From 1881af706e2ac07117b717feebd7c4ea03c888d7 Mon Sep 17 00:00:00 2001
From: ti-srebot <66930949+ti-srebot@users.noreply.github.com>
Date: Wed, 8 Sep 2021 19:32:58 +0800
Subject: [PATCH] executor: make `group_concat` function consider the collation
 (#27490) (#27835)

---
 executor/aggfuncs/func_group_concat.go | 21 ++++++++++++++++-----
 executor/analyze_test.go               | 13 +++++++++++++
 2 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/executor/aggfuncs/func_group_concat.go b/executor/aggfuncs/func_group_concat.go
index c2d3b745d12fc..7d892adb54a5c 100644
--- a/executor/aggfuncs/func_group_concat.go
+++ b/executor/aggfuncs/func_group_concat.go
@@ -26,8 +26,8 @@ import (
 	"github.com/pingcap/tidb/types"
 	"github.com/pingcap/tidb/util/chunk"
 	"github.com/pingcap/tidb/util/codec"
+	"github.com/pingcap/tidb/util/collate"
 	"github.com/pingcap/tidb/util/dbterror"
-	"github.com/pingcap/tidb/util/hack"
 	"github.com/pingcap/tidb/util/set"
 )
 
@@ -175,10 +175,16 @@ func (e *groupConcatDistinct) ResetPartialResult(pr PartialResult) {
 func (e *groupConcatDistinct) UpdatePartialResult(sctx sessionctx.Context, rowsInGroup []chunk.Row, pr PartialResult) (err error) {
 	p := (*partialResult4GroupConcatDistinct)(pr)
 	v, isNull := "", false
+
+	collators := make([]collate.Collator, 0, len(e.args))
+	for _, arg := range e.args {
+		collators = append(collators, collate.GetCollator(arg.GetType().Collate))
+	}
+
 	for _, row := range rowsInGroup {
 		p.valsBuf.Reset()
 		p.encodeBytesBuffer = p.encodeBytesBuffer[:0]
-		for _, arg := range e.args {
+		for i, arg := range e.args {
 			v, isNull, err = arg.EvalString(sctx, row)
 			if err != nil {
 				return err
@@ -186,7 +192,7 @@ func (e *groupConcatDistinct) UpdatePartialResult(sctx sessionctx.Context, rowsI
 			if isNull {
 				break
 			}
-			p.encodeBytesBuffer = codec.EncodeBytes(p.encodeBytesBuffer, hack.Slice(v))
+			p.encodeBytesBuffer = codec.EncodeBytes(p.encodeBytesBuffer, collators[i].Key(v))
 			p.valsBuf.WriteString(v)
 		}
 		if isNull {
@@ -478,10 +484,15 @@ func (e *groupConcatDistinctOrder) UpdatePartialResult(sctx sessionctx.Context,
 	p := (*partialResult4GroupConcatOrderDistinct)(pr)
 	p.topN.sctx = sctx
 	v, isNull := "", false
+	collators := make([]collate.Collator, 0, len(e.args))
+	for _, arg := range e.args {
+		collators = append(collators, collate.GetCollator(arg.GetType().Collate))
+	}
+
 	for _, row := range rowsInGroup {
 		buffer := new(bytes.Buffer)
 		p.encodeBytesBuffer = p.encodeBytesBuffer[:0]
-		for _, arg := range e.args {
+		for i, arg := range e.args {
 			v, isNull, err = arg.EvalString(sctx, row)
 			if err != nil {
 				return err
@@ -489,7 +500,7 @@ func (e *groupConcatDistinctOrder) UpdatePartialResult(sctx sessionctx.Context,
 			if isNull {
 				break
 			}
-			p.encodeBytesBuffer = codec.EncodeBytes(p.encodeBytesBuffer, hack.Slice(v))
+			p.encodeBytesBuffer = codec.EncodeBytes(p.encodeBytesBuffer, collators[i].Key(v))
 			buffer.WriteString(v)
 		}
 		if isNull {
diff --git a/executor/analyze_test.go b/executor/analyze_test.go
index 764b1c38ce692..4573394690d36 100644
--- a/executor/analyze_test.go
+++ b/executor/analyze_test.go
@@ -648,6 +648,19 @@ func (s *testSuite1) TestDefaultValForAnalyze(c *C) {
 		"└─IndexRangeScan_5 1.00 cop[tikv] table:t, index:a(a) range:[1,1], keep order:false"))
 }
 
+func (s *testSerialSuite2) TestIssue27429(c *C) {
+	collate.SetNewCollationEnabledForTest(true)
+	defer collate.SetNewCollationEnabledForTest(false)
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table test.t(id int, value varchar(20) charset utf8mb4 collate utf8mb4_general_ci, value1 varchar(20) charset utf8mb4 collate utf8mb4_bin)")
+	tk.MustExec("insert into test.t values (1, 'abc', 'abc '),(4, 'Abc', 'abc'),(3,'def', 'def ');")
+
+	tk.MustQuery("select upper(group_concat(distinct value order by 1)) from test.t;").Check(testkit.Rows("ABC,DEF"))
+	tk.MustQuery("select upper(group_concat(distinct value)) from test.t;").Check(testkit.Rows("ABC,DEF"))
+}
+
 func (s *testSerialSuite2) TestIssue20874(c *C) {
 	collate.SetNewCollationEnabledForTest(true)
 	defer collate.SetNewCollationEnabledForTest(false)