Add backwards compatibility tests for exponential_histogram (elastic#136809)

Author: JonasKunz

x-pack/plugin/mapper-exponential-histogram/build.gradle

@@ -26,9 +26,15 @@ restResources {
 dependencies {
   api project(":libs:exponential-histogram")
   api project(xpackModule('analytics'))
+
   compileOnly project(path: xpackModule('core'))
+
   testImplementation(testArtifact(project(":libs:exponential-histogram")))
+
   yamlRestTestImplementation(testArtifact(project(xpackModule('core'))))
+  clusterModules(project(xpackModule('analytics'))) //histogram field type
+  clusterModules(project(xpackModule('mapper-aggregate-metric'))) //aggregate_metric_double field type
+  clusterModules project(':modules:data-streams')
 }
 
 restResources {

x-pack/plugin/mapper-exponential-histogram/src/yamlRestTest/java/org/elasticsearch/xpack/exponentialhistogram/ExponentialHistogramYamlTestSuiteIT.java

@@ -35,7 +35,12 @@ public static Iterable<Object[]> parameters() throws Exception {
     }
 
     @ClassRule
-    public static ElasticsearchCluster cluster = ElasticsearchCluster.local().module("exponential-histogram").build();
+    public static ElasticsearchCluster cluster = ElasticsearchCluster.local()
+        .module("x-pack-aggregate-metric")
+        .module("x-pack-analytics")
+        .module("exponential-histogram")
+        .module("data-streams")
+        .build();
 
     @Override
     protected String getTestRestCluster() {

x-pack/plugin/mapper-exponential-histogram/src/yamlRestTest/resources/rest-api-spec/test/30_aggregate_metric_aggregations_compatibility.yml

@@ -0,0 +1,106 @@
+setup:
+  # Create an index template for the data stream with aggregate_metric_double field
+  - do:
+      indices.put_index_template:
+        name: test_data_stream_template
+        body:
+          index_patterns: ["test-data-stream*"]
+          data_stream: {}
+          template:
+            mappings:
+              properties:
+                histo_or_aggregate_metric:
+                  type: aggregate_metric_double
+                  metrics: [min, max, sum, value_count]
+                  default_metric: value_count
+
+  # Create the data stream
+  - do:
+      indices.create_data_stream:
+        name: test-data-stream
+
+  # Insert a document with aggregate_metric_double value
+  - do:
+      index:
+        index: test-data-stream
+        refresh: true
+        body:
+          '@timestamp': "2023-01-01T00:00:00Z"
+          histo_or_aggregate_metric:
+            min: 1.0
+            max: 10.0
+            sum: 20.0
+            value_count: 3
+
+  # Update the index template to change the field type to exponential_histogram
+  - do:
+      indices.put_index_template:
+        name: test_data_stream_template
+        body:
+          index_patterns: ["test-data-stream*"]
+          data_stream: {}
+          template:
+            mappings:
+              properties:
+                histo_or_aggregate_metric:
+                  type: exponential_histogram
+
+  # Rollover the data stream to apply the new mapping
+  - do:
+      indices.rollover:
+        alias: test-data-stream
+
+  # Insert a document with exponential_histogram value
+  - do:
+      index:
+        index: test-data-stream
+        refresh: true
+        body:
+          '@timestamp': "2023-01-02T00:00:00Z"
+          histo_or_aggregate_metric:
+            scale: 1
+            sum: 100.0
+            min: 1.0
+            max: 10.0
+            zero: { count: 1 }
+            positive: { indices: [0,1], counts: [2,3] }
+            negative: { indices: [0], counts: [1] }
+
+---
+"Value count aggregation over aggregate_metric_double and exponential_histogram":
+  - do:
+      search:
+        index: test-data-stream
+        size: 0
+        body:
+          aggs:
+            value_count_metric:
+              value_count:
+                field: histo_or_aggregate_metric
+  - match: { aggregations.value_count_metric.value: 10.0 }
+
+---
+"Sum aggregation over aggregate_metric_double and exponential_histogram":
+  - do:
+      search:
+        index: test-data-stream
+        size: 0
+        body:
+          aggs:
+            sum_metric:
+              sum:
+                field: histo_or_aggregate_metric
+  - match: { aggregations.sum_metric.value: 120.0 }
+
+---
+"Average aggregation over aggregate_metric_double and exponential_histogram":
+  - do:
+      search:
+        index: test-data-stream
+        size: 0
+        body:
+          aggs:
+            avg_metric:
+              avg:
+                field: histo_or_aggregate_metric
+  - match: { aggregations.avg_metric.value: 12.0 }

x-pack/plugin/mapper-exponential-histogram/src/yamlRestTest/resources/rest-api-spec/test/40_tdigest_histogram_aggregations_compatibility.yml

@@ -0,0 +1,102 @@
+setup:
+  # Create an index template for the data stream with histogram field
+  - do:
+      indices.put_index_template:
+        name: test_data_stream_template
+        body:
+          index_patterns: ["test-data-stream*"]
+          data_stream: {}
+          template:
+            mappings:
+              properties:
+                tdigest_or_exp_histo:
+                  type: histogram
+
+  # Create the data stream
+  - do:
+      indices.create_data_stream:
+        name: test-data-stream
+
+  # Insert a document with T-Digest histogram value
+  - do:
+      index:
+        index: test-data-stream
+        refresh: true
+        body:
+          '@timestamp': "2023-01-01T00:00:00Z"
+          tdigest_or_exp_histo:
+            values: [1.0, 2.0, 4.0]
+            counts: [2, 2, 1]
+
+  # Update the index template to change the field type to exponential_histogram
+  - do:
+      indices.put_index_template:
+        name: test_data_stream_template
+        body:
+          index_patterns: ["test-data-stream*"]
+          data_stream: {}
+          template:
+            mappings:
+              properties:
+                tdigest_or_exp_histo:
+                  type: exponential_histogram
+
+  # Rollover the data stream to apply the new mapping
+  - do:
+      indices.rollover:
+        alias: test-data-stream
+
+  # Insert a document with exponential_histogram value
+  - do:
+      index:
+        index: test-data-stream
+        refresh: true
+        body:
+          '@timestamp': "2023-01-02T00:00:00Z"
+          tdigest_or_exp_histo:
+            scale: 1
+            sum: 100.0
+            min: 1.0
+            max: 10.0
+            zero: { count: 1 }
+            positive: { indices: [0,1], counts: [1,2] }
+            negative: { indices: [0], counts: [1] }
+
+---
+"Value count aggregation over aggregate_metric_double and exponential_histogram":
+  - do:
+      search:
+        index: test-data-stream
+        size: 0
+        body:
+          aggs:
+            value_count_metric:
+              value_count:
+                field: tdigest_or_exp_histo
+  - match: { aggregations.value_count_metric.value: 10.0 }
+
+---
+"Sum aggregation over aggregate_metric_double and exponential_histogram":
+  - do:
+      search:
+        index: test-data-stream
+        size: 0
+        body:
+          aggs:
+            sum_metric:
+              sum:
+                field: tdigest_or_exp_histo
+  - match: { aggregations.sum_metric.value: 110.0 }
+
+---
+"Average aggregation over aggregate_metric_double and exponential_histogram":
+  - do:
+      search:
+        index: test-data-stream
+        size: 0
+        body:
+          aggs:
+            avg_metric:
+              avg:
+                field: tdigest_or_exp_histo
+  - match: { aggregations.avg_metric.value: 11.0 }