node.js 使用猫鼬查找和计数集合元素
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Find and Count elements of collection with Mongoose
提问by Marc Bacvanski
In Mongoose, I need to find elements in a collection and count them, and getting both the results of the find and count. I have tried
在 Mongoose 中，我需要在集合中查找元素并对其进行计数，并获得查找和计数的结果。我试过了
Model.find().count(function (err, count) {
// Get count, but cannot get results of find
});
Is there a way to get both find() and count() without calling them twice?
有没有办法同时获得 find() 和 count() 而不调用它们两次？
回答by Gergo
You can use the length of the returned array:
您可以使用返回数组的长度：
Model.find().exec(function (err, results) {
var count = results.length
});
回答by user1695032
You have to do 2 separate queries unfortunately. Festo's answer only works if you have less elements in the database than the limit.
不幸的是，您必须进行 2 个单独的查询。Festo 的答案仅在数据库中的元素少于限制时才有效。
var countQuery = Model.count();
var findQuery = Model.find().limit(2);
countQuery.exec(function (e, count) {
console.log('count', count); // can be more than 2, this is not calculated, mongo stores this value internally
})
findQuery.exec(function(e, data) {
console.log('found items', data); // will be 2 or less elements
});
回答by SirPhemmiey
As stated in the mongoose documentation and in the answer by Benjamin, the method Model.count() is deprecated. Instead of using count(), the alternatives are the following:
正如猫鼬文档和本杰明的回答中所述，不推荐使用 Model.count() 方法。除了使用 count()，替代方法如下：
SomeModel.countDocuments({}, function(err, count) {
if (err) { return handleError(err) } //handle possible errors
console.log(count)
//and do some other fancy stuff
})
or
或者
SomeModel
.estimatedDocumentCount()
.then(count => {
console.log(count)
//and do one super neat trick
})
.catch(err => {
//handle possible errors
})
回答by Pulkit chadha
You can also use mongoose-paginate plugin.
你也可以使用猫鼬分页插件。
For example:
例如：
Model.paginate({}, { offset: 100, limit: 0 }).then(function(result) {
// result.docs - Array of documents
// result.total - Total number of documents in collection that match a query
// result.limit - 0
// result.offset - 100
});
