From 758ce2192a5a9d3bd8bc4dbd8bd8ce9475d4df66 Mon Sep 17 00:00:00 2001
From: Binbin <binloveplay1314@qq.com>
Date: Sat, 29 Jul 2023 14:27:43 +0800
Subject: [PATCH] Skip WATCH if connection is already dirty (#1612)

If a conn is already marked as watched_keys_modified,
we can skip the watch. It is a cleanup and in some situations
it may save us some memory and performance gains.
---
 src/commands/cmd_txn.cc | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/commands/cmd_txn.cc b/src/commands/cmd_txn.cc
index 3138c364702..b6c94c06a67 100644
--- a/src/commands/cmd_txn.cc
+++ b/src/commands/cmd_txn.cc
@@ -98,6 +98,12 @@ class CommandWatch : public Commander {
       return {Status::RedisExecErr, "WATCH inside MULTI is not allowed"};
     }
 
+    // If a conn is already marked as watched_keys_modified, we can skip the watch.
+    if (svr->IsWatchedKeysModified(conn)) {
+      *output = redis::SimpleString("OK");
+      return Status::OK();
+    }
+
     svr->WatchKey(conn, std::vector<std::string>(args_.begin() + 1, args_.end()));
     *output = redis::SimpleString("OK");
     return Status::OK();