fix: ensure ZADD keeps the last score for duplicate members in a single command to align with Redis behavior

src/storage/src/redis_zsets.cc

@@ -307,13 +307,17 @@ Status RedisZSets::ZAdd(const Slice& key, const std::vector<ScoreMember>& score_
   *ret = 0;
   uint32_t statistic = 0;
   std::unordered_set<std::string> unique;
-  std::vector<ScoreMember> filtered_score_members;
-  for (const auto& sm : score_members) {
-    if (unique.find(sm.member) == unique.end()) {
-      unique.insert(sm.member);
-      filtered_score_members.push_back(sm);
+  std::list<storage::ScoreMember> mid_score_members;
+  for (auto it = score_members.rbegin(); it != score_members.rend(); ++it) {
+    if (unique.find(it->member) == unique.end()) {
+      unique.insert(it->member);
+      mid_score_members.push_front(*it);
     }
   }
+  std::vector<ScoreMember> filtered_score_members;
+  for (auto &item : mid_score_members) {
+    filtered_score_members.push_back(std::move(item));
+  }
 
   char score_buf[8];
   int32_t version = 0;

tests/integration/zset_test.go

@@ -233,7 +233,26 @@ var _ = Describe("Zset Commands", func() {
 			Member: "two",
 		}}))
 	})
-
+	// Caiyu's test: verify that zadd with multiple scores for the same member in 
+	//a single command only keeps the last score, consistent with Redis behavior
+	It("should ZAdd with duplicate member in one command", func() {
+		added, err := client.ZAdd(ctx, "myzset", redis.Z{
+			Score:  100,
+			Member: "one",
+		}, redis.Z{
+			Score:  98,
+			Member: "one",
+		}).Result()
+		Expect(err).NotTo(HaveOccurred())
+		Expect(added).To(Equal(int64(1)))
+
+		vals, err := client.ZRangeWithScores(ctx, "myzset", 0, -1).Result()
+		Expect(err).NotTo(HaveOccurred())
+		Expect(vals).To(Equal([]redis.Z{{
+			Score:  98,
+			Member: "one",
+		}}))
+	})
 	It("should ZAdd bytes", func() {
 		added, err := client.ZAdd(ctx, "zset", redis.Z{
 			Score:  1,