Query Processing in Blockchain Systems: Current State and Future Challenges

Abstract

When, in 2008, Satoshi Nakamoto envisioned the first distributed database management system that relied on cryptographically secured chain of blocks to store data in an immutable and tamper-resistant manner, his primary use case was the introduction of a digital currency. Owing to this use case, the blockchain system was geared towards efficient storage of data, whereas the processing of complex queries, such as provenance analyses of data history, is out of focus. The increasing use of Internet of Things technologies and the resulting digitization in many domains, however, have led to a plethora of novel use cases for a secure digital ledger. For instance, in the healthcare sector, blockchain systems are used for the secure storage and sharing of electronic health records, while the food industry applies such systems to enable a reliable food-chain traceability, e.g., to prove compliance with cold chains. In these application domains, however, querying the current state is not sufficient—comprehensive history queries are required instead. Due to these altered usage modes involving more complex query types, it is questionable whether today’s blockchain systems are prepared for this type of usage and whether such queries can be processed efficiently by them. In our paper, we therefore investigate novel use cases for blockchain systems and elicit their requirements towards a data store in terms of query capabilities. We reflect the state of the art in terms of query support in blockchain systems and assess whether it is capable of meeting the requirements of such more sophisticated use cases. As a result, we identify future research challenges with regard to query processing in blockchain systems.

Roadmap for National Adoption of Blockchain Technology Towards Securing the Food System of Qatar

“…The system also promised that trust can be earned by rewarding "miners" (nodes that verify the validity of a transaction and append valid blocks to the rest of the chain) with token incentives [24]. Such cryptographic validation processes require massive computational power and therefore make it logically insensible for a malevolent block to validate a faulty record and maintain the faulty version of the truth throughout the entirety of the chain [25].…”

Multi-State Merkle Patricia Trie (MSMPT): High-Performance Data Structures for Multi-Query Processing Based on Lightweight Blockchain

“…Lightweight blockchain also uses a combination of cryptographic techniques and optimization strategies. In a lightweight blockchain, query processing is conducted by the network nodes responsible for verifying transactions and maintaining the blockchain [46]. The information saved in a block is merely the Merkle root information, as explained in Fig.…”

A Unified Data Model for Blockchains

“…Some examples of applications are: (1) Detecting accounts used by the same user; (2) Detecting account behaviours; (3) Account clustering; (4) Wealth movements; and others. Some surveys about blockchain technology have already identified that the problem of a missing unified model exists [Przytarski et al 2021, Huang et al 2021]. However, no study has been found regarding a unified data model for blockchain data; and no study about the entities and the attributes that compose most blockchain networks.…”