From cf749c488ba1beab49d4617ec95819eb24898d4c Mon Sep 17 00:00:00 2001
From: sywu14 <wushiyuanwork@outlook.com>
Date: Tue, 26 May 2026 13:41:05 +0800
Subject: [PATCH] [ISSUE #9926] Avoid redundant list allocation in
 parsePublishMessageQueues

When namespace is empty (the common case for most users), the method
previously allocated a new ArrayList and N new MessageQueue objects on
every send call, copying identical data. Under high throughput (50K+ TPS),
this creates significant GC pressure from short-lived objects.

This change:
- Returns the original list directly when namespace is empty (zero alloc)
- Pre-allocates ArrayList capacity when namespace stripping is needed

Signed-off-by: sywu14 <wushiyuanwork@outlook.com>
---
 .../rocketmq/client/impl/MQAdminImpl.java     |  9 ++++--
 .../rocketmq/client/impl/MQAdminImplTest.java | 30 +++++++++++++++++++
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/client/src/main/java/org/apache/rocketmq/client/impl/MQAdminImpl.java b/client/src/main/java/org/apache/rocketmq/client/impl/MQAdminImpl.java
index 729e917eed4..328aedaef9a 100644
--- a/client/src/main/java/org/apache/rocketmq/client/impl/MQAdminImpl.java
+++ b/client/src/main/java/org/apache/rocketmq/client/impl/MQAdminImpl.java
@@ -157,9 +157,14 @@ public List<MessageQueue> fetchPublishMessageQueues(String topic) throws MQClien
     }
 
     public List<MessageQueue> parsePublishMessageQueues(List<MessageQueue> messageQueueList) {
-        List<MessageQueue> resultQueues = new ArrayList<>();
+        String namespace = this.mQClientFactory.getClientConfig().getNamespace();
+        if (namespace == null || namespace.isEmpty()) {
+            return messageQueueList;
+        }
+
+        List<MessageQueue> resultQueues = new ArrayList<>(messageQueueList.size());
         for (MessageQueue queue : messageQueueList) {
-            String userTopic = NamespaceUtil.withoutNamespace(queue.getTopic(), this.mQClientFactory.getClientConfig().getNamespace());
+            String userTopic = NamespaceUtil.withoutNamespace(queue.getTopic(), namespace);
             resultQueues.add(new MessageQueue(userTopic, queue.getBrokerName(), queue.getQueueId()));
         }
 
diff --git a/client/src/test/java/org/apache/rocketmq/client/impl/MQAdminImplTest.java b/client/src/test/java/org/apache/rocketmq/client/impl/MQAdminImplTest.java
index f52aba2dc00..79c58299552 100644
--- a/client/src/test/java/org/apache/rocketmq/client/impl/MQAdminImplTest.java
+++ b/client/src/test/java/org/apache/rocketmq/client/impl/MQAdminImplTest.java
@@ -44,6 +44,7 @@
 import java.net.SocketAddress;
 import java.nio.ByteBuffer;
 import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
@@ -51,6 +52,7 @@
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertSame;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyLong;
 import static org.mockito.ArgumentMatchers.anyString;
@@ -215,6 +217,34 @@ private TopicRouteData createRouteData() {
         return result;
     }
 
+    @Test
+    public void assertParsePublishMessageQueuesReturnsOriginalListWhenNoNamespace() {
+        ClientConfig clientConfig = mock(ClientConfig.class);
+        when(clientConfig.getNamespace()).thenReturn(null);
+        when(mQClientFactory.getClientConfig()).thenReturn(clientConfig);
+        MQAdminImpl adminNoNs = new MQAdminImpl(mQClientFactory);
+
+        List<MessageQueue> original = new ArrayList<>();
+        original.add(new MessageQueue("TopicA", "broker-0", 0));
+        original.add(new MessageQueue("TopicA", "broker-0", 1));
+
+        List<MessageQueue> result = adminNoNs.parsePublishMessageQueues(original);
+        assertSame(original, result);
+    }
+
+    @Test
+    public void assertParsePublishMessageQueuesStripsNamespace() {
+        List<MessageQueue> original = new ArrayList<>();
+        original.add(new MessageQueue("namespace%TopicA", "broker-0", 0));
+        original.add(new MessageQueue("namespace%TopicA", "broker-0", 1));
+
+        List<MessageQueue> result = mqAdminImpl.parsePublishMessageQueues(original);
+        assertEquals(2, result.size());
+        for (MessageQueue mq : result) {
+            assertEquals("TopicA", mq.getTopic());
+        }
+    }
+
     private List<BrokerData> createBrokerData() {
         HashMap<Long, String> brokerAddrs = new HashMap<>();
         brokerAddrs.put(MixAll.MASTER_ID, defaultBrokerAddr);