database/tidb
2
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

mdl: always enable and make it read only in nextgen (#62865)

Browse Source 
ref pingcap/tidb#61702
This commit is contained in:
D3Hunter
2025-08-07 14:11:21 +08:00
committed by GitHub
parent 5f051c78d1
commit 2d07f5c716
21 changed files with 126 additions and 34 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
pkg/ddl/ddl.go
View File

@ -1137,7 +1137,7 @@ func (d *ddl) cleanDeadTableLock(unlockTables []model.TableLockTpInfo, se model.
// SwitchMDL enables MDL or disable MDL.
func (d *ddl) SwitchMDL(enable bool) error {
isEnableBefore := vardef.EnableMDL.Load()
isEnableBefore := vardef.IsMDLEnabled()
if isEnableBefore == enable {
return nil
}
@ -1161,7 +1161,7 @@ func (d *ddl) SwitchMDL(enable bool) error {
return errors.New("please wait for all jobs done")
}
vardef.EnableMDL.Store(enable)
vardef.SetEnableMDL(enable)
err = kv.RunInNewTxn(kv.WithInternalSourceType(context.Background(), kv.InternalTxnDDL), d.store, true, func(_ context.Context, txn kv.Transaction) error {
m := meta.NewMutator(txn)
oldEnable, _, err := m.GetMetadataLock()
@ -1185,7 +1185,7 @@ func (d *ddl) SwitchMDL(enable bool) error {
// It should be called before any DDL that could break data consistency.
// This provides a safe window for async commit and 1PC to commit with an old schema.
func delayForAsyncCommit() {
if vardef.EnableMDL.Load() {
if vardef.IsMDLEnabled() {
// If metadata lock is enabled. The transaction of DDL must begin after
// pre-write of the async commit transaction, then the commit ts of DDL
// must be greater than the async commit transaction. In this case, the

4
pkg/ddl/job_scheduler.go
View File

@ -566,7 +566,7 @@ func (s *jobScheduler) transitOneJobStepAndWaitSync(wk *worker, jobCtx *jobConte
// current owner.
job := jobW.Job
if jobCtx.isUnSynced(job.ID) || (job.Started() && !jobCtx.maybeAlreadyRunOnce(job.ID)) {
if vardef.EnableMDL.Load() {
if vardef.IsMDLEnabled() {
version, err := s.sysTblMgr.GetMDLVer(s.schCtx, job.ID)
if err == nil {
jobCtx.logger.Info("the job have schema version un-synced",
@ -624,7 +624,7 @@ func (s *jobScheduler) cleanMDLInfo(job *model.Job, ownerID string) {
defer func() {
metrics.DDLCleanMDLInfoHist.Observe(time.Since(start).Seconds())
}()
if !vardef.EnableMDL.Load() {
if !vardef.IsMDLEnabled() {
return
}
var sql string

4
pkg/ddl/job_worker.go
View File

@ -308,7 +308,7 @@ func (w *worker) updateDDLJob(jobCtx *jobContext, job *model.Job, updateRawArgs
// registerMDLInfo registers metadata lock info.
func (w *worker) registerMDLInfo(job *model.Job, ver int64) error {
if !vardef.EnableMDL.Load() {
if !vardef.IsMDLEnabled() {
return nil
}
if ver == 0 {
@ -1124,7 +1124,7 @@ func updateGlobalVersionAndWaitSynced(
err = jobCtx.schemaVerSyncer.OwnerUpdateGlobalVersion(ctx, latestSchemaVersion)
if err != nil {
logutil.DDLLogger().Info("update latest schema version failed", zap.Int64("ver", latestSchemaVersion), zap.Error(err))
if vardef.EnableMDL.Load() {
if vardef.IsMDLEnabled() {
return err
}
if terror.ErrorEqual(err, context.DeadlineExceeded) {

4
pkg/ddl/schemaver/mem_syncer.go
View File

@ -68,7 +68,7 @@ func (s *MemSyncer) UpdateSelfVersion(_ context.Context, jobID int64, version in
failpoint.Return(errors.New("mock update mdl to etcd error"))
}
})
if vardef.EnableMDL.Load() {
if vardef.IsMDLEnabled() {
s.mdlSchemaVersions.Store(jobID, version)
} else {
atomic.StoreInt64(&s.selfSchemaVersion, version)
@ -117,7 +117,7 @@ func (s *MemSyncer) WaitVersionSynced(ctx context.Context, jobID int64, latestVe
case <-ctx.Done():
return errors.Trace(ctx.Err())
case <-ticker.C:
if vardef.EnableMDL.Load() {
if vardef.IsMDLEnabled() {
ver, ok := s.mdlSchemaVersions.Load(jobID)
if ok && ver.(int64) >= latestVer {
return nil

8
pkg/ddl/schemaver/syncer.go
View File

@ -282,7 +282,7 @@ func (s *etcdSyncer) UpdateSelfVersion(ctx context.Context, jobID int64, version
ver := strconv.FormatInt(version, 10)
var err error
var path string
if vardef.EnableMDL.Load() {
if vardef.IsMDLEnabled() {
// If jobID is 0, it doesn't need to put into etcd `DDLAllSchemaVersionsByJob` key.
if jobID == 0 {
return nil
@ -325,7 +325,7 @@ func (s *etcdSyncer) removeSelfVersionPath() error {
// WaitVersionSynced implements Syncer.WaitVersionSynced interface.
func (s *etcdSyncer) WaitVersionSynced(ctx context.Context, jobID int64, latestVer int64, checkAssumedSvr bool) error {
startTime := time.Now()
if !vardef.EnableMDL.Load() {
if !vardef.IsMDLEnabled() {
time.Sleep(CheckVersFirstWaitTime)
}
notMatchVerCnt := 0
@ -348,7 +348,7 @@ func (s *etcdSyncer) WaitVersionSynced(ctx context.Context, jobID int64, latestV
return errors.Trace(err)
}
if vardef.EnableMDL.Load() {
if vardef.IsMDLEnabled() {
serverInfos, err := infosync.GetServersForISSync(ctx, checkAssumedSvr)
if err != nil {
return err
@ -375,7 +375,7 @@ func (s *etcdSyncer) WaitVersionSynced(ctx context.Context, jobID int64, latestV
}
// Check all schema versions.
if vardef.EnableMDL.Load() {
if vardef.IsMDLEnabled() {
notifyCh := make(chan struct{})
var unmatchedNodeInfo atomic.Pointer[string]
matchFn := func(nodeVersions map[string]int64) bool {

2
pkg/ddl/schemaver/syncer_nokit_test.go
View File

@ -174,7 +174,7 @@ func TestSyncJobSchemaVerLoop(t *testing.T) {
require.NoError(t, err)
// job 4 is matched using WaitVersionSynced
vardef.EnableMDL.Store(true)
vardef.SetEnableMDL(true)
serverInfos := map[string]*serverinfo.ServerInfo{"aa": {StaticInfo: serverinfo.StaticInfo{ID: "aa", IP: "test", Port: 4000}}}
bytes, err := json.Marshal(serverInfos)
require.NoError(t, err)

2
pkg/ddl/schemaver/syncer_test.go
View File

@ -39,7 +39,7 @@ import (
const minInterval = 10 * time.Nanosecond // It's used to test timeout.
func TestSyncerSimple(t *testing.T) {
vardef.EnableMDL.Store(false)
vardef.SetEnableMDL(false)
if runtime.GOOS == "windows" {
t.Skip("integration.NewClusterV3 will create file contains a colon which is not allowed on Windows")
}

2
pkg/ddl/serverstate/syncer_test.go
View File

@ -43,7 +43,7 @@ func checkRespKV(t *testing.T, kvCount int, key, val string, kvs ...*mvccpb.KeyV
}
func TestStateSyncerSimple(t *testing.T) {
vardef.EnableMDL.Store(false)
vardef.SetEnableMDL(false)
if runtime.GOOS == "windows" {
t.Skip("integration.NewClusterV3 will create file contains a colon which is not allowed on Windows")
}

3
pkg/ddl/tests/metadatalock/BUILD.bazel
View File

@ -8,9 +8,10 @@ go_test(
"mdl_test.go",
],
flaky = True,
shard_count = 37,
shard_count = 38,
deps = [
"//pkg/config",
"//pkg/config/kerneltype",
"//pkg/ddl",
"//pkg/ddl/ingest/testutil",
"//pkg/errno",

17
pkg/ddl/tests/metadatalock/mdl_test.go
View File

@ -22,6 +22,7 @@ import (
"time"
"github.com/pingcap/failpoint"
"github.com/pingcap/tidb/pkg/config/kerneltype"
"github.com/pingcap/tidb/pkg/ddl"
ingesttestutil "github.com/pingcap/tidb/pkg/ddl/ingest/testutil"
mysql "github.com/pingcap/tidb/pkg/errno"
@ -1159,6 +1160,9 @@ func TestMDLEnable2Disable(t *testing.T) {
}
func TestSwitchMDL(t *testing.T) {
if kerneltype.IsNextGen() {
t.Skip("MDL is always enabled and read only in nextgen")
}
store, dom := testkit.CreateMockStoreAndDomain(t)
sv := server.CreateMockServer(t, store)
@ -1179,6 +1183,19 @@ func TestSwitchMDL(t *testing.T) {
tk.MustQuery("show global variables like 'tidb_enable_metadata_lock'").Check(testkit.Rows("tidb_enable_metadata_lock OFF"))
}
func TestSetMDLInNextGen(t *testing.T) {
if kerneltype.IsClassic() {
t.Skip("only run in nextgen")
}
store, _ := testkit.CreateMockStoreAndDomain(t)
tk := testkit.NewTestKit(t, store)
require.ErrorContains(t, tk.ExecToErr("set global tidb_enable_metadata_lock=0"),
"setting tidb_enable_metadata_lock is not supported in the next generation of TiDB")
require.ErrorContains(t, tk.ExecToErr("set global tidb_enable_metadata_lock=1"),
"setting tidb_enable_metadata_lock is not supported in the next generation of TiDB")
}
func TestMDLViewItself(t *testing.T) {
store, dom := testkit.CreateMockStoreAndDomain(t)
sv := server.CreateMockServer(t, store)

2
pkg/infoschema/issyncer/syncer.go
View File

@ -226,7 +226,7 @@ func (s *Syncer) MDLCheckLoop(ctx context.Context) {
return
}
if !vardef.EnableMDL.Load() {
if !vardef.IsMDLEnabled() {
continue
}

2
pkg/infoschema/isvalidator/validator.go
View File

@ -233,7 +233,7 @@ func (v *validator) Check(txnTS uint64, schemaVer int64, relatedPhysicalTableIDs
// is true, we need to check by schema delta.
// When switch MDL from on to off, the needCheckSchemaByDelta is false,
// and EnableMDL is also false, so we still need to check by schema delta.
if needCheckSchemaByDelta || !vardef.EnableMDL.Load() {
if needCheckSchemaByDelta || !vardef.IsMDLEnabled() {
changed := v.isRelatedTablesChanged(schemaVer, relatedPhysicalTableIDs)
if changed {
return nil, validatorapi.ResultFail

4
pkg/planner/core/logical_plans_test.go
View File

@ -507,7 +507,7 @@ func TestDupRandJoinCondsPushDown(t *testing.T) {
}
func TestTablePartition(t *testing.T) {
vardef.EnableMDL.Store(false)
vardef.SetEnableMDL(false)
definitions := []model.PartitionDefinition{
{
ID: 41,
@ -1127,7 +1127,7 @@ func TestAggPrune(t *testing.T) {
}
func TestVisitInfo(t *testing.T) {
vardef.EnableMDL.Store(false)
vardef.SetEnableMDL(false)
tests := []struct {
sql string
ans []visitInfo

4
pkg/planner/memo/group_test.go
View File

@ -98,7 +98,7 @@ func TestGroupExists(t *testing.T) {
}
func TestGroupFingerPrint(t *testing.T) {
vardef.EnableMDL.Store(false)
vardef.SetEnableMDL(false)
p := parser.New()
stmt1, err := p.ParseOneStmt("select * from t where a > 1 and a < 100", "", "")
require.NoError(t, err)
@ -230,7 +230,7 @@ func TestFirstElemAfterDelete(t *testing.T) {
}
func TestBuildKeyInfo(t *testing.T) {
vardef.EnableMDL.Store(false)
vardef.SetEnableMDL(false)
p := parser.New()
ctx := plannercore.MockContext()
defer func() {

8
pkg/session/session.go
View File

@ -3417,7 +3417,7 @@ func InitMDLVariableForBootstrap(store kv.Storage) error {
if err != nil {
return err
}
vardef.EnableMDL.Store(true)
vardef.SetEnableMDL(true)
return nil
}
@ -3461,9 +3461,9 @@ func InitMDLVariableForUpgrade(store kv.Storage) (bool, error) {
return nil
})
if isNull || !enable {
vardef.EnableMDL.Store(false)
vardef.SetEnableMDL(false)
} else {
vardef.EnableMDL.Store(true)
vardef.SetEnableMDL(true)
}
return isNull, err
}
@ -3490,7 +3490,7 @@ func InitMDLVariable(store kv.Storage) error {
}
return nil
})
vardef.EnableMDL.Store(enable)
vardef.SetEnableMDL(enable)
return err
}

15
pkg/sessionctx/vardef/BUILD.bazel
View File

@ -1,4 +1,4 @@
load("@io_bazel_rules_go//go:def.bzl", "go_library")
load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
go_library(
name = "vardef",
@ -11,6 +11,7 @@ go_library(
visibility = ["//visibility:public"],
deps = [
"//pkg/config",
"//pkg/config/kerneltype",
"//pkg/executor/join/joinversion",
"//pkg/parser/mysql",
"//pkg/util/memory",
@ -20,3 +21,15 @@ go_library(
"@org_uber_go_atomic//:atomic",
],
)
go_test(
name = "vardef_test",
timeout = "short",
srcs = ["tidb_vars_test.go"],
embed = [":vardef"],
flaky = True,
deps = [
"//pkg/config/kerneltype",
"@com_github_stretchr_testify//require",
],
)

22
pkg/sessionctx/vardef/tidb_vars.go
View File

@ -23,6 +23,7 @@ import (
"time"
"github.com/pingcap/tidb/pkg/config"
"github.com/pingcap/tidb/pkg/config/kerneltype"
"github.com/pingcap/tidb/pkg/executor/join/joinversion"
"github.com/pingcap/tidb/pkg/parser/mysql"
"github.com/pingcap/tidb/pkg/util/memory"
@ -1732,7 +1733,7 @@ var (
EnableDistTask = atomic.NewBool(DefTiDBEnableDistTask)
EnableFastCreateTable = atomic.NewBool(DefTiDBEnableFastCreateTable)
EnableNoopVariables = atomic.NewBool(DefTiDBEnableNoopVariables)
EnableMDL = atomic.NewBool(false)
enableMDL = atomic.NewBool(false)
AutoAnalyzePartitionBatchSize = atomic.NewInt64(DefTiDBAutoAnalyzePartitionBatchSize)
AutoAnalyzeConcurrency = atomic.NewInt32(DefTiDBAutoAnalyzeConcurrency)
// TODO: set value by session variable
@ -2133,3 +2134,22 @@ func SetMaxDeltaSchemaCount(cnt int64) {
func GetMaxDeltaSchemaCount() int64 {
return goatomic.LoadInt64(&MaxDeltaSchemaCount)
}
// IsMDLEnabled returns if MDL is enabled.
func IsMDLEnabled() bool {
if kerneltype.IsNextGen() {
// MDL is very useful to avoid the 'Information schema is changed' error,
// in next-gen TiDB, MDL is always enabled, as we don't have the compatibility
// debts.
// some tests might call SetEnableMDL(false) to disable MDL, but it is not
// expected in nextgen, we use this branch to ensure MDL is always enabled,
// even in test.
return true
}
return enableMDL.Load()
}
// SetEnableMDL sets the MDL enable status.
func SetEnableMDL(enabled bool) {
enableMDL.Store(enabled)
}

38
pkg/sessionctx/vardef/tidb_vars_test.go Normal file
View File

@ -0,0 +1,38 @@
// Copyright 2025 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package vardef
import (
"testing"
"github.com/pingcap/tidb/pkg/config/kerneltype"
"github.com/stretchr/testify/require"
)
func TestIsMDLEnabledInNextGen(t *testing.T) {
if kerneltype.IsClassic() {
t.Skip("only run in next-gen")
}
bak := enableMDL.Load()
t.Cleanup(func() {
SetEnableMDL(bak)
})
// IsMDLEnabled must return true regardless of the value of enableMDL.
SetEnableMDL(false)
require.True(t, IsMDLEnabled())
SetEnableMDL(true)
require.True(t, IsMDLEnabled())
}

7
pkg/sessionctx/variable/sysvar.go
View File

@ -1492,7 +1492,10 @@ var defaultSysVars = []*SysVar{
},
},
{Scope: vardef.ScopeGlobal, Name: vardef.TiDBEnableMDL, Value: BoolToOnOff(vardef.DefTiDBEnableMDL), Type: vardef.TypeBool, SetGlobal: func(_ context.Context, vars *SessionVars, val string) error {
if vardef.EnableMDL.Load() != TiDBOptOn(val) {
if kerneltype.IsNextGen() {
return errNotSupportedInNextGen.FastGenByArgs(fmt.Sprintf("setting %s", vardef.TiDBEnableMDL))
}
if vardef.IsMDLEnabled() != TiDBOptOn(val) {
err := SwitchMDL(TiDBOptOn(val))
if err != nil {
return err
@ -1500,7 +1503,7 @@ var defaultSysVars = []*SysVar{
}
return nil
}, GetGlobal: func(_ context.Context, vars *SessionVars) (string, error) {
return BoolToOnOff(vardef.EnableMDL.Load()), nil
return BoolToOnOff(vardef.IsMDLEnabled()), nil
}},
{Scope: vardef.ScopeGlobal, Name: vardef.TiDBEnableDistTask, Value: BoolToOnOff(vardef.DefTiDBEnableDistTask), Type: vardef.TypeBool, SetGlobal: func(_ context.Context, s *SessionVars, val string) error {
if vardef.EnableDistTask.Load() != TiDBOptOn(val) {

2
pkg/sessiontxn/isolation/base.go
View File

@ -133,7 +133,7 @@ func (p *baseTxnContextProvider) OnInitialize(ctx context.Context, tp sessiontxn
sessVars.TxnCtxMu.Lock()
sessVars.TxnCtx = txnCtx
sessVars.TxnCtxMu.Unlock()
if vardef.EnableMDL.Load() {
if vardef.IsMDLEnabled() {
sessVars.TxnCtx.EnableMDL = true
}

4
pkg/table/tables/bench_test.go
View File

@ -48,7 +48,7 @@ func BenchmarkAddRecordInPipelinedDML(b *testing.B) {
tb, err := dom.InfoSchema().TableByName(context.Background(), ast.NewCIStr("test"), ast.NewCIStr("t"))
require.NoError(b, err)
vardef.EnableMDL.Store(true)
vardef.SetEnableMDL(true)
// Pre-create data to be inserted
records := make([][]types.Datum, batchSize)
@ -102,7 +102,7 @@ func BenchmarkRemoveRecordInPipelinedDML(b *testing.B) {
tb, err := dom.InfoSchema().TableByName(context.Background(), ast.NewCIStr("test"), ast.NewCIStr("t"))
require.NoError(b, err)
vardef.EnableMDL.Store(true)
vardef.SetEnableMDL(true)
// Pre-create and add initial records
records := make([][]types.Datum, batchSize)