Merge pull request pingcap#7 from PatrickNicholas/2020-hackathon

store: fix replica read type for adaptive follower read
abbccdda · Jan 16, 2021 · a0338d1 · a0338d1
2 parents f268519 + 2e7ecb4
commit a0338d1
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Showing 4 changed files with 12 additions and 4 deletions.
diff --git a/executor/table_reader.go b/executor/table_reader.go
@@ -227,9 +227,12 @@ func (e *TableReaderExecutor) buildResp(ctx context.Context, ranges []*ranger.Ra
 	factor := e.ctx.GetSessionVars().NetworkFactor
 	totalCost := 0.0
 	for _, plan := range e.plans {
-		totalCost += plan.StatsCount()*factor +
+		totalCost += plan.StatsCount() * factor *
 			plan.Stats().HistColl.GetAvgRowSize(e.ctx, plan.Schema().Columns, false, true)
 	}
+
+	logutil.Eventf(ctx, "table scan %s, total cost: %d",
+		e.table.Meta().Name.L, totalCost)
 	estimater := func(r *kv.KeyRange, totalRanges []kv.KeyRange) float64 {
 		return totalCost * 1.0 / (float64(len(totalRanges)) + 1.0)
 	}

diff --git a/store/tikv/region_request.go b/store/tikv/region_request.go
@@ -234,7 +234,7 @@ func (s *RegionRequestSender) getRPCContext(
 		if req.RecommendLocalScan {
 			// We need to avoid the affection of forced replica read type here, so that the
 			// AZ/DC label matching could take effect.
-			return s.regionCache.GetTiKVRPCContext(bo, regionID, kv.ReplicaReadMixed, seed, WithMatchAZ())
+			return s.regionCache.GetTiKVRPCContext(bo, regionID, req.ReplicaReadType, seed, WithMatchAZ())
 		} else {
 			return s.regionCache.GetTiKVRPCContext(bo, regionID, req.ReplicaReadType, seed)
 		}

diff --git a/store/tikv/region_request_test.go b/store/tikv/region_request_test.go
@@ -111,7 +111,7 @@ func (s *testRegionRequestToThreeStoresSuite) TestGetRPCContext(c *C) {
 	var seed uint32 = 0
 	var regionID = RegionVerID{s.regionID, 0, 0}
 
-	req := tikvrpc.NewReplicaReadRequest(tikvrpc.CmdGet, &kvrpcpb.GetRequest{}, kv.ReplicaReadLeader, &seed)
+	req := tikvrpc.NewReplicaReadRequest(tikvrpc.CmdGet, &kvrpcpb.GetRequest{}, kv.ReplicaReadLeader, &seed, false)
 	rpcCtx, err := s.regionRequestSender.getRPCContext(s.bo, req, regionID, kv.TiKV)
 	c.Assert(err, IsNil)
 	c.Assert(rpcCtx.Peer.Id, Equals, s.leaderPeer)

diff --git a/store/tikv/tikvrpc/tikvrpc.go b/store/tikv/tikvrpc/tikvrpc.go
@@ -194,10 +194,15 @@ func NewRequest(typ CmdType, pointer interface{}, ctxs ...kvrpcpb.Context) *Requ
 // NewReplicaReadRequest returns new kv rpc request with replica read.
 func NewReplicaReadRequest(typ CmdType, pointer interface{}, replicaReadType kv.ReplicaReadType, replicaReadSeed *uint32, recommendLocalScan bool, ctxs ...kvrpcpb.Context) *Request {
 	req := NewRequest(typ, pointer, ctxs...)
+	if replicaReadType == kv.ReplicaReadLeader && recommendLocalScan {
+		// We need to avoid the affection of forced replica read type here, so that the
+		// AZ/DC label matching could take effect.
+		replicaReadType = kv.ReplicaReadMixed
+		req.RecommendLocalScan = true
+	}
 	req.ReplicaRead = replicaReadType.IsFollowerRead()
 	req.ReplicaReadType = replicaReadType
 	req.ReplicaReadSeed = replicaReadSeed
-	req.RecommendLocalScan = recommendLocalScan
 	return req
 }