Querying past transaction data from Hyperledger Fabric

Question

A ledger contains many transactions in it. How can I query the present and past transaction data from the ledger?

Answer 1

You can use the following system chaincode to query the ledger. It is used to query the peer and it also has a 
number of queries related to blocks.

https://github.com/hyperledger/fabric/tree/master/core/scc/qscc

Hope this helps!

Get your Blockchain certification today to learn more about this technology.

Thanks.

Answer 2

To get the historic data of the chaincode, you can use the ChaincodeStubInterface API.

This retrieves entire histroy for a given key. It is iterative and so you can see the changes made for the 
given key.

Look at the following example:

historyIer, err := stub.GetHistoryForKey(yourKey)

if err != nil {
    fmt.Println(errMsg)
    return shim.Error(errMsg)
}

if historyIer.HasNext() {
    modification, err := historyIer.Next()
    if err != nil {
        fmt.Println(errMsg)
        return shim.Error(errMsg)
    }
    fmt.Println("Returning information related to", string(modification.Value))
}

To make this work, you have the set the value of "enableHistoryDatabase" in core.yaml under the ledger section
as true as shown below:

ledger:

 history:
    # enableHistoryDatabase - options are true or false
    # Indicates if the history of key updates should be stored.
    # All history 'index' will be stored in goleveldb, regardless if using
    # CouchDB or alternate database for the state.
    enableHistoryDatabase: true

Comments

Can we query ledger using the transaction ID?

---

You can not query ledger using transaction ID with shim API but you can do it at application level using SDK.

Answer 3

You can use shim function and query it using the transaction key. 

GetHistoryForKey(key string)