2

私はMongoDBを使用しています。これが私のドキュメントの外観です

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

キー内の配列arr1とarr2常に同じ長さです。arr2に基づいて値を除外できるように、データを集計したいと思いますarr1。

たとえば、検索に基づいてコレクションをフィルタリングする場合、arr1次aのようなものを取得したいと思います。

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

MongoDB を使用してそれを達成する方法はありますか?

ありがとう、

ウイラ

4

1 に答える 1

2

これを試して： 

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

最初の $unwind ステージからの出力

{ "_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) }

プロジェクトの第 2 ステージ後のアウトプット

{ "_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 }

2 番目の $unwind 出力

{ "_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 }

最終的な $match 出力:

{ "_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 に答える