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ddl: Handle mlog name confliction for materialized view #68841

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12b0760
init
xzhangxian1008 May 8, 2026
cf5db17
tweaking
xzhangxian1008 May 9, 2026
546b54e
fix SchemaTracker.CreateMaterializedViewLog
xzhangxian1008 May 9, 2026
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save
xzhangxian1008 May 10, 2026
529cddf
add ut
xzhangxian1008 May 12, 2026
60ce263
refine
xzhangxian1008 Jun 1, 2026
2f422c1
merge
xzhangxian1008 Jun 1, 2026
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address comments
xzhangxian1008 Jun 3, 2026
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121 changes: 121 additions & 0 deletions pkg/ddl/ddl_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -18,9 +18,11 @@ import (
"context"
"encoding/json"
"fmt"
"math"
"strings"
"testing"
"time"
"unicode/utf8"

"github.com/pingcap/tidb/pkg/ddl/testargsv1"
"github.com/pingcap/tidb/pkg/domain/infosync"
Expand Down Expand Up @@ -174,6 +176,125 @@ func TestBuildCreateMaterializedViewLogPurgeInfoUpsertSQL(t *testing.T) {
require.Contains(t, sqlWithNull, ", NULL)")
}

func TestBuildMaterializedViewLogTableName(t *testing.T) {
oldMLogSeq := MLogTableNameSeq.Load()
oldShortSeq := MLogShortTableNameSeq.Load()
t.Cleanup(func() {
MLogTableNameSeq.Store(oldMLogSeq)
MLogShortTableNameSeq.Store(oldShortSeq)
})

const baseTableName = "base_table_name"
longPrefixedBaseTableName := materializedViewLogTablePrefix + strings.Repeat("t", mysql.MaxTableNameLength-len(materializedViewLogTablePrefix))
longBaseTableName := strings.Repeat("t", mysql.MaxTableNameLength-len(materializedViewLogTablePrefix)+1)

tests := []struct {
name string
baseTableName string
existingTables []string
expectedName string
expectedMLogSeq uint64
expectedShortSeq uint64
}{
{
name: "prefixed base name is renamed",
baseTableName: materializedViewLogTablePrefix + baseTableName,
expectedName: materializedViewLogTablePrefix + "1" + baseTableName,
expectedMLogSeq: 1,
},
{
name: "prefixed base name retries until renamed name does not conflict",
baseTableName: materializedViewLogTablePrefix + baseTableName,
existingTables: []string{
materializedViewLogTablePrefix + "1" + baseTableName,
materializedViewLogTablePrefix + "2" + baseTableName,
},
expectedName: materializedViewLogTablePrefix + "3" + baseTableName,
expectedMLogSeq: 3,
},
{
name: "prefixed base name falls back to short name when renamed name is too long",
baseTableName: longPrefixedBaseTableName,
expectedName: materializedViewLogTablePrefix + "1",
expectedMLogSeq: 1,
expectedShortSeq: 1,
},
{
name: "prefixed base name falls back to short name and retries conflict",
baseTableName: longPrefixedBaseTableName,
existingTables: []string{
materializedViewLogTablePrefix + "1",
materializedViewLogTablePrefix + "2",
},
expectedName: materializedViewLogTablePrefix + "3",
expectedMLogSeq: 1,
expectedShortSeq: 3,
},
{
name: "regular base name falls back to short name when mlog name is too long",
baseTableName: longBaseTableName,
expectedName: materializedViewLogTablePrefix + "1",
expectedShortSeq: 1,
},
{
name: "regular base name falls back to short name and retries conflict after mlog name is too long",
baseTableName: longBaseTableName,
existingTables: []string{
materializedViewLogTablePrefix + "1",
materializedViewLogTablePrefix + "2",
},
expectedName: materializedViewLogTablePrefix + "3",
expectedShortSeq: 3,
},
{
name: "regular base name falls back to short name when mlog name conflicts",
baseTableName: baseTableName,
existingTables: []string{
materializedViewLogTablePrefix + baseTableName,
},
expectedName: materializedViewLogTablePrefix + "1",
expectedShortSeq: 1,
},
{
name: "regular base name falls back to short name and retries conflict after mlog name conflicts",
baseTableName: baseTableName,
existingTables: []string{
materializedViewLogTablePrefix + baseTableName,
materializedViewLogTablePrefix + "1",
materializedViewLogTablePrefix + "2",
},
expectedName: materializedViewLogTablePrefix + "3",
expectedShortSeq: 3,
},
}

for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
MLogTableNameSeq.Store(0)
MLogShortTableNameSeq.Store(0)
exists := make(map[string]struct{}, len(tt.existingTables))
for _, tableName := range tt.existingTables {
exists[strings.ToLower(tableName)] = struct{}{}
}
tableExists := func(name pmodel.CIStr) (bool, error) {
_, ok := exists[name.L]
return ok, nil
}

name, err := GenerateMLogTableName(pmodel.NewCIStr(tt.baseTableName), tableExists)
require.NoError(t, err)
require.Equal(t, tt.expectedName, name)
require.LessOrEqual(t, utf8.RuneCountInString(strings.ToLower(name)), mysql.MaxTableNameLength)
require.Equal(t, tt.expectedMLogSeq, MLogTableNameSeq.Load())
require.Equal(t, tt.expectedShortSeq, MLogShortTableNameSeq.Load())
})
}

MLogTableNameSeq.Store(math.MaxUint64)
_, err := nextMLogTableNameNumber(&MLogTableNameSeq, "out of range")
require.ErrorContains(t, err, "out of range")
}

func TestBuildMViewRefreshOutOfPlaceCutoverInvolvingSchemaInfo(t *testing.T) {
const (
oldMViewID int64 = 101
Expand Down
54 changes: 39 additions & 15 deletions pkg/ddl/executor.go
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Original file line number Diff line number Diff line change
Expand Up @@ -109,8 +109,9 @@ type Executor interface {
DropSchema(ctx sessionctx.Context, stmt *ast.DropDatabaseStmt) error
CreateTable(ctx sessionctx.Context, stmt *ast.CreateTableStmt) error
CreateMaterializedView(ctx sessionctx.Context, stmt *ast.CreateMaterializedViewStmt) error
CreateMaterializedViewLog(ctx sessionctx.Context, stmt *ast.CreateMaterializedViewLogStmt) error
CreateMaterializedViewLog(ctx sessionctx.Context, stmt *ast.CreateMaterializedViewLogStmt, mlogTableName string) error
CreateView(ctx sessionctx.Context, stmt *ast.CreateViewStmt) error
GenerateMLogTableName(ctx sessionctx.Context, s *ast.CreateMaterializedViewLogStmt) (string, error)
DropTable(ctx sessionctx.Context, stmt *ast.DropTableStmt) (err error)
DropMaterializedView(ctx sessionctx.Context, stmt *ast.DropMaterializedViewStmt) error
DropMaterializedViewLog(ctx sessionctx.Context, stmt *ast.DropMaterializedViewLogStmt) error
Expand Down Expand Up @@ -1063,7 +1064,40 @@ func (e *executor) CreateTable(ctx sessionctx.Context, s *ast.CreateTableStmt) (
return e.CreateTableWithInfo(ctx, schema.Name, tbInfo, involvingRef, WithOnExist(onExist))
}

func (e *executor) CreateMaterializedViewLog(ctx sessionctx.Context, s *ast.CreateMaterializedViewLogStmt) error {
// GenerateMLogTableName implements the DDL interface.
func (e *executor) GenerateMLogTableName(ctx sessionctx.Context, s *ast.CreateMaterializedViewLogStmt) (string, error) {
is := e.infoCache.GetLatest()
schemaName := s.Table.Schema
if schemaName.O == "" {
if ctx.GetSessionVars().CurrentDB == "" {
return "", errors.Trace(plannererrors.ErrNoDB)
}
schemaName = pmodel.NewCIStr(ctx.GetSessionVars().CurrentDB)
}

baseTable, err := is.TableByName(e.ctx, schemaName, s.Table.Name)
if err != nil {
return "", err
}
if baseTable.Meta().IsView() || baseTable.Meta().IsSequence() || baseTable.Meta().TempTableType != model.TempTableNone {
return "", dbterror.ErrWrongObject.GenWithStackByArgs(schemaName, s.Table.Name, "BASE TABLE")
}
if baseInfo := baseTable.Meta().MaterializedViewBase; baseInfo != nil && baseInfo.MLogID != 0 {
return "", infoschema.ErrTableExists.GenWithStackByArgs(fmt.Sprintf("mlog of %s.%s has been created before", schemaName, baseTable.Meta().Name.O))
}

mlogName, err := GenerateMLogTableName(
baseTable.Meta().Name,
getExistenceOfMLogTableNameChecker(e.ctx, is, schemaName),
)
if err != nil {
return "", err
}

return mlogName, nil
}

func (e *executor) CreateMaterializedViewLog(ctx sessionctx.Context, s *ast.CreateMaterializedViewLogStmt, mlogTableName string) error {
is := e.infoCache.GetLatest()
schemaName := s.Table.Schema
if schemaName.O == "" {
Expand All @@ -1085,18 +1119,8 @@ func (e *executor) CreateMaterializedViewLog(ctx sessionctx.Context, s *ast.Crea
if baseTable.Meta().IsView() || baseTable.Meta().IsSequence() || baseTable.Meta().TempTableType != model.TempTableNone {
return dbterror.ErrWrongObject.GenWithStackByArgs(schemaName, s.Table.Name, "BASE TABLE")
}

mlogName := "$mlog$" + baseTable.Meta().Name.O
mlogNameCIStr := pmodel.NewCIStr(mlogName)
if err := checkTooLongTable(mlogNameCIStr); err != nil {
return err
}
_, err = is.TableByName(e.ctx, schemaName, mlogNameCIStr)
if err == nil {
return infoschema.ErrTableExists.GenWithStackByArgs(ast.Ident{Schema: schemaName, Name: mlogNameCIStr})
}
if !infoschema.ErrTableNotExists.Equal(err) {
return err
if baseInfo := baseTable.Meta().MaterializedViewBase; baseInfo != nil && baseInfo.MLogID != 0 {
return infoschema.ErrTableExists.GenWithStackByArgs(fmt.Sprintf("mlog of %s.%s has been created before", schemaName, baseTable.Meta().Name.O))
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}

colMap := make(map[string]*model.ColumnInfo, len(baseTable.Meta().Columns))
Expand Down Expand Up @@ -1147,7 +1171,7 @@ func (e *executor) CreateMaterializedViewLog(ctx sessionctx.Context, s *ast.Crea
}

createTableStmt := &ast.CreateTableStmt{
Table: &ast.TableName{Schema: schemaName, Name: mlogNameCIStr},
Table: &ast.TableName{Schema: schemaName, Name: pmodel.NewCIStr(mlogTableName)},
Cols: colDefs,
Options: s.Options,
}
Expand Down
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