Question

我正在使用mongodb将信息存储到数据库中。但是我不知道我将管道用于从中获取数据的同一集合吗？让我用一个例子来解释它：

我在集合“清单”示例中有一些文档：-

{
  "_id" : 1, 
  "review" : "this is a review", 
  "bot_id" : 1 
}
{
"_id" : 2,
"review" : "this is a second review",
"type" : "reply",
"reply_to" : 1,
"bot_id" : 1
}
{
"_id" : 3,
"review" : "this is a third review",
"type" : "reply",
"reply_to" : 1,
"bot_id" : 1
}
{
  "_id" : 4, 
  "review" : "this is a another review", 
  "bot_id" : 2
}
{
  "_id" : 5,
  "review" : "this is a fifth review",
  "type" : "reply",
  "reply_to" : 2,
  "bot_id" : 1
}

我必须获取结果，例如第一个文档的_id附加到第二个，第三个文档的reply_to字段，并且匹配项将位于bot_id字段，第一个文档就像是父文档，然后第二个和第三个文档将充当第一个文档的子文档，然后使用_id:4也是父文档。谁能解释得到我想要的输出后我应该执行什么查询？

我想要的输出：-

{
  "_id" : 1, 
  "review" : "this is a review", 
  "bot_id" : 1
  "replies":[
     {
       "_id" : 2,
       "review" : "this is a second review",
       "type" : "reply",
       "reply_to" : 1,
       "bot_id" : 1,
       "replies":[
            {
               "_id" : 5,
               "review" : "this is a fifth review",
               "type" : "reply",
               "reply_to" : 2,
               "bot_id" : 1,
            }
        ]
      },
      {
        "_id" : 3,
        "review" : "this is a third review",
        "type" : "reply",
        "reply_to" : 1,
        "bot_id" : 1
       }
   ]
}
{
  "_id" : 4, 
  "review" : "this is a another review", 
  "bot_id" : 2
}

Answer 1

我可以通过使用$graphLookup 聚合，如下所示来为您提供一级 reply_to ：

db.collectionName.aggregate([
{
    $match: {"reply_to" : null }
}, 
{
    $graphLookup: { 
        from: "collectionName", 
        startWith:"$_id" , 
        connectFromField: "_id", 
        connectToField: "reply_to", 
        as: "replies"
    }    
}]).pretty()

输出为：

{
    "_id" : 1,
    "review" : "this is a review",
    "bot_id" : 1,
    "replies" : [
        {
            "_id" : 3,
            "review" : "this is a third review",
            "type" : "reply",
            "reply_to" : 1,
            "bot_id" : 1
        },
        {
            "_id" : 5,
            "review" : "this is a fifth review",
            "type" : "reply",
            "reply_to" : 2,
            "bot_id" : 1
        },
        {
            "_id" : 2,
            "review" : "this is a second review",
            "type" : "reply",
            "reply_to" : 1,
            "bot_id" : 1
        }
    ]
}
{
    "_id" : 4,
    "review" : "this is a another review",
    "bot_id" : 2,
    "replies" : [ ]
}

在更高层次上，您已经签出graph lookup的正式文档

如何在同一集合中应用递归聚合？

1 个答案: