ChaincodeCountRecord.go

package main

import (
	"encoding/json"
	"strconv"

	"github.com/hyperledger/fabric/core/chaincode/shim"
	"github.com/hyperledger/fabric/protos/ledger/queryresult"
	"github.com/hyperledger/fabric/protos/peer"
)


// CountStudent : by college ID & department ID
func CountStudent(stub shim.ChaincodeStubInterface, collegeId, departmentId string) (int, error) {
	// No need to validate electioinType and candidateID, caller will handle this
	queryString := "{\"selector\":{\"doc_type\":\"student\",\"college_id\":\"" + collegeId + "\",\"department_id\":\"" + departmentId + "\"}}"

	var pageSize int32 = 1000
	bookmark := ""
	page := 0

	var resultsIterator shim.StateQueryIteratorInterface
	var responseMetadata *peer.QueryResponseMetadata
	var err error
	lastPageBookmark := ""
	recordCount := 0

	for true {
		resultsIterator, responseMetadata, err = stub.GetQueryResultWithPagination(queryString, pageSize, bookmark)
		if err != nil {
			return 0, err
		}

		if bookmark == responseMetadata.Bookmark {
			break
		}
		page++
		lastPageBookmark = bookmark
		// responseMetadata will be "nil" if the record is 0 at first page
		bookmark = responseMetadata.Bookmark
		if responseMetadata.Bookmark == "nil" {
			break
		}
	}

	defer resultsIterator.Close()

	// optimize count by: (limit * (total_page -1) + number of record at last page)
	// Do this no need to loop and count record in every page
	recordCount = int(pageSize) * (page - 1)
	resultsIterator, responseMetadata, err = stub.GetQueryResultWithPagination(queryString, pageSize, lastPageBookmark)
	if err != nil {
		return 0, err
	}
	for resultsIterator.HasNext() {
		_, err := resultsIterator.Next()
		if err != nil {
			return 0, err
		}
		recordCount++
	}

	return recordCount, nil
}