需要有关 Mongo 查询的帮助

Question

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

我们需要一个查询来获取以“dn”、“9t”、“dr”、“9v”、“9u”开头的地理哈希的位置，并且每个地理哈希只有一个位置应该是 return编辑。例如，我们有 3 个位置，其 geohash 以“dn”开头，但它应该只 return 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

Answer 1

如果您总是检查 geoHash 的前两个字符，请尝试以下查询：

db.locations.aggregate([
    {
        $match: {
            geoHash: {
                $regex: '^dn|^9t|^dr|^9v|^9u',
                $options: 'i'
            }
        }
    },
    {
        $addFields: {
            geoHashSubStr: {
                $substr: ["$geoHash", 0, 2]
            }
        }
    },
    {
        $group: {
            _id: "$geoHashSubStr",
            // Group other fields based on your requirement.
            location: {
                $first: "$location"
            }
        }
    }
])

Answer 2

给你。

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

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

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

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