Implementing ZADD If Key Exists
2 days ago
- #Redis
- #Performance Optimization
- #Atomic Operations
- Performance optimizations required implementing a Redis ZADD operation only if the sorted set exists, without creating a new set.
- Initial non-atomic solution involved checking key existence before ZADD, but needed an atomic approach.
- AI suggested using a pipeline, which was incorrect as it always performed ZADD regardless of key existence.
- AI then proposed a LUA script for atomicity, but LUA was rejected due to potential performance issues.
- WATCH command was introduced as an alternative, but testing revealed it didn't work as expected with key expiration.
- Final solution used TTL check to ensure key existence with a buffer, leveraging simplicity and performance.
- The approach tolerates rare cases of non-TTL keys, which can be cleaned up with SCAN.