From fe09892107ef805afd2f49d31edf9a90302baa62 Mon Sep 17 00:00:00 2001
From: AilinKid <314806019@qq.com>
Date: Wed, 3 Jan 2024 12:29:29 +0800
Subject: [PATCH] fix agg push down rule mistake order by item inside agg
 function

Signed-off-by: AilinKid <314806019@qq.com>
---
 pkg/planner/core/rule_aggregation_push_down.go   |  2 +-
 tests/integrationtest/r/expression/issues.result | 15 +++++++++++++++
 tests/integrationtest/t/expression/issues.test   |  8 +++++++-
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/pkg/planner/core/rule_aggregation_push_down.go b/pkg/planner/core/rule_aggregation_push_down.go
index 5c5b4c0db664a..c3dcf84312fce 100644
--- a/pkg/planner/core/rule_aggregation_push_down.go
+++ b/pkg/planner/core/rule_aggregation_push_down.go
@@ -608,7 +608,7 @@ func (a *aggregationPushDownSolver) aggPushDown(p LogicalPlan, opt *logicalOptim
 							break
 						}
 					}
-					for j, item := range newAggOrderItems {
+					for j, item := range newAggOrderItems[i] {
 						if item == nil {
 							continue
 						}
diff --git a/tests/integrationtest/r/expression/issues.result b/tests/integrationtest/r/expression/issues.result
index 0463b4e6c7fc0..ca2c8e2dcd66d 100644
--- a/tests/integrationtest/r/expression/issues.result
+++ b/tests/integrationtest/r/expression/issues.result
@@ -3177,3 +3177,18 @@ a	b
 update test.t set b = 0 where (a, b) in (('a', 1), (null, 0));
 SHOW WARNINGS;
 Level	Code	Message
+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	100.00	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	100.00	root		CARTESIAN inner join
+      ├─TableReader(Build)	10.00	root		data:Selection
+      │ └─Selection	10.00	cop[tikv]		eq(test.ast.i, "astp2019121731703151")
+      │   └─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("astp2019121731703151", test.acc.m)
+          └─TableFullScan	10000.00	cop[tikv]	table:b	keep order:false, stats:pseudo
diff --git a/tests/integrationtest/t/expression/issues.test b/tests/integrationtest/t/expression/issues.test
index 09512a12fbb8b..4c74962b84244 100644
--- a/tests/integrationtest/t/expression/issues.test
+++ b/tests/integrationtest/t/expression/issues.test
@@ -2154,4 +2154,10 @@ create table test.t (a varchar(10), b tinyint(1));
 insert into test.t values ("abc", 1);
 select * from test.t where (a, b) in (('a', 1), (null, 0));
 update test.t set b = 0 where (a, b) in (('a', 1), (null, 0));
-SHOW WARNINGS;
\ No newline at end of file
+SHOW WARNINGS;
+
+# 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;