From a8711d9cf9baed19c68e66467a4a5935918830ff Mon Sep 17 00:00:00 2001
From: Arenatlx <314806019@qq.com>
Date: Fri, 25 Mar 2022 11:32:34 +0800
Subject: [PATCH] cherry pick #33311 to release-6.0

Signed-off-by: ti-srebot <ti-srebot@pingcap.com>
---
 parser/ast/dml.go                |  4 +++-
 parser/ast/dml_test.go           |  6 +++---
 planner/core/integration_test.go | 15 +++++++++++++++
 3 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/parser/ast/dml.go b/parser/ast/dml.go
index 5a8041fb3e939..1da250553bac0 100644
--- a/parser/ast/dml.go
+++ b/parser/ast/dml.go
@@ -119,7 +119,9 @@ func (*Join) resultSet() {}
 // We get (t1 join t3) left join t2, the semantics is correct.
 func NewCrossJoin(left, right ResultSetNode) (n *Join) {
 	rj, ok := right.(*Join)
-	if !ok || rj.Right == nil {
+	// don't break the explicit parents name scope constraints.
+	// this kind of join re-order can be done in logical-phase after the name resolution.
+	if !ok || rj.Right == nil || rj.ExplicitParens {
 		return &Join{Left: left, Right: right, Tp: CrossJoin}
 	}
 
diff --git a/parser/ast/dml_test.go b/parser/ast/dml_test.go
index f569543f701ea..f7bfd78e25901 100644
--- a/parser/ast/dml_test.go
+++ b/parser/ast/dml_test.go
@@ -229,11 +229,11 @@ func TestJoinRestore(t *testing.T) {
 		//{"(select a from t) t1 join t t2, t3;", "((SELECT `a` FROM `t`) AS `t1` JOIN `t` AS `t2`) JOIN `t3`"},
 	}
 	testChangedCases := []NodeRestoreTestCase{
-		{"(a al left join b bl on al.a1 > bl.b1) join (a ar right join b br on ar.a1 > br.b1)", "((`a` AS `al` LEFT JOIN `b` AS `bl` ON `al`.`a1`>`bl`.`b1`) JOIN `b` AS `br`) LEFT JOIN `a` AS `ar` ON `ar`.`a1`>`br`.`b1`"},
+		{"(a al left join b bl on al.a1 > bl.b1) join (a ar right join b br on ar.a1 > br.b1)", "(`a` AS `al` LEFT JOIN `b` AS `bl` ON `al`.`a1`>`bl`.`b1`) JOIN (`a` AS `ar` RIGHT JOIN `b` AS `br` ON `ar`.`a1`>`br`.`b1`)"},
 		{"a al left join b bl on al.a1 > bl.b1, a ar right join b br on ar.a1 > br.b1", "(`a` AS `al` LEFT JOIN `b` AS `bl` ON `al`.`a1`>`bl`.`b1`) JOIN (`a` AS `ar` RIGHT JOIN `b` AS `br` ON `ar`.`a1`>`br`.`b1`)"},
-		{"t1 join (t2 right join t3 on t2.a > t3.a join (t4 right join t5 on t4.a > t5.a))", "(((`t1` JOIN `t2`) RIGHT JOIN `t3` ON `t2`.`a`>`t3`.`a`) JOIN `t5`) LEFT JOIN `t4` ON `t4`.`a`>`t5`.`a`"},
+		{"t1 join (t2 right join t3 on t2.a > t3.a join (t4 right join t5 on t4.a > t5.a))", "`t1` JOIN ((`t2` RIGHT JOIN `t3` ON `t2`.`a`>`t3`.`a`) JOIN (`t4` RIGHT JOIN `t5` ON `t4`.`a`>`t5`.`a`))"},
 		{"t1 join t2 right join t3 on t2.a=t3.a", "(`t1` JOIN `t2`) RIGHT JOIN `t3` ON `t2`.`a`=`t3`.`a`"},
-		{"t1 join (t2 right join t3 on t2.a=t3.a)", "(`t1` JOIN `t3`) LEFT JOIN `t2` ON `t2`.`a`=`t3`.`a`"},
+		{"t1 join (t2 right join t3 on t2.a=t3.a)", "`t1` JOIN (`t2` RIGHT JOIN `t3` ON `t2`.`a`=`t3`.`a`)"},
 	}
 	extractNodeFunc := func(node Node) Node {
 		return node.(*SelectStmt).From.TableRefs
diff --git a/planner/core/integration_test.go b/planner/core/integration_test.go
index f66e3bf5a0817..48bd7fb3f9c03 100644
--- a/planner/core/integration_test.go
+++ b/planner/core/integration_test.go
@@ -75,6 +75,21 @@ func TestShowSubquery(t *testing.T) {
 	))
 }
 
+func TestJoinOperatorRightAssociative(t *testing.T) {
+	store, clean := testkit.CreateMockStore(t)
+	defer clean()
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t(a int, b int)")
+	tk.MustExec("insert into t values(1,10),(2,20)")
+	// make sure this join won't rewrite as left-associative join like (t0 join t1) join t2 when explicit parent existed.
+	// mysql will detect the t0.a is out of it's join parent scope and errors like ERROR 1054 (42S22): Unknown column 't0.a' in 'on clause'
+	err := tk.ExecToErr("select t1.* from t t0 cross join (t t1 join t t2 on 100=t0.a);")
+	require.Error(t, err)
+	require.EqualError(t, err, "[planner:1054]Unknown column 't0.a' in 'on clause'")
+}
+
 func TestPpdWithSetVar(t *testing.T) {
 	store, clean := testkit.CreateMockStore(t)
 	defer clean()