planner: Introduce a new global variable to control the historical st…

…atistics feature (#30646)
pingcap · Dec 14, 2021 · c30d34f · c30d34f
1 parent dd7f71f
commit c30d34f
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Showing 3 changed files with 13 additions and 1 deletion.
diff --git a/executor/set_test.go b/executor/set_test.go
@@ -587,6 +587,12 @@ func (s *testSerialSuite1) TestSetVar(c *C) {
 	tk.MustExec("set global tidb_enable_tso_follower_proxy = 0")
 	tk.MustQuery("select @@tidb_enable_tso_follower_proxy").Check(testkit.Rows("0"))
 	c.Assert(tk.ExecToErr("set tidb_enable_tso_follower_proxy = 1"), NotNil)
+
+	tk.MustQuery("select @@tidb_enable_historical_stats").Check(testkit.Rows("0"))
+	tk.MustExec("set global tidb_enable_historical_stats = 1")
+	tk.MustQuery("select @@tidb_enable_historical_stats").Check(testkit.Rows("1"))
+	tk.MustExec("set global tidb_enable_historical_stats = 0")
+	tk.MustQuery("select @@tidb_enable_historical_stats").Check(testkit.Rows("0"))
 }
 
 func (s *testSuite5) TestTruncateIncorrectIntSessionVar(c *C) {

diff --git a/sessionctx/variable/sysvar.go b/sessionctx/variable/sysvar.go
@@ -1205,7 +1205,11 @@ var defaultSysVars = []*SysVar{
 	{Scope: ScopeSession, Name: PluginDir, Value: "/data/deploy/plugin", GetSession: func(s *SessionVars) (string, error) {
 		return config.GetGlobalConfig().Plugin.Dir, nil
 	}},
-
+	{Scope: ScopeGlobal, Name: TiDBEnableHistoricalStats, Value: Off, Type: TypeBool, GetGlobal: func(s *SessionVars) (string, error) {
+		return getTiDBTableValue(s, "tidb_enable_historical_stats", Off)
+	}, SetGlobal: func(s *SessionVars, val string) error {
+		return setTiDBTableValue(s, "tidb_enable_historical_stats", val, "Current historical statistics enable status")
+	}},
 	/* tikv gc metrics */
 	{Scope: ScopeGlobal, Name: TiDBGCEnable, Value: On, Type: TypeBool, GetGlobal: func(s *SessionVars) (string, error) {
 		return getTiDBTableValue(s, "tikv_gc_enable", On)

diff --git a/sessionctx/variable/tidb_vars.go b/sessionctx/variable/tidb_vars.go
@@ -620,6 +620,8 @@ const (
 	TiDBGCScanLockMode = "tidb_gc_scan_lock_mode"
 	// TiDBEnableEnhancedSecurity restricts SUPER users from certain operations.
 	TiDBEnableEnhancedSecurity = "tidb_enable_enhanced_security"
+	// TiDBEnableHistoricalStats enables the historical statistics feature (default off)
+	TiDBEnableHistoricalStats = "tidb_enable_historical_stats"
 )
 
 // TiDB intentional limits