c# - ElasticSearch 6.0.1-SQL DISTINCT子句-NEST C#

Question

我需要使用NEST从文档中返回所有类别DISTINCTS(无重复)。
在SQL中，它看起来像这样:

SELECT DISTINCT Category  
  FROM Log  
  ORDER BY Category ASC 

在ElasticSearch内部，我这样做:

GET log/_search
{
  "size":"0",
  "aggs" : {
  "alias_category" : {
  "terms" : { "field" : "category.keyword" }
  }
  }
}

我如何使用NEST做到这一点？

public ICollection<string> SelectAllCategoriesDistinct(ElasticClient client)
    {
        var searchResponse = client.Search<LogElasticSearch>(s => s
                                        .Query(q => q
                                            .Terms(t => t
                                                .Field(f => f.Category)
                                            )
                                        )
                                     );
        return (ICollection<string>)searchResponse;
    }

Answer 1

我找到了一种方法。这不是一种优雅的方法，但是我在elastico网站(https://discuss.elastic.co/t/c-nest-best-way-of-accessing-properties-of-iaggregate-object/85384/2)中发现了这种方法:

public ICollection<string> SelectAllCategoriesDistinct(ElasticClient client)
    {
        var searchResponse = 
            client.Search<LogElasticSearch>(s => s
                .Size(0)
                .Aggregations(agg => agg
                    .Terms("categories", t => t
                        .Field("category.keyword")
                    )                  
                )
            );
       
        var aggregation = searchResponse.Aggregations.Values;
        var listOfCategories = new List<string>();

        if (searchResponse.Aggregations.Values.FirstOrDefault().GetType() == typeof(BucketAggregate))
        {
            foreach (IBucket bucket in ((BucketAggregate)aggregation.FirstOrDefault()).Items)
            {
                if (bucket.GetType() == typeof(KeyedBucket<object>))
                {
                    var valueKey = ((KeyedBucket<object>)bucket).Key;
                    listOfCategories.Add(valueKey.ToString());
                }
            } 
        }

        return listOfCategories.OrderBy(c => c).ToList();
    }

如果有人知道一种更好的方法，请帮助我进行改进，但是这样才能达到目标。