使用 java mongo db driver api 将数组作为 MongoDB 中的值进行排序

Question

在 MongoDB 中使用数组作为值进行排序

我有两个字段的集合，一个以字符串作为值，第二个字符串数组作为值。

例如

{"name" : "User-1",  "locations" : ["India", "USA", "UK"]}
{"name" : "User-2",  "locations" : ["Russia", "UK", "USA"]}
{"name" : "User-3",  "locations" : ["UK", "Japan", "India"]}
{"name" : "User-4",  "locations" : ["Japan", "USA", "UK"]}
{"name" : "User-5",  "locations" : ["India", "Italy", "Japan"]}

我想对字段“位置”进行排序。

输出必须是

{"name" : "User-5",  "locations" : ["India", "Italy", "Japan"]}
{"name" : "User-1",  "locations" : ["India", "USA", "UK"]}
{"name" : "User-4",  "locations" : ["Japan", "USA", "UK"]}
{"name" : "User-2",  "locations" : ["Russia", "UK", "USA"]}
{"name" : "User-3",  "locations" : ["UK", "Japan", "India"]}

我们如何使用 mongo db java driver api 做到这一点。

谢谢

Answer 1

您可以使用"dot notation" 为数组中的每个项目按顺序指定排序：

 db.docs.find().sort({ "locations.0": 1, "locations.1": 1, "locations.2": 1 })

这会产生：

{ "name" : "User-5", "locations" : [ "India", "Italy", "Japan" ] }
{ "name" : "User-1", "locations" : [ "India", "USA", "UK" ] }
{ "name" : "User-4", "locations" : [ "Japan", "USA", "UK" ] }
{ "name" : "User-2", "locations" : [ "Russia", "UK", "USA" ] }
{ "name" : "User-3", "locations" : [ "UK", "Japan", "India" ] }

所以它基本上按照数组中每个元素的顺序来考虑偏好。

使用基本的 Java API，您只需提供相同的排序参数：

collection.find().sort(
    new Document("locations.0",1)
        .append("locations.1",1)
        .append("locations.2",1)
);

Answer 2

在 mongo 控制台中试试这个。这里使用 mongodb 聚合框架：

db.users.aggregate({$sort:{'locations':1}})

它对我的工作令人惊讶。我已经使用各种测试样本进行了测试。如果有，请检查角落案例。以下是其中一个测试用例：

> db.users.aggregate({$sort:{'locations':1}})
{ "_id" : ObjectId("5656ce39cb0a925b3d5d16ea"), "name" : "User-6", "locations" : [ "India", "Italy", "Alabama" ] }
{ "_id" : ObjectId("5656ce44cb0a925b3d5d16eb"), "name" : "User-6", "locations" : [ "India", "Italy", "Glabama" ] }
{ "_id" : ObjectId("5656ce75cb0a925b3d5d16ed"), "name" : "User-8", "locations" : [ "India", "Italy", "Glabama", "Cloverfield" ] }
{ "_id" : ObjectId("5656ce63cb0a925b3d5d16ec"), "name" : "User-7", "locations" : [ "India", "Italy", "Glabama", "Govindam" ] }
{ "_id" : ObjectId("5656a65ecb0a925b3d5d16e9"), "name" : "User-5", "locations" : [ "India", "Italy", "Japan" ] }
{ "_id" : ObjectId("5656a65ecb0a925b3d5d16e5"), "name" : "User-1", "locations" : [ "India", "USA", "UK" ] }
{ "_id" : ObjectId("5656a65ecb0a925b3d5d16e8"), "name" : "User-4", "locations" : [ "Japan", "USA", "UK" ] }
{ "_id" : ObjectId("5656a65ecb0a925b3d5d16e6"), "name" : "User-2", "locations" : [ "Russia", "UK", "USA" ] }
{ "_id" : ObjectId("5656a65ecb0a925b3d5d16e7"), "name" : "User-3", "locations" : [ "UK", "Japan", "India" ] }

在 Java API 中应该是这样的：

AggregateIterable<Document> iterable = db.getCollection("users").aggregate(asList(
  new Document("$sort", new Document("locations", 1))));