From 5f51b4adea35173bbe556fbad041a5485fd8ad10 Mon Sep 17 00:00:00 2001
From: joseph0926 <joseph0926@naver.com>
Date: Sun, 20 Jul 2025 11:41:22 +0900
Subject: [PATCH] perf(query-core/queriesObserver): replace indexOf with
 WeakMap for O(1) observer lookup

---
 packages/query-core/src/queriesObserver.ts | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/packages/query-core/src/queriesObserver.ts b/packages/query-core/src/queriesObserver.ts
index 853e490abd6..b3e426f6b12 100644
--- a/packages/query-core/src/queriesObserver.ts
+++ b/packages/query-core/src/queriesObserver.ts
@@ -44,6 +44,7 @@ export class QueriesObserver<
   #lastCombine?: CombineFn<TCombinedResult>
   #lastResult?: Array<QueryObserverResult>
   #observerMatches: Array<QueryObserverMatch> = []
+  #indexMap: WeakMap<QueryObserver, number> = new WeakMap()
 
   constructor(
     client: QueryClient,
@@ -129,6 +130,11 @@ export class QueriesObserver<
       this.#observers = newObservers
       this.#result = newResult
 
+      this.#indexMap = new WeakMap()
+      newObservers.forEach((observer, index) => {
+        this.#indexMap.set(observer, index)
+      })
+
       if (!this.hasListeners()) {
         return
       }
@@ -252,8 +258,8 @@ export class QueriesObserver<
   }
 
   #onUpdate(observer: QueryObserver, result: QueryObserverResult): void {
-    const index = this.#observers.indexOf(observer)
-    if (index !== -1) {
+    const index = this.#indexMap.get(observer)
+    if (index !== undefined) {
       this.#result = replaceAt(this.#result, index, result)
       this.#notify()
     }