perf: bail out if staleTime stays the same

packages/query-core/src/__tests__/queryCache.test.tsx

@@ -55,7 +55,7 @@ describe('queryCache', () => {
       const unsubScribeObserver = observer.subscribe(vi.fn())
 
       await waitFor(() => {
-        expect(events.length).toBe(10)
+        expect(events.length).toBe(8)
       })
 
       expect(events).toEqual([
@@ -64,11 +64,9 @@ describe('queryCache', () => {
         'observerAdded', // 3. Observer added
         'observerResultsUpdated', // 4. Observer result updated -> fetching
         'updated', // 5. Query updated -> fetching
-        'updated', // 6. { type: 'stale' }
-        'observerResultsUpdated', // 7. Observer result updated -> success
-        'updated', // 8. Query updated -> success
-        'observerResultsUpdated', // 9. Observer result updated -> stale
-        'updated', // 6. { type: 'stale' }
+        'observerResultsUpdated', // 6. Observer result updated -> success
+        'updated', // 7. Query updated -> success
+        'updated', // 8. Query updated -> stale
       ])
 
       queries.forEach((query) => {

packages/query-core/src/__tests__/queryObserver.test.tsx

@@ -1002,12 +1002,10 @@ describe('queryObserver', () => {
     await sleep(1)
     unsubscribe()
     expect(results.length).toBe(4)
-    expect(keys.length).toBe(4)
+    expect(keys.length).toBe(3)
     expect(keys[0]).toBe(null) // First Query - status: 'pending', fetchStatus: 'idle'
     expect(keys[1]).toBe(null) // First Query - status: 'pending', fetchStatus: 'fetching'
-    // we call placeholderData again when result is created due to stale transition
-    expect(keys[2]).toBe(null)
-    expect(keys[3]).toBe(key1) // Second Query - status: 'pending', fetchStatus: 'fetching'
+    expect(keys[2]).toBe(key1) // Second Query - status: 'pending', fetchStatus: 'fetching'
 
     expect(results[0]).toMatchObject({
       data: undefined,

packages/query-core/src/query.ts

@@ -175,6 +175,7 @@ export class Query<
   #defaultOptions?: QueryOptions<TQueryFnData, TError, TData, TQueryKey>
   #abortSignalConsumed: boolean
   #staleTimeoutId?: ReturnType<typeof setTimeout>
+  #currentStaleTime?: number
 
   constructor(config: QueryConfig<TQueryFnData, TError, TData, TQueryKey>) {
     super()
@@ -294,17 +295,24 @@ export class Query<
   }
 
   updateStaleTimer(): void {
-    this.#clearStaleTimeout()
     const staleTime = this.staleTime()
 
+    // same staleTime as last time, so we have nothing to do
+    if (staleTime === this.#currentStaleTime) {
+      return
+    }
+
+    this.#clearStaleTimeout()
+    this.#currentStaleTime = staleTime
+
     const time = timeUntilStale(this.state.dataUpdatedAt, staleTime)
 
     const triggerStale = () => {
       this.#notify({ type: 'stale' })
     }
-
-    if (time === 0) {
-      // no timer necessary,
+    if (time === 0 && !this.isStaleByTime(staleTime)) {
+      // no timer necessary, time zero is always stale,
+      // but we aren't currently stale, so we instantly trigger it
       triggerStale()
       return
     }