ddl, variable: add system variable to control Clustered Index feature

ddl/ddl_api.go

@@ -1269,19 +1269,23 @@ func buildTableInfo(
 			if err != nil {
 				return nil, err
 			}
-			if len(constr.Keys) == 1 && !config.GetGlobalConfig().AlterPrimaryKey {
-				switch lastCol.Tp {
-				case mysql.TypeLong, mysql.TypeLonglong,
-					mysql.TypeTiny, mysql.TypeShort, mysql.TypeInt24:
+			if !config.GetGlobalConfig().AlterPrimaryKey {
+				singleIntPK := isSingleIntPK(constr, lastCol)
+				clusteredIdx := ctx.GetSessionVars().EnableClusteredIndex
+				if singleIntPK || clusteredIdx {
 					// Primary key cannot be invisible.
 					if constr.Option != nil && constr.Option.Visibility == ast.IndexVisibilityInvisible {
 						return nil, ErrPKIndexCantBeInvisible
 					}
-
+				}
+				if singleIntPK {
 					tbInfo.PKIsHandle = true
 					// Avoid creating index for PK handle column.
 					continue
 				}
+				if clusteredIdx {
+					tbInfo.IsCommonHandle = true
+				}
 			}
 		}
 
@@ -1329,6 +1333,18 @@ func buildTableInfo(
 	return
 }
 
+func isSingleIntPK(constr *ast.Constraint, lastCol *model.ColumnInfo) bool {
+	if len(constr.Keys) != 1 {
+		return false
+	}
+	switch lastCol.Tp {
+	case mysql.TypeLong, mysql.TypeLonglong,
+		mysql.TypeTiny, mysql.TypeShort, mysql.TypeInt24:
+		return true
+	}
+	return false
+}
+
 // checkTableInfoValidExtra is like checkTableInfoValid, but also assumes the
 // table info comes from untrusted source and performs further checks such as
 // name length and column count.
@@ -1505,7 +1521,6 @@ func buildTableInfoWithStmt(ctx sessionctx.Context, s *ast.CreateTableStmt, dbCh
 	if err = handleTableOptions(s.Options, tbInfo); err != nil {
 		return nil, errors.Trace(err)
 	}
-
 	return tbInfo, nil
 }
 

ddl/serial_test.go

@@ -1112,3 +1112,56 @@ func (s *testSerialSuite) TestInvisibleIndex(c *C) {
 	tk.MustQuery("select * from t6").Check(testkit.Rows("1 2"))
 	tk.MustGetErrCode("alter table t6 drop primary key", errno.ErrPKIndexCantBeInvisible)
 }
+
+func (s *testSerialSuite) TestCreateClusteredIndex(c *C) {
+	tk := testkit.NewTestKitWithInit(c, s.store)
+	tk.Se.GetSessionVars().EnableClusteredIndex = true
+	tk.MustExec("CREATE TABLE t1 (a int primary key, b int)")
+	tk.MustExec("CREATE TABLE t2 (a varchar(255) primary key, b int)")
+	tk.MustExec("CREATE TABLE t3 (a int, b int, c int, primary key (a, b))")
+	tk.MustExec("CREATE TABLE t4 (a int, b int, c int)")
+	ctx := tk.Se.(sessionctx.Context)
+	is := domain.GetDomain(ctx).InfoSchema()
+	tbl, err := is.TableByName(model.NewCIStr("test"), model.NewCIStr("t1"))
+	c.Assert(err, IsNil)
+	c.Assert(tbl.Meta().PKIsHandle, IsTrue)
+	c.Assert(tbl.Meta().IsCommonHandle, IsFalse)
+	tbl, err = is.TableByName(model.NewCIStr("test"), model.NewCIStr("t2"))
+	c.Assert(err, IsNil)
+	c.Assert(tbl.Meta().IsCommonHandle, IsTrue)
+	tbl, err = is.TableByName(model.NewCIStr("test"), model.NewCIStr("t3"))
+	c.Assert(err, IsNil)
+	c.Assert(tbl.Meta().IsCommonHandle, IsTrue)
+	tbl, err = is.TableByName(model.NewCIStr("test"), model.NewCIStr("t4"))
+	c.Assert(err, IsNil)
+	c.Assert(tbl.Meta().IsCommonHandle, IsFalse)
+
+	config.GetGlobalConfig().AlterPrimaryKey = true
+	tk.MustExec("CREATE TABLE t5 (a varchar(255) primary key, b int)")
+	tk.MustExec("CREATE TABLE t6 (a int, b int, c int, primary key (a, b))")
+	is = domain.GetDomain(ctx).InfoSchema()
+	tbl, err = is.TableByName(model.NewCIStr("test"), model.NewCIStr("t5"))
+	c.Assert(err, IsNil)
+	c.Assert(tbl.Meta().IsCommonHandle, IsFalse)
+	tbl, err = is.TableByName(model.NewCIStr("test"), model.NewCIStr("t6"))
+	c.Assert(err, IsNil)
+	c.Assert(tbl.Meta().IsCommonHandle, IsFalse)
+	config.GetGlobalConfig().AlterPrimaryKey = false
+
+	tk.MustExec("CREATE TABLE t21 like t2")
+	tk.MustExec("CREATE TABLE t31 like t3")
+	is = domain.GetDomain(ctx).InfoSchema()
+	tbl, err = is.TableByName(model.NewCIStr("test"), model.NewCIStr("t21"))
+	c.Assert(err, IsNil)
+	c.Assert(tbl.Meta().IsCommonHandle, IsTrue)
+	tbl, err = is.TableByName(model.NewCIStr("test"), model.NewCIStr("t31"))
+	c.Assert(err, IsNil)
+	c.Assert(tbl.Meta().IsCommonHandle, IsTrue)
+
+	tk.Se.GetSessionVars().EnableClusteredIndex = false
+	tk.MustExec("CREATE TABLE t7 (a varchar(255) primary key, b int)")
+	is = domain.GetDomain(ctx).InfoSchema()
+	tbl, err = is.TableByName(model.NewCIStr("test"), model.NewCIStr("t7"))
+	c.Assert(err, IsNil)
+	c.Assert(tbl.Meta().IsCommonHandle, IsFalse)
+}

session/session.go

@@ -2054,6 +2054,7 @@ var builtinGlobalVariable = []string{
 	variable.TiDBIsolationReadEngines,
 	variable.TiDBStoreLimit,
 	variable.TiDBAllowAutoRandExplicitInsert,
+	variable.TiDBEnableClusteredIndex,
 }
 
 var (

sessionctx/variable/session.go

@@ -606,6 +606,9 @@ type SessionVars struct {
 
 	// OptimizerUseInvisibleIndexes indicates whether optimizer can use invisible index
 	OptimizerUseInvisibleIndexes bool
+
+	// EnableClusteredIndex indicates whether to enable clustered index when creating a new table.
+	EnableClusteredIndex bool
 }
 
 // PreparedParams contains the parameters of the current prepared statement when executing it.
@@ -694,6 +697,7 @@ func NewSessionVars() *SessionVars {
 		PrevFoundInPlanCache:        DefTiDBFoundInPlanCache,
 		FoundInPlanCache:            DefTiDBFoundInPlanCache,
 		AllowAutoRandExplicitInsert: DefTiDBAllowAutoRandExplicitInsert,
+		EnableClusteredIndex:        DefTiDBEnableClusteredIndex,
 	}
 	vars.KVVars = kv.NewVariables(&vars.Killed)
 	vars.Concurrency = Concurrency{
@@ -1296,6 +1300,8 @@ func (s *SessionVars) SetSystemVar(name string, val string) error {
 		config.GetGlobalConfig().EnableCollectExecutionInfo = TiDBOptOn(val)
 	case TiDBAllowAutoRandExplicitInsert:
 		s.AllowAutoRandExplicitInsert = TiDBOptOn(val)
+	case TiDBEnableClusteredIndex:
+		s.EnableClusteredIndex = TiDBOptOn(val)
 	}
 	s.systems[name] = val
 	return nil

sessionctx/variable/sysvar.go

@@ -722,6 +722,7 @@ var defaultSysVars = []*SysVar{
 	{ScopeSession, TiDBFoundInPlanCache, BoolToIntStr(DefTiDBFoundInPlanCache)},
 	{ScopeSession, TiDBEnableCollectExecutionInfo, BoolToIntStr(logutil.DefaultTiDBEnableSlowLog)},
 	{ScopeSession, TiDBAllowAutoRandExplicitInsert, boolToOnOff(DefTiDBAllowAutoRandExplicitInsert)},
+	{ScopeGlobal | ScopeSession, TiDBEnableClusteredIndex, BoolToIntStr(DefTiDBEnableClusteredIndex)},
 }
 
 // SynonymsSysVariables is synonyms of system variables.

sessionctx/variable/tidb_vars.go

@@ -396,6 +396,9 @@ const (
 
 	// TiDBEnableCollectExecutionInfo indicates that whether execution info is collected.
 	TiDBEnableCollectExecutionInfo = "tidb_enable_collect_execution_info"
+
+	// TiDBEnableClusteredIndex indicates if clustered index feature is enabled.
+	TiDBEnableClusteredIndex = "tidb_enable_clustered_index"
 )
 
 // Default TiDB system variable values.
@@ -491,6 +494,7 @@ const (
 	DefTiDBFoundInPlanCache            = false
 	DefTidbEnableCollectExecutionInfo  = false
 	DefTiDBAllowAutoRandExplicitInsert = false
+	DefTiDBEnableClusteredIndex        = false
 )
 
 // Process global variables.

sessionctx/variable/varsutil.go

@@ -441,7 +441,7 @@ func ValidateSetSystemVar(vars *SessionVars, name string, value string, scope Sc
 		TiDBCheckMb4ValueInUTF8, TiDBEnableSlowLog, TiDBRecordPlanInSlowLog,
 		TiDBScatterRegion, TiDBGeneralLog, TiDBConstraintCheckInPlace,
 		TiDBEnableVectorizedExpression, TiDBFoundInPlanCache, TiDBEnableCollectExecutionInfo,
-		TiDBAllowAutoRandExplicitInsert:
+		TiDBAllowAutoRandExplicitInsert, TiDBEnableClusteredIndex:
 		fallthrough
 	case GeneralLog, AvoidTemporalUpgrade, BigTables, CheckProxyUsers, LogBin,
 		CoreFile, EndMakersInJSON, SQLLogBin, OfflineMode, PseudoSlaveMode, LowPriorityUpdates,