planner: enable non-prep plan cache by default (#43145)

ref #36598

session/bootstrap.go

@@ -857,11 +857,14 @@ const (
 	// version 141 set the value of `tidb_session_plan_cache_size` to "tidb_prepared_plan_cache_size" if there is no `tidb_session_plan_cache_size`.
 	// This will only happens when we upgrade a cluster before 7.1.
 	version141 = 141
+	// version 142 insert "tidb_enable_non_prepared_plan_cache|0" to mysql.GLOBAL_VARIABLES if there is no tidb_enable_non_prepared_plan_cache.
+	// This will only happens when we upgrade a cluster before 6.5.
+	version142 = 142
 )
 
 // currentBootstrapVersion is defined as a variable, so we can modify its value for testing.
 // please make sure this is the largest version
-var currentBootstrapVersion int64 = version140
+var currentBootstrapVersion int64 = version142
 
 // DDL owner key's expired time is ManagerSessionTTL seconds, we should wait the time and give more time to have a chance to finish it.
 var internalSQLTimeout = owner.ManagerSessionTTL + 15
@@ -991,6 +994,7 @@ var (
 		upgradeToVer139,
 		upgradeToVer140,
 		upgradeToVer141,
+		upgradeToVer142,
 	}
 )
 
@@ -2467,6 +2471,25 @@ func upgradeToVer141(s Session, ver int64) {
 		mysql.SystemDB, mysql.GlobalVariablesTable, variable.TiDBSessionPlanCacheSize, val)
 }
 
+func upgradeToVer142(s Session, ver int64) {
+	if ver >= version142 {
+		return
+	}
+	ctx := kv.WithInternalSourceType(context.Background(), kv.InternalTxnBootstrap)
+	rs, err := s.ExecuteInternal(ctx, "SELECT VARIABLE_VALUE FROM %n.%n WHERE VARIABLE_NAME=%?;",
+		mysql.SystemDB, mysql.GlobalVariablesTable, variable.TiDBEnableNonPreparedPlanCache)
+	terror.MustNil(err)
+	req := rs.NewChunk(nil)
+	err = rs.Next(ctx, req)
+	terror.MustNil(err)
+	if req.NumRows() != 0 {
+		return
+	}
+
+	mustExecute(s, "INSERT HIGH_PRIORITY IGNORE INTO %n.%n VALUES (%?, %?);",
+		mysql.SystemDB, mysql.GlobalVariablesTable, variable.TiDBEnableNonPreparedPlanCache, variable.Off)
+}
+
 func writeOOMAction(s Session) {
 	comment := "oom-action is `log` by default in v3.0.x, `cancel` by default in v4.0.11+"
 	mustExecute(s, `INSERT HIGH_PRIORITY INTO %n.%n VALUES (%?, %?, %?) ON DUPLICATE KEY UPDATE VARIABLE_VALUE= %?`,

session/bootstrap_test.go

@@ -1903,12 +1903,20 @@ func TestTiDBNonPrepPlanCacheUpgradeFrom540To700(t *testing.T) {
 	err = txn.Commit(context.Background())
 	require.NoError(t, err)
 	mustExec(t, seV54, fmt.Sprintf("update mysql.tidb set variable_value=%d where variable_name='tidb_server_version'", ver54))
+	mustExec(t, seV54, fmt.Sprintf("delete from mysql.GLOBAL_VARIABLES where variable_name='%s'", variable.TiDBEnableNonPreparedPlanCache))
 	mustExec(t, seV54, "commit")
 	unsetStoreBootstrapped(store.UUID())
 	ver, err := getBootstrapVersion(seV54)
 	require.NoError(t, err)
 	require.Equal(t, int64(ver54), ver)
 
+	// We are now in 5.4, check TiDBCostModelVersion should not exist.
+	res := mustExecToRecodeSet(t, seV54, fmt.Sprintf("select * from mysql.GLOBAL_VARIABLES where variable_name='%s'", variable.TiDBEnableNonPreparedPlanCache))
+	chk := res.NewChunk(nil)
+	err = res.Next(ctx, chk)
+	require.NoError(t, err)
+	require.Equal(t, 0, chk.NumRows())
+
 	// Upgrade to 7.0
 	domCurVer, err := BootstrapSession(store)
 	require.NoError(t, err)
@@ -1919,8 +1927,8 @@ func TestTiDBNonPrepPlanCacheUpgradeFrom540To700(t *testing.T) {
 	require.Equal(t, currentBootstrapVersion, ver)
 
 	// We are now in 7.0
-	res := mustExecToRecodeSet(t, seCurVer, fmt.Sprintf("select * from mysql.GLOBAL_VARIABLES where variable_name='%s'", variable.TiDBEnableNonPreparedPlanCache))
-	chk := res.NewChunk(nil)
+	res = mustExecToRecodeSet(t, seCurVer, fmt.Sprintf("select * from mysql.GLOBAL_VARIABLES where variable_name='%s'", variable.TiDBEnableNonPreparedPlanCache))
+	chk = res.NewChunk(nil)
 	err = res.Next(ctx, chk)
 	require.NoError(t, err)
 	require.Equal(t, 1, chk.NumRows())

sessionctx/variable/tidb_vars.go

@@ -1200,7 +1200,7 @@ const (
 	DefTiDBEnableFastReorg                         = true
 	DefTiDBDDLDiskQuota                            = 100 * 1024 * 1024 * 1024 // 100GB
 	DefExecutorConcurrency                         = 5
-	DefTiDBEnableNonPreparedPlanCache              = false
+	DefTiDBEnableNonPreparedPlanCache              = true
 	DefTiDBNonPreparedPlanCacheSize                = 100
 	DefTiDBPlanCacheMaxPlanSize                    = 2 * size.MB
 	DefTiDBEnableTiFlashReadForWriteStmt           = true