我正在使用Nodejs和MongoDB与expressjs和mongoose库,创建一个包含用户,文章和评论模式的博客API。以下是我使用的架构。
const UsersSchema = new mongoose.Schema({
username: { type: String },
email: { type: String },
date_created: { type: Date },
last_modified: { type: Date }
});
const ArticleSchema = new mongoose.Schema({
id: { type: String, required: true },
text: { type: String, required: true },
posted_by: { type: Schema.Types.ObjectId, ref: 'User', required: true },
images: [{ type: String }],
date_created: { type: Date },
last_modified: { type: Date }
});
const CommentSchema = new mongoose.Schema({
id: { type: String, required: true },
commented_by: { type: Schema.Types.ObjectId, ref: 'User', required: true },
article: { type: Schema.Types.ObjectId, ref: 'Article' },
text: { type: String, required: true },
date_created: { type: Date },
last_modified: { type: Date }
});
您可以在下面使用 mongodb 3.6 及更高版本的聚合$lookup
Article.aggregate([
{ "$match": { "posted_by": mongoose.Types.ObjectId(id) } },
{ "$lookup": {
"from": Comment.collection.name,
"let": { "id": "$_id" },
"pipeline": [
{ "$match": { "$expr": { "$eq": [ "$article", "$$id" ] } } }
],
"as": "comments"
}},
{ "$addFields": {
"comments_no": { "$size": "$comments" },
"hasCommented": { "$in": [mongoose.Types.ObjectId(id), "$comments.commented_by"] }
}}
])