planner/core: fix the 'for update' condition for the point get query (#…

…11771)

planner/core/point_get_plan.go

@@ -156,7 +156,8 @@ func TryFastPlan(ctx sessionctx.Context, node ast.Node) Plan {
 				// 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.
 				// See https://dev.mysql.com/doc/refman/5.7/en/innodb-locking-reads.html
-				if ctx.GetSessionVars().InTxn() {
+				sessVars := ctx.GetSessionVars()
+				if !sessVars.IsAutocommit() || sessVars.InTxn() {
 					fp.Lock = true
 					fp.IsForUpdate = true
 				}

planner/core/point_get_plan_test.go

@@ -171,25 +171,27 @@ func (s *testPointGetSuite) TestPointGetPlanCache(c *C) {
 func (s *testPointGetSuite) TestPointGetForUpdate(c *C) {
 	tk := testkit.NewTestKit(c, s.store)
 	tk.MustExec("use test")
-	tk.MustExec("create table fu (id int primary key)")
-	tk.MustExec("insert into fu values (6)")
-	tk.MustQuery("select * from fu where id = 6 for update").Check(testkit.Rows("6"))
+	tk.MustExec("create table fu (id int primary key, val int)")
+	tk.MustExec("insert into fu values (6, 6)")
 
 	// In autocommit mode, outside a transaction, "for update" doesn't take effect.
-	res := tk.MustQuery("explain select * from fu where id = 6 for update")
-	// Point_Get_1	1.00	root	table:fu, handle:6
-	opInfo := res.Rows()[0][3]
-	selectLock := strings.Contains(fmt.Sprintf("%s", opInfo), "lock")
-	c.Assert(selectLock, IsFalse)
+	checkUseForUpdate(tk, c, false)
 
 	tk.MustExec("begin")
-	tk.MustQuery("select * from fu where id = 6 for update").Check(testkit.Rows("6"))
-	res = tk.MustQuery("explain select * from fu where id = 6 for update")
-	// Point_Get_1	1.00	root	table:fu, handle:6
-	opInfo = res.Rows()[0][3]
-	selectLock = strings.Contains(fmt.Sprintf("%s", opInfo), "lock")
-	c.Assert(selectLock, IsTrue)
+	checkUseForUpdate(tk, c, true)
+	tk.MustExec("rollback")
 
+	tk.MustExec("set @@session.autocommit = 0")
+	checkUseForUpdate(tk, c, true)
 	tk.MustExec("rollback")
+}
+
+func checkUseForUpdate(tk *testkit.TestKit, c *C, expectLock bool) {
+	res := tk.MustQuery("explain select * from fu where id = 6 for update")
+	// Point_Get_1	1.00	root	table:fu, handle:6
+	opInfo := res.Rows()[0][3]
+	selectLock := strings.Contains(fmt.Sprintf("%s", opInfo), "lock")
+	c.Assert(selectLock, Equals, expectLock)
 
+	tk.MustQuery("select * from fu where id = 6 for update").Check(testkit.Rows("6 6"))
 }