Mongodb返回多个子数组结果并排除其他返回结果

Question

我有以下带有节点数组的集合：

{
"_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 return 所有具有“-user” = "Zulu99" 的节点并排除其他任何内容？

我尝试了以下查询，但它只是 return 它找到的第一个节点 "Zulu99":

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

Answer 1

你需要的是"aggregation" and the $map and the $setDifference个运算符

db.collection.aggregate([ 
    { 
        "$match": { 
            "node.-user": "Zulu99", 
            "node.-lat": "-37.6787103" 
        }
    },
    { 
        "$project": { 
            "node": { 
                "$setDifference": [{ 
                    "$map": { 
                        "input": "$node",
                        "as": "n", 
                        "in": { 
                            "$cond": [
                                { "$eq": [ "$$n.-user", "Zulu99" ]}, 
                                "$$n", 
                                false 
                            ]
                        } 
                    }
                }, 
                [false]]
            }
        }
    }
])

从 MongoDB 3.2 开始，您可以使用 $filter 运算符

db.collection.aggregate([
    { 
        "$match":  { 
            "node.-user": "Zulu99",
            "node.-lat": "-37.6787103"
        }
    }, 
    { "$project": {
        "node": {
            "$filter": {
                "input": "$node",
                "as": "n",
                "cond": { "$eq": [ "$$node.n", "Zulu99" ] }
            }
        }
    }}
])

产生：

{
        "_id" : ObjectId("55acf6187d4c31475417fa62"),
        "node" : [
                {
                        "-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"
                }
        ]
}

Answer 2

如果您的文档大小超过 aggregation $unwind 会创建 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，如下所示：

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

编辑

如果你想要多个条件，那么使用 $cond 和 $and 像这样

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 或不，如果你想检查 -lat and -lon 到 $gt or $lt 然后首先你应该改变您的文档中 lat and lon 的数据类型看起来像 String 所以首先更改数据类型 String to number 然后使用 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，就像这样：

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 and lte 条件，请遵循此聚合：

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()

Mongodb返回多个子数组结果并排除其他返回结果

Mongodb returning multiple sub array results and excluding other returned results

mongodb

mongodb-query

aggregation-framework