Add AggregationsHelper for SerialDifferencing (#2826)

Use lag in the usage test that return values

Author: russcam

src/Nest/Aggregations/AggregationsHelper.cs

@@ -46,6 +46,8 @@ public AggregationsHelper(IReadOnlyDictionary<string, IAggregate> aggregations)
 
 		public ValueAggregate BucketScript(string key) => this.TryGet<ValueAggregate>(key);
 
+		public ValueAggregate SerialDifferencing(string key) => this.TryGet<ValueAggregate>(key);
+
 		public KeyedValueAggregate MaxBucket(string key) => this.TryGet<KeyedValueAggregate>(key);
 
 		public KeyedValueAggregate MinBucket(string key) => this.TryGet<KeyedValueAggregate>(key);
@@ -153,7 +155,6 @@ public TermsAggregate<TKey> Terms<TKey>(string key)
 
 		public MatrixStatsAggregate MatrixStats(string key) => this.TryGet<MatrixStatsAggregate>(key);
 
-
 		private TAggregate TryGet<TAggregate>(string key)
 			where TAggregate : class, IAggregate
 		{

src/Tests/Aggregations/Pipeline/MovingAverage/MovingAverageHoltLinearAggregationUsageTests.cs

@@ -24,7 +24,7 @@ public MovingAverageHoltLinearAggregationUsageTests(ReadOnlyCluster cluster, End
 					date_histogram = new
 					{
 						field = "startedOn",
-						interval = "month",
+						interval = "month"
 					},
 					aggs = new
 					{
@@ -44,7 +44,7 @@ public MovingAverageHoltLinearAggregationUsageTests(ReadOnlyCluster cluster, End
 								settings = new
 								{
 									alpha = 0.5,
-									beta = 0.5,
+									beta = 0.5
 								}
 							}
 						}
@@ -90,7 +90,7 @@ public MovingAverageHoltLinearAggregationUsageTests(ReadOnlyCluster cluster, End
 						Model = new HoltLinearModel
 						{
 							Alpha = 0.5f,
-							Beta = 0.5f,
+							Beta = 0.5f
 						}
 					}
 			}

src/Tests/Aggregations/Pipeline/MovingAverage/MovingAverageHoltWintersAggregationUsageTests.cs

@@ -23,7 +23,7 @@ public MovingAverageHoltWintersUsageTests(ReadOnlyCluster cluster, EndpointUsage
 					date_histogram = new
 					{
 						field = "startedOn",
-						interval = "month",
+						interval = "month"
 					},
 					aggs = new
 					{
@@ -39,15 +39,15 @@ public MovingAverageHoltWintersUsageTests(ReadOnlyCluster cluster, EndpointUsage
 							moving_avg = new
 							{
 								buckets_path = "commits",
-								window = 60,
+								window = 4,
 								model = "holt_winters",
 								settings = new
 								{
 									type = "mult",
 									alpha = 0.5,
 									beta = 0.5,
 									gamma = 0.5,
-									period = 30,
+									period = 2,
 									pad = false
 								}
 							}
@@ -69,14 +69,14 @@ public MovingAverageHoltWintersUsageTests(ReadOnlyCluster cluster, EndpointUsage
 						)
 						.MovingAverage("commits_moving_avg", mv => mv
 							.BucketsPath("commits")
-							.Window(60)
+							.Window(4)
 							.Model(m => m
 								.HoltWinters(hw => hw
 									.Type(HoltWintersType.Multiplicative)
 									.Alpha(0.5f)
 									.Beta(0.5f)
 									.Gamma(0.5f)
-									.Period(30)
+									.Period(2)
 									.Pad(false)
 								)
 							)
@@ -96,14 +96,14 @@ public MovingAverageHoltWintersUsageTests(ReadOnlyCluster cluster, EndpointUsage
 					new SumAggregation("commits", "numberOfCommits") &&
 					new MovingAverageAggregation("commits_moving_avg", "commits")
 					{
-						Window = 60,
+						Window = 4,
 						Model = new HoltWintersModel
 						{
 							Type = HoltWintersType.Multiplicative,
 							Alpha = 0.5f,
 							Beta = 0.5f,
 							Gamma = 0.5f,
-							Period = 30,
+							Period = 2,
 							Pad = false
 						}
 					}
@@ -113,6 +113,35 @@ public MovingAverageHoltWintersUsageTests(ReadOnlyCluster cluster, EndpointUsage
 		protected override void ExpectResponse(ISearchResponse<Project> response)
 		{
 			response.ShouldBeValid();
+
+			var projectsPerMonth = response.Aggs.DateHistogram("projects_started_per_month");
+			projectsPerMonth.Should().NotBeNull();
+			projectsPerMonth.Buckets.Should().NotBeNull();
+			projectsPerMonth.Buckets.Count.Should().BeGreaterThan(0);
+
+			int bucketCount = 0;
+			foreach (var item in projectsPerMonth.Buckets)
+			{
+				bucketCount++;
+
+				var commits = item.Sum("commits");
+				commits.Should().NotBeNull();
+				commits.Value.Should().BeGreaterThan(0);
+
+				var movingAverage = item.MovingAverage("commits_moving_avg");
+
+				// Moving Average specifies a window of 4 so
+				// moving average values should exist from 5th bucketr onwards
+				if (bucketCount <= 4)
+				{
+					movingAverage.Should().BeNull();
+				}
+				else
+				{
+					movingAverage.Should().NotBeNull();
+					movingAverage.Value.Should().BeGreaterThan(0);
+				}
+			}
 		}
 	}
 }

src/Tests/Aggregations/Pipeline/SerialDifferencing/SerialDifferencingAggregationUsageTests.cs

@@ -22,7 +22,7 @@ public SerialDifferencingAggregationUsageTests(ReadOnlyCluster cluster, Endpoint
 					date_histogram = new
 					{
 						field = "startedOn",
-						interval = "month",
+						interval = "month"
 					},
 					aggs = new
 					{
@@ -33,12 +33,12 @@ public SerialDifferencingAggregationUsageTests(ReadOnlyCluster cluster, Endpoint
 								field = "numberOfCommits"
 							}
 						},
-						thirtieth_difference = new
+						second_difference = new
 						{
 							serial_diff = new
 							{
 								buckets_path = "commits",
-								lag = 30
+								lag = 2
 							}
 						}
 					}
@@ -56,9 +56,9 @@ public SerialDifferencingAggregationUsageTests(ReadOnlyCluster cluster, Endpoint
 						.Sum("commits", sm => sm
 							.Field(p => p.NumberOfCommits)
 						)
-						.SerialDifferencing("thirtieth_difference", d => d
+						.SerialDifferencing("second_difference", d => d
 							.BucketsPath("commits")
-							.Lag(30)
+							.Lag(2)
 						)
 					)
 				)
@@ -73,9 +73,9 @@ public SerialDifferencingAggregationUsageTests(ReadOnlyCluster cluster, Endpoint
 				Interval = DateInterval.Month,
 				Aggregations =
 					new SumAggregation("commits", "numberOfCommits") &&
-					new SerialDifferencingAggregation("thirtieth_difference", "commits")
+					new SerialDifferencingAggregation("second_difference", "commits")
 					{
-						Lag = 30
+						Lag = 2
 					}
 			}
 		};
@@ -89,11 +89,28 @@ protected override void ExpectResponse(ISearchResponse<Project> response)
 			projectsPerMonth.Buckets.Should().NotBeNull();
 			projectsPerMonth.Buckets.Count.Should().BeGreaterThan(0);
 
+			var differenceCount = 0;
+
 			foreach (var item in projectsPerMonth.Buckets)
 			{
+				differenceCount++;
 				var commits = item.Sum("commits");
 				commits.Should().NotBeNull();
 				commits.Value.Should().NotBe(null);
+
+				var secondDifference = item.SerialDifferencing("second_difference");
+
+				// serial differencing specified a lag of 2, so
+				// only expect values from the 3rd bucket onwards
+				if (differenceCount <= 2)
+				{
+					secondDifference.Should().BeNull();
+				}
+				else
+				{
+					secondDifference.Should().NotBeNull();
+					secondDifference.Value.Should().NotBe(null);
+				}
 			}
 		}
 	}