2

我正在使用 MongoDB，这就是我的文档的样子

{
    "_id": 1,
   "arr1": ["a", "a", "b", "c"],
   "arr2": [1, 4, 2, 3 ],
},
{
    "_id": 2,
   "arr1": ["z", "a", "b", "a"],
   "arr2": [1, 4, 2, 3 ],
}

arr1键中的数组arr2总是具有相同的长度。我想汇总数据，以便我可以过滤掉arr2基于arr1.

例如，如果我根据arr1查找过滤我的收藏a，我想得到类似的东西：

{ "_id": 1, "arr1": "a", "arr2": 1},
{ "_id": 1, "arr1": "a", "arr2": 4 },
{ "_id": 2, "arr1": "a", "arr2": 3 },
{ "_id": 2, "arr1": "a", "arr2": 3 }

有什么方法可以使用 MongoDB 来实现吗？

谢谢，

乌拉

4

1 回答 1

2

尝试这个： 

db.col1.aggregate([
   {  $unwind: 
         { path:"$arr2", includeArrayIndex: "i"}},
   {  $project: 
         {
           "arr2":1,
           "arr1": { $slice: ["$arr1","$i",1] }}
          },
   {$unwind: "$arr1"}
   {$match: { "arr1":"a" }}
 ])

第一个 $unwind 阶段的输出

{ "_id" : 1, "arr1" : [ "a", "a", "b", "c" ], "arr2" : 1, "i" : NumberLong(0) }
{ "_id" : 1, "arr1" : [ "a", "a", "b", "c" ], "arr2" : 4, "i" : NumberLong(1) }
{ "_id" : 1, "arr1" : [ "a", "a", "b", "c" ], "arr2" : 2, "i" : NumberLong(2) }
{ "_id" : 1, "arr1" : [ "a", "a", "b", "c" ], "arr2" : 3, "i" : NumberLong(3) }
{ "_id" : 2, "arr1" : [ "z", "a", "b", "a" ], "arr2" : 1, "i" : NumberLong(0) }
{ "_id" : 2, "arr1" : [ "z", "a", "b", "a" ], "arr2" : 4, "i" : NumberLong(1) }
{ "_id" : 2, "arr1" : [ "z", "a", "b", "a" ], "arr2" : 2, "i" : NumberLong(2) }
{ "_id" : 2, "arr1" : [ "z", "a", "b", "a" ], "arr2" : 3, "i" : NumberLong(3) }

项目二期后投入使用

{ "_id" : 1, "arr1" : [ "a" ], "arr2" : 1 }
{ "_id" : 1, "arr1" : [ "a" ], "arr2" : 4 }
{ "_id" : 1, "arr1" : [ "b" ], "arr2" : 2 }
{ "_id" : 1, "arr1" : [ "c" ], "arr2" : 3 }
{ "_id" : 2, "arr1" : [ "z" ], "arr2" : 1 }
{ "_id" : 2, "arr1" : [ "a" ], "arr2" : 4 }
{ "_id" : 2, "arr1" : [ "b" ], "arr2" : 2 }
{ "_id" : 2, "arr1" : [ "a" ], "arr2" : 3 }

第二个 $unwind 输出

{ "_id" : 1, "arr1" : "a", "arr2" : 1 }
{ "_id" : 1, "arr1" : "a", "arr2" : 4 }
{ "_id" : 1, "arr1" : "b", "arr2" : 2 }
{ "_id" : 1, "arr1" : "c", "arr2" : 3 }
{ "_id" : 2, "arr1" : "z", "arr2" : 1 }
{ "_id" : 2, "arr1" : "a", "arr2" : 4 }
{ "_id" : 2, "arr1" : "b", "arr2" : 2 }
{ "_id" : 2, "arr1" : "a", "arr2" : 3 }

最终 $match 输出：

{ "_id" : 1, "arr1" : [ "a" ], "arr2" : 1 }
{ "_id" : 1, "arr1" : [ "a" ], "arr2" : 4 }
{ "_id" : 2, "arr1" : [ "a" ], "arr2" : 4 }
{ "_id" : 2, "arr1" : [ "a" ], "arr2" : 3 }
于 2016-05-14T05:53:20.390 回答