[英]Destructure arrays within the MongoDB aggregation pipeline
我想知道是否有可能在我仍在 MongoDB 聚合管道中时解构数组,这将使我的代码更加整洁。
例如,我有以下聚合管道。
await User.aggregate([
{ $match: { _id: userID } },
{
$project: { chatLogs: 1, username: 1, profilePicURL: 1 },
},
{ $unwind: "$chatLogs" },
{
$lookup: {
from: "users",
let: { recipientID: "$chatLogs.recipientID" },
pipeline: [
{
$match: { $expr: { $eq: ["$_id", "$$recipientID"] } },
},
{ $project: { profilePicURL: 1 } },
],
as: "chatLogs.recipientID",
},
},
]);
这在查询时给出以下结果:
{
"_id": "5f2ffb54eea9c2180a732afa",
"username": "joe",
"profilePicURL": "/images/profile/default_profile.png",
"chatLogs": {
"recipientID": [
{
"_id": "5f2faf5ad18a76073729f475",
"profilePicURL": "/images/profile/default_profile.png"
}
],
"chat": "5f30b6c3d117441c2abda1ba"
}
}
就我而言,因为“recipientID”代表默认的 MongoDB id,所以它总是唯一的。 因此,我更喜欢以下内容,其中生成的收件人 ID 字段不再是无意义的数组
预期结果:
{
"_id": "5f2ffb54eea9c2180a732afa",
"username": "joe",
"profilePicURL": "/images/profile/default_profile.png",
"chatLogs": {
"recipientID": {
"_id": "5f2faf5ad18a76073729f475",
"profilePicURL": "/images/profile/default_profile.png"
}
"chat": "5f30b6c3d117441c2abda1ba"
}
}
您可以在最后一个管道中使用$unwind
解构recipientID
数组,
await User.aggregate([
... // your all pipelines
// add this line
{ $unwind: "$chatLogs.recipientID" }
]);
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