Cloud-native databases leverage cloud infrastructure to provide highly available and elastically scalable data management, and they have experienced rapid development in recent years. As a transparent, tamper-proof, and traceable database system, blockchain sharding is the most direct and promising solution for scaling up blockchain systems. By taking advantage of the elastic scalability of cloud infrastructure, more flexible scaling can be achieved. This study first summarizes three key technical challenges addressed by current blockchain sharding: the security of node partitioning, efficient on-chain data sharding, and cross-shard transaction processing. It reviews the research status of these three issues, introduces and compares the corresponding solutions for each issue, and also discusses the new challenges these solutions face in cloud-native environments. Then, around these three dimensions, a comprehensive analysis and comparison of all solutions are conducted from the perspective of the overall impact on the blockchain system. Finally, the paper analyzes the development trends in blockchain sharding technology and points out several research directions that deserve further exploration.