replace Metadata in query with pageSize and bookmark (hyperledger#1024)

The range query receives metadata such as pagination limit.
The execute query at couchdb receives metadata such as the
pagination bookmark and pagination limit.
ValidateRangeMetadata() and ValidateQueryMetadata() validate
the received metadata.

However, the term metadata is confusing with the statemetadata
which stores the key-based endorsement. Hence, we replace
Metadata in range and execute query API with Pagination.
As we have removed the metadata map, we also removed
ValidateRangeMetadata() and ValidateQueryMetadata() as they
are not needed anymore.

Signed-off-by: senthil <cendhu@gmail.com>

core/chaincode/handler.go

@@ -710,14 +710,9 @@ func (h *Handler) HandleGetStateByRange(msg *pb.ChaincodeMessage, txContext *Tra
 	}
 
 	totalReturnLimit := h.calculateTotalReturnLimit(metadata)
-
 	iterID := h.UUIDGenerator.New()
-
 	var rangeIter commonledger.ResultsIterator
-	var paginationInfo map[string]interface{}
-
 	isPaginated := false
-
 	namespaceID := txContext.NamespaceID
 	collection := getStateByRange.Collection
 	if isCollectionSet(collection) {
@@ -730,21 +725,15 @@ func (h *Handler) HandleGetStateByRange(msg *pb.ChaincodeMessage, txContext *Tra
 		rangeIter, err = txContext.TXSimulator.GetPrivateDataRangeScanIterator(namespaceID, collection,
 			getStateByRange.StartKey, getStateByRange.EndKey)
 	} else if isMetadataSetForPagination(metadata) {
-		paginationInfo, err = createPaginationInfoFromMetadata(metadata, totalReturnLimit, pb.ChaincodeMessage_GET_STATE_BY_RANGE)
-		if err != nil {
-			return nil, err
-		}
 		isPaginated = true
-
 		startKey := getStateByRange.StartKey
-
 		if isMetadataSetForPagination(metadata) {
 			if metadata.Bookmark != "" {
 				startKey = metadata.Bookmark
 			}
 		}
-		rangeIter, err = txContext.TXSimulator.GetStateRangeScanIteratorWithMetadata(namespaceID,
-			startKey, getStateByRange.EndKey, paginationInfo)
+		rangeIter, err = txContext.TXSimulator.GetStateRangeScanIteratorWithPagination(namespaceID,
+			startKey, getStateByRange.EndKey, metadata.PageSize)
 	} else {
 		rangeIter, err = txContext.TXSimulator.GetStateRangeScanIterator(namespaceID, getStateByRange.StartKey, getStateByRange.EndKey)
 	}
@@ -838,10 +827,7 @@ func (h *Handler) HandleGetQueryResult(msg *pb.ChaincodeMessage, txContext *Tran
 
 	totalReturnLimit := h.calculateTotalReturnLimit(metadata)
 	isPaginated := false
-
 	var executeIter commonledger.ResultsIterator
-	var paginationInfo map[string]interface{}
-
 	namespaceID := txContext.NamespaceID
 	collection := getQueryResult.Collection
 	if isCollectionSet(collection) {
@@ -853,13 +839,9 @@ func (h *Handler) HandleGetQueryResult(msg *pb.ChaincodeMessage, txContext *Tran
 		}
 		executeIter, err = txContext.TXSimulator.ExecuteQueryOnPrivateData(namespaceID, collection, getQueryResult.Query)
 	} else if isMetadataSetForPagination(metadata) {
-		paginationInfo, err = createPaginationInfoFromMetadata(metadata, totalReturnLimit, pb.ChaincodeMessage_GET_QUERY_RESULT)
-		if err != nil {
-			return nil, err
-		}
 		isPaginated = true
-		executeIter, err = txContext.TXSimulator.ExecuteQueryWithMetadata(namespaceID,
-			getQueryResult.Query, paginationInfo)
+		executeIter, err = txContext.TXSimulator.ExecuteQueryWithPagination(namespaceID,
+			getQueryResult.Query, metadata.Bookmark, metadata.PageSize)
 
 	} else {
 		executeIter, err = txContext.TXSimulator.ExecuteQuery(namespaceID, getQueryResult.Query)
@@ -952,22 +934,6 @@ func getQueryMetadataFromBytes(metadataBytes []byte) (*pb.QueryMetadata, error)
 	return nil, nil
 }
 
-func createPaginationInfoFromMetadata(metadata *pb.QueryMetadata, totalReturnLimit int32, queryType pb.ChaincodeMessage_Type) (map[string]interface{}, error) {
-	paginationInfoMap := make(map[string]interface{})
-
-	switch queryType {
-	case pb.ChaincodeMessage_GET_QUERY_RESULT:
-		paginationInfoMap["bookmark"] = metadata.Bookmark
-	case pb.ChaincodeMessage_GET_STATE_BY_RANGE:
-		// this is a no-op for range query
-	default:
-		return nil, errors.New("query type must be either GetQueryResult or GetStateByRange")
-	}
-
-	paginationInfoMap["limit"] = totalReturnLimit
-	return paginationInfoMap, nil
-}
-
 func (h *Handler) calculateTotalReturnLimit(metadata *pb.QueryMetadata) int32 {
 	totalReturnLimit := int32(h.TotalQueryLimit)
 	if metadata != nil {