MongoDB 聚合框架查询:$group、$project、$addFields 和 $reduce。
用例:我在集合中有多个带有嵌套文档数组的文档，需要一个结果分组依据和每个组项目的总和作为累积量。此外，在年份(日期)上设置匹配参数，如果年份匹配，则只有该年份文档应该分组并返回体积(嵌套文档数组)的总和。
以下是集合中的文档:
{
"_id": "1",
"LSD": {
"name": "TDL 05",
"LSDNumber": "031"
},
"POD": [{
"Volume": 35.40,
"VolUnit": "m3"
},
{
"Volume": 20.75,
"VolUnit": "m3"
},
{
"Volume": 15,
"VolUnit": "m3"
}
],
"createdon": {
"$date": "2014-08-02T18:49:17.000Z"
}
},
{
"_id": "2",
"LSD": {
"name": "Stock Watering",
"LSDNumber": "01"
},
"POD": [{
"Volume": 105,
"VolUnit": "m3"
},
{
"Volume": 70,
"VolUnit": "m3"
},
{
"Volume": 35,
"VolUnit": "m3"
}
],
"createdon": {
"$date": "2014-08-02T18:49:17.000Z"
}
},
{
"_id": "3",
"LSD": {
"name": "TDL 30 Stock Water",
"LSDNumber": "030"
},
"POD": [{
"Volume": 87,
"VolUnit": "m3"
}],
"createdon": {
"$date": "2019-08-02T18:49:17.000Z"
}
},
{
"_id": "4",
"LSD": {
"name": "TDL 30 Stock Water",
"LSDNumber": "030"
},
"POD": [{
"Volume": 25.12,
"VolUnit": "m3"
}],
"createdon": {
"$date": "2019-08-02T18:49:17.000Z"
}
},
{
"_id": "5",
"LSD": {
"name": "TDL 05",
"LSDNumber": "031"
},
"POD": [
{
"Volume": 21,
"VolUnit": "m3"
}
],
"createdon": {
"$date": "2014-08-02T18:49:17.000Z"
}
}
我有一个查询(C# 驱动程序 2.0)，按“LSD.LSDNumber”和“POD.Volume”的总和分组。这里没有添加匹配参数。这很好用。
查询:
{
aggregate([{
"$group": {
"_id": "$LSD.LSDNumber",
"doc": {
"$push": "$POD"
},
"data": {
"$first": "$$ROOT"
}
}
}, {
"$addFields": {
"LSDNumber": "$_id",
"GroupByDocCount": {
"$size": "$doc"
},
"Cumulative": {
"$reduce": {
"input": "$doc",
"initialValue": [],
"in": {
"$concatArrays": ["$$value", "$$this"]
}
}
}
}
}, {
"$project": {
"LSDNumber": 1,
"GroupByDocCount": 1,
"CumulativeVol": {
"$sum": "$Cumulative.Volume"
}
}
}])
}
结果如下。
{
"LSDNumber":"031",
"GroupByDocCount": 2,
"CumulativeVol": 92.15
},
{
"LSDNumber":"030",
"GroupByDocCount": 2,
"CumulativeVol": 112.12
},
{
"LSDNumber":"01",
"GroupByDocCount": 1,
"CumulativeVol": 210
}
但是，我想按年份(在“createdon”)日期以及分组依据(LSD.LSDNumber)和体积总和(POD.Volume)获取文档匹配。 例如，如果年份是 2014 年，则结果应如下所示。
{
"LSDNumber":"031",
"GroupByDocCount": 2,
"CumulativeVol": 92.15,
"Year": 2014
},
{
"LSDNumber":"01",
"GroupByDocCount": 1,
"CumulativeVol": 210,
"Year": 2014
}
我正在尝试的查询始终不返回任何内容。
{
aggregate([{
"$project": {
"LSDNumber": 1,
"GroupByDocCount": 1,
"CumulativeVol": {
"$sum": "$Cumulative.Volume"
},
"year": {
"$year": "$data.createdon"
}
}
}, {
"$match": {
"year": 2014
}
}, {
"$group": {
"_id": "$LSD.LSDNumber",
"year": {
"$first": "$year"
},
"doc": {
"$push": "$POD"
},
"data": {
"$first": "$$ROOT"
}
}
}, {
"$addFields": {
"LSDNumber": "$_id",
"yearCreate": "$year",
"GroupByDocCount": {
"$size": "$doc"
},
"Cumulative": {
"$reduce": {
"input": "$doc",
"initialValue": [],
"in": {
"$concatArrays": ["$$value", "$$this"]
}
}
}
}
}])
}
这里出了什么问题。任何帮助将不胜感激!!
最佳答案
您可以在 $addField 管道中添加 Year 变量，然后添加 $match。
{
"$group": {
"_id": "$LSD.LSDNumber",
"doc": {
"$push": "$POD"
},
"data": {
"$first": "$$ROOT"
}
}
}, {
"$addFields": {
"LSDNumber": "$_id",
"GroupByDocCount": {
"$size": "$doc"
},
"Cumulative": {
"$reduce": {
"input": "$doc",
"initialValue": [],
"in": {
"$concatArrays": ["$$value", "$$this"]
}
}
},
"Year": {
"$year": "$data.createdon"
}
}
}, {
"$match" : {"Year" : 2014}
}, {
"$project": {
"LSDNumber": 1,
"GroupByDocCount": 1,
"CumulativeVol": {
"$sum": "$Cumulative.Volume"
},
"Year" : "$Year"
}
}
=== 结果 ===
/* 1 */
{
"_id" : "01",
"LSDNumber" : "01",
"GroupByDocCount" : 1,
"CumulativeVol" : 210,
"Year" : 2014
}
/* 2 */
{
"_id" : "031",
"LSDNumber" : "031",
"GroupByDocCount" : 2,
"CumulativeVol" : 92.15,
"Year" : 2014
}
关于MongoDB $reduce(aggregation) 将嵌套文档在数组中的总和分组并按组计数，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/57888745/