From b8b802c8ed6dd352c47865af15dc37aebd399ff9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Gast=C3=B3n=20Fournier?= <gaston@getunleash.ai>
Date: Fri, 19 Aug 2022 11:45:41 +0200
Subject: [PATCH] refactor: improve performance of collapseHourlyMetrics
 (#1945)

---
 src/lib/util/collapseHourlyMetrics.ts | 50 ++++++++-------------------
 1 file changed, 15 insertions(+), 35 deletions(-)

diff --git a/src/lib/util/collapseHourlyMetrics.ts b/src/lib/util/collapseHourlyMetrics.ts
index 9b0bd75803..f28c3bce45 100644
--- a/src/lib/util/collapseHourlyMetrics.ts
+++ b/src/lib/util/collapseHourlyMetrics.ts
@@ -1,17 +1,6 @@
 import { IClientMetricsEnv } from '../types/stores/client-metrics-store-v2';
 import { startOfHour } from 'date-fns';
 
-const groupBy = <T>(list: T[], createKey: (item: T) => string): T[][] => {
-    const groups = list.reduce((acc, item) => {
-        const key = createKey(item);
-        acc[key] = acc[key] ?? [];
-        acc[key].push(item);
-        return acc;
-    }, {} as Record<string, T[]>);
-
-    return Object.values(groups);
-};
-
 const createMetricKey = (metric: IClientMetricsEnv): string => {
     return [
         metric.featureName,
@@ -21,31 +10,22 @@ const createMetricKey = (metric: IClientMetricsEnv): string => {
     ].join();
 };
 
-const sumYesNo = (
-    metrics: IClientMetricsEnv[],
-): Pick<IClientMetricsEnv, 'yes' | 'no'> => {
-    return metrics.reduce(
-        (acc, metric) => ({
-            yes: acc.yes + metric.yes,
-            no: acc.no + metric.no,
-        }),
-        {
-            yes: 0,
-            no: 0,
-        },
-    );
-};
-
 export const collapseHourlyMetrics = (
     metrics: IClientMetricsEnv[],
 ): IClientMetricsEnv[] => {
-    const hourlyMetrics = metrics.map((metric) => ({
-        ...metric,
-        timestamp: startOfHour(metric.timestamp),
-    }));
-
-    return groupBy(hourlyMetrics, createMetricKey).flatMap((group) => ({
-        ...group[0],
-        ...sumYesNo(group),
-    }));
+    const grouped = new Map<string, IClientMetricsEnv>();
+    metrics.forEach((metric) => {
+        const hourlyMetric = {
+            ...metric,
+            timestamp: startOfHour(metric.timestamp),
+        };
+        const key = createMetricKey(hourlyMetric);
+        if (!grouped[key]) {
+            grouped[key] = hourlyMetric;
+        } else {
+            grouped[key].yes = metric.yes + (grouped[key].yes || 0);
+            grouped[key].no = metric.no + (grouped[key].no || 0);
+        }
+    });
+    return Object.values(grouped);
 };