Support for other_bucket and other_bucket_key on Filters Aggregation

Closes #1686

Author: russcam

Diff for: src/Nest/Aggregations/Bucket/Filters/FiltersAggregation.cs

@@ -11,12 +11,35 @@ public interface IFiltersAggregation : IBucketAggregation
 	{
 		[JsonProperty("filters")]
 		Union<INamedFiltersContainer, List<QueryContainer>> Filters { get; set; }
+
+		[JsonProperty("other_bucket")]
+		bool? OtherBucket { get; set; }
+
+		[JsonProperty("other_bucket_key")]
+		string OtherBucketKey { get; set; } 
 	}
 
 	public class FiltersAggregation : BucketAggregationBase, IFiltersAggregation
 	{
 		public Union<INamedFiltersContainer, List<QueryContainer>> Filters { get; set; }
 
+		/// <summary>
+		/// Gets or sets whether to add a bucket to the response which will contain all documents 
+		/// that do not match any of the given filters. 
+		/// When set to <c>true</c>, the other bucket will be returned either in a bucket
+		/// (named "_other_" by default) if named filters are being used,
+		///  or as the last bucket if anonymous filters are being used
+		/// When set to <c>false</c>, does not compute
+		/// the other bucket.
+		/// </summary>
+		public bool? OtherBucket { get; set; }
+
+		/// <summary>
+		/// Gets or sets the key for the other bucket to a value other than the default "_other_". 
+		/// Setting this parameter will implicitly set the <see cref="OtherBucket"/> parameter to true
+		/// </summary>
+		public string OtherBucketKey { get; set; }
+
 		internal FiltersAggregation() { }
 
 		public FiltersAggregation(string name) : base(name) { }
@@ -31,6 +54,33 @@ public class FiltersAggregationDescriptor<T>
 	{
 		Union<INamedFiltersContainer, List<QueryContainer>> IFiltersAggregation.Filters { get; set; }
 
+		bool? IFiltersAggregation.OtherBucket{ get; set; }
+
+		string IFiltersAggregation.OtherBucketKey{ get; set; }
+
+		/// <summary>
+		/// Adds a bucket to the response which will contain all documents 
+		/// that do not match any of the given filters. 
+		/// When set to <c>true</c>, the other bucket will be returned either in a bucket
+		/// (named "_other_" by default) if named filters are being used,
+		///  or as the last bucket if anonymous filters are being used
+		/// When set to <c>false</c>, does not compute
+		/// the other bucket. 
+		/// </summary>
+		/// <param name="otherBucket">whether to set the other bucket</param>
+		/// <returns>the <see cref="FiltersAggregationDescriptor{T}"/></returns>
+		public FiltersAggregationDescriptor<T> OtherBucket(bool otherBucket = true) =>
+			Assign(a => a.OtherBucket = otherBucket);
+
+		/// <summary>
+		/// Sets the key for the other bucket to a value other than the default "_other_". 
+		/// Setting this parameter will implicitly set the <see cref="OtherBucket"/> parameter to true
+		/// </summary>
+		/// <param name="otherBucketKey">the name for the other bucket</param>
+		/// <returns>the <see cref="FiltersAggregationDescriptor{T}"/></returns>
+		public FiltersAggregationDescriptor<T> OtherBucketKey(string otherBucketKey) =>
+			Assign(a => a.OtherBucketKey = otherBucketKey);
+
 		public FiltersAggregationDescriptor<T> NamedFilters(Func<NamedFiltersContainerDescriptor<T>, IPromise<INamedFiltersContainer>> selector) =>
 			Assign(a => a.Filters = new Union<INamedFiltersContainer, List<QueryContainer>>(selector?.Invoke(new NamedFiltersContainerDescriptor<T>())?.Value));
 

Diff for: src/Tests/Aggregations/Bucket/Filters/FiltersAggregationUsageTests.cs

@@ -11,7 +11,8 @@ namespace Tests.Aggregations.Bucket.Filters
 {
 	/**
 	 * Defines a multi bucket aggregations where each bucket is associated with a filter. 
-	 * Each bucket will collect all documents that match its associated filter.
+	 * Each bucket will collect all documents that match its associated filter. For documents
+	 * that do not match any filter, these will be collected in the other bucket.
 	 *
 	 * Be sure to read the elasticsearch documentation {ref}/search-aggregations-bucket-filters-aggregation.html[on this subject here]
 	*/
@@ -29,6 +30,8 @@ public FiltersAggregationUsageTests(ReadOnlyCluster i, EndpointUsage usage) : ba
 				{
 					filters = new
 					{
+						other_bucket = true,
+						other_bucket_key = "other_states_of_being",
 						filters = new
 						{
 							belly_up = new { term = new { state = new { value = "BellyUp" } } },
@@ -47,6 +50,8 @@ public FiltersAggregationUsageTests(ReadOnlyCluster i, EndpointUsage usage) : ba
 		protected override Func<SearchDescriptor<Project>, ISearchRequest> Fluent => s => s
 			.Aggregations(aggs => aggs
 				.Filters("projects_by_state", agg => agg
+					.OtherBucket()
+					.OtherBucketKey("other_states_of_being")
 					.NamedFilters(filters => filters
 						.Filter("belly_up", f => f.Term(p => p.State, StateOfBeing.BellyUp))
 						.Filter("stable", f => f.Term(p => p.State, StateOfBeing.Stable))
@@ -63,6 +68,8 @@ public FiltersAggregationUsageTests(ReadOnlyCluster i, EndpointUsage usage) : ba
 			{
 				Aggregations = new FiltersAggregation("projects_by_state")
 				{
+					OtherBucket = true,
+					OtherBucketKey = "other_states_of_being",
 					Filters = new NamedFiltersContainer
 					{
 							{ "belly_up", Query<Project>.Term(p=>p.State, StateOfBeing.BellyUp) },
@@ -97,6 +104,9 @@ protected override void ExpectResponse(ISearchResponse<Project> response)
 			namedResult.Should().NotBeNull();
 			namedResult.DocCount.Should().BeGreaterThan(0);
 
+			namedResult = filterAgg.NamedBucket("other_states_of_being");
+			namedResult.Should().NotBeNull();
+			namedResult.DocCount.Should().Be(0);
 		}
 	}
 
@@ -114,6 +124,7 @@ public AnonymousUsage(ReadOnlyCluster i, EndpointUsage usage) : base(i, usage) {
 				{
 					filters = new
 					{
+						other_bucket = true,
 						filters = new[] {
 								new { term = new { state = new { value = "BellyUp" } }},
 								new { term = new { state = new { value = "Stable" } }},
@@ -131,6 +142,7 @@ public AnonymousUsage(ReadOnlyCluster i, EndpointUsage usage) : base(i, usage) {
 		protected override Func<SearchDescriptor<Project>, ISearchRequest> Fluent => s => s
 			.Aggregations(aggs => aggs
 				.Filters("projects_by_state", agg => agg
+					.OtherBucket()
 					.AnonymousFilters(
 						f => f.Term(p => p.State, StateOfBeing.BellyUp),
 						f => f.Term(p => p.State, StateOfBeing.Stable),
@@ -147,6 +159,7 @@ public AnonymousUsage(ReadOnlyCluster i, EndpointUsage usage) : base(i, usage) {
 			{
 				Aggregations = new FiltersAggregation("projects_by_state")
 				{
+					OtherBucket = true,
 					Filters = new List<QueryContainer>
 					{
 							 Query<Project>.Term(p=>p.State, StateOfBeing.BellyUp) ,
@@ -169,11 +182,14 @@ protected override void ExpectResponse(ISearchResponse<Project> response)
 			var filterAgg = response.Aggs.Filters("projects_by_state");
 			filterAgg.Should().NotBeNull();
 			var results = filterAgg.AnonymousBuckets();
-			results.Count.Should().Be(3);
-			foreach (var singleBucket in results)
+			results.Count.Should().Be(4);
+
+			foreach (var singleBucket in results.Take(3))
 			{
 				singleBucket.DocCount.Should().BeGreaterThan(0);
 			}
+
+			results.Last().DocCount.Should().Be(0);
 		}
 	}
 }