[GitHub] [kafka] guozhangwang commented on a change in pull request #9020: KAFKA-10271 Performance regression while fetching a key from a single partition

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guozhangwang commented on a change in pull request #9020:
URL: https://github.com/apache/kafka/pull/9020#discussion_r498533922



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File path: streams/src/main/java/org/apache/kafka/streams/state/internals/WrappingStoreProvider.java
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@@ -46,11 +46,22 @@ public void setStoreQueryParameters(final StoreQueryParameters storeQueryParamet
     public <T> List<T> stores(final String storeName,
                               final QueryableStoreType<T> queryableStoreType) {
         final List<T> allStores = new ArrayList<>();
-        for (final StreamThreadStateStoreProvider provider : storeProviders) {
-            final List<T> stores = provider.stores(storeQueryParameters);
-            allStores.addAll(stores);
+        for (final StreamThreadStateStoreProvider storeProvider : storeProviders) {
+            final List<T> stores = storeProvider.stores(storeQueryParameters);
+            if (!stores.isEmpty()) {
+                allStores.addAll(stores);
+                if (storeQueryParameters.partition() != null) {
+                    break;
+                }
+            }
         }
         if (allStores.isEmpty()) {
+            if (storeQueryParameters.partition() != null) {
+                throw new InvalidStateStoreException(
+                        String.format("The specified partition %d for store %s does not exist.",

Review comment:
       Got it, in that case how about we just encode the partition in the thrown's message so that upon throwing, people can still check if the partition is `null` or not when debugging?
   
   Otherwise, this PR all LGTM :)




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