Filter Aggregation Usageedit

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 exampleedit

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 exampleedit

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 Responsesedit

The AggregateDictionary found on `.Aggregations on ISearchResponse<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 Filteredit

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

Fluent DSL exampleedit

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

Object Initializer syntax exampleedit

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

Example json output. 

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

Handling Responsesedit

response.ShouldNotBeValid();