MongoDB：使用嵌套的$ group进行聚合
[英]MongoDB: Aggregate with nested $group
问题描述
I have the following query: 
我有以下查询：
db.test.aggregate([
{
$match: {
'type': 'energy'
}
},
{
$limit: 10000
},
{
$addFields: {
day: {
$dateToString: {
date: "$when.date",
format: "%d/%m/%Y"
}
},
sensor: "$id"
},
},
{
$project: {
_id: 1,
sensor: 1,
when: 1,
value: 1,
day: 1
}
},
{
$group: {
_id: "$day",
data: {
$push: "$$ROOT"
},
}
},
{
$sort: {
'data': 1
}
}
])
Which returns this data format: 返回此数据格式：
{
"_id" : "05/04/2018",
"data" : [
{
"_id" : ObjectId("5ac66be9b02d5c18fd4106c7"),
"value" : 0,
"when" : {
"date" : ISODate("2018-04-05T13:53:22.703-03:00"),
"unix" : 1522947202,
"milli" : 1522947202703
},
"day" : "05/04/2018",
"sensor" : "sen3"
},
{
"_id" : ObjectId("5ac66be9b02d5c18fd4106c8"),
"value" : 0,
"when" : {
"date" : ISODate("2018-04-05T13:53:22.705-03:00"),
"unix" : 1522947202,
"milli" : 1522947202705
},
"day" : "05/04/2018",
"sensor" : "sen4"
}
]
},
{
"_id" : "06/04/2018",
"data" : [
{
"_id" : ObjectId("5ac7e5d2efe88a4e76c008d2"),
"value" : 0,
"when" : {
"date" : ISODate("2018-04-06T18:25:38.885-03:00"),
"unix" : 1523049938,
"milli" : 1523049938885
},
"day" : "06/04/2018",
"sensor" : "sen3"
},
{
"_id" : ObjectId("5ac7e5e4efe88a4e76c008d5"),
"value" : 0,
"when" : {
"date" : ISODate("2018-04-06T18:25:56.105-03:00"),
"unix" : 1523049956,
"milli" : 1523049956105
},
"day" : "06/04/2018",
"sensor" : "sen3"
}
]
},
...
Note that we have in each "data" document, different types of sensors (sen3, sen4, ... ,senN). 请注意，我们在每个“数据”文档中都有不同类型的传感器（sen3，sen4，...，senN）。
I'm trying to aggregate this result once more, agrouping the data by sensor, to get the output something like this: 我试图再次聚合这个结果，通过传感器对数据进行聚合，得到如下输出：
{
"_id" : "05/04/2018",
"sen3" : [
{
"_id" : ObjectId("5ac66be9b02d5c18fd4106c7"),
"value" : 0,
"when" : {
"date" : ISODate("2018-04-05T13:53:22.703-03:00"),
"unix" : 1522947202,
"milli" : 1522947202703
},
"day" : "05/04/2018",
"sensor" : "sen3"
},
{
"_id" : ObjectId("5ac66be9b02d5c18fd4106c7"),
"value" : 0,
"when" : {
"date" : ISODate("2018-04-05T13:53:22.703-03:00"),
"unix" : 1522947202,
"milli" : 1522947202703
},
"day" : "05/04/2018",
"sensor" : "sen3"
}
],
"sen4" : [
{
"_id" : ObjectId("5ac66be9b02d5c18fd4106c8"),
"value" : 0,
"when" : {
"date" : ISODate("2018-04-05T13:53:22.705-03:00"),
"unix" : 1522947202,
"milli" : 1522947202705
},
"day" : "05/04/2018",
"sensor" : "sen4"
},
{
"_id" : ObjectId("5ac66be9b02d5c18fd4106c8"),
"value" : 0,
"when" : {
"date" : ISODate("2018-04-05T13:53:22.705-03:00"),
"unix" : 1522947202,
"milli" : 1522947202705
},
"day" : "05/04/2018",
"sensor" : "sen4"
}
]
},
{
"_id" : "06/04/2018",
"sen3" : [
{
"_id" : ObjectId("5ac7e5d2efe88a4e76c008d2"),
"value" : 0,
"when" : {
"date" : ISODate("2018-04-06T18:25:38.885-03:00"),
"unix" : 1523049938,
"milli" : 1523049938885
},
"day" : "06/04/2018",
"sensor" : "sen3"
},
{
"_id" : ObjectId("5ac7e5e4efe88a4e76c008d5"),
"value" : 0,
"when" : {
"date" : ISODate("2018-04-06T18:25:56.105-03:00"),
"unix" : 1523049956,
"milli" : 1523049956105
},
"day" : "06/04/2018",
"sensor" : "sen3"
}
],
"sen4": [
{
"_id" : ObjectId("5ac7e7a7efe88a4e76c008de"),
"value" : 0,
"when" : {
"date" : ISODate("2018-04-06T18:33:27.365-03:00"),
"unix" : 1523050407,
"milli" : 1523050407365
},
"day" : "06/04/2018",
"sensor" : "sen4"
},
{
"_id" : ObjectId("5ac7e7a7efe88a4e76c008de"),
"value" : 0,
"when" : {
"date" : ISODate("2018-04-06T18:33:27.365-03:00"),
"unix" : 1523050407,
"milli" : 1523050407365
},
"day" : "06/04/2018",
"sensor" : "sen4"
}
]
}
In short: I want to group the data in days , sensors and inside each sensor the results that belongs with that day and sensor. 简而言之：我想在几天内将数据分组， 传感器和每个传感器内部的数据分别属于当天和传感器。
I'm trying to create a nested $group but in all tentatives it goes wrong. 我正在尝试创建一个嵌套的$group但在所有试验中它都会出错。
Is this possible to do and case yes, how? 这是可能的吗和案例是，怎么样？
1 个解决方案
解决方案1
2 已采纳 2018-08-26 04:03:58
You can try below aggregation in mongodb 3.6 and above 您可以在mongodb 3.6及更高版本中尝试以下聚合
db.collection.aggregate([
{ "$match": { "type": "energy" }},
{ "$limit": 10000 },
{ "$addFields": {
"day": { "$dateToString": { "date": "$when.date", "format": "%d/%m/%Y" }},
"sensor": "$id"
}},
{ "$project": { "_id": 1, "sensor": 1, "when": 1, "value": 1, "day": 1 }},
{ "$group": {
"_id": { "day": "$day", "sensor": "$sensor" },
"data": { "$push": "$$ROOT" }
}},
{ "$group": {
"_id": { "day": "$_id.day" },
"data": { "$push": { "k": "$_id.sensor", "v": "$data" }}
}},
{ "$addFields": { "data": { "$arrayToObject": "$data" }}},
{ "$replaceRoot": { "newRoot": { "$mergeObjects": [ "$_id", "$data" ] }}}
])
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