Javascript 带有NodeJS的复杂MongoDB集合查询

我在

MongoDB

中收集了大量文档，例如以下结构：

{ "key" : "a" ,"data" : "value1" , "lastname" : "Doe" }<br>
{ "key" : "ab" , "data" : "value1" , "lastname" : "Doe" }<br>
{ "key" : "abc" ,   "data" : "value1" , "lastname" : "Doe" } <<< <br>
{ "key" : "d" ,     "data" : "value2" , "lastname" : "Doe" }<br>
{ "key" : "df" ,    "data" : "value2" , "lastname" : "Doe" }<br>
{ "key" : "dfg" ,   "data" : "value2" , "lastname" : "Doe" } <<< <br>

---

通过创建两个单独的查询，我可以在两个过程中提取数据，但我想看看这是否可以在一个过程中完成。

尚未完全格式化：

db.coll.aggregate([
 {$project: {key:1, root: '$$ROOT', lastname: 1, data: 1, keyLength: {$strLenBytes: '$key'}, keyIndexes: {$range:[0,  {$strLenBytes: '$key'}]}}}, 
 {$unwind: '$keyIndexes'}, 
 {$group: {items: {$push: '$root'}, count: {$sum: 1}, _id: {$substrBytes: ['$key', '$keyIndexes', 1]}}}, 
 {$match: {count: 1}}, 
 {$group: {_id: '$items.lastname', items: {$push: {$arrayElemAt: ['$items', 0]}}}}
]).pretty()
{
    "_id" : [
        "Doe"
    ],
    "items" : [
        {
            "_id" : ObjectId("58f62e5433530ab32f554fd6"),
            "key" : "abc",
            "data" : "value1",
            "lastname" : "Doe"
        },
        {
            "_id" : ObjectId("58f62e5433530ab32f554fd9"),
            "key" : "dfg",
            "data" : "value2",
            "lastname" : "Doe"
        }
    ]
}

可能重复的

db.coll.aggregate([
 {$project: {key:1, root: '$$ROOT', lastname: 1, data: 1, keyLength: {$strLenBytes: '$key'}, keyIndexes: {$range:[0,  {$strLenBytes: '$key'}]}}}, 
 {$unwind: '$keyIndexes'}, 
 {$group: {items: {$push: '$root'}, count: {$sum: 1}, _id: {$substrBytes: ['$key', '$keyIndexes', 1]}}}, 
 {$match: {count: 1}}, 
 {$group: {_id: '$items.lastname', items: {$push: {$arrayElemAt: ['$items', 0]}}}}
]).pretty()
{
    "_id" : [
        "Doe"
    ],
    "items" : [
        {
            "_id" : ObjectId("58f62e5433530ab32f554fd6"),
            "key" : "abc",
            "data" : "value1",
            "lastname" : "Doe"
        },
        {
            "_id" : ObjectId("58f62e5433530ab32f554fd9"),
            "key" : "dfg",
            "data" : "value2",
            "lastname" : "Doe"
        }
    ]
}