Question

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 ],
}

键arr1和arr2中的数组始终具有相同的长度。我想汇总数据，以便根据arr2过滤掉arr1中的值。

例如，如果我根据arr1寻找a过滤我的收藏品，我希望得到类似的内容：

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

使用MongoDB是否有一些方法可以实现？

谢谢，

Uirá

Answer 1

试试这个：

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 Stage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) }

在第二个项目阶段之后输出

{ "_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 }

秒$展开输出

{ "_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 }

MongoDB - 根据另一个数组过滤数组

1 个答案: