From 8ed0d4759bb8d39d8d487856b5b8fb8350498e01 Mon Sep 17 00:00:00 2001
From: tangenta <tangenta@126.com>
Date: Mon, 18 Dec 2023 19:03:22 +0800
Subject: [PATCH] ddl: disable fast reorg and dist task execution for system
 tables (#49542)

close pingcap/tidb#49506
---
 pkg/ddl/ddl_api.go             | 18 ++++++++++++------
 pkg/ddl/multi_schema_change.go |  2 +-
 pkg/session/BUILD.bazel        |  2 ++
 pkg/session/bootstrap_test.go  | 10 ++++++++++
 4 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/pkg/ddl/ddl_api.go b/pkg/ddl/ddl_api.go
index cdb91ea8ec6e7..0d513fd2c9d6d 100644
--- a/pkg/ddl/ddl_api.go
+++ b/pkg/ddl/ddl_api.go
@@ -7092,7 +7092,7 @@ func (d *ddl) CreatePrimaryKey(ctx sessionctx.Context, ti ast.Ident, indexName m
 		Args:       []interface{}{unique, indexName, indexPartSpecifications, indexOption, sqlMode, nil, global},
 		Priority:   ctx.GetSessionVars().DDLReorgPriority,
 	}
-	reorgMeta, err := newReorgMetaFromVariables(d, job, ctx)
+	reorgMeta, err := newReorgMetaFromVariables(job, ctx)
 	if err != nil {
 		return err
 	}
@@ -7349,7 +7349,7 @@ func (d *ddl) createIndex(ctx sessionctx.Context, ti ast.Ident, keyType ast.Inde
 		Charset:    chs,
 		Collate:    coll,
 	}
-	reorgMeta, err := newReorgMetaFromVariables(d, job, ctx)
+	reorgMeta, err := newReorgMetaFromVariables(job, ctx)
 	if err != nil {
 		return err
 	}
@@ -7365,24 +7365,30 @@ func (d *ddl) createIndex(ctx sessionctx.Context, ti ast.Ident, keyType ast.Inde
 	return errors.Trace(err)
 }
 
-func newReorgMetaFromVariables(d *ddl, job *model.Job, sctx sessionctx.Context) (*model.DDLReorgMeta, error) {
+func newReorgMetaFromVariables(job *model.Job, sctx sessionctx.Context) (*model.DDLReorgMeta, error) {
 	reorgMeta := NewDDLReorgMeta(sctx)
 	reorgMeta.IsDistReorg = variable.EnableDistTask.Load()
 	reorgMeta.IsFastReorg = variable.EnableFastReorg.Load()
 	if reorgMeta.IsDistReorg && !reorgMeta.IsFastReorg {
 		return nil, dbterror.ErrUnsupportedDistTask
 	}
-	isUpgradingSysDB := d.stateSyncer.IsUpgradingState() && hasSysDB(job)
-	if isUpgradingSysDB {
+	if hasSysDB(job) {
 		if reorgMeta.IsDistReorg {
-			logutil.BgLogger().Info("cannot use distributed task execution because the job on system DB is in upgrade state",
+			logutil.BgLogger().Info("cannot use distributed task execution on system DB",
 				zap.String("category", "ddl"), zap.Stringer("job", job))
 		}
 		reorgMeta.IsDistReorg = false
+		reorgMeta.IsFastReorg = false
+		failpoint.Inject("reorgMetaRecordFastReorgDisabled", func(_ failpoint.Value) {
+			LastReorgMetaFastReorgDisabled = true
+		})
 	}
 	return reorgMeta, nil
 }
 
+// LastReorgMetaFastReorgDisabled is used for test.
+var LastReorgMetaFastReorgDisabled bool
+
 func buildFKInfo(fkName model.CIStr, keys []*ast.IndexPartSpecification, refer *ast.ReferenceDef, cols []*table.Column) (*model.FKInfo, error) {
 	if len(keys) != len(refer.IndexPartSpecifications) {
 		return nil, infoschema.ErrForeignKeyNotMatch.GenWithStackByArgs(fkName, "Key reference and table reference don't match")
diff --git a/pkg/ddl/multi_schema_change.go b/pkg/ddl/multi_schema_change.go
index 90cc38721e971..9c2e0162f73e3 100644
--- a/pkg/ddl/multi_schema_change.go
+++ b/pkg/ddl/multi_schema_change.go
@@ -47,7 +47,7 @@ func (d *ddl) MultiSchemaChange(ctx sessionctx.Context, ti ast.Ident) error {
 		ReorgMeta:       nil,
 	}
 	if containsDistTaskSubJob(subJobs) {
-		job.ReorgMeta, err = newReorgMetaFromVariables(d, job, ctx)
+		job.ReorgMeta, err = newReorgMetaFromVariables(job, ctx)
 		if err != nil {
 			return err
 		}
diff --git a/pkg/session/BUILD.bazel b/pkg/session/BUILD.bazel
index b4c484de4123f..c3a961b05d4ff 100644
--- a/pkg/session/BUILD.bazel
+++ b/pkg/session/BUILD.bazel
@@ -136,6 +136,7 @@ go_test(
         "//pkg/autoid_service",
         "//pkg/bindinfo",
         "//pkg/config",
+        "//pkg/ddl",
         "//pkg/domain",
         "//pkg/executor",
         "//pkg/expression",
@@ -157,6 +158,7 @@ go_test(
         "//pkg/util/chunk",
         "//pkg/util/logutil",
         "//pkg/util/sqlexec",
+        "@com_github_pingcap_failpoint//:failpoint",
         "@com_github_pingcap_log//:log",
         "@com_github_stretchr_testify//require",
         "@com_github_tikv_client_go_v2//tikv",
diff --git a/pkg/session/bootstrap_test.go b/pkg/session/bootstrap_test.go
index 3c5b82d7b4e25..2edafb93b0b76 100644
--- a/pkg/session/bootstrap_test.go
+++ b/pkg/session/bootstrap_test.go
@@ -21,7 +21,9 @@ import (
 	"testing"
 	"time"
 
+	"github.com/pingcap/failpoint"
 	"github.com/pingcap/tidb/pkg/bindinfo"
+	"github.com/pingcap/tidb/pkg/ddl"
 	"github.com/pingcap/tidb/pkg/domain"
 	"github.com/pingcap/tidb/pkg/meta"
 	"github.com/pingcap/tidb/pkg/parser/auth"
@@ -1585,10 +1587,18 @@ func TestTiDBUpgradeToVer136(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, int64(ver135), ver)
 
+	MustExec(t, seV135, "ALTER TABLE mysql.tidb_background_subtask DROP INDEX idx_task_key;")
+	require.NoError(t, failpoint.Enable("github.com/pingcap/tidb/pkg/ddl/reorgMetaRecordFastReorgDisabled", `return`))
+	t.Cleanup(func() {
+		require.NoError(t, failpoint.Disable("github.com/pingcap/tidb/pkg/ddl/reorgMetaRecordFastReorgDisabled"))
+	})
+	MustExec(t, seV135, "set global tidb_ddl_enable_fast_reorg = 1")
 	dom, err := BootstrapSession(store)
 	require.NoError(t, err)
 	ver, err = getBootstrapVersion(seV135)
 	require.NoError(t, err)
+	require.True(t, ddl.LastReorgMetaFastReorgDisabled)
+
 	require.Less(t, int64(ver135), ver)
 	dom.Close()
 }