Ravendb mapreduce按多个字段分组

Question

我们有一个包含流媒体视频的网站,我们希望在上周,月份和年份(滚动窗口)显示三个最受关注视频的报告.

每次观看视频时,我们都会在ravendb中存储一个文档:

public class ViewedContent
{
    public string Id { get; set; }
    public int ProductId { get; set; }
    public DateTime DateViewed { get; set; }
}

我们无法确定如何定义最能支持生成这三个报告的索引/ mapreduces.

我们尝试了以下map/reduce.

public class ViewedContentResult
{
    public int ProductId { get; set; }
    public DateTime DateViewed { get; set; }
    public int Count { get; set; }
}

public class ViewedContentIndex :
        AbstractIndexCreationTask<ViewedContent, ViewedContentResult>
{
    public ViewedContentIndex()
    {
        Map = docs => from doc in docs
                      select new
                                 {
                                     doc.ProductId,
                                     DateViewed = doc.DateViewed.Date,
                                     Count = 1
                                 };

        Reduce = results => from result in results
                            group result by result.DateViewed
                            into agg
                            select new
                                       {
                                           ProductId = agg.Key,
                                           Count = agg.Sum(x => x.Count)
                                       };
    }
}

但是,此查询会引发错误:

var lastSevenDays = session.Query<ViewedContent, ViewedContentIndex>()
                .Where( x => x.DateViewed > DateTime.UtcNow.Date.AddDays(-7) );

错误:"DateViewed未编入索引"

最终,我们想查询类似于:

var lastSevenDays = session.Query<ViewedContent, ViewedContentIndex>()
                .Where( x => x.DateViewed > DateTime.UtcNow.Date.AddDays(-7) )
                .GroupBy( x => x.ProductId )
                .OrderBy( x => x.Count )

这实际上并没有编译,因为OrderBy是错误的; Count在这里不是有效的属性.

任何帮助在这里将不胜感激.

Answer 1

如果你在SQL土地上,每个报告都是一个不同的GROUP BY,它告诉你需要三个索引 - 一个只有月份,一个按周,一个月,一个一年(或者可能略有不同,取决于关于你实际上将如何进行查询.

现在,你有一个DateTime - 这会出现一些问题 - 你真正想要做的是索引DateTime的Year组件,日期时间的Month组件和该日期时间的Day组件.(或者只是其中的一个或两个,具体取决于您要生成哪个报告.

我只是在这里引用你的代码,所以很明显它不会编译,但是:

public class ViewedContentIndex :
    AbstractIndexCreationTask<ViewedContent, ViewedContentResult>
{
public ViewedContentIndex()
{
    Map = docs => from doc in docs
                  select new
                             {
                                 doc.ProductId,
                                 Day = doc.DateViewed.Day,
                                 Month = doc.DateViewed.Month,
                                 Year = doc.DateViewed.Year
                                 Count = 1
                             };

    Reduce = results => from result in results
                        group result by new {
                             doc.ProductId,
                             doc.DateViewed.Day,
                             doc.DateViewed.Month,
                             doc.DateViewed.Year
                        }
                        into agg
                        select new
                                   {
                                       ProductId = agg.Key.ProductId,
                                       Day = agg.Key.Day,
                                       Month = agg.Key.Month,
                                       Year = agg.Key.Year  
                                       Count = agg.Sum(x => x.Count)
                                   };
}

}

希望你可以通过这个看到我想要实现的目标 - 你想要你的组中的所有组件,因为它们使你的分组独特.

我不记得RavenDB是否允许你用DateTimes做这个,而我还没有在这台计算机上得到它,所以不能验证这一点,但理论仍然是一样的.

所以,要重新迭代

您希望按周+产品ID为报表编制索引您希望按月添加报表索引+产品ID您希望按年度+产品ID为报表编制索引

我希望这有帮助,对不起我不能给你一个可编辑的例子,缺乏乌鸦使它有点困难:-)