Cloud-native databases leverage cloud infrastructure to provide highly available and elastically scalable data management, and they have experienced rapid development in recent years. Blockchain is a transparent, tamper-resistant, and traceable database system, with sharding being the most direct and promising approach to scale, it can also achieve elastic scalability by utilizing cloud infrastructure. This paper first summarizes the three key technical challenges that need to be addressed in blockchain sharding: ensuring the security of node partitioning, on-chain data sharding and cross-shard transaction processing. It reviews the current state of research on these issues and introduces and compares the corresponding solutions, this paper also discusses the new challenges these solutions face in cloud-native environments. Then, a more comprehensive analysis and comparison of all solutions are conducted from the perspective of the whole blockchain system. Finally, the paper analyzes the development trends in blockchain sharding technology and presented several research directions that deserve further exploration.