需要有关 Mongo 查询的帮助

问题描述

我们有以下数据：

[
{
    "location" : {
            "type" : "POINT","coordinates" : [
                -92.41151,35.11683
            ]
    },"geoHash" : "dr72jwgnbbst"
},{
    "location" : {
            "type" : "POINT","coordinates" : [
                -89.58342,36.859161
            ]
    },"geoHash" : "dn6qtkr5xk8m"
},"coordinates" : [
                -86.038762,36.519016
            ]
    },"geoHash" : "dn6zf0h6xtcp"
},"coordinates" : [
                -98.3081936,26.2143207
            ]
    },"geoHash" : "9udj4unjmp9f"
},"coordinates" : [
                -98.5377275,29.4878928
            ]
    },"geoHash" : "9v1zv8p52t8u"
},"coordinates" : [
                -73.7018126,42.641387
            ]
    },"geoHash" : "dreddfeup69m"
},"coordinates" : [
                -111.865295,33.431942
            ]
    },"geoHash" : "9tbqnqn5jtwq"
},"coordinates" : [
                -79.810763,34.174603
            ]
    },"geoHash" : "dnp4rv796rtz"
}]

我们需要查询以获取以“dn”、“9t”、“dr”、“9v”、“9u”开头的 geohashes 的位置，并且每个 geo hash 只应返回一个位置。例如，我们有 3 个位置的 geohash 以“dn”开头，但它应该只返回任何一个位置。 输出：

"dr" -> "location" : {
        "type" : "POINT","coordinates" : [
            -92.41151,35.11683
        ]
    }
"dn" ->     "location" : {
        "type" : "POINT","coordinates" : [
            -89.58342,36.859161
        ]
    }
"9u" ->     "location" : {
        "type" : "POINT","coordinates" : [
            -98.3081936,26.2143207
        ]
    }
"9v" -> "location" : {
        "type" : "POINT","coordinates" : [
            -98.5377275,29.4878928
        ]
    }
"9t" ->     "location" : {
        "type" : "POINT","coordinates" : [
            -111.865295,33.431942
        ]
    } 

谢谢

解决方法

如果您总是检查 geoHash 的前两个字符，请尝试 bebow 查询：

db.locations.aggregate([
    {
        $match: {
            geoHash: {
                $regex: '^dn|^9t|^dr|^9v|^9u',$options: 'i'
            }
        }
    },{
        $addFields: {
            geoHashSubStr: {
                $substr: ["$geoHash",2]
            }
        }
    },{
        $group: {
            _id: "$geoHashSubStr",// Group other fields based on your requirement.
            location: {
                $first: "$location"
            }
        }
    }
])

,

给你。

1. 按 geoHash 的前 2 个字符对所有结果进行分组。
2. 仅投影该数组的第一个元素。

db.collection.aggregate([
  {
    $group: {
      _id: {
        $substr: [
          "$geoHash",2
        ]
      },locations: {
        $push: "$location"
      }
    }
  },{
    "$project": {
      _id: true,location: {
        $arrayElemAt: [
          "$locations",0
        ]
      }
    }
  }
])

游乐场：https://mongoplayground.net/p/C_Jh5cPtldd