mongodb返回多个子数组结果并排除其他返回结果 [英] Mongodb returning multiple sub array results and excluding other returned results

问题描述

我有以下带有节点数组的集合:

I have the following collection with a node array:

{
"_id" : ObjectId("55acf6187d4c31475417fa62"),
"node" : [
    {
        "-id" : "29331496",
        "-uid" : "1899168",
        "-changeset" : "26313303",
        "-lat" : "-37.6104102",
        "-lon" : "144.9459817",
        "-timestamp" : "2014-10-25T03:36:51Z",
        "-user" : "heyitsstevo",
        "-visible" : "true",
        "-version" : "6"
    },
    {
        "-id" : "29331497",
        "-uid" : "1899168",
        "-version" : "2",
        "-lon" : "144.9451088",
        "-timestamp" : "2014-10-25T03:36:51Z",
        "-user" : "heyitsstevo",
        "-visible" : "true",
        "-changeset" : "26313303",
        "-lat" : "-37.601881"
    },
    {
        "-id" : "29331498",
        "-timestamp" : "2014-10-25T03:36:51Z",
        "-version" : "3",
        "-uid" : "1899168",
        "-user" : "heyitsstevo",
        "-visible" : "true",
        "-changeset" : "26313303",
        "-lat" : "-37.6011267",
        "-lon" : "144.9448575"
    },
    {
        "-lon" : "144.943302",
        "-id" : "29331499",
        "-timestamp" : "2011-11-23T03:21:40Z",
        "-user" : "melb_guy",
        "-version" : "9",
        "-uid" : "11111",
        "-visible" : "true",
        "-changeset" : "9916439",
        "-lat" : "-37.5983291"
    },
    {
        "-id" : "60648717",
        "-uid" : "46482",
        "-user" : "Zulu99",
        "-lat" : "-37.6796337",
        "-lon" : "144.9220639",
        "-timestamp" : "2009-12-12T21:29:36Z",
        "-visible" : "true",
        "-version" : "2",
        "-changeset" : "3358816"
    },
    {
        "-id" : "60648718",
        "-timestamp" : "2009-12-12T21:29:35Z",
        "-uid" : "46482",
        "-version" : "2",
        "-changeset" : "3358816",
        "-user" : "Zulu99",
        "-visible" : "true",
        "-lat" : "-37.6787103",
        "-lon" : "144.9224609"
    },
    {
        "-id" : "60648719",
        "-timestamp" : "2009-12-12T21:28:58Z",
        "-user" : "Leon K",
        "-version" : "2",
        "-changeset" : "3358816",
        "-uid" : "Zulu99",
        "-visible" : "true",
        "-lat" : "-37.677841",
        "-lon" : "144.9227344"
    }
]
}

如何返回所有具有-user"=Zulu99"的节点并排除其他任何内容?

How do I return all nodes that have the "-user" = "Zulu99" and exclude anything else?

我尝试了以下查询，但它只返回它找到的第一个带有Zulu99"的节点:

I have tried the following query but it only returns the first node it finds with "Zulu99":

db.osm.find( { }, { node: {$elemMatch: {'-user': 'Zulu99'}}} )

推荐答案

如果您的文档大小大于 aggregation $unwind 会创建 笛卡尔积问题，即每个数组对象创建多个文档，因此它会创建减慢聚合查询，如果你想避免这种情况问题使用 $redact 如下:

If your documents size more then aggregation $unwind creates Cartesian Product problem i.e every array object creates multiple documents so it creates slow down aggregation query, If you want avoid this problem use $redact as like below :

db.collectionName.aggregate({
  "$match": {
    "node.-user": "Zulu99"
  }
}, {
  "$redact": {
    "$cond": {
      "if": {
        "$eq": [{
          "$ifNull": ["$-user", "Zulu99"]
        }, "Zulu99"]
      },
      "then": "$$DESCEND",
      "else": "$$PRUNE"
    }
  }
}).pretty()

<小时>

编辑

如果你想要多个条件，那么像这样使用 $cond 和 $and

If you want to multiple conditions then used $cond with $and like this

db.collectionName.aggregate({
  "$match": {
    "node.-user": "Zulu99",
    "node.-lat": "-37.6787103"
  }
}, {
  "$redact": {
    "$cond": {
      "if": {
        "$and": [{
          "$eq": [{
            "$ifNull": ["$-user", "Zulu99"]
          }, "Zulu99"]
        }, {
          "$eq": [{
            "$ifNull": ["$-lat", "-37.6787103"]
          }, "-37.6787103"]
        }]
      },
      "then": "$$DESCEND",
      "else": "$$PRUNE"
    }
  }
}).pretty()

在上面的查询中你得到 lat 检查是否等于 -37.6787103，如果你想检查 -lat 和 -lon 到 $gt 或 $lt 那么首先你应该在你的文档中更改 lat 和 lon 的数据类型，它看起来像 String 所以首先将数据类型 String 更改为 number 然后使用 比较运算符.

In above query you get that lat check whether is equal to -37.6787103 or not, if you want to check -lat and -lon to $gt or $lt then first you should changed your data type of both lat and lon in your documents it looks like String so first changed data type String to number then used comparison operator.

第二件事，如果你只想匹配 node 数组对象然后在 readact 之后使用 group 像这样:

Second things if you want only matched node array object then used group after readact like this :

db.collectionName.aggregate({
  "$match": {
    "node.-user": "Zulu99",
    "node.-lat": "-37.6787103"
  }
}, {
  "$redact": {
    "$cond": {
      "if": {
        "$and": [{
          "$eq": [{
            "$ifNull": ["$-user", "Zulu99"]
          }, "Zulu99"]
        }, {
          "$eq": [{
            "$ifNull": ["$-lat", "-37.6787103"]
          }, "-37.6787103"]
        }]
      },
      "then": "$$DESCEND",
      "else": "$$PRUNE"
    }
  }
}, {
  "$group": {
    "_id": "$_id",
    "node": {
      "$first": "$node" // use $first 
    }
  }
}).pretty()

新编辑

如果您想找出 gte 和 lte 条件，请按照以下聚合:

If you want to find out gte and lte condition then follow this aggregation :

db.collectionName.aggregate({
"$project": {
 "check": {
  "$setDifference": [{
      "$map": {
        "input": "$node",
        "as": "node1",
        "in": {
          "$cond": {
            "if": {
              "$and": [{
                "$and": [{
                  "$gte": ["$$node1.-lon", 100]
                }, {
                  "$lte": ["$$node1.-lon", 150]
                }]
              }, {
                "$and": [{
                  "$gte": ["$$node1.-lat", -50]
                }, {
                  "$lte": ["$$node1.-lat", -10]
                }]
              }]
            },
            "then": "$$node1",
            "else": false
          }
        }
      }
    },
    [false]
  ]
 }
}
}).pretty()

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