[Backport 7.x] Add normalize aggregation

docs/aggregations.asciidoc

@@ -277,6 +277,8 @@ There are many different types of pipeline aggregation, each computing different
 
 * <<moving-function-aggregation-usage,Moving Function Aggregation Usage>>
 
+* <<normalize-aggregation-usage,Normalize Aggregation Usage>>
+
 * <<percentiles-bucket-aggregation-usage,Percentiles Bucket Aggregation Usage>>
 
 * <<serial-differencing-aggregation-usage,Serial Differencing Aggregation Usage>>
@@ -321,6 +323,8 @@ include::aggregations/pipeline/moving-average/moving-average-simple-aggregation-
 
 include::aggregations/pipeline/moving-function/moving-function-aggregation-usage.asciidoc[]
 
+include::aggregations/pipeline/normalize/normalize-aggregation-usage.asciidoc[]
+
 include::aggregations/pipeline/percentiles-bucket/percentiles-bucket-aggregation-usage.asciidoc[]
 
 include::aggregations/pipeline/serial-differencing/serial-differencing-aggregation-usage.asciidoc[]

docs/aggregations/pipeline/normalize/normalize-aggregation-usage.asciidoc

@@ -0,0 +1,106 @@
+:ref_current: https://www.elastic.co/guide/en/elasticsearch/reference/master
+
+:github: https://github.com/elastic/elasticsearch-net
+
+:nuget: https://www.nuget.org/packages
+
+////
+IMPORTANT NOTE
+==============
+This file has been generated from https://github.com/elastic/elasticsearch-net/tree/master/src/Tests/Tests/Aggregations/Pipeline/Normalize/NormalizeAggregationUsageTests.cs. 
+If you wish to submit a PR for any spelling mistakes, typos or grammatical errors for this file,
+please modify the original csharp file found at the link and submit the PR with that change. Thanks!
+////
+
+[[normalize-aggregation-usage]]
+=== Normalize Aggregation Usage
+
+A parent pipeline aggregation which calculates the specific normalized/rescaled value for a specific bucket value.
+Values that cannot be normalized, will be skipped using the skip gap policy.
+
+NOTE: Valid for Elasticsearch 7.9.0+ with at least basic license level
+
+==== Fluent DSL example
+
+[source,csharp]
+----
+a => a
+.DateHistogram("projects_started_per_month", dh => dh
+    .Field(p => p.StartedOn)
+    .CalendarInterval(DateInterval.Month)
+    .Aggregations(aa => aa
+        .Sum("commits", sm => sm
+            .Field(p => p.NumberOfCommits)
+        )
+        .Normalize("percent_of_commits", aaa => aaa
+            .BucketsPath("commits")
+            .Method(NormalizeMethod.PercentOfSum)
+            .Format("00.00%")
+        )
+    )
+)
+----
+
+==== Object Initializer syntax example
+
+[source,csharp]
+----
+new DateHistogramAggregation("projects_started_per_month")
+{
+    Field = "startedOn",
+    CalendarInterval = DateInterval.Month,
+    Aggregations = new SumAggregation("commits", "numberOfCommits") &&
+        new NormalizeAggregation("percent_of_commits", "commits")
+        {
+            Method = NormalizeMethod.PercentOfSum,
+            Format = "00.00%"
+        }
+}
+----
+
+[source,javascript]
+.Example json output
+----
+{
+  "projects_started_per_month": {
+    "date_histogram": {
+      "field": "startedOn",
+      "calendar_interval": "month"
+    },
+    "aggs": {
+      "commits": {
+        "sum": {
+          "field": "numberOfCommits"
+        }
+      },
+      "percent_of_commits": {
+        "normalize": {
+          "buckets_path": "commits",
+          "method": "percent_of_sum",
+          "format": "00.00%"
+        }
+      }
+    }
+  }
+}
+----
+
+==== Handling Responses
+
+[source,csharp]
+----
+response.ShouldBeValid();
+
+var projectsPerMonth = response.Aggregations.DateHistogram("projects_started_per_month");
+projectsPerMonth.Should().NotBeNull();
+projectsPerMonth.Buckets.Should().NotBeNull();
+projectsPerMonth.Buckets.Count.Should().BeGreaterThan(0);
+
+foreach (var bucket in projectsPerMonth.Buckets)
+{
+    var normalize = bucket.Normalize("percent_of_commits");
+    normalize.Value.Should().BeGreaterOrEqualTo(0);
+    normalize.ValueAsString.Should().NotBeNullOrEmpty();
+}
+----
+

docs/code-standards/descriptors.asciidoc

@@ -211,6 +211,7 @@ var methods = from d in YieldAllDescriptors()
     where !(m.Name == nameof(RankFeatureSigmoidFunctionDescriptor.Pivot) && dt == typeof(RankFeatureSigmoidFunctionDescriptor))
     where !(m.Name == nameof(DateHistogramGroupSourceDescriptor<object>.CalendarInterval) && dt == typeof(DateHistogramGroupSourceDescriptor<>))
     where !(m.Name == nameof(DateHistogramGroupSourceDescriptor<object>.FixedInterval) && dt == typeof(DateHistogramGroupSourceDescriptor<>))
+    where !(m.Name == nameof(NormalizeAggregationDescriptor.Method) && dt == typeof(NormalizeAggregationDescriptor))
 
     select new {m, d, p};
 

src/Nest/Aggregations/AggregateDictionary.cs

@@ -122,6 +122,8 @@ public FiltersAggregate Filters(string key)
 
 		public SingleBucketAggregate Nested(string key) => TryGet<SingleBucketAggregate>(key);
 
+		public ValueAggregate Normalize(string key) => TryGet<ValueAggregate>(key);
+
 		public SingleBucketAggregate ReverseNested(string key) => TryGet<SingleBucketAggregate>(key);
 
 		public SingleBucketAggregate Children(string key) => TryGet<SingleBucketAggregate>(key);

src/Nest/Aggregations/AggregationContainer.cs

@@ -202,6 +202,10 @@ public interface IAggregationContainer
 		[DataMember(Name = "nested")]
 		INestedAggregation Nested { get; set; }
 
+		/// <inheritdoc cref="INormalizeAggregation"/>
+		[DataMember(Name = "normalize")]
+		INormalizeAggregation Normalize { get; set; }
+
 		/// <inheritdoc cref="IParentAggregation"/>
 		[DataMember(Name = "parent")]
 		IParentAggregation Parent { get; set; }
@@ -356,6 +360,9 @@ public class AggregationContainer : IAggregationContainer
 
 		public INestedAggregation Nested { get; set; }
 
+		/// <inheritdoc cref="INormalizeAggregation"/>
+		public INormalizeAggregation Normalize { get; set; }
+
 		/// <inheritdoc cref="IParentAggregation"/>
 		public IParentAggregation Parent { get; set; }
 
@@ -513,6 +520,8 @@ public class AggregationContainerDescriptor<T> : DescriptorBase<AggregationConta
 
 		INestedAggregation IAggregationContainer.Nested { get; set; }
 
+		INormalizeAggregation IAggregationContainer.Normalize { get; set; }
+
 		IParentAggregation IAggregationContainer.Parent { get; set; }
 
 		IPercentileRanksAggregation IAggregationContainer.PercentileRanks { get; set; }
@@ -672,6 +681,12 @@ Func<NestedAggregationDescriptor<T>, INestedAggregation> selector
 		) =>
 			_SetInnerAggregation(name, selector, (a, d) => a.Nested = d);
 
+		/// <inheritdoc cref="INormalizeAggregation"/>
+		public AggregationContainerDescriptor<T> Normalize(string name,
+			Func<NormalizeAggregationDescriptor, INormalizeAggregation> selector
+		) =>
+			_SetInnerAggregation(name, selector, (a, d) => a.Normalize = d);
+
 		/// <inheritdoc cref="IParentAggregation"/>
 		public AggregationContainerDescriptor<T> Parent<TParent>(string name,
 			Func<ParentAggregationDescriptor<T, TParent>, IParentAggregation> selector

src/Nest/Aggregations/Pipeline/Normalize/NormalizeAggregation.cs

@@ -0,0 +1,91 @@
+// Licensed to Elasticsearch B.V under one or more agreements.
+// Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information
+
+using System.Runtime.Serialization;
+using Elasticsearch.Net;
+using Elasticsearch.Net.Utf8Json;
+
+namespace Nest
+{
+	/// <summary>
+	/// A parent pipeline aggregation which calculates the specific normalized/rescaled value for a specific bucket value.
+	/// Values that cannot be normalized, will be skipped using the skip gap policy.
+	/// <para />
+	/// Valid in Elasticsearch 7.9.0+ with at least basic license level.
+	/// </summary>
+	[InterfaceDataContract]
+	[ReadAs(typeof(NormalizeAggregation))]
+	public interface INormalizeAggregation : IPipelineAggregation
+	{
+		[DataMember(Name = "method")]
+		NormalizeMethod Method { get; set; }
+	}
+
+	/// <inheritdoc cref="INormalizeAggregation"/>
+	public class NormalizeAggregation
+		: PipelineAggregationBase, INormalizeAggregation
+	{
+		internal NormalizeAggregation() { }
+
+		public NormalizeAggregation(string name, SingleBucketsPath bucketsPath)
+			: base(name, bucketsPath) { }
+
+		internal override void WrapInContainer(AggregationContainer c) => c.Normalize = this;
+
+		/// <inheritdoc cref ="INormalizeAggregation.Method"/>
+		public NormalizeMethod Method { get; set; }
+	}
+
+	/// <inheritdoc cref="INormalizeAggregation"/>
+	public class NormalizeAggregationDescriptor
+		: PipelineAggregationDescriptorBase<NormalizeAggregationDescriptor, INormalizeAggregation, SingleBucketsPath>
+			, INormalizeAggregation
+	{
+		NormalizeMethod INormalizeAggregation.Method { get; set; }
+
+		/// <inheritdoc cref ="INormalizeAggregation.Method"/>
+		public NormalizeAggregationDescriptor Method(NormalizeMethod method) =>
+			Assign(method, (a, v) => a.Method = v);
+	}
+
+	[StringEnum]
+	public enum NormalizeMethod
+	{
+		/// <summary>
+		/// rescales the data such that the minimum number is zero, and the maximum number is 1, with the rest normalized linearly in-between.
+		/// </summary>
+		[EnumMember(Value = "rescale_0_1")]
+		RescaleZeroToOne,
+
+		/// <summary>
+		/// rescales the data such that the minimum number is zero, and the maximum number is 1, with the rest normalized linearly in-between.
+		/// </summary>
+		[EnumMember(Value = "rescale_0_100")]
+		RescaleZeroToOneHundred,
+
+		/// <summary>
+		/// normalizes each value so that it represents a percentage of the total sum it attributes to.
+		/// </summary>
+		[EnumMember(Value = "percent_of_sum")]
+		PercentOfSum,
+
+		/// <summary>
+		/// normalizes such that each value is normalized by how much it differs from the average.
+		/// </summary>
+		[EnumMember(Value = "mean")]
+		Mean,
+
+		/// <summary>
+		/// normalizes such that each value represents how far it is from the mean relative to the standard deviation
+		/// </summary>
+		[EnumMember(Value = "zscore")]
+		Zscore,
+
+		/// <summary>
+		/// normalizes such that each value is exponentiated and relative to the sum of the exponents of the original values.
+		/// </summary>
+		[EnumMember(Value = "softmax")]
+		Softmax
+	}
+}

src/Nest/Aggregations/Visitor/AggregationVisitor.cs

@@ -72,6 +72,8 @@ public interface IAggregationVisitor
 
 		void Visit(INestedAggregation aggregation);
 
+		void Visit(INormalizeAggregation aggregation);
+
 		void Visit(IParentAggregation aggregation);
 
 		void Visit(IReverseNestedAggregation aggregation);
@@ -233,6 +235,8 @@ public virtual void Visit(IRareTermsAggregation aggregation) { }
 
 		public virtual void Visit(INestedAggregation aggregation) { }
 
+		public virtual void Visit(INormalizeAggregation aggregation) { }
+
 		public virtual void Visit(IParentAggregation aggregation) { }
 
 		public virtual void Visit(ICardinalityAggregation aggregation) { }

src/Nest/Aggregations/Visitor/AggregationWalker.cs

@@ -122,6 +122,10 @@ public void Walk(IAggregationContainer aggregation, IAggregationVisitor visitor)
 				v.Visit(d);
 				Accept(v, d.Aggregations);
 			});
+			AcceptAggregation(aggregation.Normalize, visitor, (v, d) =>
+			{
+				v.Visit(d);
+			});
 			AcceptAggregation(aggregation.Parent, visitor, (v, d) =>
 			{
 				v.Visit(d);