ddl: add a switch for alter partition alter placement

ddl/ddl_api.go

@@ -2430,7 +2430,11 @@ func (d *ddl) AlterTable(ctx sessionctx.Context, ident ast.Ident, specs []*ast.A
 			isAlterTable := true
 			err = d.RenameTable(ctx, ident, newIdent, isAlterTable)
 		case ast.AlterTableAlterPartition:
-			err = d.AlterTablePartition(ctx, ident, spec)
+			if ctx.GetSessionVars().EnableAlterPlacement {
+				err = d.AlterTablePartition(ctx, ident, spec)
+			} else {
+				err = errors.New("alter table partition alter partition is switched off by tidb_enable_alter_placement")
+			}
 		case ast.AlterTablePartition:
 			// Prevent silent succeed if user executes ALTER TABLE x PARTITION BY ...
 			err = errors.New("alter table partition is unsupported")

ddl/placement_sql_test.go

@@ -29,7 +29,12 @@ func (s *testDBSuite1) TestAlterTableAlterPartition(c *C) {
 	tk := testkit.NewTestKit(c, s.store)
 	tk.MustExec("use test")
 	tk.MustExec("drop table if exists t1")
-	defer tk.MustExec("drop table if exists t1")
+
+	tk.Se.GetSessionVars().EnableAlterPlacement = true
+	defer func() {
+		tk.MustExec("drop table if exists t1")
+		tk.Se.GetSessionVars().EnableAlterPlacement = false
+	}()
 
 	tk.MustExec(`create table t1 (c int)
 PARTITION BY RANGE (c) (
@@ -290,7 +295,11 @@ add placement policy
 func (s *testDBSuite1) TestPlacementPolicyCache(c *C) {
 	tk := testkit.NewTestKit(c, s.store)
 	tk.MustExec("use test")
-	defer tk.MustExec("drop table if exists t1")
+	tk.Se.GetSessionVars().EnableAlterPlacement = true
+	defer func() {
+		tk.MustExec("drop table if exists t1")
+		tk.Se.GetSessionVars().EnableAlterPlacement = false
+	}()
 
 	initTable := func() []string {
 		bundles := make(map[string]*placement.Bundle)
@@ -333,7 +342,11 @@ func (s *testSerialDBSuite) TestTxnScopeConstraint(c *C) {
 	tk := testkit.NewTestKit(c, s.store)
 	tk.MustExec("use test")
 	tk.MustExec("drop table if exists t1")
-	defer tk.MustExec("drop table if exists t1")
+	tk.Se.GetSessionVars().EnableAlterPlacement = true
+	defer func() {
+		tk.MustExec("drop table if exists t1")
+		tk.Se.GetSessionVars().EnableAlterPlacement = false
+	}()
 
 	tk.MustExec(`create table t1 (c int)
 PARTITION BY RANGE (c) (
@@ -474,7 +487,11 @@ func (s *testDBSuite1) TestAbortTxnIfPlacementChanged(c *C) {
 	tk := testkit.NewTestKit(c, s.store)
 	tk.MustExec("use test")
 	tk.MustExec("drop table if exists tp1")
-	defer tk.MustExec("drop table if exists tp1")
+	tk.Se.GetSessionVars().EnableAlterPlacement = true
+	defer func() {
+		tk.MustExec("drop table if exists tp1")
+		tk.Se.GetSessionVars().EnableAlterPlacement = false
+	}()
 
 	tk.MustExec(`create table tp1 (c int)
 PARTITION BY RANGE (c) (
@@ -485,6 +502,11 @@ PARTITION BY RANGE (c) (
 	c.Assert(err, IsNil)
 	tk1 := testkit.NewTestKitWithSession(c, s.store, se1)
 	tk1.MustExec("use test")
+
+	tk1.Se.GetSessionVars().EnableAlterPlacement = true
+	defer func() {
+		tk1.Se.GetSessionVars().EnableAlterPlacement = false
+	}()
 	_, err = tk.Exec(`alter table tp1 alter partition p0
 add placement policy
 	constraints='["+   zone   =   sh  "]'
@@ -529,6 +551,11 @@ func (s *testDBSuite1) TestGlobalTxnState(c *C) {
 	tk := testkit.NewTestKit(c, s.store)
 	tk.MustExec("use test")
 
+	tk.Se.GetSessionVars().EnableAlterPlacement = true
+	defer func() {
+		tk.Se.GetSessionVars().EnableAlterPlacement = false
+	}()
+
 	tk.MustExec(`create table t1 (c int)
 PARTITION BY RANGE (c) (
 	PARTITION p0 VALUES LESS THAN (6),

session/session.go

@@ -2286,6 +2286,7 @@ var builtinGlobalVariable = []string{
 	variable.TiDBEnableChangeColumnType,
 	variable.TiDBEnableChangeMultiSchema,
 	variable.TiDBEnablePointGetCache,
+	variable.TiDBEnableAlterPlacement,
 	variable.TiDBEnableAmendPessimisticTxn,
 	variable.TiDBMemQuotaApplyCache,
 	variable.TiDBEnableParallelApply,

sessionctx/variable/session.go

@@ -578,6 +578,9 @@ type SessionVars struct {
 	// EnablePointGetCache is used to cache value for point get for read only scenario.
 	EnablePointGetCache bool
 
+	// EnableAlterPlacement indicates whether a user can alter table partition placement rules.
+	EnableAlterPlacement bool
+
 	// WaitSplitRegionFinish defines the split region behaviour is sync or async.
 	WaitSplitRegionFinish bool
 
@@ -922,6 +925,7 @@ func NewSessionVars() *SessionVars {
 		EnableChangeColumnType:       DefTiDBChangeColumnType,
 		EnableChangeMultiSchema:      DefTiDBChangeMultiSchema,
 		EnablePointGetCache:          DefTiDBPointGetCache,
+		EnableAlterPlacement:         DefTiDBEnableAlterPlacement,
 		EnableAmendPessimisticTxn:    DefTiDBEnableAmendPessimisticTxn,
 		PartitionPruneMode:           *atomic2.NewString(DefTiDBPartitionPruneMode),
 		TxnScope:                     config.GetGlobalConfig().TxnScope,
@@ -1632,6 +1636,8 @@ func (s *SessionVars) SetSystemVar(name string, val string) error {
 		s.EnableChangeMultiSchema = TiDBOptOn(val)
 	case TiDBEnablePointGetCache:
 		s.EnablePointGetCache = TiDBOptOn(val)
+	case TiDBEnableAlterPlacement:
+		s.EnableAlterPlacement = TiDBOptOn(val)
 	case TiDBEnableAmendPessimisticTxn:
 		s.EnableAmendPessimisticTxn = TiDBOptOn(val)
 	case TiDBTxnScope:

sessionctx/variable/sysvar.go

@@ -1047,6 +1047,7 @@ var defaultSysVars = []*SysVar{
 	{Scope: ScopeGlobal, Name: TiDBEnableChangeColumnType, Value: BoolToOnOff(DefTiDBChangeColumnType), Type: TypeBool},
 	{Scope: ScopeGlobal, Name: TiDBEnableChangeMultiSchema, Value: BoolToOnOff(DefTiDBChangeMultiSchema), Type: TypeBool},
 	{Scope: ScopeGlobal, Name: TiDBEnablePointGetCache, Value: BoolToOnOff(DefTiDBPointGetCache), Type: TypeBool},
+	{Scope: ScopeGlobal, Name: TiDBEnableAlterPlacement, Value: BoolToOnOff(DefTiDBEnableAlterPlacement), Type: TypeBool},
 	{Scope: ScopeSession, Name: TiDBForcePriority, Value: mysql.Priority2Str[DefTiDBForcePriority]},
 	{Scope: ScopeSession, Name: TiDBEnableRadixJoin, Value: BoolToOnOff(DefTiDBUseRadixJoin), Type: TypeBool},
 	{Scope: ScopeGlobal | ScopeSession, Name: TiDBOptJoinReorderThreshold, Value: strconv.Itoa(DefTiDBOptJoinReorderThreshold), Type: TypeUnsigned, MinValue: 0, MaxValue: 63},

sessionctx/variable/tidb_vars.go

@@ -355,6 +355,9 @@ const (
 	// TiDBEnablePointGetCache is used to control whether to enable the point get cache for special scenario.
 	TiDBEnablePointGetCache = "tidb_enable_point_get_cache"
 
+	// TiDBEnableAlterPlacement is used to control whether to enable alter table partition.
+	TiDBEnableAlterPlacement = "tidb_enable_alter_placement"
+
 	// tidb_max_delta_schema_count defines the max length of deltaSchemaInfos.
 	// deltaSchemaInfos is a queue that maintains the history of schema changes.
 	TiDBMaxDeltaSchemaCount = "tidb_max_delta_schema_count"
@@ -572,6 +575,7 @@ const (
 	DefTiDBChangeColumnType             = false
 	DefTiDBChangeMultiSchema            = false
 	DefTiDBPointGetCache                = false
+	DefTiDBEnableAlterPlacement         = false
 	DefTiDBHashAggPartialConcurrency    = ConcurrencyUnset
 	DefTiDBHashAggFinalConcurrency      = ConcurrencyUnset
 	DefTiDBWindowConcurrency            = ConcurrencyUnset