txn: fix the incorrect untouch used in optimistic transactions(#30447)

session/session.go

@@ -69,6 +69,7 @@ import (
 	"github.com/pingcap/tidb/sessionctx/variable"
 	"github.com/pingcap/tidb/statistics"
 	"github.com/pingcap/tidb/statistics/handle"
+	"github.com/pingcap/tidb/store/driver/txn"
 	"github.com/pingcap/tidb/store/tikv"
 	tikvstore "github.com/pingcap/tidb/store/tikv/kv"
 	tikvutil "github.com/pingcap/tidb/store/tikv/util"
@@ -544,14 +545,15 @@ func (s *session) doCommit(ctx context.Context) error {
 
 type temporaryTableKVFilter map[int64]tableutil.TempTable
 
-func (m temporaryTableKVFilter) IsUnnecessaryKeyValue(key, value []byte, flags tikvstore.KeyFlags) bool {
+func (m temporaryTableKVFilter) IsUnnecessaryKeyValue(key, value []byte, flags tikvstore.KeyFlags) (bool, error) {
 	tid := tablecodec.DecodeTableID(key)
 	if _, ok := m[tid]; ok {
-		return true
+		return true, nil
 	}
 
 	// This is the default filter for all tables.
-	return tablecodec.IsUntouchedIndexKValue(key, value)
+	defaultFilter := txn.TiDBKVFilter{}
+	return defaultFilter.IsUnnecessaryKeyValue(key, value, flags)
 }
 
 // errIsNoisy is used to filter DUPLCATE KEY errors.

store/driver/txn/txn_driver.go

@@ -29,6 +29,8 @@ import (
 	tikverr "github.com/pingcap/tidb/store/tikv/error"
 	tikvstore "github.com/pingcap/tidb/store/tikv/kv"
 	"github.com/pingcap/tidb/tablecodec"
+	"github.com/pingcap/tidb/util/logutil"
+	"go.uber.org/zap"
 )
 
 type tikvTxn struct {
@@ -235,6 +237,15 @@ func (txn *tikvTxn) extractKeyExistsErr(key kv.Key) error {
 type TiDBKVFilter struct{}
 
 // IsUnnecessaryKeyValue defines which kinds of KV pairs from TiDB needn't be committed.
-func (f TiDBKVFilter) IsUnnecessaryKeyValue(key, value []byte, flags tikvstore.KeyFlags) bool {
-	return tablecodec.IsUntouchedIndexKValue(key, value)
+func (f TiDBKVFilter) IsUnnecessaryKeyValue(key, value []byte, flags tikvstore.KeyFlags) (bool, error) {
+	isUntouchedValue := tablecodec.IsUntouchedIndexKValue(key, value)
+	if isUntouchedValue && flags.HasPresumeKeyNotExists() {
+		logutil.BgLogger().Error("unexpected path the untouched key value with PresumeKeyNotExists flag",
+			zap.Stringer("key", kv.Key(key)), zap.Stringer("value", kv.Key(value)),
+			zap.Uint16("flags", uint16(flags)), zap.Stack("stack"))
+		return false, errors.Errorf(
+			"unexpected path the untouched key=%s value=%s contains PresumeKeyNotExists flag keyFlags=%v",
+			kv.Key(key).String(), kv.Key(value).String(), flags)
+	}
+	return isUntouchedValue, nil
 }

store/tikv/2pc.go

@@ -323,7 +323,7 @@ func (c *twoPhaseCommitter) extractKeyExistsErr(err *tikverr.ErrKeyExist) error
 // KVFilter is a filter that filters out unnecessary KV pairs.
 type KVFilter interface {
 	// IsUnnecessaryKeyValue returns whether this KV pair should be committed.
-	IsUnnecessaryKeyValue(key, value []byte, flags kv.KeyFlags) bool
+	IsUnnecessaryKeyValue(key, value []byte, flags kv.KeyFlags) (bool, error)
 }
 
 func (c *twoPhaseCommitter) initKeysAndMutations() error {
@@ -353,7 +353,13 @@ func (c *twoPhaseCommitter) initKeysAndMutations() error {
 		} else {
 			value = it.Value()
 			if len(value) > 0 {
-				isUnnecessaryKV := filter != nil && filter.IsUnnecessaryKeyValue(key, value, flags)
+				var isUnnecessaryKV bool
+				if filter != nil {
+					isUnnecessaryKV, err = filter.IsUnnecessaryKeyValue(key, value, flags)
+					if err != nil {
+						return err
+					}
+				}
 				if isUnnecessaryKV {
 					if !flags.HasLocked() {
 						continue

table/tables/index.go

@@ -168,8 +168,22 @@ func (c *index) Create(sctx sessionctx.Context, txn kv.Transaction, indexedValue
 		// should not overwrite the key with un-commit flag.
 		// So if the key exists, just do nothing and return.
 		v, err := txn.GetMemBuffer().Get(ctx, key)
-		if err == nil && len(v) != 0 {
-			return nil, nil
+		if err == nil {
+			if len(v) != 0 {
+				return nil, nil
+			}
+			// The key is marked as deleted in the memory buffer, as the existence check is done lazily
+			// for optimistic transactions by default. The "untouched" key could still exist in the store,
+			// it's needed to commit this key to do the existence check so unset the untouched flag.
+			if !txn.IsPessimistic() {
+				keyFlags, err := txn.GetMemBuffer().GetFlags(key)
+				if err != nil {
+					return nil, err
+				}
+				if keyFlags.HasPresumeKeyNotExists() {
+					opt.Untouched = false
+				}
+			}
 		}
 	}
 

table/tables/tables_test.go

@@ -746,3 +746,29 @@ func (ts *testSuite) TestViewColumns(c *C) {
 			"Warning|1356|View 'test.va' references invalid table(s) or column(s) or function(s) or definer/invoker of view lack rights to use them"))
 	}
 }
+
+func (ts *testSuite) TestConstraintCheckForOptimisticUntouched(c *C) {
+	se, err := session.CreateSession4Test(ts.store)
+	c.Assert(err, IsNil)
+	c.Assert(se.Auth(&auth.UserIdentity{Username: "root", Hostname: "%"}, nil, nil), IsTrue)
+	tk := testkit.NewTestKitWithSession(c, ts.store, se)
+
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists test_optimistic_untouched_flag;")
+	tk.MustExec(`create table test_optimistic_untouched_flag(c0 int, c1 varchar(20), c2 varchar(20), unique key uk(c0));`)
+	tk.MustExec(`insert into test_optimistic_untouched_flag(c0, c1, c2) values (1, null, 'green');`)
+
+	// Insert a row with duplicated entry on the unique key, the commit should fail.
+	tk.MustExec("begin optimistic;")
+	tk.MustExec(`insert into test_optimistic_untouched_flag(c0, c1, c2) values (1, 'red', 'white');`)
+	tk.MustExec(`delete from test_optimistic_untouched_flag where c1 is null;`)
+	tk.MustExec("update test_optimistic_untouched_flag set c2 = 'green' where c2 between 'purple' and 'white';")
+	err = tk.ExecToErr("commit")
+	c.Assert(err, NotNil)
+
+	tk.MustExec("begin optimistic;")
+	tk.MustExec(`insert into test_optimistic_untouched_flag(c0, c1, c2) values (1, 'red', 'white');`)
+	tk.MustExec("update test_optimistic_untouched_flag set c2 = 'green' where c2 between 'purple' and 'white';")
+	err = tk.ExecToErr("commit")
+	c.Assert(err, NotNil)
+}