具有多个条件和切片的MongoDB查询 [英] MongoDB Query with multiple conditions and slice

问题描述

我有这个猫鼬查询:

 return Domain.find({domain:req.params.domain})
 .where('date').equals(date)
 .exec(function (err, domain) {
    if (!err) {
      if (!isEmpty(domain[0].visitors)) {
        domain[0]['visitors'] = domain[0].visitors.slice(0,99);
      }
  }

我想直接在数据库中切片，而不是在检索对象之后.猫鼬无法做到这一点，或者它没有记录在案，或者我没有找到文件.

I want to slice directly in the database and not after retrieving object. Mongoose cannot do this or it is not documented or I did not find documentation.

因此，我通过使用collection关键字来回退到node.js本机MongoDB驱动程序.

So I fall back to node.js native MongoDB Driver by using the collection keyword.

我的代码现在看起来如下所示，但失败了:

My code looks now as follow and fails:

return Domain.collection.find(

  { "domain":req.params.domain }, 
  { "date":date }, 
  { "visitors": { $slice:100 } }, 
    function(err,domain){
      if (!err) {
         res.status(200).send({
           domain:domain
         });
      }

完整代码: https://gist.github.com/nottinhill/b3837d4c913b9e5dd879

我尝试在MongoDB控制台中构造一个可以使用的查询，但是无法使这个简单的查询正常工作. MongoDB文档未显示如何在两个条件下进行查询.我要:

I tried in MongoDB console to construct a query that will work, but cannot get this simple query to work. MongoDB documentation does not show how to query with two conditions. I want to:

我想要的伪代码:

find
   giveBack wholeDomainObject
   where domain == domain
   where date == date
   also slice visitorsArray

推荐答案

投影是单个对象定义.另外，您可以查询"事物，而不是在符合条件的特定字段之外的投影中进行匹配. $slice 是特例默认情况下不排除投影中的其他字段:

Projection is a single object definition. Also you "query" for things rather than ask for matches in projections other than specific fields matching criteria. $slice is a special case that does not exclude other fields in the projection by default:

Domain.collection.find(
  { "domain":req.params.domain, "date": date }, 
  { "visitors": { "$slice":100 } }, 
  function(err,domain){
     // process results here
  }
);

可能还要注意，此处的$slice(就像JavaScript一样)是定义的条目数"，而不是数组索引中的n-1引用.

Probably also to note that the $slice here ( just like JavaScript ) is a defined "number of entries" and not a n-1 reference as in an array index.

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