elastic
diff --git a/‎x-pack/solutions/observability/plugins/apm/server/routes/correlations/queries/fetch_duration_percentiles.test.ts‎
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diff --git a/‎x-pack/solutions/observability/plugins/apm/server/routes/correlations/queries/fetch_duration_percentiles.ts‎
Lines changed: 17 additions & 3 deletions b/‎x-pack/solutions/observability/plugins/apm/server/routes/correlations/queries/fetch_duration_percentiles.ts‎
Lines changed: 17 additions & 3 deletions
diff --git a/‎x-pack/solutions/observability/plugins/apm/server/routes/correlations/queries/has_exponential_histogram_mapping.test.ts‎
Lines changed: 74 additions & 0 deletions b/‎x-pack/solutions/observability/plugins/apm/server/routes/correlations/queries/has_exponential_histogram_mapping.test.ts‎
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diff --git a/‎x-pack/solutions/observability/plugins/apm/server/routes/correlations/queries/has_exponential_histogram_mapping.ts‎
Lines changed: 36 additions & 0 deletions b/‎x-pack/solutions/observability/plugins/apm/server/routes/correlations/queries/has_exponential_histogram_mapping.ts‎
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@@ -0,0 +1,147 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import { LatencyDistributionChartType } from '../../../../common/latency_distribution_chart_types';
+import type { APMEventClient } from '../../../lib/helpers/create_es_client/create_apm_event_client';
+import { fetchDurationPercentiles } from './fetch_duration_percentiles';
+
+const percentileValues = {
+  '1.0': 10,
+  '5.0': 20,
+  '25.0': 50,
+  '50.0': 100,
+  '75.0': 200,
+  '95.0': 400,
+  '99.0': 800,
+};
+
+function createApmEventClient({
+  fieldTypes = {},
+}: {
+  fieldTypes?: Record<string, { type: string }>;
+} = {}) {
+  return {
+    fieldCaps: jest.fn().mockResolvedValue({
+      fields: {
+        'transaction.duration.histogram': fieldTypes,
+      },
+    }),
+    search: jest.fn().mockResolvedValue({
+      hits: { total: { value: 1, relation: 'eq' } },
+      aggregations: {
+        duration_percentiles: { values: percentileValues },
+      },
+    }),
+  } as unknown as APMEventClient & {
+    fieldCaps: jest.Mock;
+    search: jest.Mock;
+  };
+}
+
+const baseParams = {
+  start: 0,
+  end: 1,
+  environment: 'ENVIRONMENT_ALL' as const,
+  kuery: '',
+  query: { match_all: {} },
+  chartType: LatencyDistributionChartType.transactionLatency,
+};
+
+describe('fetchDurationPercentiles', () => {
+  it('keeps HDR percentiles for raw transaction events', async () => {
+    const apmEventClient = createApmEventClient();
+
+    await fetchDurationPercentiles({
+      ...baseParams,
+      apmEventClient,
+      searchMetrics: false,
+    });
+
+    expect(apmEventClient.fieldCaps).not.toHaveBeenCalled();
+    expect(apmEventClient.search).toHaveBeenCalledWith(
+      'get_duration_percentiles',
+      expect.objectContaining({
+        aggs: {
+          duration_percentiles: {
+            percentiles: expect.objectContaining({
+              field: 'transaction.duration.us',
+              hdr: { number_of_significant_value_digits: 3 },
+            }),
+          },
+        },
+      }),
+      expect.anything()
+    );
+  });
+
+  it('keeps HDR percentiles for classic histogram mappings', async () => {
+    const apmEventClient = createApmEventClient({
+      fieldTypes: {
+        histogram: { type: 'histogram' },
+      },
+    });
+
+    await fetchDurationPercentiles({
+      ...baseParams,
+      apmEventClient,
+      searchMetrics: true,
+    });
+
+    expect(apmEventClient.fieldCaps).toHaveBeenCalledWith(
+      'get_duration_field_caps',
+      expect.objectContaining({
+        fields: ['transaction.duration.histogram'],
+        include_empty_fields: true,
+      })
+    );
+    expect(apmEventClient.fieldCaps.mock.calls[0][1].index_filter).toBeUndefined();
+    expect(apmEventClient.search.mock.calls[0][1].aggs.duration_percentiles.percentiles).toEqual(
+      expect.objectContaining({
+        field: 'transaction.duration.histogram',
+        hdr: { number_of_significant_value_digits: 3 },
+      })
+    );
+  });
+
+  it('omits HDR percentiles when the duration field is exponential_histogram', async () => {
+    const apmEventClient = createApmEventClient({
+      fieldTypes: {
+        exponential_histogram: { type: 'exponential_histogram' },
+      },
+    });
+
+    await fetchDurationPercentiles({
+      ...baseParams,
+      apmEventClient,
+      searchMetrics: true,
+    });
+
+    const percentilesAgg =
+      apmEventClient.search.mock.calls[0][1].aggs.duration_percentiles.percentiles;
+    expect(percentilesAgg.field).toBe('transaction.duration.histogram');
+    expect(percentilesAgg.hdr).toBeUndefined();
+  });
+
+  it('omits HDR percentiles when histogram and exponential_histogram mappings are mixed', async () => {
+    const apmEventClient = createApmEventClient({
+      fieldTypes: {
+        histogram: { type: 'histogram' },
+        exponential_histogram: { type: 'exponential_histogram' },
+      },
+    });
+
+    await fetchDurationPercentiles({
+      ...baseParams,
+      apmEventClient,
+      searchMetrics: true,
+    });
+
+    expect(
+      apmEventClient.search.mock.calls[0][1].aggs.duration_percentiles.percentiles.hdr
+    ).toBeUndefined();
+  });
+});
@@ -6,6 +6,7 @@
  */
 
 import { SIGNIFICANT_VALUE_DIGITS } from '../../../../common/correlations/constants';
+import { TRANSACTION_DURATION_HISTOGRAM } from '../../../../common/es_fields/apm';
 import type { LatencyDistributionChartType } from '../../../../common/latency_distribution_chart_types';
 import { getCommonCorrelationsQuery } from './get_common_correlations_query';
 import type {
@@ -20,6 +21,7 @@ import {
 } from '../utils';
 import type { APMEventClient } from '../../../lib/helpers/create_es_client/create_apm_event_client';
 import { getBackwardCompatibleDocumentTypeFilter } from '../../../lib/helpers/transactions';
+import { hasExponentialHistogramMapping } from './has_exponential_histogram_mapping';
 
 export const fetchDurationPercentiles = async ({
   chartType,
@@ -62,6 +64,14 @@ export const fetchDurationPercentiles = async ({
     ? getDurationFieldFromEntityType(entityType, isOtel)
     : getDurationField(chartType!, searchMetrics, isOtel);
 
+  const omitHdr =
+    durationField === TRANSACTION_DURATION_HISTOGRAM &&
+    (await hasExponentialHistogramMapping({
+      apmEventClient,
+      eventType,
+      durationField,
+    }));
+
   const params = {
     apm: { events: [eventType] },
     track_total_hits: true,
@@ -76,10 +86,14 @@ export const fetchDurationPercentiles = async ({
     aggs: {
       duration_percentiles: {
         percentiles: {
-          hdr: {
-            number_of_significant_value_digits: SIGNIFICANT_VALUE_DIGITS,
-          },
           field: durationField,
+          ...(omitHdr
+            ? {}
+            : {
+                hdr: {
+                  number_of_significant_value_digits: SIGNIFICANT_VALUE_DIGITS,
+                },
+              }),
           ...(Array.isArray(percents) ? { percents } : {}),
         },
       },
 
@@ -0,0 +1,74 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import { ProcessorEvent } from '@kbn/observability-plugin/common';
+import type { APMEventClient } from '../../../lib/helpers/create_es_client/create_apm_event_client';
+import { hasExponentialHistogramMapping } from './has_exponential_histogram_mapping';
+
+describe('hasExponentialHistogramMapping', () => {
+  const baseParams = {
+    eventType: ProcessorEvent.metric,
+    durationField: 'transaction.duration.histogram',
+  };
+
+  it('returns false when the field is not mapped', async () => {
+    const apmEventClient = {
+      fieldCaps: jest.fn().mockResolvedValue({ fields: {} }),
+    } as unknown as APMEventClient;
+
+    await expect(hasExponentialHistogramMapping({ ...baseParams, apmEventClient })).resolves.toBe(
+      false
+    );
+  });
+
+  it('returns false for classic histogram mappings', async () => {
+    const apmEventClient = {
+      fieldCaps: jest.fn().mockResolvedValue({
+        fields: {
+          'transaction.duration.histogram': {
+            histogram: { type: 'histogram' },
+          },
+        },
+      }),
+    } as unknown as APMEventClient;
+
+    await expect(hasExponentialHistogramMapping({ ...baseParams, apmEventClient })).resolves.toBe(
+      false
+    );
+  });
+
+  it('returns true when any mapping is exponential_histogram', async () => {
+    const apmEventClient = {
+      fieldCaps: jest.fn().mockResolvedValue({
+        fields: {
+          'transaction.duration.histogram': {
+            histogram: { type: 'histogram' },
+            exponential_histogram: { type: 'exponential_histogram' },
+          },
+        },
+      }),
+    } as unknown as APMEventClient;
+
+    await expect(hasExponentialHistogramMapping({ ...baseParams, apmEventClient })).resolves.toBe(
+      true
+    );
+  });
+
+  it('requests empty-field mappings without a time filter', async () => {
+    const apmEventClient = {
+      fieldCaps: jest.fn().mockResolvedValue({ fields: {} }),
+    } as unknown as APMEventClient;
+
+    await hasExponentialHistogramMapping({ ...baseParams, apmEventClient });
+
+    expect(apmEventClient.fieldCaps).toHaveBeenCalledWith('get_duration_field_caps', {
+      apm: { events: [ProcessorEvent.metric] },
+      fields: ['transaction.duration.histogram'],
+      include_empty_fields: true,
+    });
+  });
+});
@@ -0,0 +1,36 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import { ES_FIELD_TYPES } from '@kbn/field-types';
+import type { ProcessorEvent } from '@kbn/observability-plugin/common';
+import type { APMEventClient } from '../../../lib/helpers/create_es_client/create_apm_event_client';
+
+/** True when any index maps the duration field as exponential_histogram (HDR percentiles are invalid). */
+export async function hasExponentialHistogramMapping({
+  apmEventClient,
+  eventType,
+  durationField,
+}: {
+  apmEventClient: APMEventClient;
+  eventType: ProcessorEvent;
+  durationField: string;
+}): Promise<boolean> {
+  // Do not time-filter or skip empty fields: HDR fails on mapping even when
+  // matching shards have 0 hits in the selected range.
+  const fieldCaps = await apmEventClient.fieldCaps('get_duration_field_caps', {
+    apm: { events: [eventType] },
+    fields: [durationField],
+    include_empty_fields: true,
+  });
+
+  const fieldTypes = fieldCaps.fields[durationField];
+  if (!fieldTypes) {
+    return false;
+  }
+
+  return Object.keys(fieldTypes).includes(ES_FIELD_TYPES.EXPONENTIAL_HISTOGRAM);
+}