Question

我有一个这样的实体：

public class Event
{
    public string Code;
    public DateTimeOffset DateTime;
}

我想按Code过滤，然后按DateTime.Date分组。我尝试过：

var results = session
    .Query<Event>()
    .Where(e => e.Code == "123")
    .GroupBy(e => e.DateTime.Date)
    .ToList();

但是出现以下错误：

Raven.Client.Exceptions.InvalidQueryException: Field 'Code' isn't neither an aggregation operation nor part of the group by key
Query: from Events group by DateTime.Date where Code = $p0
Parameters: {"p0":"123"}

从结果查询中可以看出，在where子句之后添加了group by子句，这解释了错误。

那么如何在RavenDB中执行此查询？

编辑：

我使用的code“ 123”只是一个例子。我需要它是一个传递给查询的变量，像这样：

var results = session
    .Query<Event>()
    .Where(e => e.Code == code)
    .GroupBy(e => e.DateTime.Date)
    .ToList();

Answer 1

首先，请了解以下内容中的 dynamic aggregation query syntax ：
https://demo.ravendb.net/demos/auto-indexes/auto-map-reduce-index

但是，在您的情况下，您需要定义一个静态地图减少索引来为您计算：
（将（过滤后的）每个唯一日期的文件）
即

 public class Result
 {
     public string  Date { get; set; }
     public int NumberOfDocs { get; set; }
 }

 Map = events => from event in events
     where event.Code == "123"
     select new Result  
     {           
        Date = event.DateTime.Date
        NumberOfDocs = 1         
     }     

 Reduce = results => from result in results  
     group result by result.Date into g
     select new Result 
     {
        Date = g.Key,
        Count = g.Sum(x => x.NumberOfDocs )
     }

==>在以下位置了解 Static Map-Reduce Index ：
https://demo.ravendb.net/demos/static-indexes/map-reduce-index
按照详细的演练进行操作。

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更新：要使用以下map-reduce索引汇总每个代码和日期“夫妇” 的文档数量，然后可以使用“代码”

进行查询

public class Result
{
      public string Code { get; set; }
      public string  Date { get; set; }
      public int NumberOfDocs { get; set; }
}

         Map = events => from event in events        
             select new Result  
             {          
                Code = event.Code
                Date = event.DateTime.Date             
                NumberOfDocs = 1         
             }     

         Reduce = results => from result in results  
             group result by new 
             {
               result.Code,
               result.Date
             }
             into g
             select new Result 
             {
                Code = g.Key.Code
                Date = g.Key.DateTime.Date,
                NumberOfDocs = g.Sum(x => x.NumberOfDocs )
             }

然后查询

List<Result> queryResults = session.Query< Result, <Index_Name> >()
                    .Where(x => x.Code == "some-code-number")
                    .ToList();

然后您也可以在代码中完成

queryResults.GroupBy(x => x.Date)

用GroupBy之前的位置查询

1 个答案:

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