Hyperledger Fabric 中的借记和贷记（更改）state 数据

Question

All examples for Hyperledger Fabric seem to focus on posting a new state that just overwrite the previous state of a record, for example owner A is replaced by owner B for car 1.

I haven't found any example of "stateful" change of state though. For example when we have a bank account record in the state, with a balance. We would post a debit or credit transaction to the ledger that would need to read the current balance of the account, and decrease or increase it. This would possibly involve putting a lock on the account state record until the change is completed. Are there any examples of this, how can this be done properly in chaincode to ensure data consistency?

Answer 1

Hyperledger Fabric has an example of bank-transfer-like here - high throughput

Because of the Read-Write set, we can not make a chaincode which modify the same key multiple times at the same time ([MVCC_READ_CONFLICT] error). You can read more about RW set here , or this article

The key idea of this sample is that it makes a unique key with the same prefix for every transaction: varName~op~value~txID, where a transaction params include:

• varName: account
• op: + or - operator
• value: transaction value
• txID: this will make the key unique

After that, at the GET query phase, it uses GetStateByPartialCompositeKey() function to get theses records which include the account in the key and then sum up to get the current balance of that account

Hope this can give you some ideas!