Mongo查询更新年份取决于内部文档字段

Question

这是我的数据。我想更改年份，但它应该只对文档阵列的第一项有效

{
"_id": {
"$oid": "62053aa8aa1cfbe8c4e72662"
},
"school": "Test",
"reports": [
{
"year": "2020",     // This has to be changed to 2019
"createdAt": {
"$date": "2022-02-10T17:05:25.682Z"
},
"pid": {
"$oid": "620545d5097761628f32365a"
},
"details": {
"end_date": {
"$date": "2020-03-31T00:00:00.000Z"   // when end date is prior to July 01 of the $year mentioned.
}
}
}, {
"year": "2020",
"createdAt": {
"$date": "2022-03-14T19:08:38.125Z"
},
"pid": {
"$oid": "622f92b68a408531d4b784de"
},
"details": {
"end_date": {
"$date": "2021-03-31T00:00:00.000Z"
}
}
}
]
}

在上述数据中，如果details.end_date在当前提到的年份的7月1日之前，我想将年份减少到上一年。但它应该只更改嵌入数组的第一项。

例如，

If Year is 2020 and details.end_date is prior to 01-July-2020, then change the year to 2019
If Year is 2020 and details.end_date is after 01-July-2020, then do not change the year
If Year is 2021 and details.end_date is prior to 01-July-2021, then change the year to 2020
If Year is 2021 and details.end_date is after 01-July-2021, then do not change the year

Answer 1

您可以在聚合管道中执行以下操作：

1. 隔离reports阵列的第一个元素，以便于使用$arrayElemAt进行处理
2. 使用$cond来导出具有$month的年份值。使用$toInt和$toString进行类型转换
3. 使用CCD_ 7将处理后的第一个Elem追加回报告数组。只保留"；尾部；(即没有第一个elem(使用$slice
4. $merge将结果更新回集合

db.collection.aggregate([
{
"$addFields": {
"firstElem": {
"$arrayElemAt": [
"$reports",
0
]
}
}
},
{
"$addFields": {
"firstElem.year": {
"$cond": {
"if": {
$lt: [
{
"$month": "$firstElem.end_date"
},
7
]
},
"then": {
"$toString": {
"$subtract": [
{
"$toInt": "$firstElem.year"
},
1
]
}
},
"else": "$firstElem.year"
}
}
}
},
{
"$addFields": {
"reports": {
"$concatArrays": [
[
"$firstElem"
],
{
"$slice": [
"$reports",
1,
{
"$subtract": [
{
"$size": "$reports"
},
1
]
}
]
}
]
}
}
},
{
"$project": {
firstElem: false
}
},
{
"$merge": {
"into": "collection",
"on": "_id",
"whenMatched": "replace"
}
}
])

这是Mongo游乐场供您参考。