如何使用$groupby和转换不同值mongodb

Question

如何使用$if $else分组条件MongoDB转换数据？

这个操场应该返回两个属于"测试者2"one_answers"测试者3"文本的对象，如果我在历史集合中有多个对象，它也应该检查最后一个对象，而不是所有对象如何可能

所以条件应该说，如果历史的日期是$gt，那么主集合应该不返回任何其他内容，返回匹配的条件数据。

db.main.aggregate([
{
$lookup: {
from: "history",
localField: "history_id",
foreignField: "history_id",
as: "History"
}
},
{
$unwind: "$History"
},
{
"$match": {
$expr: {
$cond: {
if: {
$eq: [
"5e4e74eb380054797d9db623",
"$History.user_id"
]
},
then: {
$and: [
{
$gt: [
"$date",
"$History.date"
]
},
{
$eq: [
"5e4e74eb380054797d9db623",
"$History.user_id"
]
}
]
},
else: {}
}
}
}
}
])

MongoPlayground

Answer 1

如果我正确理解你，那就是你想要做的：

db.main.aggregate([
{
$lookup: {
from: "history",
let: {
main_history_id: "$history_id",
main_user_id: { $toString: "$sender_id" }
},
pipeline: [
{
$match: {
$expr: {
$and: [
{
$eq: [
"$history_id",
"$$main_history_id"
]
},
{
$eq: [
"$user_id",
"$$main_user_id"
]
}
]
}
}
}
],
as: "History"
}
},
{
$unwind: {
path: "$History",
preserveNullAndEmptyArrays: true
}
},
{
$sort: {
_id: 1,
"History.history_id": 1,
"History.date": 1
}
},
{
$group: {
_id: "$_id",
data: { $last: "$$ROOT" },
History: { $last: "$History" }
}
},
{
$replaceRoot: {
newRoot: {
$mergeObjects: [
"$data",
{ History: "$History" }
]
}
}
},
{
"$match": {
$expr: {
$or: [
{
$eq: [
{ $type: "$History.date" },
"missing"
]
},
{
$ne: [
"5e4e74eb380054797d9db623",
"$History.user_id"
]
},
{
$and: [
{
$eq: [
"5e4e74eb380054797d9db623",
"$History.user_id"
]
},
{
$gte: [
"$date",
"$History.date"
]
}
]
}
]
}
}
}
])

MongoPlayground