Set ServerStatusInTrans flag

session.go

@@ -137,6 +137,7 @@ func (s *session) FinishTxn(rollback bool) error {
 	}
 	defer func() {
 		s.txn = nil
+		variable.GetSessionVars(s).SetStatusInTrans(false)
 	}()
 
 	if rollback {
@@ -345,6 +346,7 @@ func (s *session) GetTxn(forceNew bool) (kv.Transaction, error) {
 	}
 	if forceNew {
 		err = s.txn.Commit()
+		variable.GetSessionVars(s).SetStatusInTrans(false)
 		if err != nil {
 			return nil, err
 		}

sessionctx/variable/session.go

@@ -38,9 +38,6 @@ type SessionVars struct {
 	// Client Capability
 	ClientCapability uint32 // Client capability
 
-	// Disable autocommit
-	DisableAutocommit bool
-
 	// Found rows
 	FoundRows uint64
 }
@@ -102,19 +99,29 @@ func (s *SessionVars) SetStatus(status uint16) {
 	s.Status = status
 }
 
+// SetStatusInTrans sets the status flags about ServerStatusInTrans.
+func (s *SessionVars) SetStatusInTrans(isInTrans bool) {
+	if isInTrans {
+		s.Status |= mysql.ServerStatusInTrans
+		return
+	}
+	s.Status &= (^mysql.ServerStatusInTrans)
+}
+
 // GetNextPreparedStmtID generates and return the next session scope prepared statement id
 func (s *SessionVars) GetNextPreparedStmtID() uint32 {
 	s.preparedStmtID++
 	return s.preparedStmtID
 }
 
-// IsAutocommit checks if it is in autocommit enviroment
-func IsAutocommit(ctx context.Context) bool {
+// ShouldAutocommit checks if it is in autocommit enviroment
+func ShouldAutocommit(ctx context.Context) bool {
 	// With START TRANSACTION, autocommit remains disabled until you end
 	// the transaction with COMMIT or ROLLBACK.
 	if GetSessionVars(ctx).Status&mysql.ServerStatusAutocommit > 0 &&
-		!GetSessionVars(ctx).DisableAutocommit {
+		GetSessionVars(ctx).Status&mysql.ServerStatusInTrans == 0 {
 		return true
 	}
+
 	return false
 }

stmt/stmts/select.go

@@ -147,7 +147,7 @@ func (s *SelectStmt) Plan(ctx context.Context) (plan.Plan, error) {
 		}
 	}
 	lock := s.Lock
-	if variable.IsAutocommit(ctx) {
+	if variable.ShouldAutocommit(ctx) {
 		// Locking of rows for update using SELECT FOR UPDATE only applies when autocommit
 		// is disabled (either by beginning transaction with START TRANSACTION or by setting
 		// autocommit to 0. If autocommit is enabled, the rows matching the specification are not locked.

stmt/stmts/transaction.go

@@ -63,7 +63,7 @@ func (s *BeginStmt) Exec(ctx context.Context) (_ rset.Recordset, err error) {
 	// With START TRANSACTION, autocommit remains disabled until you end
 	// the transaction with COMMIT or ROLLBACK. The autocommit mode then
 	// reverts to its previous state.
-	variable.GetSessionVars(ctx).DisableAutocommit = true
+	variable.GetSessionVars(ctx).SetStatusInTrans(true)
 	return
 }
 
@@ -96,7 +96,7 @@ func (s *CommitStmt) SetText(text string) {
 // Exec implements the stmt.Statement Exec interface.
 func (s *CommitStmt) Exec(ctx context.Context) (_ rset.Recordset, err error) {
 	err = ctx.FinishTxn(false)
-	variable.GetSessionVars(ctx).DisableAutocommit = false
+	variable.GetSessionVars(ctx).SetStatusInTrans(false)
 	return
 }
 
@@ -129,6 +129,6 @@ func (s *RollbackStmt) SetText(text string) {
 // Exec implements the stmt.Statement Exec interface.
 func (s *RollbackStmt) Exec(ctx context.Context) (_ rset.Recordset, err error) {
 	err = ctx.FinishTxn(true)
-	variable.GetSessionVars(ctx).DisableAutocommit = false
+	variable.GetSessionVars(ctx).SetStatusInTrans(false)
 	return
 }

tidb.go

@@ -161,7 +161,7 @@ func runStmt(ctx context.Context, s stmt.Statement, args ...interface{}) (rset.R
 		stmt.ClearExecArgs(ctx)
 	}
 	// MySQL DDL should be auto-commit
-	if err == nil && (s.IsDDL() || variable.IsAutocommit(ctx)) {
+	if err == nil && (s.IsDDL() || variable.ShouldAutocommit(ctx)) {
 		err = ctx.FinishTxn(false)
 	}
 	return rs, errors.Trace(err)

tidb_test.go

@@ -28,6 +28,7 @@ import (
 	"github.com/pingcap/tidb/kv"
 	mysql "github.com/pingcap/tidb/mysqldef"
 	"github.com/pingcap/tidb/rset"
+	"github.com/pingcap/tidb/sessionctx/variable"
 	"github.com/pingcap/tidb/util/errors2"
 )
 
@@ -462,6 +463,41 @@ func (s *testSessionSuite) TestAutoincrementID(c *C) {
 	mustExecSQL(c, se, s.dropDBSQL)
 }
 
+func checkInTrans(c *C, se Session, stmt string, expect uint16) {
+	mustExecSQL(c, se, stmt)
+	if expect == 0 {
+		c.Assert(se.(*session).txn, IsNil)
+	} else {
+		c.Assert(se.(*session).txn, NotNil)
+	}
+	ret := variable.GetSessionVars(se.(*session)).Status & mysql.ServerStatusInTrans
+	c.Assert(ret, Equals, expect)
+}
+
+// See: https://dev.mysql.com/doc/internals/en/status-flags.html
+func (s *testSessionSuite) TestInTrans(c *C) {
+	store := newStore(c, s.dbName)
+	se := newSession(c, store, s.dbName)
+	checkInTrans(c, se, "drop table if exists t;", 0)
+	checkInTrans(c, se, "create table t (id BIGINT PRIMARY KEY AUTO_INCREMENT NOT NULL)", 0)
+	checkInTrans(c, se, "insert t values ()", 0)
+	checkInTrans(c, se, "begin", 1)
+	checkInTrans(c, se, "insert t values ()", 1)
+	checkInTrans(c, se, "drop table if exists t;", 0)
+	checkInTrans(c, se, "create table t (id BIGINT PRIMARY KEY AUTO_INCREMENT NOT NULL)", 0)
+	checkInTrans(c, se, "insert t values ()", 0)
+	checkInTrans(c, se, "commit", 0)
+	checkInTrans(c, se, "insert t values ()", 0)
+
+	checkInTrans(c, se, "drop table if exists t;", 0)
+	checkInTrans(c, se, "create table t (id BIGINT PRIMARY KEY AUTO_INCREMENT NOT NULL)", 0)
+	checkInTrans(c, se, "begin", 1)
+	checkInTrans(c, se, "insert t values ()", 1)
+	checkInTrans(c, se, "rollback", 0)
+
+	mustExecSQL(c, se, s.dropDBSQL)
+}
+
 // See: http://dev.mysql.com/doc/refman/5.7/en/commit.html
 func (s *testSessionSuite) TestRowLock(c *C) {
 	store := newStore(c, s.dbName)