From 9148ff9f44555d681a401b3f33681f7dc2414b6b Mon Sep 17 00:00:00 2001
From: djshow832 <zhangming@pingcap.com>
Date: Mon, 17 May 2021 22:31:39 +0800
Subject: [PATCH] ddl, transaction: DDL on temporary tables won't affect
 transactions (#24534)

---
 domain/schema_validator.go |  5 +++--
 session/session.go         |  6 ++++++
 session/session_test.go    | 39 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/domain/schema_validator.go b/domain/schema_validator.go
index b983eff1d6203..a8baa49db93b9 100644
--- a/domain/schema_validator.go
+++ b/domain/schema_validator.go
@@ -234,8 +234,9 @@ func (s *schemaValidator) Check(txnTS uint64, schemaVer int64, relatedPhysicalTa
 
 	// Schema changed, result decided by whether related tables change.
 	if schemaVer < s.latestSchemaVer {
-		// The DDL relatedPhysicalTableIDs is empty.
-		if len(relatedPhysicalTableIDs) == 0 {
+		// When a transaction executes a DDL, relatedPhysicalTableIDs is nil.
+		// When a transaction only contains DML on temporary tables, relatedPhysicalTableIDs is [].
+		if relatedPhysicalTableIDs == nil {
 			logutil.BgLogger().Info("the related physical table ID is empty", zap.Int64("schemaVer", schemaVer),
 				zap.Int64("latestSchemaVer", s.latestSchemaVer))
 			return nil, ResultFail
diff --git a/session/session.go b/session/session.go
index e13be2045e941..78a60a6ebaecf 100644
--- a/session/session.go
+++ b/session/session.go
@@ -505,8 +505,14 @@ func (s *session) doCommit(ctx context.Context) error {
 
 	// Get the related table or partition IDs.
 	relatedPhysicalTables := s.GetSessionVars().TxnCtx.TableDeltaMap
+	// Get accessed global temporary tables in the transaction.
+	temporaryTables := s.GetSessionVars().TxnCtx.GlobalTemporaryTables
 	physicalTableIDs := make([]int64, 0, len(relatedPhysicalTables))
 	for id := range relatedPhysicalTables {
+		// Schema change on global temporary tables doesn't affect transactions.
+		if _, ok := temporaryTables[id]; ok {
+			continue
+		}
 		physicalTableIDs = append(physicalTableIDs, id)
 	}
 	// Set this option for 2 phase commit to validate schema lease.
diff --git a/session/session_test.go b/session/session_test.go
index 9845e757470f0..f7267e3a13259 100644
--- a/session/session_test.go
+++ b/session/session_test.go
@@ -2131,6 +2131,45 @@ func (s *testSchemaSerialSuite) TestSchemaCheckerSQL(c *C) {
 	c.Assert(err, NotNil)
 }
 
+func (s *testSchemaSerialSuite) TestSchemaCheckerTempTable(c *C) {
+	tk := testkit.NewTestKitWithInit(c, s.store)
+	tk1 := testkit.NewTestKitWithInit(c, s.store)
+
+	// create table
+	tk.MustExec(`drop table if exists normal_table`)
+	tk.MustExec(`create table normal_table (id int, c int);`)
+	defer tk.MustExec(`drop table if exists normal_table`)
+	tk.MustExec(`drop table if exists temp_table`)
+	tk.MustExec(`create global temporary table temp_table (id int, c int) on commit delete rows;`)
+	defer tk.MustExec(`drop table if exists temp_table`)
+
+	// The schema version is out of date in the first transaction, and the SQL can't be retried.
+	atomic.StoreUint32(&session.SchemaChangedWithoutRetry, 1)
+	defer func() {
+		atomic.StoreUint32(&session.SchemaChangedWithoutRetry, 0)
+	}()
+
+	// It's fine to change the schema of temporary tables.
+	tk.MustExec(`begin;`)
+	tk1.MustExec(`alter table temp_table modify column c bigint;`)
+	tk.MustExec(`insert into temp_table values(3, 3);`)
+	tk.MustExec(`commit;`)
+
+	// Truncate will modify table ID.
+	tk.MustExec(`begin;`)
+	tk1.MustExec(`truncate table temp_table;`)
+	tk.MustExec(`insert into temp_table values(3, 3);`)
+	tk.MustExec(`commit;`)
+
+	// It reports error when also changing the schema of a normal table.
+	tk.MustExec(`begin;`)
+	tk1.MustExec(`alter table normal_table modify column c bigint;`)
+	tk.MustExec(`insert into temp_table values(3, 3);`)
+	tk.MustExec(`insert into normal_table values(3, 3);`)
+	_, err := tk.Exec(`commit;`)
+	c.Assert(terror.ErrorEqual(err, domain.ErrInfoSchemaChanged), IsTrue, Commentf("err %v", err))
+}
+
 func (s *testSchemaSuite) TestPrepareStmtCommitWhenSchemaChanged(c *C) {
 	tk := testkit.NewTestKitWithInit(c, s.store)
 	tk1 := testkit.NewTestKitWithInit(c, s.store)