From 1e6cdd80d24ec863efb8986f59c491fde27f0143 Mon Sep 17 00:00:00 2001
From: Jan Wedel <jan.wedel@bosch.io>
Date: Wed, 17 Jul 2024 17:47:11 +0200
Subject: [PATCH 1/2] Improves chart update performance for a large number of
 datasets

Fixes #11814 partly
---
 src/core/core.controller.js | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/core/core.controller.js b/src/core/core.controller.js
index 3c643e8ba3f..9a66d2a795b 100644
--- a/src/core/core.controller.js
+++ b/src/core/core.controller.js
@@ -852,8 +852,7 @@ class Chart {
   getDatasetMeta(datasetIndex) {
     const dataset = this.data.datasets[datasetIndex];
     const metasets = this._metasets;
-    let meta = metasets.filter(x => x && x._dataset === dataset).pop();
-
+    let meta = metasets[datasetIndex];
     if (!meta) {
       meta = {
         type: null,
@@ -869,7 +868,7 @@ class Chart {
         _parsed: [],
         _sorted: false
       };
-      metasets.push(meta);
+      metasets[datasetIndex] = meta;
     }
 
     return meta;

From 1dbef4430fca1555cae03af673b8ac15f13f2682 Mon Sep 17 00:00:00 2001
From: Jan Wedel <jan.wedel@bosch.io>
Date: Thu, 14 Nov 2024 22:06:42 +0100
Subject: [PATCH 2/2] Fixes some broken unit tests for dataset removal and
 reordering

---
 src/core/core.controller.js | 30 ++++++++++++++++--------------
 1 file changed, 16 insertions(+), 14 deletions(-)

diff --git a/src/core/core.controller.js b/src/core/core.controller.js
index 9a66d2a795b..f59143db86c 100644
--- a/src/core/core.controller.js
+++ b/src/core/core.controller.js
@@ -404,30 +404,31 @@ class Chart {
     const metasets = this._metasets;
     const numData = this.data.datasets.length;
     const numMeta = metasets.length;
+    const sortedMetasetByIndex = this.data.datasets.map(currentDataset => metasets.find(currentMetaset => currentMetaset._dataset === currentDataset));
 
-    metasets.sort((a, b) => a.index - b.index);
     if (numMeta > numData) {
       for (let i = numData; i < numMeta; ++i) {
         this._destroyDatasetMeta(i);
       }
-      metasets.splice(numData, numMeta - numData);
+      sortedMetasetByIndex.splice(numData, numMeta - numData);
     }
-    this._sortedMetasets = metasets.slice(0).sort(compare2Level('order', 'index'));
+    this._metasets = sortedMetasetByIndex;
+    this._sortedMetasets = sortedMetasetByIndex.slice(0).sort(compare2Level('order', 'index'));
   }
 
   /**
-	 * @private
-	 */
-  _removeUnreferencedMetasets() {
+   * @private
+   */
+  _rebuildMetasets() {
     const {_metasets: metasets, data: {datasets}} = this;
-    if (metasets.length > datasets.length) {
-      delete this._stacks;
-    }
-    metasets.forEach((meta, index) => {
-      if (datasets.filter(x => x === meta._dataset).length === 0) {
-        this._destroyDatasetMeta(index);
-      }
+    const newMetasets = [];
+
+    datasets.forEach((dataset) => {
+      const matchingMetaset = metasets.find(metaset => dataset === metaset._dataset);
+      newMetasets.push(matchingMetaset);
     });
+
+    this._metasets = newMetasets;
   }
 
   buildOrUpdateControllers() {
@@ -435,11 +436,12 @@ class Chart {
     const datasets = this.data.datasets;
     let i, ilen;
 
-    this._removeUnreferencedMetasets();
+    this._rebuildMetasets();
 
     for (i = 0, ilen = datasets.length; i < ilen; i++) {
       const dataset = datasets[i];
       let meta = this.getDatasetMeta(i);
+
       const type = dataset.type || this.config.type;
 
       if (meta.type && meta.type !== type) {