Reverse Nested Aggregation Usage

Fluent DSL example

a => a
.Nested("tags", n => n
    .Path(p => p.Tags)
    .Aggregations(aa => aa
        .Terms("tag_names", t => t
            .Field(p => p.Tags.Suffix("name"))
            .Aggregations(aaa => aaa
                .ReverseNested("tags_to_project", r => r
                    .Aggregations(aaaa => aaaa
                        .Terms("top_projects_per_tag", tt => tt
                            .Field(p => p.Name)
                        )
                    )
                )
            )
        )
    )
)

Object Initializer syntax example

edit

new NestedAggregation("tags")
{
    Path = "tags",
    Aggregations = new TermsAggregation("tag_names")
    {
        Field = "tags.name",
        Aggregations = new ReverseNestedAggregation("tags_to_project")
        {
            Aggregations = new TermsAggregation("top_projects_per_tag")
            {
                Field = Field<Project>(p => p.Name)
            }
        }
    }
}

Example json output.

{
  "tags": {
    "nested": {
      "path": "tags"
    },
    "aggs": {
      "tag_names": {
        "terms": {
          "field": "tags.name"
        },
        "aggs": {
          "tags_to_project": {
            "reverse_nested": {},
            "aggs": {
              "top_projects_per_tag": {
                "terms": {
                  "field": "name"
                }
              }
            }
          }
        }
      }
    }
  }
}

Handling Responses

edit

response.ShouldBeValid();
var tags = response.Aggregations.Nested("tags");
tags.Should().NotBeNull();
var tagNames = tags.Terms("tag_names");
tagNames.Should().NotBeNull();
foreach (var tagName in tagNames.Buckets)
{
    tagName.Key.Should().NotBeNullOrEmpty();
    tagName.DocCount.Should().BeGreaterThan(0);
    var tagsToProjects = tagName.ReverseNested("tags_to_project");
    tagsToProjects.Should().NotBeNull();
    var topProjectsPerTag = tagsToProjects.Terms("top_projects_per_tag");
    topProjectsPerTag.Should().NotBeNull();
    foreach (var topProject in topProjectsPerTag.Buckets)
    {
        topProject.Key.Should().NotBeNullOrEmpty();
        topProject.DocCount.Should().BeGreaterThan(0);
    }
}

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