Golang BatchRequest.Requests方法代碼示例

// SendBatch implements Sender.
// TODO(tschottdorf): We actually don't want to chop EndTransaction off for
// single-range requests (but that happens now since EndTransaction has the
// isAlone flag). Whether it is one or not is unknown right now (you can only
// find out after you've sent to the Range/looked up a descriptor that suggests
// that you're multi-range. In those cases, the wrapped sender should return an
// error so that we split and retry once the chunk which contains
// EndTransaction (i.e. the last one).
func (cs *chunkingSender) SendBatch(ctx context.Context, ba proto.BatchRequest) (*proto.BatchResponse, error) {
	if len(ba.Requests) < 1 {
		panic("empty batch")
	}

	// Deterministically create ClientCmdIDs for all parts of the batch if
	// a CmdID is already set (otherwise, leave them empty).
	var nextID func() proto.ClientCmdID
	empty := proto.ClientCmdID{}
	if empty == ba.CmdID {
		nextID = func() proto.ClientCmdID {
			return empty
		}
	} else {
		rng := rand.New(rand.NewSource(ba.CmdID.Random))
		id := ba.CmdID
		nextID = func() proto.ClientCmdID {
			curID := id             // copy
			id.Random = rng.Int63() // adjust for next call
			return curID
		}
	}

	parts := ba.Split()
	var rplChunks []*proto.BatchResponse
	for _, part := range parts {
		ba.Requests = part
		ba.CmdID = nextID()
		rpl, err := cs.f(ctx, ba)
		if err != nil {
			return nil, err
		}
		// Propagate transaction from last reply to next request. The final
		// update is taken and put into the response's main header.
		ba.Txn.Update(rpl.Header().Txn)

		rplChunks = append(rplChunks, rpl)
	}

	reply := rplChunks[0]
	for _, rpl := range rplChunks[1:] {
		reply.Responses = append(reply.Responses, rpl.Responses...)
	}
	reply.ResponseHeader = rplChunks[len(rplChunks)-1].ResponseHeader
	reply.Txn = ba.Txn
	return reply, nil
}

//.........這裏部分代碼省略.........
			return nil, err
		}

		first := br == nil
		if first {
			// 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 {
				panic(err)
				// TODO(tschottdorf): return nil, err
			}
		}

		// 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 first {
				// 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.
				ba.Requests = append([]proto.RequestUnion(nil), ba.Requests...)
			}
			for i, union := range ba.Requests {
				args := union.GetValue()
				if _, ok := args.(*proto.NoopRequest); ok {
					// NoopRequests are skipped.
					continue
				}
				boundedArg, ok := args.(proto.Bounded)
				if !ok {
					// Non-bounded request. We will have to query all ranges.
					needAnother = true
					continue
				}
				prevBound := boundedArg.GetBound()
				cReply, ok := curReply.Responses[i].GetValue().(proto.Countable)
				if !ok || prevBound <= 0 {
					// Request bounded, but without max results. Again, will
					// need to query everything we can. The case in which the reply
					// isn't countable occurs when the request wasn't active for
					// that range (since it didn't apply to it), so the response
					// is a NoopResponse.
					needAnother = true
					continue
				}
				nextBound := prevBound - cReply.Count()
				if nextBound <= 0 {
					// We've hit max results for this piece of the batch. Mask
					// it out (we've copied the requests slice above, so this
					// is kosher).
					ba.Requests[i].Reset() // necessary (no one-of?)
					if !ba.Requests[i].SetValue(&proto.NoopRequest{}) {
						panic("RequestUnion excludes NoopRequest")
					}
					continue
				}
				// The request isn't saturated yet.
				needAnother = true
				boundedArg.SetBound(nextBound)
			}
		}

		// If this was the last range accessed by this call, exit loop.
		if !needAnother {
			return br, nil
		}

		if isReverse {
			// In next iteration, query previous range.
			// We use the StartKey of the current descriptor as opposed to the
			// EndKey of the previous one since that doesn't have bugs when
			// stale descriptors come into play.
			to = prev(ba, desc.StartKey)
		} else {
			// In next iteration, query next range.
			// It's important that we use the EndKey of the current descriptor
			// as opposed to the StartKey of the next one: if the former is stale,
			// it's possible that the next range has since merged the subsequent
			// one, and unless both descriptors are stale, the next descriptor's
			// StartKey would move us to the beginning of the current range,
			// resulting in a duplicate scan.
			from = next(ba, desc.EndKey)
		}
		trace.Event("querying next range")
	}
}