From 2c7976583f7aa6566d86c8469df8b77a8586b950 Mon Sep 17 00:00:00 2001
From: Yifan Xu <30385241+xuyifangreeneyes@users.noreply.github.com>
Date: Tue, 12 Apr 2022 12:50:34 +0800
Subject: [PATCH] planner, util/ranger: fix wrong optimize order by (#30273)
 (#30551)

close pingcap/tidb#30271
---
 planner/core/integration_test.go | 13 +++++++++++++
 util/ranger/detacher.go          |  5 +++++
 2 files changed, 18 insertions(+)

diff --git a/planner/core/integration_test.go b/planner/core/integration_test.go
index ab7c048c8b431..c897974556754 100644
--- a/planner/core/integration_test.go
+++ b/planner/core/integration_test.go
@@ -4359,3 +4359,16 @@ func (s *testIntegrationSuite) TestIssue27797(c *C) {
 	result = tk.MustQuery("select col2 from IDT_HP24172 where col1 = 8388607 and col1 in (select col1 from IDT_HP24172);")
 	result.Check(testkit.Rows("<nil>"))
 }
+
+func (s *testIntegrationSerialSuite) TestIssue30271(c *C) {
+	defer collate.SetNewCollationEnabledForTest(false)
+	collate.SetNewCollationEnabledForTest(true)
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t(a char(10), b char(10), c char(10), index (a, b, c)) collate utf8mb4_bin;")
+	tk.MustExec("insert into t values ('b', 'a', '1'), ('b', 'A', '2'), ('c', 'a', '3');")
+	tk.MustExec("set names utf8mb4 collate utf8mb4_general_ci;")
+	tk.MustQuery("select * from t where (a>'a' and b='a') or (b = 'A' and a < 'd') order by a,c;").Check(testkit.Rows("b a 1", "b A 2", "c a 3"))
+
+}
diff --git a/util/ranger/detacher.go b/util/ranger/detacher.go
index 6a07c531275cf..c3952ddad7296 100644
--- a/util/ranger/detacher.go
+++ b/util/ranger/detacher.go
@@ -18,6 +18,7 @@ import (
 
 	"github.com/pingcap/errors"
 	"github.com/pingcap/parser/ast"
+	"github.com/pingcap/parser/charset"
 	"github.com/pingcap/parser/model"
 	"github.com/pingcap/tidb/expression"
 	"github.com/pingcap/tidb/sessionctx"
@@ -704,7 +705,11 @@ func isSameValue(sc *stmtctx.StatementContext, lhs, rhs *valueInfo) (bool, error
 	if lhs == nil || rhs == nil || lhs.mutable || rhs.mutable || lhs.value.Kind() != rhs.value.Kind() {
 		return false, nil
 	}
+	collation := lhs.value.Collation()
+	// binary collator may not the best choice, but it can make sure the result is correct.
+	lhs.value.SetCollation(charset.CollationBin)
 	cmp, err := lhs.value.CompareDatum(sc, rhs.value)
+	lhs.value.SetCollation(collation)
 	if err != nil {
 		return false, err
 	}