Node.js 如何在mongoose中排序、选择和查询子文档
所以我尝试对子文档进行排序,但也选择了所有内容。似乎我无法使用常规查询,因此我尝试了w/Node.js 如何在mongoose中排序、选择和查询子文档,node.js,mongodb,mongoose,aggregation-framework,Node.js,Mongodb,Mongoose,Aggregation Framework,所以我尝试对子文档进行排序,但也选择了所有内容。似乎我无法使用常规查询,因此我尝试了w/aggregate mongoose = require("mongoose"); mongoose.connect("localhost:27017", function(err) { mongoose.connection.db.dropDatabase(); Story = mongoose.model("Story", { title: String, comments: [{
aggregate
mongoose = require("mongoose");
mongoose.connect("localhost:27017", function(err) {
mongoose.connection.db.dropDatabase();
Story = mongoose.model("Story", {
title: String,
comments: [{
author: String,
content: String
}]
});
sample = new Story({
title: "Foobar",
comments: [
{
author: "A author",
content: "1 Content"
},
{
author: "B author",
content: "2 Content"
}
]
});
sample.save(function(err, doc) {
Story.aggregate([
{ $match: {
_id: doc._id
}},
{ $unwind: "$comments" },
{ $project: {"comments": 1}},
{ $sort: {"comments.author": -1}}
], function (err, result) {
if (err) {
console.log(err);
return;
}
console.log(result);
});
})
});
这几乎奏效了:
[ { _id: 541c0f8098f85ac41c240de4,
comments:
{ author: 'B author',
content: '2 Content',
_id: 541c0f8098f85ac41c240de5 } },
{ _id: 541c0f8098f85ac41c240de4,
comments:
{ author: 'A author',
content: '1 Content',
_id: 541c0f8098f85ac41c240de6 } } ]
但我想要的是:
[ { author: 'B author',
content: '2 Content',
_id: 541c0f8098f85ac41c240de5 },
{ author: 'A author',
content: '1 Content',
_id: 541c0f8098f85ac41c240de6 } ]
我可以使用lodash,但有没有办法只使用mongodb?您可以更改
$project
以重新调整输出以提供所需的结构:
Story.aggregate([
{ $unwind: "$comments" },
{ $project: {
author: '$comments.author',
content: '$comments.content',
_id: '$comments._id'
}},
{ $sort: {author: -1}}
], function (err, result) { ...
输出:
[ { _id: 541c2776149002af52ed3c4a,
author: 'B author',
content: '2 Content' },
{ _id: 541c2776149002af52ed3c4b,
author: 'A author',
content: '1 Content' } ]
非常好,谢谢!有没有一种方法可以自动做到这一点?不指定字段?@Vinz243不,您需要单独命名投影中的每个字段,因为您希望它们位于顶层。