fix explain test

cmd/explaintest/r/explain_easy.result

@@ -6,6 +6,7 @@ insert into t2 values(1, 0), (2, 1);
 create table t3 (a bigint, b bigint, c bigint, d bigint);
 create table t4 (a int, b int, c int, index idx(a, b), primary key(a));
 set @@session.tidb_opt_agg_push_down = 1;
+set @@session.tidb_opt_insubq_to_join_and_agg=1;
 explain select * from t3 where exists (select s.a from t3 s having sum(s.a) = t3.a );
 id	count	task	operator info
 Projection_12	8000.00	root	test.t3.a, test.t3.b, test.t3.c, test.t3.d
@@ -452,3 +453,4 @@ Projection_4	2666.67	root	test.t.a
   └─Selection_6	2666.67	cop	gt(test.t.a, 0)
     └─TableScan_5	3333.33	cop	table:t, range:(0,+inf], keep order:false, stats:pseudo
 drop table if exists t;
+set @@session.tidb_opt_insubq_to_join_and_agg=1;

cmd/explaintest/r/explain_easy_stats.result

@@ -9,6 +9,7 @@ load stats 's/explain_easy_stats_t3.json';
 create table index_prune(a bigint(20) NOT NULL, b bigint(20) NOT NULL, c tinyint(4) NOT NULL, primary key(a, b), index idx_b_c_a(b, c, a));
 load stats 's/explain_easy_stats_index_prune.json';
 set @@session.tidb_opt_agg_push_down = 1;
+set @@session.tidb_opt_insubq_to_join_and_agg=1;
 explain select * from t3 where exists (select s.a from t3 s having sum(s.a) = t3.a );
 id	count	task	operator info
 Projection_12	1600.00	root	test.t3.a, test.t3.b, test.t3.c, test.t3.d
@@ -190,3 +191,4 @@ explain select * from index_prune WHERE a = 1010010404050976781 AND b = 26467085
 id	count	task	operator info
 Point_Get_1	1.00	root	table:index_prune, index:a b
 drop table if exists t1, t2, t3, index_prune;
+set @@session.tidb_opt_insubq_to_join_and_agg=1;

cmd/explaintest/t/explain_easy.test

@@ -7,6 +7,7 @@ create table t3 (a bigint, b bigint, c bigint, d bigint);
 create table t4 (a int, b int, c int, index idx(a, b), primary key(a));
 
 set @@session.tidb_opt_agg_push_down = 1;
+set @@session.tidb_opt_insubq_to_join_and_agg=1;
 
 explain select * from t3 where exists (select s.a from t3 s having sum(s.a) = t3.a );
 explain select * from t1;
@@ -99,3 +100,4 @@ explain select * from t where _tidb_rowid > 0;
 explain select a, _tidb_rowid from t where a > 0;
 explain select * from t where _tidb_rowid > 0 and a > 0;
 drop table if exists t;
+set @@session.tidb_opt_insubq_to_join_and_agg=1;

cmd/explaintest/t/explain_easy_stats.test

@@ -9,6 +9,7 @@ load stats 's/explain_easy_stats_t3.json';
 create table index_prune(a bigint(20) NOT NULL, b bigint(20) NOT NULL, c tinyint(4) NOT NULL, primary key(a, b), index idx_b_c_a(b, c, a));
 load stats 's/explain_easy_stats_index_prune.json';
 set @@session.tidb_opt_agg_push_down = 1;
+set @@session.tidb_opt_insubq_to_join_and_agg=1;
 
 
 explain select * from t3 where exists (select s.a from t3 s having sum(s.a) = t3.a );
@@ -56,3 +57,4 @@ explain select * from index_prune WHERE a = 1010010404050976781 AND b = 26467085
 explain select * from index_prune WHERE a = 1010010404050976781 AND b = 26467085526790 GROUP BY b ORDER BY a limit 1;
 
 drop table if exists t1, t2, t3, index_prune;
+set @@session.tidb_opt_insubq_to_join_and_agg=1;