$maxDistance - Amazon DocumentDB
示例（MongoDB 外壳）代码示例

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$maxDistance

Amazon DocumentDB 中的$maxDistance运算符用于指定距离 GeoJSON 点的最大距离（以米为单位），文档必须在该距离之内才能包含在查询结果中。此运算符与运$nearSphere算符配合使用以执行地理空间查询。

参数

  • $maxDistance：距离参考点的最大距离（以米为单位），文档必须在该距离之内才能包含在查询结果中。

示例（MongoDB 外壳）

以下示例演示如何使用 Amazon DocumentDB 中的$maxDistance运算符来查找距离波士顿 100 千米范围内的所有州首府。

创建示例文档

db.capitals.insert([
  { state: "Massachusetts", city: "Boston", location: { type: "Point", coordinates: [-71.0589, 42.3601] } },
  { state: "Rhode Island", city: "Providence", location: { type: "Point", coordinates: [-71.4128, 41.8239] } },
  { state: "New Hampshire", city: "Concord", location: { type: "Point", coordinates: [-71.5383, 43.2067] } },
  { state: "Vermont", city: "Montpelier", location: { type: "Point", coordinates: [-72.5751, 44.2604] } }
]);

查询示例

db.capitals.find(
  {
    location: {
      $nearSphere: {
        $geometry: { type: "Point", coordinates: [-71.0589, 42.3601] },
        $maxDistance: 100000
      }
    }
  },
  { state: 1, city: 1, _id: 0 }
);

输出

[
  { "state": "Rhode Island", "city": "Providence" },
  { "state": "New Hampshire", "city": "Concord" }
]

代码示例

要查看使用该$maxDistance命令的代码示例，请选择要使用的语言的选项卡：

Node.js
const { MongoClient } = require('mongodb');

async function findCapitalsNearBoston() {
  const client = await MongoClient.connect('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false');
  const db = client.db('test');
  const capitals = db.collection('capitals');

  const result = await capitals.find({
    location: {
      $nearSphere: {
        $geometry: { type: "Point", coordinates: [-71.0589, 42.3601] },
        $maxDistance: 100000
      }
    }
  }, {
    projection: { state: 1, city: 1, _id: 0 }
  }).toArray();

  console.log(result);
  await client.close();
}

findCapitalsNearBoston();
Python
from pymongo import MongoClient

def find_capitals_near_boston():
    client = MongoClient('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false')
    db = client.test
    capitals = db.capitals

    result = list(capitals.find(
        {
            "location": {
                "$nearSphere": {
                    "$geometry": { "type": "Point", "coordinates": [-71.0589, 42.3601] },
                    "$maxDistance": 100000
                }
            }
        },
        {"state": 1, "city": 1, "_id": 0}
    ))

    print(result)
    client.close()

find_capitals_near_boston()