// fillSkippedResponses after meeting the batch key max limit for range
// requests.
func fillSkippedResponses(
	ba roachpb.BatchRequest, br *roachpb.BatchResponse, nextSpan roachpb.RSpan,
) {
	// Some requests might have NoopResponses; we must replace them with empty
	// responses of the proper type.
	for i, req := range ba.Requests {
		if _, ok := br.Responses[i].GetInner().(*roachpb.NoopResponse); !ok {
			continue
		}
		var reply roachpb.Response
		switch t := req.GetInner().(type) {
		case *roachpb.ScanRequest:
			reply = &roachpb.ScanResponse{}

		case *roachpb.ReverseScanRequest:
			reply = &roachpb.ReverseScanResponse{}

		case *roachpb.DeleteRangeRequest:
			reply = &roachpb.DeleteRangeResponse{}

		case *roachpb.BeginTransactionRequest, *roachpb.EndTransactionRequest:
			continue

		default:
			panic(fmt.Sprintf("bad type %T", t))
		}
		union := roachpb.ResponseUnion{}
		union.MustSetInner(reply)
		br.Responses[i] = union
	}
	// Set the ResumeSpan for future batch requests.
	isReverse := ba.IsReverse()
	for i, resp := range br.Responses {
		req := ba.Requests[i].GetInner()
		if !roachpb.IsRange(req) {
			continue
		}
		hdr := resp.GetInner().Header()
		origSpan := req.Header()
		if isReverse {
			if hdr.ResumeSpan != nil {
				// The ResumeSpan.Key might be set to the StartKey of a range;
				// correctly set it to the Key of the original request span.
				hdr.ResumeSpan.Key = origSpan.Key
			} else if roachpb.RKey(origSpan.Key).Less(nextSpan.EndKey) {
				// Some keys have yet to be processed.
				hdr.ResumeSpan = &origSpan
				if nextSpan.EndKey.Less(roachpb.RKey(origSpan.EndKey)) {
					// The original span has been partially processed.
					hdr.ResumeSpan.EndKey = nextSpan.EndKey.AsRawKey()
				}
			}
		} else {
			if hdr.ResumeSpan != nil {
				// The ResumeSpan.EndKey might be set to the EndKey of a
				// range; correctly set it to the EndKey of the original
				// request span.
				hdr.ResumeSpan.EndKey = origSpan.EndKey
			} else if nextSpan.Key.Less(roachpb.RKey(origSpan.EndKey)) {
				// Some keys have yet to be processed.
				hdr.ResumeSpan = &origSpan
				if roachpb.RKey(origSpan.Key).Less(nextSpan.Key) {
					// The original span has been partially processed.
					hdr.ResumeSpan.Key = nextSpan.Key.AsRawKey()
				}
			}
		}
		br.Responses[i].GetInner().SetHeader(hdr)
	}
}

//.........这里部分代码省略.........

		ba.Txn.Update(curReply.Txn)

		if br == nil {
			// First response from a Range.
			br = curReply
		} else {
			// This was the second or later call in a cross-Range request.
			// Combine the new response with the existing one.
			if err := br.Combine(curReply); err != nil {
				return nil, roachpb.NewError(err), false
			}
		}

		if ba.MaxScanResults > 0 {
			// Count how many results we received.
			var numResults int64
			for _, resp := range curReply.Responses {
				if cResp, ok := resp.GetInner().(roachpb.Countable); ok {
					numResults += cResp.Count()
				}
			}
			if numResults > ba.MaxScanResults {
				panic(fmt.Sprintf("received %d results, limit was %d", numResults, ba.MaxScanResults))
			}
			ba.MaxScanResults -= numResults
			if ba.MaxScanResults == 0 {
				// We are done with this batch. Some requests might have NoopResponses; we must
				// replace them with empty responses of the proper type.
				for i, req := range ba.Requests {
					if _, ok := br.Responses[i].GetInner().(*roachpb.NoopResponse); !ok {
						continue
					}
					union := roachpb.ResponseUnion{}
					var reply roachpb.Response
					if _, ok := req.GetInner().(*roachpb.ScanRequest); ok {
						reply = &roachpb.ScanResponse{}
					} else {
						_ = req.GetInner().(*roachpb.ReverseScanRequest)
						reply = &roachpb.ReverseScanResponse{}
					}
					union.MustSetInner(reply)
					br.Responses[i] = union
				}
				return br, nil, false
			}
		}

		// If this request has a bound (such as MaxResults in
		// ScanRequest) and we are going to query at least one more range,
		// check whether enough rows have been retrieved.
		// TODO(tschottdorf): need tests for executing a multi-range batch
		// with various bounded requests which saturate at different times.
		if needAnother {
			// Start with the assumption that all requests are saturated.
			// Below, we look at each and decide whether that's true.
			// Everything that is indeed saturated is "masked out" from the
			// batch request; only if that's all requests does needAnother
			// remain false.
			needAnother = false
			if br == nil {
				// Clone ba.Requests. This is because we're multi-range, and
				// some requests may be bounded, which could lead to them being
				// masked out once they're saturated. We don't want to risk
				// removing requests that way in the "master copy" since that
				// could lead to omitting requests in certain retry scenarios.