From 9f4a9c2327c1b9bdebb35c57b1651f1ec4f067f2 Mon Sep 17 00:00:00 2001
From: Yarchik <spoko.dev@gmail.com>
Date: Thu, 2 Jul 2026 12:47:04 +0100
Subject: [PATCH] fix: key unordered bulk insertedIds by originating operation
 index

---
 src/bulk/unordered.ts  |  2 +-
 test/unit/bulk.test.ts | 63 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 64 insertions(+), 1 deletion(-)
 create mode 100644 test/unit/bulk.test.ts

diff --git a/src/bulk/unordered.ts b/src/bulk/unordered.ts
index 97a134613b0..35add067b3b 100644
--- a/src/bulk/unordered.ts
+++ b/src/bulk/unordered.ts
@@ -97,7 +97,7 @@ export class UnorderedBulkOperation extends BulkOperationBase {
     if (batchType === BatchType.INSERT) {
       this.s.currentInsertBatch = this.s.currentBatch;
       this.s.bulkResult.insertedIds.push({
-        index: this.s.bulkResult.insertedIds.length,
+        index: this.s.currentIndex - 1,
         _id: (document as Document)._id
       });
     } else if (batchType === BatchType.UPDATE) {
diff --git a/test/unit/bulk.test.ts b/test/unit/bulk.test.ts
new file mode 100644
index 00000000000..88d44826593
--- /dev/null
+++ b/test/unit/bulk.test.ts
@@ -0,0 +1,63 @@
+import { expect } from 'chai';
+
+import {
+  DEFAULT_PK_FACTORY,
+  MongoDBCollectionNamespace,
+  OrderedBulkOperation,
+  UnorderedBulkOperation
+} from '../mongodb';
+
+describe('Bulk Operation insertedIds', function () {
+  function makeFakeCollection() {
+    const topology = {
+      lastHello() {
+        return { maxBsonObjectSize: 16 * 1024 * 1024, maxWriteBatchSize: 1000 };
+      },
+      s: { options: {} }
+    };
+    const collection: any = {
+      client: { topology },
+      topology,
+      db: { options: {} },
+      bsonOptions: {},
+      s: {
+        namespace: new MongoDBCollectionNamespace('test', 'coll'),
+        pkFactory: DEFAULT_PK_FACTORY,
+        bsonOptions: {},
+        collection: undefined
+      }
+    };
+    collection.s.collection = collection;
+    return collection;
+  }
+
+  function addMixedOperations(bulk: OrderedBulkOperation | UnorderedBulkOperation) {
+    bulk.raw({ insertOne: { document: { _id: 'a', x: 1 } } });
+    bulk.raw({ updateOne: { filter: { x: 1 }, update: { $set: { y: 2 } } } });
+    bulk.raw({ insertOne: { document: { _id: 'b', x: 3 } } });
+    bulk.raw({ deleteOne: { filter: { x: 3 } } });
+    bulk.raw({ insertOne: { document: { _id: 'c', x: 5 } } });
+  }
+
+  it('ordered bulk keys insertedIds by the originating operation index', function () {
+    const bulk = new OrderedBulkOperation(makeFakeCollection(), { ordered: true } as any);
+    addMixedOperations(bulk);
+    const insertedIds = (bulk as any).s.bulkResult.insertedIds;
+    expect(insertedIds).to.deep.equal([
+      { index: 0, _id: 'a' },
+      { index: 2, _id: 'b' },
+      { index: 4, _id: 'c' }
+    ]);
+  });
+
+  it('unordered bulk keys insertedIds by the originating operation index', function () {
+    const bulk = new UnorderedBulkOperation(makeFakeCollection(), { ordered: false } as any);
+    addMixedOperations(bulk);
+    const insertedIds = (bulk as any).s.bulkResult.insertedIds;
+    expect(insertedIds).to.deep.equal([
+      { index: 0, _id: 'a' },
+      { index: 2, _id: 'b' },
+      { index: 4, _id: 'c' }
+    ]);
+  });
+});