我正在尝试将集合中的文档聚合为嵌套图。以下是我正在使用的评论商店应用程序的示例数据 -
帖子收藏:
{
"_id" : "1",
"text" : "hey",
}
{
"_id" : "2",
"text" : "hello",
"replyTo" : "1"
}
{
"_id" : "3",
"text" : "What's up?",
"replyTo" : "2"
}
{
"_id" : "4",
"text" : "How are you",
"replyTo" : "1"
}
{
"_id" : "5",
"text" : "Knock, knock!",
}
我期待的结果应该是:
{
"_id": "1",
"text": "hey",
"replies": [
{
"_id": "2",
"text": "hello",
"replyTo": "1",
"replies": [
{
"_id": "3",
"text": "What's up?",
"replyTo": "2"
}
]
},
{
"_id": "4",
"text": "How are you",
"replyTo": "1"
}
]
}
{
"_id" : "5",
"text" : "Knock, knock!",
}
我尝试了$ graphLookup,它递归处理文档,但结果是一个扁平数组,这不是我所期望的 -
db.posts.aggregate(
[
{
"$graphLookup" : {
"from" : "posts",
"startWith" : "$_id",
"connectFromField" : "_id",
"connectToField" : "replyTo",
"as" : "replies"
}
}
],
{
"allowDiskUse" : false
}
);
结果:
{
"_id" : "1",
"text" : "hey",
"slug_path" : "1",
"replies" : [
{
"_id" : "2",
"text" : "hello",
"slug_path" : "1/2",
"replyTo" : "1"
},
{
"_id" : "4",
"text" : "How are you",
"slug_path" : "1/4",
"replyTo" : "1"
},
{
"_id" : "3",
"text" : "what's up?",
"slug_path" : "1/2/3",
"replyTo" : "2"
}
]
}
{
"_id" : "2",
"text" : "hello",
"slug_path" : "1/2",
"replyTo" : "1",
"replies" : [
{
"_id" : "3",
"text" : "what's up?",
"slug_path" : "1/2/3",
"replyTo" : "2"
}
]
}
{
"_id" : "4",
"text" : "How are you",
"slug_path" : "1/4",
"replyTo" : "1",
"replies" : [
]
}
{
"_id" : "3",
"text" : "what's up?",
"slug_path" : "1/2/3",
"replyTo" : "2",
"replies" : [
]
}
{
"_id" : "5",
"text" : "Knock, knock!",
"replies" : [
]`
}
有没有办法可以实现我期待的聚合类型?
由于 Davinder
答案 0 :(得分:0)
我最终放弃了$ graphLookup,因为它只能提供1级父子关系,并且不能递归地创建树状结构作为结果。我能够在Java中完全创建树状结构,并且程序从性能角度快速运行。