From 94dae7cd7da7b47dae7fa07cbd34b4e6c4791111 Mon Sep 17 00:00:00 2001
From: Walter Rafelsberger <walter.rafelsberger@elastic.co>
Date: Thu, 15 Dec 2022 10:46:30 +0100
Subject: [PATCH] fix to fetch correct histogram for groups with multiple
 values for a field

---
 .../server/routes/explain_log_rate_spikes.ts  |  8 +---
 .../routes/queries/get_group_filter.test.ts   | 37 +++++++++++++++++++
 .../server/routes/queries/get_group_filter.ts | 33 +++++++++++++++++
 3 files changed, 72 insertions(+), 6 deletions(-)
 create mode 100644 x-pack/plugins/aiops/server/routes/queries/get_group_filter.test.ts
 create mode 100644 x-pack/plugins/aiops/server/routes/queries/get_group_filter.ts

diff --git a/x-pack/plugins/aiops/server/routes/explain_log_rate_spikes.ts b/x-pack/plugins/aiops/server/routes/explain_log_rate_spikes.ts
index 7da7a345eca3900..19ecf20ec34be69 100644
--- a/x-pack/plugins/aiops/server/routes/explain_log_rate_spikes.ts
+++ b/x-pack/plugins/aiops/server/routes/explain_log_rate_spikes.ts
@@ -47,6 +47,7 @@ import { fetchIndexInfo } from './queries/fetch_index_info';
 import { dropDuplicates, fetchFrequentItems } from './queries/fetch_frequent_items';
 import { getHistogramQuery } from './queries/get_histogram_query';
 import { getChangePointGroups } from './queries/get_change_point_groups';
+import { getGroupFilter } from './queries/get_group_filter';
 
 // 10s ping frequency to keep the stream alive.
 const PING_FREQUENCY = 10000;
@@ -478,12 +479,7 @@ export const defineExplainLogRateSpikesRoute = (
                   }
 
                   if (overallTimeSeries !== undefined) {
-                    const histogramQuery = getHistogramQuery(
-                      request.body,
-                      cpg.group.map((d) => ({
-                        term: { [d.fieldName]: d.fieldValue },
-                      }))
-                    );
+                    const histogramQuery = getHistogramQuery(request.body, getGroupFilter(cpg));
 
                     let cpgTimeSeries: NumericChartData;
                     try {
diff --git a/x-pack/plugins/aiops/server/routes/queries/get_group_filter.test.ts b/x-pack/plugins/aiops/server/routes/queries/get_group_filter.test.ts
new file mode 100644
index 000000000000000..b2c15d70e83f93f
--- /dev/null
+++ b/x-pack/plugins/aiops/server/routes/queries/get_group_filter.test.ts
@@ -0,0 +1,37 @@
+/*
+ * 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 { finalChangePointGroups } from '../../../common/__mocks__/artificial_logs/final_change_point_groups';
+
+import { getGroupFilter } from './get_group_filter';
+
+describe('getGroupFilter', () => {
+  it('gets a query filter for the change points of a group with multiple values per field', () => {
+    expect(getGroupFilter(finalChangePointGroups[0])).toStrictEqual([
+      {
+        term: {
+          response_code: '500',
+        },
+      },
+      {
+        terms: {
+          url: ['home.php', 'login.php'],
+        },
+      },
+    ]);
+  });
+
+  it('gets a query filter for the change points of a group with just a single field/value', () => {
+    expect(getGroupFilter(finalChangePointGroups[1])).toStrictEqual([
+      {
+        term: {
+          user: 'Peter',
+        },
+      },
+    ]);
+  });
+});
diff --git a/x-pack/plugins/aiops/server/routes/queries/get_group_filter.ts b/x-pack/plugins/aiops/server/routes/queries/get_group_filter.ts
new file mode 100644
index 000000000000000..fdd97eb10107214
--- /dev/null
+++ b/x-pack/plugins/aiops/server/routes/queries/get_group_filter.ts
@@ -0,0 +1,33 @@
+/*
+ * 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 * as estypes from '@elastic/elasticsearch/lib/api/typesWithBodyKey';
+
+import type { ChangePointGroup } from '@kbn/ml-agg-utils';
+
+// Transforms a list of change point items from a group in a query filter.
+// Uses a `term` filter for single field value combinations.
+// For fields with multiple values it creates a single `terms` filter that includes
+// all values. This avoids queries not returning any results otherwise because
+// separate `term` filter for multiple values for the same field would rule each other out.
+export function getGroupFilter(
+  changePointGroup: ChangePointGroup
+): estypes.QueryDslQueryContainer[] {
+  return Object.entries(
+    changePointGroup.group.reduce<Record<string, Array<string | number>>>((p, c) => {
+      if (p[c.fieldName]) {
+        p[c.fieldName].push(c.fieldValue);
+      } else {
+        p[c.fieldName] = [c.fieldValue];
+      }
+      return p;
+    }, {})
+  ).reduce<estypes.QueryDslQueryContainer[]>((p, [key, values]) => {
+    p.push(values.length > 1 ? { terms: { [key]: values } } : { term: { [key]: values[0] } });
+    return p;
+  }, []);
+}