From dbe814c2af5b12d8a341a482c2ada54ef6244220 Mon Sep 17 00:00:00 2001
From: ti-srebot <66930949+ti-srebot@users.noreply.github.com>
Date: Fri, 11 Dec 2020 14:09:53 +0800
Subject: [PATCH] infoschema: fix inaccurate statistics of TIDB_HOT_REGIONS
 (#21278) (#21319)

Signed-off-by: Ryan Leung <rleungx@gmail.com>
---
 store/helper/helper.go      |  1 +
 store/helper/helper_test.go | 25 +++++++++++++++++++++----
 store/tikv/test_util.go     |  2 +-
 3 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/store/helper/helper.go b/store/helper/helper.go
index 9fadb60961b5f..315c1fec2d0c8 100644
--- a/store/helper/helper.go
+++ b/store/helper/helper.go
@@ -188,6 +188,7 @@ type HotTableIndex struct {
 func (h *Helper) FetchRegionTableIndex(metrics map[uint64]RegionMetric, allSchemas []*model.DBInfo) ([]HotTableIndex, error) {
 	hotTables := make([]HotTableIndex, 0, len(metrics))
 	for regionID, regionMetric := range metrics {
+		regionMetric := regionMetric
 		t := HotTableIndex{RegionID: regionID, RegionMetric: &regionMetric}
 		region, err := h.RegionCache.LocateRegionByID(tikv.NewBackoffer(context.Background(), 500), regionID)
 		if err != nil {
diff --git a/store/helper/helper_test.go b/store/helper/helper_test.go
index 30879e50c278e..cd35a1af2e10f 100644
--- a/store/helper/helper_test.go
+++ b/store/helper/helper_test.go
@@ -24,6 +24,7 @@ import (
 	"github.com/gorilla/mux"
 	. "github.com/pingcap/check"
 	"github.com/pingcap/log"
+	"github.com/pingcap/parser/model"
 	"github.com/pingcap/tidb/store/helper"
 	"github.com/pingcap/tidb/store/mockstore"
 	"github.com/pingcap/tidb/store/mockstore/mocktikv"
@@ -63,8 +64,13 @@ func (s *mockStore) TLSConfig() *tls.Config {
 func (s *HelperTestSuite) SetUpSuite(c *C) {
 	go s.mockPDHTTPServer(c)
 	time.Sleep(100 * time.Millisecond)
-	mvccStore := mocktikv.MustNewMVCCStore()
-	mockTikvStore, err := mockstore.NewMockTikvStore(mockstore.WithMVCCStore(mvccStore))
+	mockTikvStore, err := mockstore.NewMockTikvStore(
+		mockstore.WithCluster(func() *mocktikv.Cluster {
+			cluster := mocktikv.NewCluster()
+			mocktikv.BootstrapWithMultiRegions(cluster, []byte("x"))
+			return cluster
+		}()),
+	)
 	s.store = &mockStore{
 		mockTikvStore.(tikv.Storage),
 		[]string{"127.0.0.1:10100/"},
@@ -79,7 +85,13 @@ func (s *HelperTestSuite) TestHotRegion(c *C) {
 	}
 	regionMetric, err := helper.FetchHotRegion(pdapi.HotRead)
 	c.Assert(err, IsNil, Commentf("err: %+v", err))
-	c.Assert(fmt.Sprintf("%v", regionMetric), Equals, "map[1:{100 1 0}]")
+	dbInfo := &model.DBInfo{
+		Name: model.NewCIStr("test"),
+	}
+	c.Assert(fmt.Sprintf("%v", regionMetric), Equals, "map[3:{100 1 0} 4:{200 2 0}]")
+	res, err := helper.FetchRegionTableIndex(regionMetric, []*model.DBInfo{dbInfo})
+	c.Assert(err, IsNil, Commentf("err: %+v", err))
+	c.Assert(res[0].RegionMetric, Not(Equals), res[1].RegionMetric)
 }
 
 func (s *HelperTestSuite) TestTiKVRegionsInfo(c *C) {
@@ -123,9 +135,14 @@ func (s *HelperTestSuite) mockHotRegionResponse(w http.ResponseWriter, req *http
 		RegionsStat: []helper.RegionStat{
 			{
 				FlowBytes: 100,
-				RegionID:  1,
+				RegionID:  3,
 				HotDegree: 1,
 			},
+			{
+				FlowBytes: 200,
+				RegionID:  4,
+				HotDegree: 2,
+			},
 		},
 	}
 	resp := helper.StoreHotRegionInfos{
diff --git a/store/tikv/test_util.go b/store/tikv/test_util.go
index e63abc405309e..bb4d39cb1c07a 100644
--- a/store/tikv/test_util.go
+++ b/store/tikv/test_util.go
@@ -16,7 +16,7 @@ package tikv
 import (
 	"github.com/google/uuid"
 	"github.com/pingcap/errors"
-	"github.com/pingcap/pd/client"
+	pd "github.com/pingcap/pd/client"
 	"github.com/pingcap/tidb/kv"
 )