planner, util/ranger: fix wrong optimize order by (#30273) (#30552)

close #30271

planner/core/integration_test.go

@@ -4786,3 +4786,16 @@ func (s *testIntegrationSuite) TestIssues29711(c *C) {
 		))
 
 }
+
+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"))
+
+}

util/ranger/detacher.go

@@ -20,6 +20,7 @@ import (
 	"github.com/pingcap/errors"
 	"github.com/pingcap/tidb/expression"
 	"github.com/pingcap/tidb/parser/ast"
+	"github.com/pingcap/tidb/parser/charset"
 	"github.com/pingcap/tidb/parser/model"
 	"github.com/pingcap/tidb/sessionctx"
 	"github.com/pingcap/tidb/sessionctx/stmtctx"
@@ -716,7 +717,11 @@ 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
 	}