MSET change it to batch write instead of batch per key (apache#1634)

The previous implementation which wrote the batch per key,
we should change it to a single batch. Also use the multi-key
lock before the write operations instead of inside the loop.

This is mention in apache#1631, found by hulk.

Co-authored-by: mwish <1506118561@qq.com>

src/types/redis_string.cc

@@ -371,28 +371,33 @@ rocksdb::Status String::MSet(const std::vector<StringPair> &pairs, uint64_t ttl,
     expire = now + ttl;
   }
 
-  // Data race, key string maybe overwrite by other key while didn't lock the key here,
+  // Data race, key string maybe overwrite by other key while didn't lock the keys here,
   // to improve the set performance
   std::string ns_key;
+  std::optional<MultiLockGuard> guard;
+  if (lock) {
+    std::vector<std::string> lock_keys;
+    lock_keys.reserve(pairs.size());
+    for (const StringPair &pair : pairs) {
+      AppendNamespacePrefix(pair.key, &ns_key);
+      lock_keys.emplace_back(ns_key);
+    }
+    guard.emplace(storage_->GetLockManager(), lock_keys);
+  }
+
+  auto batch = storage_->GetWriteBatchBase();
+  WriteBatchLogData log_data(kRedisString);
+  batch->PutLogData(log_data.Encode());
   for (const auto &pair : pairs) {
     std::string bytes;
     Metadata metadata(kRedisString, false);
     metadata.expire = expire;
     metadata.Encode(&bytes);
     bytes.append(pair.value.data(), pair.value.size());
-    auto batch = storage_->GetWriteBatchBase();
-    WriteBatchLogData log_data(kRedisString);
-    batch->PutLogData(log_data.Encode());
     AppendNamespacePrefix(pair.key, &ns_key);
     batch->Put(metadata_cf_handle_, ns_key, bytes);
-    std::optional<LockGuard> guard;
-    if (lock) {
-      guard.emplace(storage_->GetLockManager(), ns_key);
-    }
-    auto s = storage_->Write(storage_->DefaultWriteOptions(), batch->GetWriteBatch());
-    if (!s.ok()) return s;
   }
-  return rocksdb::Status::OK();
+  return storage_->Write(storage_->DefaultWriteOptions(), batch->GetWriteBatch());
 }
 
 rocksdb::Status String::MSetNX(const std::vector<StringPair> &pairs, uint64_t ttl, bool *flag) {