From 1a33bef5cd2a1284d1c8a7d502c73ecd7cc1a5ed Mon Sep 17 00:00:00 2001
From: Sergey Zelenov <sergey.zelenov@mongodb.com>
Date: Wed, 30 Sep 2026 11:55:28 +0200
Subject: [PATCH] fix(NODE-7863): reduce memory usage when iterating large
 cursor batches

---
 src/cmap/wire_protocol/on_demand/document.ts    | 17 +++++------------
 .../wire_protocol/on_demand/document.test.ts    |  6 ++++++
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/src/cmap/wire_protocol/on_demand/document.ts b/src/cmap/wire_protocol/on_demand/document.ts
index 133c9e78ff9..c68e7059766 100644
--- a/src/cmap/wire_protocol/on_demand/document.ts
+++ b/src/cmap/wire_protocol/on_demand/document.ts
@@ -124,19 +124,12 @@ export class OnDemandDocument {
     }
 
     if (typeof name === 'number') {
-      if (this.isArray) {
-        if (name < this.elements.length) {
-          const element = this.elements[name];
-          const cachedElement = { element, value: undefined };
-          this.cache[name] = cachedElement;
-          this.indexFound[name] = true;
-          return cachedElement;
-        } else {
-          return null;
-        }
-      } else {
-        return null;
+      // Array elements are addressed directly by index, so there is nothing to speed up by
+      // caching them.
+      if (this.isArray && name < this.elements.length) {
+        return { element: this.elements[name], value: undefined };
       }
+      return null;
     }
 
     for (let index = 0; index < this.elements.length; index++) {
diff --git a/test/unit/cmap/wire_protocol/on_demand/document.test.ts b/test/unit/cmap/wire_protocol/on_demand/document.test.ts
index 34e337f85a7..34b6e9a0114 100644
--- a/test/unit/cmap/wire_protocol/on_demand/document.test.ts
+++ b/test/unit/cmap/wire_protocol/on_demand/document.test.ts
@@ -99,6 +99,12 @@ describe('class OnDemandDocument', () => {
       expect(array.get(1, BSONType.int)).to.equal(1);
     });
 
+    it('does not cache elements accessed by number', () => {
+      array.get(1, BSONType.int);
+      expect(array).to.not.have.nested.property('cache.1');
+      expect(array).to.not.have.nested.property('indexFound.1');
+    });
+
     it('does not support access by number for objects', () => {
       expect(document.get(233, BSONType.int)).to.be.null;
       expect(document.get('233', BSONType.int)).to.equal(3);