tikv: fix primary selection when delete-your-writes (#18244) (#18250)

* cherry pick #18244 to release-4.0

Signed-off-by: ti-srebot <ti-srebot@pingcap.com>

* fix test compile

Co-authored-by: lysu <sulifx@gmail.com>

store/tikv/2pc.go

@@ -159,6 +159,11 @@ type twoPhaseCommitter struct {
 	regionTxnSize map[uint64]int
 	// Used by pessimistic transaction and large transaction.
 	ttlManager
+
+	testingKnobs struct {
+		acAfterCommitPrimary chan struct{}
+		bkAfterCommitPrimary chan struct{}
+	}
 }
 
 type committerMutations struct {
@@ -328,6 +333,9 @@ func (c *twoPhaseCommitter) initKeysAndMutations() error {
 				lockIdx++
 			}
 		}
+		if len(c.primaryKey) == 0 && op != pb.Op_CheckNotExists {
+			c.primaryKey = k
+		}
 		mutations.push(op, k, value, isPessimisticLock)
 		entrySize := len(k) + len(v)
 		if entrySize > kv.TxnEntrySizeLimit {
@@ -569,6 +577,10 @@ func (c *twoPhaseCommitter) doActionOnGroupMutations(bo *Backoffer, action twoPh
 		if err != nil {
 			return errors.Trace(err)
 		}
+		if actionIsCommit && c.testingKnobs.bkAfterCommitPrimary != nil && c.testingKnobs.acAfterCommitPrimary != nil {
+			c.testingKnobs.acAfterCommitPrimary <- struct{}{}
+			<-c.testingKnobs.bkAfterCommitPrimary
+		}
 		batches = batches[1:]
 	}
 	if actionIsCommit && !actionCommit.retry {

store/tikv/2pc_test.go

@@ -666,6 +666,50 @@ func (s *testCommitterSuite) TestElapsedTTL(c *C) {
 	c.Assert(lockInfo.LockTtl-atomic.LoadUint64(&ManagedLockTTL), Less, uint64(150))
 }
 
+func (s *testCommitterSuite) TestDeleteYourWriteCauseGhostPrimary(c *C) {
+	s.cluster.SplitKeys(s.mvccStore, kv.Key("d"), kv.Key("a"), 4)
+	k1 := kv.Key("a") // insert but deleted key at first pos in txn1
+	k2 := kv.Key("b") // insert key at second pos in txn1
+	k3 := kv.Key("c") // insert key in txn1 and will be conflict read by txn2
+
+	// insert k1, k2, k2 and delete k1
+	txn1 := s.begin(c)
+	txn1.DelOption(kv.Pessimistic)
+	txn1.SetOption(kv.PresumeKeyNotExists, nil)
+	txn1.SetOption(kv.PresumeKeyNotExistsError, kv.NewExistErrInfo("name", "value"))
+	txn1.store.txnLatches = nil
+	txn1.Get(context.Background(), k1)
+	txn1.Set(k1, []byte{0})
+	txn1.Set(k2, []byte{1})
+	txn1.Set(k3, []byte{2})
+	txn1.Delete(k1)
+	committer1, err := newTwoPhaseCommitter(txn1, 0)
+	c.Assert(err, IsNil)
+	// setup test knob in txn's committer
+	committer1.testingKnobs.acAfterCommitPrimary = make(chan struct{})
+	committer1.testingKnobs.bkAfterCommitPrimary = make(chan struct{})
+	txn1.committer = committer1
+	var txn1Done sync.WaitGroup
+	txn1Done.Add(1)
+	go func() {
+		err1 := txn1.Commit(context.Background())
+		c.Assert(err1, IsNil)
+		txn1Done.Done()
+	}()
+	// resume after after primary key be committed
+	<-txn1.committer.testingKnobs.acAfterCommitPrimary
+
+	// start txn2 to read k3(prewrite success and primary should be committed)
+	txn2 := s.begin(c)
+	txn2.DelOption(kv.Pessimistic)
+	txn2.store.txnLatches = nil
+	v, err := txn2.Get(context.Background(), k3)
+	c.Assert(err, IsNil) // should resolve lock and read txn1 k3 result instead of rollback it.
+	c.Assert(v[0], Equals, byte(2))
+	txn1.committer.testingKnobs.bkAfterCommitPrimary <- struct{}{}
+	txn1Done.Wait()
+}
+
 // TestAcquireFalseTimeoutLock tests acquiring a key which is a secondary key of another transaction.
 // The lock's own TTL is expired but the primary key is still alive due to heartbeats.
 func (s *testCommitterSuite) TestAcquireFalseTimeoutLock(c *C) {