transaction: always lock keys with presume not exists flag (#19071)

* transaction: lock delete unique index key

* always lock for key with presume not exists flag

Co-authored-by: ti-srebot <66930949+ti-srebot@users.noreply.github.com>

executor/write_test.go

@@ -32,6 +32,7 @@ import (
 	"github.com/pingcap/tidb/types"
 	"github.com/pingcap/tidb/util/mock"
 	"github.com/pingcap/tidb/util/testkit"
+	"github.com/pingcap/tidb/util/testutil"
 )
 
 type testBypassSuite struct{}
@@ -836,6 +837,16 @@ func (s *testSuite4) TestInsertOnDupUpdateDefault(c *C) {
 	tk.MustGetErrCode("insert into t2 values (4,default,default) on duplicate key update a=default(a), c=default(c);", mysql.ErrBadGeneratedColumn)
 	tk.MustGetErrCode("insert into t2 values (4,default,default) on duplicate key update a=default(a), c=default(a);", mysql.ErrBadGeneratedColumn)
 	tk.MustExec("drop table t1, t2")
+
+	tk.MustExec("set @@tidb_txn_mode = 'pessimistic'")
+	tk.MustExec("create table t ( c_int int, c_string varchar(40) collate utf8mb4_bin , primary key (c_string), unique key (c_int));")
+	tk.MustExec("insert into t values (22, 'gold witch'), (24, 'gray singer'), (21, 'silver sight');")
+	tk.MustExec("begin;")
+	err := tk.ExecToErr("insert into t values (21,'black warlock'), (22, 'dark sloth'), (21,  'cyan song') on duplicate key update c_int = c_int + 1, c_string = concat(c_int, ':', c_string);")
+	c.Assert(kv.ErrKeyExists.Equal(err), IsTrue)
+	tk.MustExec("commit;")
+	tk.MustQuery("select * from t order by c_int;").Check(testutil.RowsWithSep("|", "21|silver sight", "22|gold witch", "24|gray singer"))
+	tk.MustExec("drop table t;")
 }
 
 func (s *testSuite4) TestReplace(c *C) {

session/tidb_test.go

@@ -196,6 +196,9 @@ func (s *testMainSuite) TestKeysNeedLock(c *C) {
 		{indexKey, deleteVal, false},
 	}
 	for _, tt := range tests {
-		c.Assert(keyNeedToLock(tt.key, tt.val), Equals, tt.need)
+		c.Assert(keyNeedToLock(tt.key, tt.val, 0), Equals, tt.need)
 	}
+	flag := kv.KeyFlags(1)
+	c.Assert(flag.HasPresumeKeyNotExists(), IsTrue)
+	c.Assert(keyNeedToLock(indexKey, deleteVal, flag), IsTrue)
 }

session/txn.go

@@ -294,20 +294,23 @@ func (st *TxnState) KeysNeedToLock() ([]kv.Key, error) {
 	keys := make([]kv.Key, 0, st.countHint())
 	buf := st.Transaction.GetMemBuffer()
 	buf.InspectStage(st.stagingHandle, func(k kv.Key, flags kv.KeyFlags, v []byte) {
-		if !keyNeedToLock(k, v) {
+		if !keyNeedToLock(k, v, flags) {
 			return
 		}
 		keys = append(keys, k)
 	})
 	return keys, nil
 }
 
-func keyNeedToLock(k, v []byte) bool {
+func keyNeedToLock(k, v []byte, flags kv.KeyFlags) bool {
 	isTableKey := bytes.HasPrefix(k, tablecodec.TablePrefix())
 	if !isTableKey {
 		// meta key always need to lock.
 		return true
 	}
+	if flags.HasPresumeKeyNotExists() {
+		return true
+	}
 	isDelete := len(v) == 0
 	if isDelete {
 		// only need to delete row key.