myModel.find({}, function(err, items){
console.log(items.length); // big number
});
如何将返回的项目限制为仅插入的最新10项?
在最新的mongoose中(编写本文时为3.8.1),你会做两件事:(1)你必须将单个参数传递给sort(),它必须是一个约束数组或一个约束,(2) )execFind()消失了,取而代之的是exec()。因此,使用mongoose 3.8.1你会这样做:
var q = models.Post.find({published: true}).sort({'date': -1}).limit(20);
q.exec(function(err, posts) {
// `posts` will be of length 20
});
或者你可以像这样将它链接在一起:
models.Post
.find({published: true})
.sort({'date': -1})
.limit(20)
.exec(function(err, posts) {
// `posts` will be of length 20
});
像这样,使用.limit():
var q = models.Post.find({published: true}).sort('date', -1).limit(20);
q.execFind(function(err, posts) {
// `posts` will be of length 20
});
我有点懒,所以我喜欢简单的事情:
let users = await Users.find({}, null,{limit: 50});
models.Post.find({published: true}, {sort: {'date': -1}, limit: 20}, function(err, posts) {
// `posts` with sorted length of 20
});
出于某种原因,我无法使用提议的答案,但我找到另一种变体,使用select,对我有用:
models.Post.find().sort('-date').limit(10).select('published').exec(function(e, data){
...
});
API可能改变了吗?我使用的是3.8.19版本
...另外确保使用:
mongoose.Promise = Promise;
这为当地的ES6承诺设定了猫鼬承诺。没有这个添加我得到:
弃用警告:Mongoose:mpromise(mongoose的默认承诺库)已被弃用,请插入您自己的promise库:http://mongoosejs.com/docs/promises.html
查找参数
参数find函数取如下:
«Object»
。«Object|String»
可选字段返回,请参阅Query.prototype.select()«Object»
可选参见Query.prototype.setOptions()«Function»
如何限制
const Post = require('./models/Post');
Post.find(
{ published: true },
null,
{ sort: { 'date': 'asc' }, limit: 20 },
function(error, posts) {
if (error) return `${error} while finding from post collection`;
return posts; // posts with sorted length of 20
}
);
额外信息
Mongoose允许您以不同的方式查询您的收藏,例如:Official Documentation
// named john and at least 18
MyModel.find({ name: 'john', age: { $gte: 18 }});
// executes, passing results to callback
MyModel.find({ name: 'john', age: { $gte: 18 }}, function (err, docs) {});
// executes, name LIKE john and only selecting the "name" and "friends" fields
MyModel.find({ name: /john/i }, 'name friends', function (err, docs) { })
// passing options
MyModel.find({ name: /john/i }, null, { skip: 10 })
// passing options and executes
MyModel.find({ name: /john/i }, null, { skip: 10 }, function (err, docs) {});
// executing a query explicitly
var query = MyModel.find({ name: /john/i }, null, { skip: 10 })
query.exec(function (err, docs) {});
// using the promise returned from executing a query
var query = MyModel.find({ name: /john/i }, null, { skip: 10 });
var promise = query.exec();
promise.addBack(function (err, docs) {});