upgrade: add a variable to make insert ddl job force to queue (#36614) (

#36618)

close #36601

ddl/ddl_worker.go

@@ -294,7 +294,8 @@ func (d *ddl) limitDDLJobs() {
 func (d *ddl) addBatchDDLJobs(tasks []*limitJobTask) {
 	startTime := time.Now()
 	var err error
-	if variable.EnableConcurrentDDL.Load() {
+	// DDLForce2Queue is a flag to tell DDL worker to always push the job to the DDL queue.
+	if variable.EnableConcurrentDDL.Load() && !variable.DDLForce2Queue.Load() {
 		err = d.addBatchDDLJobs2Table(tasks)
 	} else {
 		err = d.addBatchDDLJobs2Queue(tasks)

session/bootstrap.go

@@ -789,16 +789,17 @@ func upgrade(s Session) {
 	}
 	// Only upgrade from under version92 and this TiDB is not owner set.
 	// The owner in older tidb does not support concurrent DDL, we should add the internal DDL to job queue.
-	original := variable.EnableConcurrentDDL.Load()
 	if ver < version92 && !domain.GetDomain(s).DDL().OwnerManager().IsOwner() {
-		variable.EnableConcurrentDDL.Store(false)
+		// use another variable DDLForce2Queue but not EnableConcurrentDDL since in upgrade it may set global variable, the initial step will
+		// overwrite variable EnableConcurrentDDL.
+		variable.DDLForce2Queue.Store(true)
 	}
 	// Do upgrade works then update bootstrap version.
 	for _, upgrade := range bootstrapVersion {
 		upgrade(s, ver)
 	}
 
-	variable.EnableConcurrentDDL.Store(original)
+	variable.DDLForce2Queue.Store(false)
 	updateBootstrapVer(s)
 	ctx := kv.WithInternalSourceType(context.Background(), kv.InternalTxnBootstrap)
 	_, err = s.ExecuteInternal(ctx, "COMMIT")

sessionctx/variable/tidb_vars.go

@@ -1043,6 +1043,7 @@ var (
 	PreparedPlanCacheSize             = atomic.NewUint64(DefTiDBPrepPlanCacheSize)
 	PreparedPlanCacheMemoryGuardRatio = atomic.NewFloat64(DefTiDBPrepPlanCacheMemoryGuardRatio)
 	EnableConcurrentDDL               = atomic.NewBool(DefTiDBEnableConcurrentDDL)
+	DDLForce2Queue                    = atomic.NewBool(false)
 	EnableNoopVariables               = atomic.NewBool(DefTiDBEnableNoopVariables)
 )