From 6cff35892c2c29a7d2951d00dc9e8d0668469b52 Mon Sep 17 00:00:00 2001
From: rebelice <yangrebelice@gmail.com>
Date: Wed, 7 Apr 2021 14:18:16 +0800
Subject: [PATCH] *: don't allocate SessionIndexUsageCollector when
 indexUsageLease equals 0 (#23861)

---
 session/session.go               |  4 +++-
 session/tidb.go                  |  7 ++++++-
 session/tidb_test.go             | 21 +++++++++++++++++++++
 statistics/handle/handle_test.go |  4 ++++
 4 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/session/session.go b/session/session.go
index 8e068da8851d7..f529647248af7 100644
--- a/session/session.go
+++ b/session/session.go
@@ -2092,7 +2092,9 @@ func CreateSessionWithOpt(store kv.Storage, opt *Opt) (Session, error) {
 	// which periodically updates stats using the collected data.
 	if do.StatsHandle() != nil && do.StatsUpdating() {
 		s.statsCollector = do.StatsHandle().NewSessionStatsCollector()
-		s.idxUsageCollector = do.StatsHandle().NewSessionIndexUsageCollector()
+		if GetIndexUsageSyncLease() > 0 {
+			s.idxUsageCollector = do.StatsHandle().NewSessionIndexUsageCollector()
+		}
 	}
 
 	return s, nil
diff --git a/session/tidb.go b/session/tidb.go
index 8dc13ed580d65..85732b457f7a6 100644
--- a/session/tidb.go
+++ b/session/tidb.go
@@ -65,7 +65,7 @@ func (dm *domainMap) Get(store kv.Storage) (d *domain.Domain, err error) {
 
 	ddlLease := time.Duration(atomic.LoadInt64(&schemaLease))
 	statisticLease := time.Duration(atomic.LoadInt64(&statsLease))
-	idxUsageSyncLease := time.Duration(atomic.LoadInt64(&indexUsageSyncLease))
+	idxUsageSyncLease := GetIndexUsageSyncLease()
 	err = util.RunWithRetry(util.DefaultMaxRetries, util.RetryInterval, func() (retry bool, err1 error) {
 		logutil.BgLogger().Info("new domain",
 			zap.String("store", store.UUID()),
@@ -161,6 +161,11 @@ func SetIndexUsageSyncLease(lease time.Duration) {
 	atomic.StoreInt64(&indexUsageSyncLease, int64(lease))
 }
 
+// GetIndexUsageSyncLease returns the index usage sync lease time.
+func GetIndexUsageSyncLease() time.Duration {
+	return time.Duration(atomic.LoadInt64(&indexUsageSyncLease))
+}
+
 // DisableStats4Test disables the stats for tests.
 func DisableStats4Test() {
 	SetStatsLease(-1)
diff --git a/session/tidb_test.go b/session/tidb_test.go
index 02e9571c18482..e6d9fb5c5541b 100644
--- a/session/tidb_test.go
+++ b/session/tidb_test.go
@@ -215,3 +215,24 @@ func (s *testMainSuite) TestKeysNeedLock(c *C) {
 	c.Assert(flag.HasPresumeKeyNotExists(), IsTrue)
 	c.Assert(keyNeedToLock(indexKey, deleteVal, flag), IsTrue)
 }
+
+func (s *testMainSuite) TestIndexUsageSyncLease(c *C) {
+	store, err := mockstore.NewMockStore()
+	c.Assert(err, IsNil)
+	do, err := BootstrapSession(store)
+	c.Assert(err, IsNil)
+	do.SetStatsUpdating(true)
+	st, err := CreateSessionWithOpt(store, nil)
+	c.Assert(err, IsNil)
+	se, ok := st.(*session)
+	c.Assert(ok, IsTrue)
+	c.Assert(se.idxUsageCollector, IsNil)
+
+	SetIndexUsageSyncLease(1)
+	defer SetIndexUsageSyncLease(0)
+	st, err = CreateSessionWithOpt(store, nil)
+	c.Assert(err, IsNil)
+	se, ok = st.(*session)
+	c.Assert(ok, IsTrue)
+	c.Assert(se.idxUsageCollector, NotNil)
+}
diff --git a/statistics/handle/handle_test.go b/statistics/handle/handle_test.go
index c2dd99cd39970..68ca14f1a5603 100644
--- a/statistics/handle/handle_test.go
+++ b/statistics/handle/handle_test.go
@@ -1995,6 +1995,8 @@ type statsSerialSuite struct {
 
 func (s *statsSerialSuite) TestIndexUsageInformation(c *C) {
 	defer cleanEnv(c, s.store, s.do)
+	session.SetIndexUsageSyncLease(1)
+	defer session.SetIndexUsageSyncLease(0)
 	tk := testkit.NewTestKit(c, s.store)
 	tk.MustExec("use test")
 	tk.MustExec("create table t_idx(a int, b int)")
@@ -2034,6 +2036,8 @@ func (s *statsSerialSuite) TestIndexUsageInformation(c *C) {
 
 func (s *statsSerialSuite) TestGCIndexUsageInformation(c *C) {
 	defer cleanEnv(c, s.store, s.do)
+	session.SetIndexUsageSyncLease(1)
+	defer session.SetIndexUsageSyncLease(0)
 	tk := testkit.NewTestKit(c, s.store)
 	tk.MustExec("use test")
 	tk.MustExec("create table t_idx(a int, b int)")