  Blockchain is one of the most popular distributed ledger technologies. It can
solve the trust issue among enterprises. Hyperledger Fabric is a permissioned
blockchain aiming at enterprise-grade business applications. However, compared
to traditional distributed database solutions, one issue of blockchain based
application development is the limited data access. For Fabric, the ledger data
can only be retrieved by limited interfaces provided by Fabric SDKs or
chaincode. In order to meet the requirements of data query and provide flexible
query functions for real applications built on Fabric, this paper proposed a
ledger data query platform called Ledgerdata Refiner. With ledger data analysis
middleware, we provide sufficient interfaces for users to retrieve block or
transaction efficiently. It is also able to track historical operations for any
specific state. In addition, schemas of ledger state have been analyzed and
clustered, which enable users to perform rich queries against ledger data.
Finally, we validate the effectiveness of our query platform on a real
application.
