An Ethereum-Based Electronic Health Record System with SQL Query Support

Blockchains’ power of decentralization, immutability, and transparency has found its application in many fields. The blockchain is an append-only structure. As the blockchain grows, accessing blocks from the past in an efficient manner has become a challenging task. Further, blockchains were not initially envisioned to be read-heavy systems. With the passage of time, more and more applications are using blockchains and therefore blockchains need to provide active support for high read loads concerning the history state as well. To facilitate data querying in blockchain, we have proposed an SQL query processing feature in the Ethereum blockchain through a decentralized application. More specifically, we build an Ethereum-based Electronic Health Record (EHR) system with SQL query support. The following approaches for query processing have been explored and implemented: (i) linearly scanning blockchain, (ii) scanning only from a userspecified block, (iii) replication in database, (iv) indexing in a database, and (v) using smart contracts. Our timing analysis across these implementations reveals that the smart contracts-based approach has reasonable performance gains compared the other approaches.