[英]MongoDB, Aggregate $match not working on ObjectId
I have a schema that is:我有一个架构是:
var photoSchema = new mongoose.Schema({
id: String, // Unique ID identifying this photo
file_name: String,
date_time: {type: Date, default: Date.now},
user_id: mongoose.Schema.Types.ObjectId, // The user id of the user who created the photo.
comments: [commentSchema] // Comment objects representing the comments made on this photo.
});
var Photo = mongoose.model('Photo', photoSchema);
I am trying to find the photo from a specific user with most number of comments.我试图从评论数量最多的特定用户那里找到照片。 Here is what I have done:
这是我所做的:
Photo.aggregate([
{
$project: {
id: 1,
file_name: 1,
date_time: 1,
user_id: 1,
comments: 1,
length: {$size: "$comments"}
}
},
{
$match: {
user_id: mongoose.Schema.Types.ObjectId(request.params.id)
}
},
{
$sort: { length: -1 }
}
], function (err, info2){
if (err) {
// Query returned an error.
console.error('Doing /user/usage/:id error:', err);
response.status(400).send(JSON.stringify(err));
return;
}
console.log(info2);
finalOutput.most_commented = info2[0];
response.end(JSON.stringify(finalOutput));
});
I only get an empty array [] in the console.log, I know the $match is not working because if I remove $match clause, it gives me the photo with max comments across the entire table.我只在 console.log 中得到一个空数组 [],我知道 $match 不起作用,因为如果我删除 $match 子句,它会为我提供整个表中带有最大评论的照片。 I want to filter and get the photo which belong to 1 specific user, based on their user_id.
我想根据他们的 user_id 过滤并获取属于 1 个特定用户的照片。
I don't understand what I am doing wrong.我不明白我做错了什么。 I have tried:
我试过了:
1. $match: {user_id: mongoose.Schema.Types.ObjectId(request.params.id)} 1. $match: {user_id: mongoose.Schema.Types.ObjectId(request.params.id)}
2. $match: {user_id: request.params.id} 2. $match: {user_id: request.params.id}
3. $match: {"user_id": request.params.id} 3. $match: {"user_id": request.params.id}
First Step
第一步
const ObjectId = require('mongoose').Types.ObjectId
Second Step
第二步
{ $match : { _id: ObjectId("606c74d5f9e3f30f8caa3451")} }
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