Revert "Fix the issue that leader change with new leader info cause i…

…nvalidStore state and lead to unnecessary backoff (tikv#1115) (tikv#1337)" (tikv#4)

This reverts commit 9e1b9eb.

Co-authored-by: rishabh_mittal <[email protected]>

internal/locate/region_request.go

@@ -40,13 +40,11 @@ import (
 	"fmt"
 	"math"
 	"math/rand"
-	"reflect"
 	"strconv"
 	"strings"
 	"sync"
 	"sync/atomic"
 	"time"
-	"unsafe"
 
 	"go.uber.org/zap"
 	"google.golang.org/grpc/codes"
@@ -1007,17 +1005,6 @@ func (s *replicaSelector) proxyReplica() *replica {
 	return nil
 }
 
-// sliceIdentical checks whether two slices are referencing the same block of memory. Two `nil`s are also considered
-// the same.
-func sliceIdentical[T any](a, b []T) bool {
-	if len(a) != len(b) {
-		return false
-	}
-	aHeader := (*reflect.SliceHeader)(unsafe.Pointer(&a))
-	bHeader := (*reflect.SliceHeader)(unsafe.Pointer(&b))
-	return aHeader.Data == bHeader.Data
-}
-
 func (s *replicaSelector) refreshRegionStore() {
 	oldRegionStore := s.regionStore
 	newRegionStore := s.region.getStore()
@@ -1030,7 +1017,7 @@ func (s *replicaSelector) refreshRegionStore() {
 	// So we just compare the address here.
 	// When stores change, we mark this replicaSelector as invalid to let the caller
 	// recreate a new replicaSelector.
-	if !sliceIdentical(oldRegionStore.stores, newRegionStore.stores) {
+	if &oldRegionStore.stores != &newRegionStore.stores {
 		s.state = &invalidStore{}
 		return
 	}

internal/locate/region_request3_test.go

@@ -137,82 +137,6 @@ func (s *testRegionRequestToThreeStoresSuite) TestSwitchPeerWhenNoLeader() {
 	resp, _, err := s.regionRequestSender.SendReq(bo, req, loc.Region, time.Second)
 	s.Nil(err)
 	s.NotNil(resp)
-	s.Nil(resp.GetRegionError())
-}
-
-func (s *testRegionRequestToThreeStoresSuite) TestSwitchPeerWhenNoLeaderErrorWithNewLeaderInfo() {
-	cnt := 0
-	var location *KeyLocation
-	cli := &fnClient{fn: func(ctx context.Context, addr string, req *tikvrpc.Request, timeout time.Duration) (response *tikvrpc.Response, err error) {
-		cnt++
-		switch cnt {
-		case 1:
-			region := s.cache.GetCachedRegionWithRLock(location.Region)
-			s.NotNil(region)
-			leaderPeerIdx := int(region.getStore().workTiKVIdx)
-			peers := region.meta.Peers
-			// return no leader with new leader info
-			response = &tikvrpc.Response{Resp: &kvrpcpb.GetResponse{
-				RegionError: &errorpb.Error{NotLeader: &errorpb.NotLeader{
-					RegionId: req.RegionId,
-					Leader:   peers[(leaderPeerIdx+1)%len(peers)],
-				}},
-			}}
-		case 2:
-			response = &tikvrpc.Response{Resp: &kvrpcpb.GetResponse{
-				Value: []byte("a"),
-			}}
-		default:
-			return nil, fmt.Errorf("unexpected request")
-		}
-		return response, err
-	}}
-
-	req := tikvrpc.NewRequest(tikvrpc.CmdGet, &kvrpcpb.GetRequest{Key: []byte("a")}, kvrpcpb.Context{})
-	req.ReplicaReadType = kv.ReplicaReadLeader
-	var err error
-	location, err = s.cache.LocateKey(s.bo, []byte("a"))
-	s.Nil(err)
-	s.NotNil(location)
-	bo := retry.NewBackoffer(context.Background(), 1000)
-	resp, _, err := NewRegionRequestSender(s.cache, cli).SendReqCtx(bo, req, location.Region, time.Second, tikvrpc.TiKV)
-	s.Nil(err)
-	s.NotNil(resp)
-	regionErr, err := resp.GetRegionError()
-	s.Nil(err)
-	s.Nil(regionErr)
-	// It's unreasoneable to retry in upper layer, such as cop request, the upper layer will need to rebuild cop request and retry, there are some unnecessary overhead.
-	s.Equal(cnt, 2)
-	r := s.cache.GetCachedRegionWithRLock(location.Region)
-	s.True(r.isValid())
-}
-
-func (s *testRegionRequestToThreeStoresSuite) TestSliceIdentical() {
-	a := make([]int, 0)
-	b := a
-	s.True(sliceIdentical(a, b))
-	// This is not guaranteed.
-	// b = make([]int, 0)
-	// s.False(sliceIdentical(a, b))
-
-	a = append(a, 1, 2, 3)
-	b = a
-	s.True(sliceIdentical(a, b))
-	b = a[:2]
-	s.False(sliceIdentical(a, b))
-	b = a[1:]
-	s.False(sliceIdentical(a, b))
-	a = a[1:]
-	s.True(sliceIdentical(a, b))
-
-	a = nil
-	b = nil
-
-	s.True(sliceIdentical(a, b))
-	a = make([]int, 0)
-	s.False(sliceIdentical(a, b))
-	a = append(a, 1)
-	s.False(sliceIdentical(a, b))
 }
 
 func (s *testRegionRequestToThreeStoresSuite) loadAndGetLeaderStore() (*Store, string) {