planner: fix agg push down rule mistake order by item inside agg func…

…tion (#50002) (#50018)

close #49986

pkg/planner/core/rule_aggregation_push_down.go

@@ -606,7 +606,7 @@ func (a *aggregationPushDownSolver) aggPushDown(p LogicalPlan, opt *logicalOptim
 							break
 						}
 					}
-					for j, item := range newAggOrderItems {
+					for j, item := range newAggOrderItems[i] {
 						if item == nil {
 							continue
 						}

tests/integrationtest/r/statistics/integration.result

@@ -49,3 +49,18 @@ Sort	4.00	root		statistics__integration.t1.a, statistics__integration.t2.a
   │   └─TableFullScan	2.00	cop[tikv]	table:t2	keep order:false
   └─TableReader(Probe)	4.00	root		data:TableFullScan
     └─TableFullScan	4.00	cop[tikv]	table:t1	keep order:false
+drop table if exists test.t;
+create table if not exists test.ast (i varchar(20));
+create table if not exists test.acc (j varchar(20), k varchar(20), l varchar(20), m varchar(20));
+explain format='brief' with t as(select i, (case when b.j = '20001' then b.l else b.k end) an from test.ast a inner join test.acc b on (a.i = b.m) and a.i = 'astp2019121731703151'), t1 as (select i, group_concat(an order by an separator '; ') an from t group by i) select * from t1;
+id	estRows	task	access object	operator info
+Projection	8.00	root		test.ast.i, Column#32
+└─HashAgg	8.00	root		group by:Column#37, funcs:group_concat(Column#34 order by Column#35 separator "; ")->Column#32, funcs:firstrow(Column#36)->test.ast.i
+  └─Projection	12.50	root		case(eq(test.acc.j, 20001), test.acc.l, test.acc.k)->Column#34, case(eq(test.acc.j, 20001), test.acc.l, test.acc.k)->Column#35, test.ast.i->Column#36, test.ast.i->Column#37
+    └─HashJoin	12.50	root		inner join, equal:[eq(test.ast.i, test.acc.m)]
+      ├─TableReader(Build)	10.00	root		data:Selection
+      │ └─Selection	10.00	cop[tikv]		eq(test.ast.i, "astp2019121731703151"), not(isnull(test.ast.i))
+      │   └─TableFullScan	10000.00	cop[tikv]	table:a	keep order:false, stats:pseudo
+      └─TableReader(Probe)	10.00	root		data:Selection
+        └─Selection	10.00	cop[tikv]		eq(test.acc.m, "astp2019121731703151"), not(isnull(test.acc.m))
+          └─TableFullScan	10000.00	cop[tikv]	table:b	keep order:false, stats:pseudo

tests/integrationtest/t/statistics/integration.test

@@ -22,3 +22,10 @@ explain format = 'brief' select * from t2 left join t1 on t1.a=t2.a order by t1.
 explain format = 'brief' select * from t1 right join t2 on t1.a=t2.a order by t1.a, t2.a;
 explain format = 'brief' select * from t2 right join t1 on t1.a=t2.a order by t1.a, t2.a;
 
+# TestIssue49986
+drop table if exists test.t;
+create table if not exists test.ast (i varchar(20));
+create table if not exists test.acc (j varchar(20), k varchar(20), l varchar(20), m varchar(20));
+explain format='brief' with t as(select i, (case when b.j = '20001' then b.l else b.k end) an from test.ast a inner join test.acc b on (a.i = b.m) and a.i = 'astp2019121731703151'), t1 as (select i, group_concat(an order by an separator '; ') an from t group by i) select * from t1;
+
+