From 622ec0d9f0d7db643136599d687c3e30bb0a9ce9 Mon Sep 17 00:00:00 2001
From: HuaiyuXu <391585975@qq.com>
Date: Tue, 28 Apr 2020 13:00:40 +0800
Subject: [PATCH] executor, types: copy enum/set instead of refer the
 underlying data (#16858)

---
 executor/aggfuncs/func_first_row.go |  5 +++--
 executor/executor_test.go           | 23 +++++++++++++++++++++++
 types/enum.go                       |  9 +++++++++
 types/set.go                        |  9 +++++++++
 4 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/executor/aggfuncs/func_first_row.go b/executor/aggfuncs/func_first_row.go
index b37c41ec128a9..432fcd805bcc8 100644
--- a/executor/aggfuncs/func_first_row.go
+++ b/executor/aggfuncs/func_first_row.go
@@ -487,7 +487,7 @@ func (e *firstRow4Enum) UpdatePartialResult(sctx sessionctx.Context, rowsInGroup
 		if err != nil {
 			return err
 		}
-		p.gotFirstRow, p.isNull, p.val = true, d.IsNull(), d.GetMysqlEnum()
+		p.gotFirstRow, p.isNull, p.val = true, d.IsNull(), d.GetMysqlEnum().Copy()
 		break
 	}
 	return nil
@@ -500,6 +500,7 @@ func (*firstRow4Enum) MergePartialResult(sctx sessionctx.Context, src PartialRes
 	}
 	return nil
 }
+
 func (e *firstRow4Enum) AppendFinalResult2Chunk(sctx sessionctx.Context, pr PartialResult, chk *chunk.Chunk) error {
 	p := (*partialResult4FirstRowEnum)(pr)
 	if p.isNull || !p.gotFirstRow {
@@ -533,7 +534,7 @@ func (e *firstRow4Set) UpdatePartialResult(sctx sessionctx.Context, rowsInGroup
 		if err != nil {
 			return err
 		}
-		p.gotFirstRow, p.isNull, p.val = true, d.IsNull(), d.GetMysqlSet()
+		p.gotFirstRow, p.isNull, p.val = true, d.IsNull(), d.GetMysqlSet().Copy()
 		break
 	}
 	return nil
diff --git a/executor/executor_test.go b/executor/executor_test.go
index 97652307d8387..df4a65c0ec35a 100644
--- a/executor/executor_test.go
+++ b/executor/executor_test.go
@@ -4449,3 +4449,26 @@ func (s *testSuite1) TestIssue16025(c *C) {
 	tk.MustQuery("SELECT * FROM t0 WHERE c0;").Check(testkit.Rows())
 
 }
+
+func (s *testSuite1) TestIssue16854(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test;")
+	tk.MustExec("drop table if exists t;")
+	tk.MustExec("CREATE TABLE `t` (	`a` enum('WAITING','PRINTED','STOCKUP','CHECKED','OUTSTOCK','PICKEDUP','WILLBACK','BACKED') DEFAULT NULL)")
+	tk.MustExec("insert into t values(1),(2),(3),(4),(5),(6),(7);")
+	for i := 0; i < 7; i++ {
+		tk.MustExec("insert into t select * from t;")
+	}
+	tk.MustExec("set @@tidb_max_chunk_size=100;")
+	tk.MustQuery("select distinct a from t order by a").Check(testkit.Rows("WAITING", "PRINTED", "STOCKUP", "CHECKED", "OUTSTOCK", "PICKEDUP", "WILLBACK"))
+	tk.MustExec("drop table t")
+
+	tk.MustExec("CREATE TABLE `t` (	`a` set('WAITING','PRINTED','STOCKUP','CHECKED','OUTSTOCK','PICKEDUP','WILLBACK','BACKED') DEFAULT NULL)")
+	tk.MustExec("insert into t values(1),(2),(3),(4),(5),(6),(7);")
+	for i := 0; i < 7; i++ {
+		tk.MustExec("insert into t select * from t;")
+	}
+	tk.MustExec("set @@tidb_max_chunk_size=100;")
+	tk.MustQuery("select distinct a from t order by a").Check(testkit.Rows("WAITING", "PRINTED", "WAITING,PRINTED", "STOCKUP", "WAITING,STOCKUP", "PRINTED,STOCKUP", "WAITING,PRINTED,STOCKUP"))
+	tk.MustExec("drop table t")
+}
diff --git a/types/enum.go b/types/enum.go
index 45c15a3d2208f..1aafdc345bcf4 100644
--- a/types/enum.go
+++ b/types/enum.go
@@ -18,6 +18,7 @@ import (
 	"strings"
 
 	"github.com/pingcap/errors"
+	"github.com/pingcap/tidb/util/stringutil"
 )
 
 // Enum is for MySQL enum type.
@@ -26,6 +27,14 @@ type Enum struct {
 	Value uint64
 }
 
+// Copy deep copy an Enum.
+func (e Enum) Copy() Enum {
+	return Enum{
+		Name:  stringutil.Copy(e.Name),
+		Value: e.Value,
+	}
+}
+
 // String implements fmt.Stringer interface.
 func (e Enum) String() string {
 	return e.Name
diff --git a/types/set.go b/types/set.go
index 0a337780c452f..57145855c9c43 100644
--- a/types/set.go
+++ b/types/set.go
@@ -18,6 +18,7 @@ import (
 	"strings"
 
 	"github.com/pingcap/errors"
+	"github.com/pingcap/tidb/util/stringutil"
 )
 
 var zeroSet = Set{Name: "", Value: 0}
@@ -38,6 +39,14 @@ func (e Set) ToNumber() float64 {
 	return float64(e.Value)
 }
 
+// Copy deep copy a Set.
+func (e Set) Copy() Set {
+	return Set{
+		Name:  stringutil.Copy(e.Name),
+		Value: e.Value,
+	}
+}
+
 // ParseSetName creates a Set with name.
 func ParseSetName(elems []string, name string) (Set, error) {
 	if len(name) == 0 {