sequentialize non-ROW events

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>

go/vt/vttablet/tabletmanager/vreplication/vplayer_parallel_producer.go

@@ -278,7 +278,24 @@ func (p *parallelProducer) process(ctx context.Context, events chan *binlogdatap
 		// case t := <-ticker.C:
 		// 	lastGoodTime = t
 		case event := <-events:
-			// processEvent(ctx, event)
+			log.Errorf("========== QQQ process event type: %v", event.Type)
+			canApplyInParallel := false
+			switch event.Type {
+			case binlogdatapb.VEventType_BEGIN,
+				binlogdatapb.VEventType_FIELD,
+				binlogdatapb.VEventType_ROW,
+				binlogdatapb.VEventType_COMMIT,
+				binlogdatapb.VEventType_GTID:
+				// We can parallelize these events.
+				canApplyInParallel = true
+			}
+			if !canApplyInParallel {
+				// As an example, thus could be a DDL.
+				// Wait for all existing workers to complete
+				if err := p.commitAll(ctx, nil); err != nil {
+					return err
+				}
+			}
 			workerIndex := p.assignTransactionToWorker(event.SequenceNumber, event.CommitParent)
 			worker := p.workers[workerIndex]
 			// We know the worker has enough capacity and thus the following will not block.
@@ -288,6 +305,12 @@ func (p *parallelProducer) process(ctx context.Context, events chan *binlogdatap
 				return ctx.Err()
 			case worker.events <- event:
 			}
+			if !canApplyInParallel {
+				// Say this was a DDL. Then we need to wait until it is absolutely complete, before we allow the next event to be processed.
+				if err := <-worker.commitEvents(); err != nil {
+					return err
+				}
+			}
 		}
 	}
 }