Skip the tiflash job.

test:
1. create table t(id int);
2. ALTER TABLE t SET TIFLASH REPLICA 3 LOCATION LABELS "rack", "host", "abc";            // model.ActionSetTiFlashReplica
3. curl -X POST -d '{"id":45,"region_count":3,"flash_region_count":3}' https://127.0.0.1:10080/tiflash/replica  // model.ActionUpdateTiFlashReplicaStatus
4. performance write on table t and check can still replicate.

ref: pingcap/tidb#12453

drainer/schema.go

@@ -262,6 +262,17 @@ func (s *Schema) handlePreviousDDLJobIfNeed(version int64) error {
 	return nil
 }
 
+func skipFlash(job *model.Job) bool {
+	switch job.Type {
+	case model.ActionUpdateTiFlashReplicaStatus: // empty job.Query
+		return true
+	case model.ActionSetTiFlashReplica:
+		return true
+	}
+
+	return false
+}
+
 // handleDDL has four return values,
 // the first value[string]: the schema name
 // the second value[string]: the table name

drainer/syncer.go

@@ -388,6 +388,10 @@ ForLoop:
 		} else if jobID > 0 {
 			log.Debug("get ddl binlog job", zap.Stringer("job", b.job))
 
+			if skipFlash(b.job) {
+				continue
+			}
+
 			// Notice: the version of DDL Binlog we receive are Monotonically increasing
 			// DDL (with version 10, commit ts 100) -> DDL (with version 9, commit ts 101) would never happen
 			s.schema.addJob(b.job)