*: only create TemporaryTableAttachedInfoSchema if needed

ddl/db_integration_test.go

@@ -3801,8 +3801,15 @@ func TestCreateTempTableInTxn(t *testing.T) {
 	tk := testkit.NewTestKit(t, store)
 	tk.MustExec("use test")
 	tk.MustExec("begin")
-	tk.MustExec("create temporary table t1(id int)")
-	tk.MustQuery("select * from t1")
+	// new created temporary table should be visible
+	tk.MustExec("create temporary table t1(id int primary key, v int)")
+	tk.MustQuery("select * from t1").Check(testkit.Rows())
+	// new inserted data should be visible
+	tk.MustExec("insert into t1 values(123, 456)")
+	tk.MustQuery("select * from t1 where id=123").Check(testkit.Rows("123 456"))
+	// truncate table will clear data but table still visible
+	tk.MustExec("truncate table t1")
+	tk.MustQuery("select * from t1 where id=123").Check(testkit.Rows())
 	tk.MustExec("commit")
 
 	tk1 := testkit.NewTestKit(t, store)
@@ -3812,6 +3819,16 @@ func TestCreateTempTableInTxn(t *testing.T) {
 	tk1.MustExec("create temporary table t1(id int)")
 	tk1.MustExec("insert into tt select * from t1")
 	tk1.MustExec("drop table tt")
+
+	tk2 := testkit.NewTestKit(t, store)
+	tk2.MustExec("use test")
+	tk2.MustExec("create table t2(id int primary key, v int)")
+	tk2.MustExec("insert into t2 values(234, 567)")
+	tk2.MustExec("begin")
+	// create a new temporary table with the same name will override physical table
+	tk2.MustExec("create temporary table t2(id int primary key, v int)")
+	tk2.MustQuery("select * from t2 where id=234").Check(testkit.Rows())
+	tk2.MustExec("commit")
 }
 
 // See https://github.com/pingcap/tidb/issues/29327

domain/domain.go

@@ -70,6 +70,15 @@ import (
 	"google.golang.org/grpc/keepalive"
 )
 
+// NewMockDomain is only used for test
+func NewMockDomain() *Domain {
+	do := &Domain{
+		infoCache: infoschema.NewCache(1),
+	}
+	do.infoCache.Insert(infoschema.MockInfoSchema(nil), 1)
+	return do
+}
+
 // Domain represents a storage space. Different domains can use the same database name.
 // Multiple domains can be used in parallel without synchronization.
 type Domain struct {
@@ -332,11 +341,6 @@ func canSkipSchemaCheckerDDL(tp model.ActionType) bool {
 
 // InfoSchema gets the latest information schema from domain.
 func (do *Domain) InfoSchema() infoschema.InfoSchema {
-	if do.infoCache == nil {
-		// Return nil is for test purpose where domain is not well initialized in session context.
-		// In real implementation, the code will not reach here.
-		return nil
-	}
 	return do.infoCache.GetLatest()
 }
 

executor/ddl.go

@@ -269,7 +269,12 @@ func (e *DDLExec) createSessionTemporaryTable(s *ast.CreateTableStmt) error {
 		return err
 	}
 
-	return e.tempTableDDL.CreateLocalTemporaryTable(dbInfo, tbInfo)
+	if err = e.tempTableDDL.CreateLocalTemporaryTable(dbInfo, tbInfo); err != nil {
+		return err
+	}
+
+	sessiontxn.GetTxnManager(e.ctx).OnLocalTemporaryTableCreated()
+	return nil
 }
 
 func (e *DDLExec) executeCreateView(s *ast.CreateViewStmt) error {

planner/core/mock.go

@@ -402,7 +402,7 @@ func MockContext() sessionctx.Context {
 		Client: &mock.Client{},
 	}
 	ctx.GetSessionVars().CurrentDB = "test"
-	do := &domain.Domain{}
+	do := domain.NewMockDomain()
 	if err := do.CreateStatsHandle(ctx); err != nil {
 		panic(fmt.Sprintf("create mock context panic: %+v", err))
 	}

session/schema_amender_test.go

@@ -258,7 +258,7 @@ func TestAmendCollectAndGenMutations(t *testing.T) {
 		sessionVars: variable.NewSessionVars(),
 	}
 	se.mu.values = make(map[fmt.Stringer]interface{})
-	domain.BindDomain(se, &domain.Domain{})
+	domain.BindDomain(se, domain.NewMockDomain())
 	startStates := []model.SchemaState{model.StateNone, model.StateDeleteOnly, model.StateWriteOnly, model.StateWriteReorganization}
 	for _, startState := range startStates {
 		endStatMap := ConstOpAddIndex[startState]

session/txnmanager.go

@@ -192,6 +192,14 @@ func (m *txnManager) OnStmtRetry(ctx context.Context) error {
 	return m.ctxProvider.OnStmtRetry(ctx)
 }
 
+// OnLocalTemporaryTableCreated is the hook that should be called when a temporary table created.
+// The provider will update its state then
+func (m *txnManager) OnLocalTemporaryTableCreated() {
+	if m.ctxProvider != nil {
+		m.ctxProvider.OnLocalTemporaryTableCreated()
+	}
+}
+
 func (m *txnManager) AdviseWarmup() error {
 	if m.ctxProvider != nil {
 		return m.ctxProvider.AdviseWarmup()

sessiontxn/interface.go

@@ -138,6 +138,8 @@ type TxnContextProvider interface {
 	OnStmtErrorForNextAction(point StmtErrorHandlePoint, err error) (StmtErrorAction, error)
 	// OnStmtRetry is the hook that should be called when a statement is retried internally.
 	OnStmtRetry(ctx context.Context) error
+	// OnLocalTemporaryTableCreated is the hook that should be called when a local temporary table created.
+	OnLocalTemporaryTableCreated()
 	// ActivateTxn activates the transaction.
 	ActivateTxn() (kv.Transaction, error)
 }
@@ -177,6 +179,8 @@ type TxnManager interface {
 	OnStmtErrorForNextAction(point StmtErrorHandlePoint, err error) (StmtErrorAction, error)
 	// OnStmtRetry is the hook that should be called when a statement retry
 	OnStmtRetry(ctx context.Context) error
+	// OnLocalTemporaryTableCreated is the hook that should be called when a local temporary table created.
+	OnLocalTemporaryTableCreated()
 	// ActivateTxn activates the transaction.
 	ActivateTxn() (kv.Transaction, error)
 	// GetCurrentStmt returns the current statement node

sessiontxn/isolation/base.go

@@ -198,6 +198,12 @@ func (p *baseTxnContextProvider) OnStmtRetry(ctx context.Context) error {
 	return nil
 }
 
+// OnLocalTemporaryTableCreated is the hook that should be called when a local temporary table created.
+func (p *baseTxnContextProvider) OnLocalTemporaryTableCreated() {
+	p.infoSchema = temptable.AttachLocalTemporaryTableInfoSchema(p.sctx, p.infoSchema)
+	p.sctx.GetSessionVars().TxnCtx.InfoSchema = p.infoSchema
+}
+
 // OnStmtErrorForNextAction is the hook that should be called when a new statement get an error
 func (p *baseTxnContextProvider) OnStmtErrorForNextAction(point sessiontxn.StmtErrorHandlePoint, err error) (sessiontxn.StmtErrorAction, error) {
 	switch point {

sessiontxn/staleread/provider.go

@@ -228,3 +228,6 @@ func (p *StalenessTxnContextProvider) GetSnapshotWithStmtReadTS() (kv.Snapshot,
 func (p *StalenessTxnContextProvider) GetSnapshotWithStmtForUpdateTS() (kv.Snapshot, error) {
 	return nil, errors.New("GetSnapshotWithStmtForUpdateTS not supported for stalenessTxnProvider")
 }
+
+// OnLocalTemporaryTableCreated will not be called for StalenessTxnContextProvider
+func (p *StalenessTxnContextProvider) OnLocalTemporaryTableCreated() {}

table/temptable/ddl_test.go

@@ -161,7 +161,7 @@ func TestTruncateLocalTemporaryTable(t *testing.T) {
 	// truncate when empty
 	err := ddl.TruncateLocalTemporaryTable(model.NewCIStr("db1"), model.NewCIStr("t1"))
 	require.True(t, infoschema.ErrTableNotExists.Equal(err))
-	require.Equal(t, 0, sessVars.LocalTemporaryTables.(*infoschema.LocalTemporaryTables).Count())
+	require.Nil(t, sessVars.LocalTemporaryTables)
 	require.Nil(t, sessVars.TemporaryTableData)
 
 	// add one table

table/temptable/infoschema.go

@@ -21,11 +21,15 @@ import (
 
 // AttachLocalTemporaryTableInfoSchema attach local temporary table information schema to is
 func AttachLocalTemporaryTableInfoSchema(sctx sessionctx.Context, is infoschema.InfoSchema) infoschema.InfoSchema {
+	localTemporaryTables := getLocalTemporaryTables(sctx)
+	if localTemporaryTables == nil {
+		return is
+	}
+
 	if _, ok := is.(*infoschema.TemporaryTableAttachedInfoSchema); ok {
 		return is
 	}
 
-	localTemporaryTables := getLocalTemporaryTables(sctx)
 	return &infoschema.TemporaryTableAttachedInfoSchema{
 		InfoSchema:           is,
 		LocalTemporaryTables: localTemporaryTables,
@@ -42,8 +46,12 @@ func DetachLocalTemporaryTableInfoSchema(is infoschema.InfoSchema) infoschema.In
 }
 
 func getLocalTemporaryTables(sctx sessionctx.Context) *infoschema.LocalTemporaryTables {
-	// Do not return nil so that new created tables can always be visited through the returned object.
-	return ensureLocalTemporaryTables(sctx)
+	localTemporaryTables := sctx.GetSessionVars().LocalTemporaryTables
+	if localTemporaryTables == nil {
+		return nil
+	}
+
+	return localTemporaryTables.(*infoschema.LocalTemporaryTables)
 }
 
 func ensureLocalTemporaryTables(sctx sessionctx.Context) *infoschema.LocalTemporaryTables {