MongoDB-在ObjectId上聚合$ match [英] MongoDB - Aggregate $match on ObjectId

问题描述

我有一个看起来像这样的模式:

I have a schema that looks like this:

var mongoose = require('mongoose');

module.exports = mongoose.model('Owner',{
    username: String,
    blocks: {type:mongoose.Schema.Types.ObjectId, ref: 'Block'},
});

我正在尝试运行查询以查看所有者是否具有对Block ID的引用.所有者具有一个ObjectId数组.当我运行db.owners.aggregate({$match: {username: 'example'}},{$unwind: "$blocks"},{$project: { _id : 1,blocks: 1}})时，它将返回:

I'm trying to run a query to see if Owner has a reference to Block's id. Owner has an array of ObjectIds. When I run db.owners.aggregate({$match: {username: 'example'}},{$unwind: "$blocks"},{$project: { _id : 1,blocks: 1}}) it returns:

{ "_id" : ObjectId("550d9dc64d9dc3d026fadfc7"), "blocks" : ObjectId("550dc117dc9605ab27070af7") }
{ "_id" : ObjectId("550d9dc64d9dc3d026fadfc7"), "blocks" : ObjectId("550dc123dc9605ab27070af8") }
{ "_id" : ObjectId("550d9dc64d9dc3d026fadfc7"), "blocks" : ObjectId("550dc12edc9605ab27070af9") }
{ "_id" : ObjectId("550d9dc64d9dc3d026fadfc7"), "blocks" : ObjectId("550dc157dc9605ab27070afa") }

如何匹配块ID?我已经尝试过db.publishers.aggregate({$match: {username: 'example'}},{$unwind: "$blocks"},{$project: { _id : 1,blocks: 1}},{$match : {"blocks._id" : '550dc157dc9605ab27070afa'}})，但这不起作用.

How can I match the block id? I've tried db.publishers.aggregate({$match: {username: 'example'}},{$unwind: "$blocks"},{$project: { _id : 1,blocks: 1}},{$match : {"blocks._id" : '550dc157dc9605ab27070afa'}}) but that doesn't work.

推荐答案

我认为您不需要这样做，可以使用简单的find()或findOne()查询:

I think you don't need aggreation for that, you can use a simple find() or findOne() query:

var Mongoose = require('mongoose');
var ObjectId = Mongoose.Types.ObjectId;

Owner.findOne({ username: 'example', blocks: new ObjectId('550dc157dc9605ab27070afa') }, function (err, owner) {
   ...
});

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