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Elastic Docs ›Elasticsearch .NET Clients [7.17] ›Aggregations ›Bucket Aggregations

Filter Aggregation Usage

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Filter Aggregation Usage

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Defines a single bucket of all the documents in the current document set context that match a specified filter. Often this will be used to narrow down the current aggregation context to a specific set of documents.

Be sure to read the Elasticsearch documentation on Filter Aggregation

Fluent DSL example

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a => a
.Filter("bethels_projects", date => date
    .Filter(q => q.Term(p => p.LeadDeveloper.FirstName, FirstNameToFind))
    .Aggregations(childAggs => childAggs
        .Terms("project_tags", avg => avg.Field(p => p.CuratedTags.First().Name.Suffix("keyword")))
    )
)

Object Initializer syntax example

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new FilterAggregation("bethels_projects")
{
    Filter = new TermQuery { Field = Field<Project>(p => p.LeadDeveloper.FirstName), Value = FirstNameToFind },
    Aggregations =
        new TermsAggregation("project_tags") { Field = Field<Project>(p => p.CuratedTags.First().Name.Suffix("keyword")) }
}

Example json output.

{
  "bethels_projects": {
    "filter": {
      "term": {
        "leadDeveloper.firstName": {
          "value": "pierce"
        }
      }
    },
    "aggs": {
      "project_tags": {
        "terms": {
          "field": "curatedTags.name.keyword"
        }
      }
    }
  }
}

Handling Responses

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The AggregateDictionary found on `.Aggregations on SearchResponse<T> has several helper methods so we can fetch our aggregation results easily in the correct type. Be sure to read more about these helper methods

response.ShouldBeValid();

var filterAgg = response.Aggregations.Filter("bethels_projects");
filterAgg.Should().NotBeNull();
filterAgg.DocCount.Should().BeGreaterThan(0);
var tags = filterAgg.Terms("project_tags");
tags.Should().NotBeNull();
tags.Buckets.Should().NotBeEmpty();

Empty Filter

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When the collection of filters is empty or all are conditionless, NEST will serialize them to an empty object.

Fluent DSL example

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a => a
.Filter("empty_filter", date => date
    .Filter(f => f
        .Bool(b => b
            .Filter(new QueryContainer[0])
        )
    )
)

Object Initializer syntax example

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new FilterAggregation("empty_filter")
{
    Filter = new BoolQuery
    {
        Filter = new List<QueryContainer>()
    }
}

Example json output.

{
  "empty_filter": {
    "filter": {}
  }
}

Handling Responses

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response.ShouldNotBeValid()
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