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Elastic Docs ›Elasticsearch.Net and NEST: the .NET clients [6.x] ›Aggregations ›Bucket Aggregations
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Terms Aggregation Usageedit

A multi-bucket value source based aggregation where buckets are dynamically built - one per unique value.

See the Elasticsearch documentation on terms aggregation for more detail.

Fluent DSL exampleedit

a => a
.Terms("states", st => st
    .Field(p => p.State)
    .MinimumDocumentCount(2)
    .Size(5)
    .ShardSize(100)
    .ExecutionHint(TermsAggregationExecutionHint.Map)
    .Missing("n/a")
    .Script(ss => ss.Source("'State of Being: '+_value"))
    .Order(o => o
        .KeyAscending()
        .CountDescending()
    )
    .Meta(m => m
        .Add("foo", "bar")
    )
)

Object Initializer syntax exampleedit

new TermsAggregation("states")
{
    Field = Field<Project>(p => p.State),
    MinimumDocumentCount = 2,
    Size = 5,
    ShardSize = 100,
    ExecutionHint = TermsAggregationExecutionHint.Map,
    Missing = "n/a",
    Script = new InlineScript("'State of Being: '+_value"),
    Order = new List<TermsOrder>
    {
        TermsOrder.KeyAscending,
        TermsOrder.CountDescending
    },
    Meta = new Dictionary<string, object>
    {
        { "foo", "bar" }
    }
}

Example json output.

{
  "states": {
    "meta": {
      "foo": "bar"
    },
    "terms": {
      "field": "state",
      "min_doc_count": 2,
      "size": 5,
      "shard_size": 100,
      "execution_hint": "map",
      "missing": "n/a",
      "script": {
        "source": "'State of Being: '+_value"
      },
      "order": [
        {
          "_key": "asc"
        },
        {
          "_count": "desc"
        }
      ]
    }
  }
}

Handling Responsesedit

response.ShouldBeValid();
var states = response.Aggregations.Terms("states");
states.Should().NotBeNull();
states.DocCountErrorUpperBound.Should().HaveValue();
states.SumOtherDocCount.Should().HaveValue();
states.Buckets.Should().NotBeNull();
states.Buckets.Count.Should().BeGreaterThan(0);
foreach (var item in states.Buckets)
{
    item.Key.Should().NotBeNullOrEmpty();
    item.DocCount.Should().BeGreaterOrEqualTo(1);
}
states.Meta.Should().NotBeNull().And.HaveCount(1);
states.Meta["foo"].Should().Be("bar");

Filtering with a regular expression patternedit

Using terms aggregation with filtering to include values using a regular expression pattern

Fluent DSL exampleedit

a => a
.Terms("states", st => st
    .Field(p => p.State.Suffix("keyword"))
    .MinimumDocumentCount(2)
    .Size(5)
    .ShardSize(100)
    .ExecutionHint(TermsAggregationExecutionHint.Map)
    .Missing("n/a")
    .Include("(Stable|VeryActive)")
    .Order(o => o
        .KeyAscending()
        .CountDescending()
    )
    .Meta(m => m
        .Add("foo", "bar")
    )
)

Object Initializer syntax exampleedit

new TermsAggregation("states")
{
    Field = Field<Project>(p => p.State.Suffix("keyword")),
    MinimumDocumentCount = 2,
    Size = 5,
    ShardSize = 100,
    ExecutionHint = TermsAggregationExecutionHint.Map,
    Missing = "n/a",
    Include = new TermsInclude("(Stable|VeryActive)"),
    Order = new List<TermsOrder>
    {
        TermsOrder.KeyAscending,
        TermsOrder.CountDescending
    },
    Meta = new Dictionary<string, object>
    {
        { "foo", "bar" }
    }
}

Example json output.

{
  "states": {
    "meta": {
      "foo": "bar"
    },
    "terms": {
      "field": "state.keyword",
      "min_doc_count": 2,
      "size": 5,
      "shard_size": 100,
      "execution_hint": "map",
      "missing": "n/a",
      "include": "(Stable|VeryActive)",
      "order": [
        {
          "_key": "asc"
        },
        {
          "_count": "desc"
        }
      ]
    }
  }
}

Handling Responsesedit

response.ShouldBeValid();
var states = response.Aggregations.Terms<StateOfBeing>("states");
states.Should().NotBeNull();
states.DocCountErrorUpperBound.Should().HaveValue();
states.SumOtherDocCount.Should().HaveValue();
states.Buckets.Should().NotBeNull();
states.Buckets.Count.Should().BeGreaterThan(0);
foreach (var item in states.Buckets)
{
    item.Key.Should().BeOfType<StateOfBeing>();
    item.DocCount.Should().BeGreaterOrEqualTo(1);
}
states.Meta.Should().NotBeNull().And.HaveCount(1);
states.Meta["foo"].Should().Be("bar");

Filtering with exact valuesedit

Using terms aggregation with filtering to include only specific values

Fluent DSL exampleedit

a => a
.Terms("states", st => st
    .Field(p => p.State.Suffix("keyword"))
    .MinimumDocumentCount(2)
    .Size(5)
    .ShardSize(100)
    .ExecutionHint(TermsAggregationExecutionHint.Map)
    .Missing("n/a")
    .Include(new[] { StateOfBeing.Stable.ToString(), StateOfBeing.VeryActive.ToString() })
    .Order(o => o
        .KeyAscending()
        .CountDescending()
    )
    .Meta(m => m
        .Add("foo", "bar")
    )
)

Object Initializer syntax exampleedit

new TermsAggregation("states")
{
    Field = Field<Project>(p => p.State.Suffix("keyword")),
    MinimumDocumentCount = 2,
    Size = 5,
    ShardSize = 100,
    ExecutionHint = TermsAggregationExecutionHint.Map,
    Missing = "n/a",
    Include = new TermsInclude(new[] { StateOfBeing.Stable.ToString(), StateOfBeing.VeryActive.ToString() }),
    Order = new List<TermsOrder>
    {
        TermsOrder.KeyAscending,
        TermsOrder.CountDescending
    },
    Meta = new Dictionary<string, object>
    {
        { "foo", "bar" }
    }
}

Example json output.

{
  "states": {
    "meta": {
      "foo": "bar"
    },
    "terms": {
      "field": "state.keyword",
      "min_doc_count": 2,
      "size": 5,
      "shard_size": 100,
      "execution_hint": "map",
      "missing": "n/a",
      "include": [
        "Stable",
        "VeryActive"
      ],
      "order": [
        {
          "_key": "asc"
        },
        {
          "_count": "desc"
        }
      ]
    }
  }
}

Handling Responsesedit

response.ShouldBeValid();
var states = response.Aggregations.Terms("states");
states.Should().NotBeNull();
states.DocCountErrorUpperBound.Should().HaveValue();
states.SumOtherDocCount.Should().HaveValue();
states.Buckets.Should().NotBeNull();
states.Buckets.Count.Should().BeGreaterThan(0);
foreach (var item in states.Buckets)
{
    item.Key.Should().NotBeNullOrEmpty();
    item.DocCount.Should().BeGreaterOrEqualTo(1);
}
states.Meta.Should().NotBeNull().And.HaveCount(1);
states.Meta["foo"].Should().Be("bar");

Filtering with partitionsedit

A terms aggregation that uses partitioning to filter the terms that are returned in the response. Further terms can be returned by issuing additional requests with an incrementing partition number.

Partitioning is available only in Elasticsearch 5.2.0+

Fluent DSL exampleedit

a => a
.Terms("commits", st => st
    .Field(p => p.NumberOfCommits)
    .Include(0, 10)
    .Size(5)
)

Object Initializer syntax exampleedit

new TermsAggregation("commits")
{
    Field = Field<Project>(p => p.NumberOfCommits),
    Include = new TermsInclude(0, 10),
    Size = 5
}

Example json output.

{
  "commits": {
    "terms": {
      "field": "numberOfCommits",
      "size": 5,
      "include": {
        "partition": 0,
        "num_partitions": 10
      }
    }
  }
}

Handling Responsesedit

response.ShouldBeValid();
var commits = response.Aggregations.Terms<int>("commits");
commits.Should().NotBeNull();
commits.DocCountErrorUpperBound.Should().HaveValue();
commits.SumOtherDocCount.Should().HaveValue();
commits.Buckets.Should().NotBeNull();
commits.Buckets.Count.Should().BeGreaterThan(0);
foreach (var item in commits.Buckets)
{
    item.Key.Should().BeGreaterThan(0);
    item.DocCount.Should().BeGreaterOrEqualTo(1);
}

Numeric fieldsedit

A terms aggregation on a numeric field

Fluent DSL exampleedit

a => a
.Terms("commits", st => st
    .Field(p => p.NumberOfCommits)
    .Missing(-1)
    .ShowTermDocCountError()
)

Object Initializer syntax exampleedit

new TermsAggregation("commits")
{
    Field = Field<Project>(p => p.NumberOfCommits),
    ShowTermDocCountError = true,
    Missing = -1
}

Example json output.

{
  "commits": {
    "terms": {
      "field": "numberOfCommits",
      "missing": -1,
      "show_term_doc_count_error": true
    }
  }
}

Handling Responsesedit

response.ShouldBeValid();
var commits = response.Aggregations.Terms<int>("commits");
commits.Should().NotBeNull();
commits.DocCountErrorUpperBound.Should().HaveValue();
commits.SumOtherDocCount.Should().HaveValue();
commits.Buckets.Should().NotBeNull();
commits.Buckets.Count.Should().BeGreaterThan(0);
foreach (var item in commits.Buckets)
{
    item.Key.Should().BeGreaterThan(0);
    item.DocCount.Should().BeGreaterOrEqualTo(1);
}
commits.Buckets.Should().Contain(b => b.DocCountErrorUpperBound.HasValue);

Nested terms aggregationsedit

A terms aggregation returns buckets that can contain more aggregations

Fluent DSL exampleedit

a => a
.Terms("commits", st => st
    .Field(p => p.NumberOfCommits)
    .Aggregations(aggs => aggs
        .Terms("state", t => t
            .Meta(m => m.Add("x", "y"))
            .Field(p => p.State)
        )
    )
)

Object Initializer syntax exampleedit

new TermsAggregation("commits")
{
    Field = Field<Project>(p => p.NumberOfCommits),
    Aggregations = new TermsAggregation("state")
    {
        Meta = new Dictionary<string, object> { { "x", "y" } },
        Field = Field<Project>(p => p.State),
    }
}

Example json output.

{
  "commits": {
    "terms": {
      "field": "numberOfCommits"
    },
    "aggs": {
      "state": {
        "meta": {
          "x": "y"
        },
        "terms": {
          "field": "state"
        }
      }
    }
  }
}

Handling Responsesedit

response.ShouldBeValid();
var commits = response.Aggregations.Terms<int>("commits");
commits.Should().NotBeNull();
commits.DocCountErrorUpperBound.Should().HaveValue();
commits.SumOtherDocCount.Should().HaveValue();
commits.Buckets.Should().NotBeNull();
commits.Buckets.Count.Should().BeGreaterThan(0);
foreach (var item in commits.Buckets)
{
    item.Key.Should().BeGreaterThan(0);
    item.DocCount.Should().BeGreaterOrEqualTo(1);
    var states = item.Terms("state");
    states.Should().NotBeNull();
    states.Buckets.Should().NotBeEmpty();
    states.Meta.Should().NotBeEmpty("meta").And.ContainKey("x");
    foreach (var b in states.Buckets)
    {
        b.DocCount.Should().BeGreaterThan(0);
        b.Key.Should().NotBeNullOrEmpty();
    }
}

Typed Keys aggregationsedit

Starting with Elasticsearch 6.x you can provide a typed_keys parameter which will prefix all the aggregation names with the type of aggregation that is returned. The following modifies the previous nested terms aggregation and sends it again but this time with the typed_keys option set. The client should treat this in a an opaque fashion so let’s assert that it does.

Fluent DSL exampleedit

f => base.Fluent(f.TypedKeys())

Object Initializer syntax exampleedit

var r = base.Initializer;
r.TypedKeys = true;
return r;
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