Golang BatchRequest.MaxSpanRequestKeys方法代码示例

//.........这里部分代码省略.........
			// If there's no transaction and op spans ranges, possibly
			// re-run as part of a transaction for consistency. The
			// case where we don't need to re-run is if the read
			// consistency is not required.
			if ba.Txn == nil && ba.IsPossibleTransaction() && ba.ReadConsistency != roachpb.INCONSISTENT {
				responseCh <- response{pErr: roachpb.NewError(&roachpb.OpRequiresTxnError{})}
				return
			}
			// If the request is more than but ends with EndTransaction, we
			// want the caller to come again with the EndTransaction in an
			// extra call.
			if l := len(ba.Requests) - 1; l > 0 && ba.Requests[l].GetInner().Method() == roachpb.EndTransaction {
				responseCh <- response{pErr: errNo1PCTxn}
				return
			}
		}

		// Determine next seek key, taking a potentially sparse batch into
		// consideration.
		var err error
		nextRS := rs
		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.
			seekKey, err = prev(ba, ri.Desc().StartKey)
			nextRS.EndKey = seekKey
		} 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.
			seekKey, err = next(ba, ri.Desc().EndKey)
			nextRS.Key = seekKey
		}
		if err != nil {
			responseCh <- response{pErr: roachpb.NewError(err)}
			return
		}

		// Send the next partial batch to the first range in the "rs" span.
		// If we're not handling a request which limits responses and we
		// can reserve one of the limited goroutines available for parallel
		// batch RPCs, send asynchronously.
		if ba.MaxSpanRequestKeys == 0 && ri.NeedAnother(rs) && ds.rpcContext != nil &&
			ds.sendPartialBatchAsync(ctx, ba, rs, ri.Desc(), ri.Token(), isFirst, responseCh) {
			// Note that we pass the batch request by value to the parallel
			// goroutine to avoid using the cloned txn.

			// Clone the txn to preserve the current txn sequence for the async call.
			if ba.Txn != nil {
				txnClone := ba.Txn.Clone()
				ba.Txn = &txnClone
			}
		} else {
			// Send synchronously if there is no parallel capacity left, there's a
			// max results limit, or this is the final request in the span.
			resp := ds.sendPartialBatch(ctx, ba, rs, ri.Desc(), ri.Token(), isFirst)
			responseCh <- resp
			if resp.pErr != nil {
				return
			}
			ba.UpdateTxn(resp.reply.Txn)

			// Check whether we've received enough responses to exit query loop.
			if ba.MaxSpanRequestKeys > 0 {
				var numResults int64
				for _, r := range resp.reply.Responses {
					numResults += r.GetInner().Header().NumKeys
				}
				if numResults > ba.MaxSpanRequestKeys {
					panic(fmt.Sprintf("received %d results, limit was %d", numResults, ba.MaxSpanRequestKeys))
				}
				ba.MaxSpanRequestKeys -= numResults
				// Exiting; fill in missing responses.
				if ba.MaxSpanRequestKeys == 0 {
					fillSkippedResponses(ba, resp.reply, seekKey)
					return
				}
			}
		}

		// Check for completion.
		if !ri.NeedAnother(rs) {
			return
		}
		isFirst = false // next range will not be first!
		rs = nextRS
	}

	// We've exited early. Return the range iterator error.
	responseCh := make(chan response, 1)
	responseCh <- response{pErr: ri.Error()}
	responseChs = append(responseChs, responseCh)
	return
}