plan: fix a bug in predicate push down phase.

executor/join_test.go

@@ -266,6 +266,17 @@ func (s *testSuite) TestJoin(c *C) {
 	tk.MustExec(`insert into t values (1);`)
 	tk.MustQuery(`select t2.a, t1.a from t t1 inner join (select "1" as a) t2 on t2.a = t1.a;`).Check(testkit.Rows("1 1"))
 	tk.MustQuery(`select t2.a, t1.a from t t1 inner join (select "2" as b, "1" as a) t2 on t2.a = t1.a;`).Check(testkit.Rows("1 1"))
+
+	tk.MustExec("drop table if exists t1, t2, t3, t4")
+	tk.MustExec("create table t1(a int, b int)")
+	tk.MustExec("create table t2(a int, b int)")
+	tk.MustExec("create table t3(a int, b int)")
+	tk.MustExec("create table t4(a int, b int)")
+	tk.MustExec("insert into t1 values(1, 1)")
+	tk.MustExec("insert into t2 values(1, 1)")
+	tk.MustExec("insert into t3 values(1, 1)")
+	tk.MustExec("insert into t4 values(1, 1)")
+	tk.MustQuery("select min(t2.b) from t1 right join t2 on t2.a=t1.a right join t3 on t2.a=t3.a left join t4 on t3.a=t4.a").Check(testkit.Rows("1"))
 }
 
 func (s *testSuite) TestJoinCast(c *C) {

plan/rule_predicate_push_down.go

@@ -144,6 +144,12 @@ func (p *LogicalJoin) PredicatePushDown(predicates []expression.Expression) (ret
 		leftCond = leftPushCond
 		rightCond = rightPushCond
 	}
+	for i := range leftCond {
+		leftCond[i] = leftCond[i].Clone()
+	}
+	for i := range rightCond {
+		rightCond[i] = rightCond[i].Clone()
+	}
 	leftRet, lCh := leftPlan.PredicatePushDown(leftCond)
 	rightRet, rCh := rightPlan.PredicatePushDown(rightCond)
 	addSelection(p, lCh, leftRet, 0)