txn: fix the point get data read for RC (pingcap#41590)

close pingcap#41581

executor/builder.go

@@ -2216,7 +2216,10 @@ func (b *executorBuilder) updateForUpdateTSIfNeeded(selectPlan plannercore.Physi
 	if !txnCtx.IsPessimistic {
 		return nil
 	}
-	if _, ok := selectPlan.(*plannercore.PointGetPlan); ok {
+
+	// The `forUpdateTS` should be refreshed for RC, or the `pointGetExecutor` may not read
+	// the latest data and no pessimistic locks would be acquired, thus the result is unexpected.
+	if _, ok := selectPlan.(*plannercore.PointGetPlan); ok && !b.ctx.GetSessionVars().IsPessimisticReadConsistency() {
 		return nil
 	}
 	// Activate the invalid txn, use the txn startTS as newForUpdateTS

tests/realtikvtest/pessimistictest/pessimistic_test.go

@@ -3199,3 +3199,40 @@ func TestPessimisticLockOnPartition(t *testing.T) {
 	require.Equal(t, int32(0), <-ch)
 	<-ch // wait for goroutine to quit.
 }
+
+func TestRCUpdateWithPointGet(t *testing.T) {
+	store, clean := realtikvtest.CreateMockStoreAndSetup(t)
+	defer clean()
+
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("drop database if exists test")
+	tk.MustExec("create database test")
+	tk.MustExec("use test")
+	tk.MustExec("set global tidb_txn_mode = 'pessimistic'")
+	tk.MustExec("set global tx_isolation = 'READ-COMMITTED'")
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t (a int key, b int)")
+
+	// Try to cover https://github.com/pingcap/tidb/issues/41581.
+	tk1 := testkit.NewTestKit(t, store)
+	tk2 := testkit.NewTestKit(t, store)
+	tk2.MustExec("use test")
+	tk1.MustExec("use test")
+	tk1.MustExec("begin pessimistic")
+	tk2.MustExec("insert into t values(5, 5)")
+	tk1.MustExec("update t set b = 22 where a = 5;")
+	require.Equal(t, uint64(1), tk1.Session().AffectedRows())
+	tk1.MustExec("commit")
+	tk2.MustQuery("select count(1) from t").Check(testkit.Rows("1"))
+
+	tk1.MustExec("begin pessimistic")
+	tk2.MustExec("insert into t values(6, 6)")
+	tk1.MustQuery("(select * from t where a = 6 for update) union all (select * from t where a = 7 for update)").Check(testkit.Rows("6 6"))
+	tk1.MustExec("commit")
+
+	tk1.MustExec("begin pessimistic")
+	tk2.MustExec("insert into t values(7, 7)")
+	tk1.MustExec("delete from t where a = 7;")
+	require.Equal(t, uint64(1), tk1.Session().AffectedRows())
+	tk1.MustExec("commit")
+}