planner: set EnableOuterJoinReorder to false by default (#37264)

cmd/explaintest/r/clustered_index.result

@@ -1,3 +1,4 @@
+set @@tidb_enable_outer_join_reorder=true;
 drop database if exists with_cluster_index;
 create database with_cluster_index;
 drop database if exists wout_cluster_index;
@@ -127,3 +128,4 @@ StreamAgg_17	1.00	root		funcs:count(Column#9)->Column#7
 └─IndexReader_18	1.00	root		index:StreamAgg_9
   └─StreamAgg_9	1.00	cop[tikv]		funcs:count(1)->Column#9
     └─IndexRangeScan_16	109.70	cop[tikv]	table:tbl_0, index:idx_3(col_0)	range:[803163,+inf], keep order:false
+set @@tidb_enable_outer_join_reorder=false;

cmd/explaintest/r/select.result

@@ -1,3 +1,4 @@
+set @@tidb_enable_outer_join_reorder=true;
 DROP TABLE IF EXISTS t;
 CREATE TABLE t (
 c1 int,
@@ -654,3 +655,4 @@ create table t3(a char(10), primary key (a));
 insert into t3 values ('a');
 select * from t3 where a > 0x80;
 Error 1105: Cannot convert string '\x80' from binary to utf8mb4
+set @@tidb_enable_outer_join_reorder=false;

cmd/explaintest/t/clustered_index.test

@@ -1,3 +1,4 @@
+set @@tidb_enable_outer_join_reorder=true;
 drop database if exists with_cluster_index;
 create database with_cluster_index;
 drop database if exists wout_cluster_index;
@@ -53,3 +54,4 @@ explain select count(*) from wout_cluster_index.tbl_0 where col_0 <= 0 ;
 
 explain select count(*) from with_cluster_index.tbl_0 where col_0 >= 803163  ;
 explain select count(*) from wout_cluster_index.tbl_0 where col_0 >= 803163  ;
+set @@tidb_enable_outer_join_reorder=false;

cmd/explaintest/t/select.test

@@ -1,3 +1,4 @@
+set @@tidb_enable_outer_join_reorder=true;
 DROP TABLE IF EXISTS t;
 
 CREATE TABLE t (
@@ -279,3 +280,4 @@ create table t3(a char(10), primary key (a));
 insert into t3 values ('a');
 --error 1105
 select * from t3 where a > 0x80;
+set @@tidb_enable_outer_join_reorder=false;

planner/core/rule_join_reorder_test.go

@@ -77,6 +77,7 @@ func TestLeadingJoinHint(t *testing.T) {
 	tk.MustExec("create table t6(a int, b int, key(a));")
 	tk.MustExec("create table t7(a int, b int, key(a));")
 	tk.MustExec("create table t8(a int, b int, key(a));")
+	tk.MustExec("set @@tidb_enable_outer_join_reorder=true")
 	runJoinReorderTestData(t, tk, "TestLeadingJoinHint")
 
 	// test cases for outer join
@@ -117,6 +118,8 @@ func TestJoinOrderHint(t *testing.T) {
 	tk.MustExec("create table t7(a int, b int, key(a));")
 	tk.MustExec("create table t8(a int, b int, key(a));")
 
+	tk.MustExec("set @@tidb_enable_outer_join_reorder=true")
+
 	// test cases for using the leading hint and straight_join hint at the same time
 	tk.MustExec("select /*+ leading(t1) straight_join() */ * from t1 join t2 on t1.a=t2.a join t3 on t2.b=t3.b")
 	tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1815 We can only use the straight_join hint, when we use the leading hint and straight_join hint at the same time, all leading hints will be invalid"))
@@ -239,6 +242,7 @@ func TestJoinOrderHint4StaticPartitionTable(t *testing.T) {
 	tk.MustExec(`create table t3(a int, b int) partition by hash(b) partitions 3`)
 
 	tk.MustExec(`set @@tidb_partition_prune_mode="static"`)
+	tk.MustExec("set @@tidb_enable_outer_join_reorder=true")
 	runJoinReorderTestData(t, tk, "TestJoinOrderHint4StaticPartitionTable")
 }
 
@@ -255,6 +259,7 @@ func TestJoinOrderHint4DynamicPartitionTable(t *testing.T) {
 	tk.MustExec(`create table t3(a int, b int) partition by hash(b) partitions 3`)
 
 	tk.MustExec(`set @@tidb_partition_prune_mode="dynamic"`)
+	tk.MustExec("set @@tidb_enable_outer_join_reorder=true")
 	runJoinReorderTestData(t, tk, "TestJoinOrderHint4DynamicPartitionTable")
 }
 
@@ -274,6 +279,7 @@ func TestJoinOrderHint4DifferentJoinType(t *testing.T) {
 	tk.MustExec("create table t6(a int, b int, key(a));")
 	tk.MustExec("create table t7(a int, b int, key(a));")
 	tk.MustExec("create table t8(a int, b int, key(a));")
+	tk.MustExec("set @@tidb_enable_outer_join_reorder=true")
 
 	runJoinReorderTestData(t, tk, "TestJoinOrderHint4DifferentJoinType")
 }
@@ -288,6 +294,7 @@ func TestJoinOrderHint4TiFlash(t *testing.T) {
 	tk.MustExec("create table t1(a int, b int, key(a));")
 	tk.MustExec("create table t2(a int, b int, key(a));")
 	tk.MustExec("create table t3(a int, b int, key(a));")
+	tk.MustExec("set @@tidb_enable_outer_join_reorder=true")
 
 	// Create virtual tiflash replica info.
 	dom := domain.GetDomain(tk.Session())

planner/core/rule_result_reorder_test.go

@@ -166,6 +166,7 @@ func TestOrderedResultModeOnJoin(t *testing.T) {
 	tk.MustExec("drop table if exists t2")
 	tk.MustExec("create table t1 (a int primary key, b int, c int, d int, key(b))")
 	tk.MustExec("create table t2 (a int primary key, b int, c int, d int, key(b))")
+	tk.MustExec("set @@tidb_enable_outer_join_reorder=true")
 	runTestData(t, tk, "TestOrderedResultModeOnJoin")
 }
 

sessionctx/variable/sysvar.go

@@ -196,7 +196,7 @@ var defaultSysVars = []*SysVar{
 		s.OptimizerSelectivityLevel = tidbOptPositiveInt32(val, DefTiDBOptimizerSelectivityLevel)
 		return nil
 	}},
-	{Scope: ScopeGlobal | ScopeSession, Name: TiDBOptimizerEnableOuterJoinReorder, Value: BoolToOnOff(DefTiDBEnableOuterJoinReorder), skipInit: true, Type: TypeBool, SetSession: func(s *SessionVars, val string) error {
+	{Scope: ScopeGlobal | ScopeSession, Name: TiDBOptimizerEnableOuterJoinReorder, Value: BoolToOnOff(DefTiDBEnableOuterJoinReorder), Type: TypeBool, SetSession: func(s *SessionVars, val string) error {
 		s.EnableOuterJoinReorder = TiDBOptOn(val)
 		return nil
 	}},

sessionctx/variable/tidb_vars.go

@@ -775,7 +775,7 @@ const (
 	DefBroadcastJoinThresholdCount               = 10 * 1024
 	DefTiDBOptimizerSelectivityLevel             = 0
 	DefTiDBOptimizerEnableNewOFGB                = false
-	DefTiDBEnableOuterJoinReorder                = true
+	DefTiDBEnableOuterJoinReorder                = false
 	DefTiDBAllowBatchCop                         = 1
 	DefTiDBAllowMPPExecution                     = true
 	DefTiDBHashExchangeWithNewCollation          = true

sessionctx/variable/varsutil_test.go

@@ -242,6 +242,9 @@ func TestVarsutil(t *testing.T) {
 	err = SetSessionSystemVar(v, TiDBOptimizerEnableOuterJoinReorder, "OFF")
 	require.NoError(t, err)
 	require.Equal(t, false, v.EnableOuterJoinReorder)
+	err = v.SetSystemVar(TiDBOptimizerEnableOuterJoinReorder, "ON")
+	require.NoError(t, err)
+	require.Equal(t, true, v.EnableOuterJoinReorder)
 
 	require.Equal(t, DefTiDBOptimizerEnableNewOFGB, v.OptimizerEnableNewOnlyFullGroupByCheck)
 	err = SetSessionSystemVar(v, TiDBOptimizerEnableNewOnlyFullGroupByCheck, "off")