javascript - 查找过去 7 天当天的最后一份文件

Question

我每小时都会向模式添加条目，以便跟踪几天内的增长，同时保持当天的当前分数。现在我希望能够提取过去一周每一天的最新记录。结果将是前 6 天午夜或午夜前后的 6 条记录，第 7 条记录是当天的最新记录。

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

我试过使用这个静态的，但它提取了 7 次完全相同的记录

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检索我想要的结果。无论如何要在这里做这个？

Answer 1

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

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，但我已尝试将她的示例改编为下面的案例。请注意，我将 createdAt default 属性从一个值更改为一个函数，并向您的模式添加了一个额外的字段 datestamp:

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()

);