
"stories.story" : "$stories.story",
"users.firstName" : "$users.firstName",
"users.storiesCount" : "$users.storiesCount",
"users.albumsCount" : "$users.albumsCount",
"stories.urlTitle" : "$stories.urlTitle",
"users._id" : "$users._id",
"users.lastName" : "$users.lastName",
"users.image" : "$users.image",
"places.placeName" : "$places.placeName",
"places._id" : "$places._id",
"categories.categoryName" : "$categories.categoryName",
"categories._id" : "$categories._id",
]
在这段代码中，我想根据 cmets.created 日期对评论进行排序。我从 db 收到的数据是
"stories":
"_id": "5f86b6b4d11dfd67b083ce9c",
"title": "Information about Khunjrab Pass.",
"createdDate": "2020-10-14T09:31:00.407Z",
"image": "Khunjerab-Pass.jpg",
"likeCount": 0,
"commentCount": 0,
"likes": [
"5f93d8571240934378d5ba06",
"5f65ed4552e1d9156af84bd8"
],
"comments": [
"_id": "5faf7e858de22b3a94bbc5a5",
"userId": "5f93d8571240934378d5ba06",
"comment": "some comment",
"createdDate": "2020-11-14T06:51:49.269Z",
"updatedDate": "2020-11-14T06:51:49.269Z",
"likes": [
"5f9a53138dca473d58ae6e39"
],
,
"_id": "5faf9a136525194c0077eddc",
"userId": "5f65c4b7a9267211bfa994ff",
"comment": "some comment",
"likes": [
"5f9a53138dca473d58ae6e39"
],
,
"_id": "5fafa5996525194c0077eddd",
"userId": "5f65c4b7a9267211bfa994ff",
"comment": "when we visited khunjrab top there was strong wind and very low temperature.",
"firstName": "Sohaib",
"lastName": "Siddique",
"createdDate": "2020-11-14T09:38:33.789Z",
"updatedDate": "2020-11-14T09:38:33.789Z",
"likes": [
"5f9a53138dca473d58ae6e39"
],
"image": "sohaib-img.jpeg"
],
"story": "Khunjerab Pass is a high mountain pass in the Karakoram Mountains, in a strategic position on the northern border of Pakistan and on the southwest border of China. Its elevation is 4,693 metres",
"urlTitle": "prince-saiful-malook-and-badri-jamala"
,
"users":
"firstName": "Sohaib",
"storiesCount": 1,
"albumsCount": 0,
"_id": "5f65c4b7a9267211bfa994ff",
"lastName": "Siddique",
"image": "sohaib-img.jpeg"
,
"places":
"placeName": "Khunjerab Pass",
"_id": "5f65e66752e1d9156af84bd4"
,
"categories":
"categoryName": "Passes",
"_id": "5f65cf7452e1d9156af84bcb"
在这个故事中，我有两个关于故事的 cmets 我想根据 cmets.createdDate 对评论进行排序，但我没有得到任何解决方案的期望结果？
提前致谢
【问题讨论】：
如果您使用的是 MongoDB4.4 版本，那么您可以使用 $function 运算符，第二个选项您需要 $unwind cmets 数组，然后使用排序阶段，然后 $group 您的 cmets。 【参考方案1】：根据您的文档，您可以应用以下聚合：
db.collection.aggregate([
"$unwind": "$stories.comments"
,
"$sort":
"stories.comments.createdDate": -1
,
"$group":
"_id": "_id",
"comments":
"$push": "$stories.comments"
,
"stories":
"$first": "$stories"
,
"users":
"$first": "$users"
,
"places":
"$first": "$places"
,
"categories":
"$first": "$categories"
,
"$set":
"stories.comments": "$comments"
,
"$project":
"comments": 0
])
【讨论】：
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