ElasticSearch C# 客户端（NEST）：访问嵌套聚合结果答案

【问题标题】：ElasticSearch C# client (NEST): access nested aggregation resultsElasticSearch C# 客户端（NEST）：访问嵌套聚合结果
【发布时间】：2015-03-21 17:08:15
【问题描述】：

我在 NEST（ElasticSearch C# 客户端）中有以下查询，注意嵌套聚合：

            var query = _elasticClient.Search<Auth5209>(s => s
                .Size(0)
                .Aggregations(a=> a
                    .Terms("incidentID", t=> t
                        .Field(f=>f.IncidentID)
                        .Size(5)
                        .Aggregations(a2 => a2
                            .Stats("authDateStats", s1=>s1.Field(f=>f.AuthEventDate))
                        )
                    )                        
                )
                );

这会正确生成以下查询：

{
  "size": 0,
  "aggs": {
    "incidentID": {
      "terms": {
        "field": "incidentID",
        "size": 5
      },
      "aggs": {
        "authDateStats": {
          "stats": {
            "field": "authEventDate"
          }
        }
      }
    }
  }
}

这给了我以下结果：

"aggregations" : {
    "incidentID" : {
        "buckets" : [{
                "key" : "0A631EB1-01EF-DC28-9503-FC28FE695C6D",
                "doc_count" : 233,
                "authDateStats" : {
                    "count" : 233,
                    "min" : 1401167036075,
                    "max" : 1401168969907,
                    "avg" : 1401167885682.6782,
                    "sum" : 326472117364064
                }
            }
        ]
    }
}

我不知道如何访问“authDateStats”部分。当我调试时，我看不到任何访问数据的方法。

【问题讨论】：

这里是使用 Nest 的嵌套聚合示例。 nest.azurewebsites.net/nest/aggregations/nested.html.

标签： c# elasticsearch aggregation

【解决方案1】：

官方文档和此处的答案都不适用于nest 2.0+。尽管 jhilden 的回答确实让我走上了正确的道路。

这是一个类似查询的工作示例，可与 Nest 2.0+ 一起使用：

        const string termsAggregation = "device_number";
        const string topHitsAggregation = "top_hits";

        var response = await _elasticsearchClient.Client.SearchAsync<CustomerDeviceModel>(s => s
            .Aggregations(a => a
                .Terms(termsAggregation, ta => ta
                    .Field(o => o.DeviceNumber)
                    .Size(int.MaxValue)
                    .Aggregations(sa => sa
                        .TopHits(topHitsAggregation, th => th
                            .Size(1)
                            .Sort(x => x.Field(f => f.Modified).Descending())
                        )
                    )
                )
            )
        );

        if (!response.IsValid)
        {
            throw new ElasticsearchException(response.DebugInformation);
        }

        var results = new List<CustomerDeviceModel>();
        var terms = response.Aggs.Terms(termsAggregation);

        foreach (var bucket in terms.Buckets)
        {
            var hit = bucket.TopHits(topHitsAggregation);
            var device = hit.Documents<CustomerDeviceModel>().First();
            results.Add(device);
        }

【讨论】：

【解决方案2】：

我猜你已经想通了，但你可以访问嵌套聚合，它只是在一个基类中，你可以在调试器的 Nest.KeyItem.base.base.Aggregations 中看到它。

【讨论】：

【解决方案3】：

这是访问内部聚合的完整工作示例：

        const string aggName = "LocationIDAgg";
        const string aggNameTopHits = "LatestForLoc";
        var response = await ElasticClient.SearchAsync<PlacementVerificationES>(s => s
            .Query(BuildQuery(filter, null))                
            .Size(int.MaxValue)
            .Aggregations(a=> a
                .Terms(aggName, t=> t
                    .Field(f=>f.LocationID)
                    .Size(100)
                    .Aggregations(innerAgg => innerAgg
                        .TopHits(aggNameTopHits, th=> th
                            .Size(1)
                            .Sort(x=>x.OnField(f=> f.Date).Descending())
                        )
                    )
                )
            )
        ).VerifySuccessfulResponse();

        //var debug = response.GetRequestString();
        var agBucket = (Bucket)response.Aggregations[aggName];

        var output = new List<PlacementVerificationForReporting>();
        // ReSharper disable once LoopCanBeConvertedToQuery
        // ReSharper disable once PossibleInvalidCastExceptionInForeachLoop
        foreach (KeyItem i in agBucket.Items)
        {
            var topHits = (TopHitsMetric)i.Aggregations[aggNameTopHits];
            var top1 = topHits.Hits<PlacementVerificationES>().Single();
            var reportingObject = RepoToReporting(top1);
            output.Add(reportingObject);
        }

        return output;

【讨论】：