查找过去7天当天的最后一个文档 [英] Find last document of the day for the last 7 days

问题描述

我每小时都会向架构添加一个条目，以便跟踪当天的增长情况，同时保持当前的当前分数。现在我希望能够提取过去一周每天的最新记录。结果将是6个记录，在午夜或午夜左右，前6天，第7个记录是当天的最新记录。

I am adding entries to a schema every hour in order to track growth over the course of days while maintaining a current score for the current day. Now I would like to be able to pull the most recent record for each day for the past week. The results would be 6 records at or around midnight for 6 days previous and the 7th being the latest for the current day.

这是我的架构：

var schema = new Schema({
  aid: { type: Number }
, name: { type: String }
, score: { type: Number }
, createdAt: { type: Date, default: Date.now() }
})

编辑

我尝试过使用此静态，但它会拉动完全相同的记录7次

I've tried using this static, but it pulls the exact same record 7 times

schema.statics.getLastWeek = function(name, fn) {
  var oneday = 60 * 60 * 24
    , now = Date.now()
    , docs = []

  for (var i = 1; i <= 7; i++) {
    this.where('name', new RegExp(name, 'i'))
    .where('createdAt')
    .gte(now - (i * oneday))
    .desc('createdAt')
    .findOne(function(err,doc){
      docs.push(doc)
    })
  }
}

如果我使用的是SQL，我会选择MAXDATE进行子查询并将其连接到我的主查询，以便检索我想要的结果。无论如何要在这里做到这一点？

If I were using SQL I would do a subquery selecting MAXDATE and join it to my main query in order to retrieve the results I want. Anyway to do this here?

推荐答案

Kristina Chodorow在她的书 MongoDB中给出了这个确切任务的详细配方：权威指南 ：

Kristina Chodorow gives a detailed recipe for this exact task in her book MongoDB: The Definitive Guide:

假设我们有一个跟踪股票价格的网站。从上午10点到下午4点每隔几美元b b分钟，它获得一个股票的最新价格，它存储在MongoDB中的
。现在，作为报告申请的一部分，
我们想要找到过去30天的收盘价。这可以通过组轻松完成
。

Suppose we have a site that keeps track of stock prices. Every few minutes from 10 a.m. to 4 p.m., it gets the latest price for a stock, which it stores in MongoDB. Now, as part of a reporting application, we want to find the closing price for the past 30 days. This can be easily accomplished using group.

我不熟悉Mongoose，但是我试图适应她的例子如下。注意我将 createdAt 默认属性从值更改为函数并添加了一个额外字段 datestamp 到您的架构：

I'm not familiar with Mongoose, however I've tried to adapt her example to your case below. Note I changed the createdAt default property from a value to a function and added an extra field datestamp to your schema:

var oneday = 24 * 60 * 60;

var schema = new Schema({
  aid: { type: Number }
, name: { type: String }
, score: { type: Number }

  // default: is a function and called every time; not a one-time value!
, createdAt: { type: Date, default: Date.now }

  // For grouping by day; documents created on same day should have same value
, datestamp: { type: Number
             , default: function () { return Math.floor(Date.now() / oneday); }
             }
});


schema.statics.getLastWeek = function(name, fn) {
    var oneweekago = Date.now() - (7 * oneday);

    ret = this.collection.group({
          // Group by this key. One document per unique datestamp is returned.
          key: "datestamp"
          // Seed document for each group in result array.
        , initial: { "createdAt": 0 }
          // Update seed document if more recent document found.
        , reduce: function(doc, prev) {
              if (doc.createdAt > prev.createdAt) {
                prev.createdAt = doc.createdAt;
                prev.score = doc.score;

                // Add other fields, if desired:
                prev.name = doc.name;
              }
          // Process only documents created within past seven days
        , condition: { "createdAt" : {"$gt": oneweekago} }
        }});

   return ret.retval;

   // Note ret, the result of group() has other useful fields like:
   // total "count" of documents,
   // number of unique "keys",
   // and "ok" is false if a problem occurred during group()

);

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